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Section 5 : Environmental Health Sciences117 Meteorology Sandip Mukherji, Kunal Chatterjee 630

118 Public Health Aspects of Adverse Effects of Extreme Hot Environment RajVir Bhalwar 634

119 Public Health Aspects of Extreme Cold Environment RajVir Bhalwar 641

120 Health Hazards at Mountains (High Altitude Terrestrial Environment) RajVir Bhalwar 647

121 Water Supply Sunil Agrawal 650

122 Excreta Disposal Rajul K Gupta 666

123 Disposal of Solid Wastes Kunal Chatterjee 680

124 Management of Biomedical Wastes Kunal Chatterjee 688

125 Public Health Aspects of Housing and Ventilation Kunal Chatterjee 696

126 Environmental Pollution : Air, Soil, Noise and Radiological Pollution Leo S Vaz 701

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117 Meteorology

Sandip Mukherji & Kunal Chatterjee

Meteorology is the science concerned with the phenomena occurring in the atmosphere. The elements, which comprise the meteorological environment, are atmospheric pressure, air temperature, humidity, rainfall, direction and speed of wind and movement of clouds and weather. In all meteorological observations, the results obtained by different observers at different stations are recorded by instruments, which are similar in form and exposed in the same manner.

Early information about the weather conditions is essential to take preventive measures against its adverse effects. This method is termed as weather forecasting and it also helps in planning for the prevention and control of diseases, predict the level of human efficiency and forecast the dangers of climatic extremes and vagaries on human life. Forecasting the weather and climate is carried out by correlating the present and previous meteorological observations with the norms observed over considerably long retrospective periods. The different elements of weather and the instruments to measure them are discussed in the subsequent paragraphs.

Measurement of Atmospheric TemperatureAtmospheric temperature measurement is an important data for weather forecasting. This is recorded by a thermometer, which is exposed in open sheds to allow free circulation of air and protected from direct rays of the sun by a thick roof. Both mercury and alcohol thermometers are used for this measurement. Mercury boils at a higher temperature, has an even expansion and is easily visible against the glass background while alcohol has the advantage of not solidifying even at very low temperatures.

Dry and Wet bulb thermometer : These are ordinary mercury thermometers, which measure the air temperature. The wet bulb is the same as dry bulb thermometer except that its bulb is kept wet by a muslin cloth fed by water from a bottle through a wick. The evaporation of water from the muslin cloth lowers temperature of the mercury. The wet bulb thermometer therefore shows a lower temperature than the dry bulb thermometer. In case both the thermometers record similar readings, then it is presumed that the air is completely saturated with moisture as happens during rains.

Maximum thermometer : This is a mercury thermometer with a very fine constriction near the neck of the bulb. It is hung up almost horizontally with the bulb end slightly lower than the other end. The capillary stem of the thermometer has a small metal indicator, which is pushed along by the mercury and fits tightly enough to remain behind when the mercury recedes. With the rise in temperature, the mercury expands and rushes across the constriction pushing the indicator. Once the temperature falls and the mercury recedes, the indicator, which fits tightly in the capillary, is measured at its lower end to give the maximum temperature reached. The thermometer is reset each time by pulling down the indicator with a magnet until it comes in contact with the mercury.

Minimum thermometer: Minimum thermometer has alcohol inside, in which a dumb-bell shaped index is immersed. When the temperature falls the spirit drags the index down towards the bulb end, but when the temperature rises the spirit expands and runs past the index. At the end of any period of observation, the position at the end of the index farthest from the bulb is considered as the minimum temperature recorded. The maximum and minimum thermometer are installed on a wooden base which is placed inside a box such as the Stevenson’s screen described below, for accurate recording of temperature.

Maximum and minimum thermometer : Here the two thermometers are conjoined and made as a glass tube with three limbs, which combines the principles of maximum and minimum thermometers. The commonest such instrument is the Six’s thermometer, which is not considered accurate for meteorological measurements and is not used by Indian Meteorological department.

Stevenson’s screen : To ensure an accuracy of measurement of air temperature, the thermometers are mounted in a box of approved pattern called as the ‘Stevenson’s screen’. It is a double louvered box whose internal dimensions are 76 cms length, 45 cms width and 48 cms height. It has a double roof, the upper one projecting 5 cms beyond the sides of the box and sloping from front to back, and has an open base. At the front is a hinged door opening downwards. The box is mounted on four posts with its door opening to the North or South depending on whether it is placed in a region in the Northern or Southern hemisphere respectively. The bulbs of thermometers are placed at a height of 120 to 180 cms from the ground, and at least 6 m away from the nearby buildings or large structures to provide unobstructed flow of air around the equipment. The thermometers are hung inside the box such that no bulb comes within 8 cms of roof or sides of the box. They can be easily read in this position without being disturbed or touched (Fig. - 1).

Fig. - 1 : Stevenson’s screen

Temperature recordings : The mean daily temperature is obtained by adding twenty-four hourly observations and dividing this by twenty-four. The temperature of a month is

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the mean of those thirty days, and the temperature of a year is the mean of those of twelve months. The temperature of the air varies at different parts of the day. It is increased by the absorption of solar radiation during the day. The variation of temperature with a maximum and a minimum, dividing the day into periods of eight and sixteen hours, is the diurnal variation with the difference called as the diurnal range.

Some simple precautions are also necessary in taking the readings in these instruments. Sufficient time should be allowed for the mercury to come to thermal equilibrium with the surrounding air. Nearness of the instruments to surfaces much hotter or cooler than the air will also give a false reading.

Measurement of Solar RadiationThe Sun’s rays warm up the atmosphere, which is measured by the instruments described above. Another factor, which contributes to rise in environmental temperature is the heat given out by hot objects on the earth’s surface, after they have absorbed heat. This heat given out is known as radiant heat and is in the infrared range of spectrum. These objects record higher temperatures than that of the surrounding atmosphere. To measure the warmth of an atmospheric condition, it is thus essential to measure the radiant heat also.

Campbell - Stokes Sunshine Recorder : The number of hours of sunshine are recorded by the Campbell-Stokes Sunshine Recorder. This comprises of a charted paper placed on a concave surface of the recorder. A solid glass globe brings to focus the sun’s rays on to this paper, which chars the paper at the point of focus. With the movement of sun throughout the day, a charred line is created on the paper, which when measured gives the number of hours of sunshine in the day (Fig. - 2).

Fig. - 2 : Campbell-Stokes sunshine recorder

Solar radiation thermometer : This instrument measures the intensity of solar radiation on a given day. It comprises of a black bulb thermometer enclosed inside a glass shield. The glass shield is devoid of air to avoid any aberrance in measurements. Black colour being absorbent of heat, the thermometer records a higher temperature than ambient air temperature, when it is exposed to sun rays. The difference in the maximum thermometer reading taken inside the Stevenson screen and the Solar radiation thermometer denotes the intensity of solar radiation.

Black Globe thermometer : The Black Globe thermometer measures the radiant heat directly. It comprises of a hollow copper globe of about 15 cms diameter, with an opening at a

side. Through this opening is inserted a calibrated mercury thermometer such that its bulb is placed in the centre of the globe. The globe is painted with matt-black paint and the equipment is suspended outside on a stand. The matt-black paint absorbs radiant heat from the surrounding objects. If the surrounding environment is windy, a black globe with 20 cms should be used. The instrument should be placed in the environment for about 20 minutes by which time it reaches equilibrium. The temperature is recorded thereafter. The globe thermometer records a higher temperature than the ordinary air temperature thermometer, since it is affected both by the air temperature and the radiant heat.

Various modifications have been made in the standard black globe thermometer such as the wet globe thermometer, which has a wet black cloth covering the sphere or the modified globe developed by Hellon & Crockford, which reaches equilibrium in 8 to 10 minutes and is made of a lighter gauge material and has an internal air stirring mechanism (Fig. - 3).

Fig. - 3 : Black Globe thermometer

Measurement of Atmospheric PressureThe atmospheric pressure close to sea level on the earth’s surface is measured as 760 mm of mercury (Hg) and is called as 1 atmosphere of pressure. This pressure falls as the altitude increases and rises as the altitude decreases at the rate of 1 atmosphere for each 33 feet depth below sea level.

Atmospheric pressure is measured with the help of an instrument called as a barometer. These could be the aneroid or mercury barometer, of which the latter are more accurate. Some of the well-known barometers are Fortin’s barometer, Kew Pattern station barometer, commonly used by the Indian Meteorological Department. The barograph is a continuous measurement of the atmospheric pressure over a 24 hour period. The instrument is a circular box, the walls of which collapse or distend when the atmospheric pressure rises or falls and are supplied with the recording device and spare charts. More sensitive barographs recording very minimal fluctuations of pressure are called as ‘Microbarographs’. The fluctuations

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seen in a barometer are considered to be of importance in determining the pattern of weather conditions. Ordinarily the barometric readings during field studies are recorded on the aneroid barometer, which needs regular calibration with the mercury barometer.

Measurement of Atmospheric HumidityAtmospheric humidity or the moisture content of air is generated from large watery surfaces, which are exposed to atmosphere. Moisture is also added to air by living animals and plants due to their constant discharge of water vapour from the lungs or leaves. The moisture content of air can be expressed in two different manners as Absolute humidity and Relative Humidity (RH). Absolute humidity is the amount of water vapour per unit weight or volume of air expressed as grams per litre or grams per cubic metre of air and is measured by absorption hygrometers. Relative humidity describes the moisture content of air at any given temperature as a percentage of the maximum possible moisture content i.e. the ratio of amount of water vapour actually present in the air to the amount that would be present where the air saturated with moisture expressed as a percentage out of 100.

The amount of water vapour necessary to cause saturation of air varies directly with the temperature, the higher the temperature of air, more the water vapour it can hold before saturation point is reached. When the air becomes completely saturated, evaporation from any surface in that area ceases altogether. If the air is cooled, the excessive moisture precipitates for the particular temperature. This is called ‘Dew Point’. Humidity has an effect on the comfort levels, though not directly on the physical health of a person. At relative humidity levels above 65 percent the air inside a room feels sticky, while air at RH below 30 percent is unpleasant.

Mason’s Hygrometer : This is the most widely used instrument for measuring humidity at the permanent meteorological stations. It consists of two similar thermometers mounted side by side on a Stevenson screen. One of them is a dry bulb thermometer, which measures the ambient air temperature. The other thermometer is the wet bulb thermometer, which is similar to the dry bulb thermometer but has its bulb covered with a muslin cloth kept moist by a cotton wick, which dips in a reservoir of distilled water. This thermometer records air temperature as influenced by the rate of evaporation from the muslin cloth. The drier the air the greater the rate of evaporation and lower would be the readings on the wet bulb. In a saturated atmosphere, the readings of dry and wet bulb coincide. The difference in the reading is called as ‘Depressions of the wet bulb’ and is inversely proportional to the atmospheric moisture. The readings recorded on the hygrometer could be used to determine the relative humidity, the vapour and the dew point with the help of hygrometric tables.

A stationary wet bulb creates a zone of higher humidity immediately surrounding it when the air movement is sluggish due to continuous evaporation of water. This may give rise to falsely higher readings on the instrument and is obviated by providing an air velocity artificially by mechanically moving the two thermometers, as is carried out in the Sling Psychrometer described below.

Whirling or Sling Psychrometer : This instrument has a dry and a wet bulb thermometer mounted side by side on a metal strip, which is fixed on a wooden frame. The frame has a handle on a side, which acts as a pivot on which the wooden frame can be rotated. The wet bulb thermometer is kept wet by a piece of wick which soaks water from a small cylindrical water container. The instrument, once ready, is whirled standing with the back to the sun at the rate of 4 rotations per second. The readings on the thermometer show a dip due to evaporation of water brought about by the air movement created due to the rotation. Successive readings are noted on the wet bulb thermometer till they do not show any further change i.e. two successive readings on the wet bulb thermometer are the same and this reading is recorded. The reading on the dry bulb thermometer is also recorded at this point of time. The two thermometer readings are used to determine the relative humidity of the air using suitable tables and charts. The rotation could also be carried out using a motorised device or a modification carried out on the psychrometer called as the ‘Assmann Psychrometer’ which draws air at the rate of 5 metres per second onto the thermometers using clockwork fan. These devices give more accurate measurements (Fig. - 4).

Fig. - 4 : Sling Psychrometer

Measurement of Air MovementAir movement determines the cooling power of air and it influences the comfort levels in an environment. The equipment used to measure air movement are Kata thermometer and anemometers. The latter could be of propeller type, thermoanemometers or the hot wire anemometers.

Kata Thermometer : The Kata thermometer is useful in measuring air velocities as low as 10 feet per minute. ‘Kata’ is a Greek word meaning ‘down’ and the Kata thermometer is an alcohol thermometer with a glass bulb 4 cm long and 1.8 cm in diameter. The bulbs are silvered to reduce the errors due to radiation. These thermometers are available to cover the following cooling ranges :

Standard Kata (Red coloured alcohol) with a cooling range ●between 100°F to 95°F.High temperature Kata (Dark Blue coloured alcohol) with a ●cooling range between 130°F to 125°F.Extra High temperature Kata (Magenta coloured alcohol) ●with a cooling range between 150°F to 145°F.

Each Kata thermometer has a given kata factor determined by the manufacturers and is provided with standard charts with

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instructions for use. Two thermometers are used to record air movement, the bulb of one is covered with a wet muslin cloth, called as the wet kata and the other is the dry kata. The two thermometers are set prior to taking readings by immersing them in hot water to warm them slightly above 130°F, when the alcohol rises to a small reservoir at the top of the instruments. The bulb of dry kata is wiped dry. Then both the instruments are suspended in air at the point of observation about 60 cms away from the observer. The time in seconds is recorded using a stop watch for the alcohol to drop across the cooling range for example, from 100°F to 95°F for the standard kata. The observations are repeated four times and after discarding the first, an average of the other three are taken and an average length of time is arrived at. The kata factor for the instrument divided by the average length of time gives the wind velocity in millicalories per square centimetre per second. Kata charts can also be used for this purpose. A dry kata reading of 6 and above and a wet kata reading of 20 and above were regarded as indices of thermal comfort (Fig. - 5).

Fig. - 5 : Kata thermometer

Anemometer : These are used to measure the unidirectional wind velocity and are of the rotating vane or the propeller type. The propeller comprises of two short metallic arms joined rigidly in the middle at right angles to each other. At each of the four free ends of these two arms is attached a half-hemispherical hollow cup with its rim in a vertical plane and the hollows of all the four looking in the same direction. This is mounted on a vertical spindle such that the arms can move free in a horizontal plane. When this is mounted on the top of tower unobstructed by trees and buildings and the wind blows from a direction, it catches one or more of these cups and sends them whirling at a speed equal or proportional to the wind velocity. The spindle is further attached to the anemometer box and there is a counter inside the box called ‘cyclometer’ to measure the wind speeds.

Thermo-anemometer and Hot Wire anemometer : A thermo-anemometer is a mercury anemometer with an electrically heated metallic coil around its bulb. A rheostat regulated the

voltage in this coil. The velocity of air can be measured upto 5000 cms per seconds or more using suitable voltage in the coil and the calibration charts.

A hot wire anemometer is made up of three pieces of electrically heated fine platinum wires. The change in resistance produced by the cooling effect of air current is measured by a potentiometer or a galvanometer. This instrument can measure very low air speeds below 100 centimetres per seconds.

Measurement of PrecipitationPrecipitation is a collective term used for all forms of water precipitated from the atmosphere such as rain, snow, hail, dew and frost. Rainfall is measured by rain-gauges in inches or millimetres per time unit (day or month). The Indian Meteorological Department uses the Symon’s rain-gauge at its rainfall measuring stations. The rain-gauge consists of a funnel for collecting rainfall, a receiving vessel and a measuring glass (Fig. - 6).

Fig. - 6 : Rain gauge

The funnel is made of copper and is cylindrical in its upper part with a diameter of 20.3 cm. The receiving vessel is a small copper can, which fits inside an outer casing. The measuring glass is calibrated and specific to a particular rain-gauge. The outer casing of the instrument alongwith the receiving vessel and collecting funnel is sunk in an open level ground in a masonry or concrete foundation. The top of the receiving funnel should be placed exactly horizontal one foot above the ground level. It should be ensured that there are no obstructions such as trees or buildings nearby. After the desired time has elapsed, the collecting funnel is removed, the receiving vessel lifted out and the contained water poured carefully into the measuring glass and read off. Similar instrument could also be used to measure snowfall.

SummaryMeteorology is the science concerned with the phenomena occurring in the atmosphere. The elements, which comprise the meteorological environment, are atmospheric pressure, air temperature, humidity, rainfall, direction and speed of wind and movement of clouds and weather. Climate and weather

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have marked effects on health and diseases. Early information about the weather conditions is essential to take preventive measures against its adverse effects. This method is termed as Weather forecasting and it also helps in planning for the prevention and control of diseases, predicts the level of human efficiency and forecast the dangers of climatic extremes and vagaries on human life.

Atmospheric temperature is recorded by a thermometer, which is exposed in open sheds to allow free circulation of air and protected from direct rays of the sun by a thick roof. Both mercury and alcohol thermometers are used for this measurement. The various instruments available for its measurement are Dry and Wet bulb thermometer, Maximum thermometer, Minimum thermometer, Maximum and minimum thermometer and Stevenson’s screen. A rise in environmental temperature is due to radiant heat and sun’s rays hence to measure the warmth of an atmospheric condition, it is essential to measure the radiant heat also. It is measured by Campbell - Stokes Sunshine Recorder, Solar radiation thermometer and Black Globe thermometer. The difference in the maximum thermometer reading taken inside the Stevenson screen and the Solar radiation thermometer denotes the intensity of solar radiation.

Atmospheric pressure is measured with the help of an instrument called as a barometer. These could be the aneroid or mercury barometer of which the latter are more accurate. Some of the well-known barometers are Fortin’s barometer, Kew Pattern station barometer commonly used by the Indian Meteorological Department and the Barograph. The barograph is a continuous measurement of the atmospheric pressure over a 24 hour period. The fluctuations seen in a barometer are considered to be of importance in determining the pattern of weather conditions.

Atmospheric humidity or the moisture content of air can be expressed in two different manners as Absolute humidity and Relative Humidity (RH). At relative humidity levels above 65 percent, the air inside a room feels sticky, while air at RH below

30 percent is unpleasant. Mason’s Hygrometer is the most widely used instrument for measuring humidity at the permanent meteorological stations. Whirling or Sling Psychrometer and Assmann Psychrometer give more accurate measurements.

Air movement determines the cooling power of air and it influences the comfort levels in an environment. The equipment used to measure air movement are Kata thermometer and anemometers. The latter could be of propeller type, thermoanemometers or the hot wire anemometers.

Precipitation is a collective term used for all forms of water precipitated from the atmosphere such as rain, snow, hail, dew and frost. Rainfall is measured by rain-gauges in inches or millimetres per time unit (day or month). The Indian Meteorological Department uses the Symon’s rain-gauge at its rainfall measuring stations.

Study ExercisesShort Notes : (1) Kata thermometer (2) Psychrometer.

MCQs1. Stevenson screen is used for measuring (a) Air Temp

(b) Cooling power of Air (c) Humidity (d) Air movement.2. Globe thermometer is used to measure (a) Air Temp

(b) Cooling power of Air (c) Humidity (d) Mean Radiant Temp.

3. The measuring liquid of kata thermometer is (a) Alcohol (b) Mercury (c) Water (d) None.

4. Kata thermometer was devised to measure (a) Air Temp (b) Cooling power of Air (c) Humidity (d) Air movement.

5. The speed with which the air should pass over the bulb in a wet bulb thermometer is (in m/Sec) (a)5 (b)10 (c)50 (d)100.

6. Air velocity is measured by (a) Anemometer (b) Psychrometer (c) Globe thermometer (d) Stevenson screen.

7. Kata thermometer can record air velocities as low as (in ft/ min) (a)10 (b)2 (c)20 (d)1.

Answers : (1) a; (2) d; (3) a; (4) d; (5) a; (6) a; (7) a.

118Public Health Aspects of Adverse Effects of Extreme Hot Environment

RajVir Bhalwar

The term “heat stress” is applied to any degree of environmental heat that causes physiological thermoregulatory mechanisms to get activated. Human beings are homoeothermic creatures whose physiology attempts to maintain a constant core body

temperature of 37°C (range 36 to 38°C). Obviously, this requires balancing of the body heat production with heat loss which is achieved by a combination of physiological mechanisms (as peripheral vasodilatation or vasoconstriction, changes in heart rate, sweating or shivering) and behavioral mechanisms (increase or decrease in voluntary physical activity, seeking appropriate shelter etc). In addition, environmental conditions viz., temperature, humidity and speed of air also greatly determine whether a person will be subjected to thermal stress. Prevention and management of thermal stress disorders therefore requires an understanding of these physiological, behavioral and environmental mechanisms and manipulating

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them appropriately. For the purpose of thermoregulation, the human body can be conceived of having two “layers“ - an outer periphery or “shell” consisting of skin, subcutaneous tissue and muscles, and an inner “core” consisting of brain, heart and viscera.

EpidemiologyAdverse effects of heat stress are an important cause of morbidity and mortality not only in developing countries, but in the developed countries as well. In India, 3,194 deaths due to heat-stroke have been recorded over the 5-year period - 1999 to 2003; the actual magnitude may be much more. The central and northern plains, western deserts and tropical forest areas of North - East have environmental conditions causing heat stress during the months of April to September. In India, more than 1600 heat related deaths were reported during the year 2003 (1).

Human (Host) Factors A wide array of host factors have been implicated in increasing the risk of heat illnesses, as shown in Box - 1.

Box - 1 : Persons at high risk of heat stress

Extremes of age (<5 years or >65 years)

Pregnancy

Occupation : military, agricultural, construction & industrial settings, labourers, sports-persons and miners

Low level of physical fitness

Lack of acclimatization to environmental heat

Obesity

High ambient temperature, high atmospheric humidity, low air velocity

Alcohol use - acute and chronic

Skin diseases : Extensive prickly heat, psoriasis, pyoderma

Sleep deprivation

Co-existing febrile illness, renal, thyroid, cardio-vascular and metabolic diseases

Previous history of heat-illness

Use of drugs or habit forming substances : Phenothiazines, anti-cholinergics, ACE-inhibitors, MAO-inhibitors, cocaine, amphetamines

Residence on floors higher than ground floor, especially top floors, and urban areas

High population density as occurs during social and religious conglomerations(Sources : References 2 - 13)

Physical activity and adverse effects of hot environment: Physical activity in a hot/humid environment is a major determinant of heat illness. With the broad group of physical activity, certain variables determine the occurrence and severity as follows :

(i) Nature of physical activity : The nature of physical activity and its strenuousness, at a given time is one of the

most important determinants, since it directly determines the metabolic heat being produced by the body which, in turn, reflects the intrinsic heat load of the body. It also needs to be noted that running or jogging at fast pace leads to very high metabolic heat production and may be particularly hazardous during hot weather.

(ii) The amount of load being carried : This could be either external load (as baggage) or as a part of body weight itself (e.g. an obese persons). For every additional kilogram of such “load”, an additional 2 kcal/hour of additional heat will be produced, when walking at ordinary pace. This would further increase as the pace increases.

(iii) The type of terrain : As compared to walking on an ordinary black topped road, the metabolic heat production will progressively increase when walking (at the same speed), on a cross country track, on recently ploughed fields, on snow or on over heavy sand, in which case the heat production may be almost two times when compared to walking on road. (The hot environmental conditions associated with sandy terrain are, in any case, additional).

(iv) The Inclination (Gradient) : Heat production increases, at a given pace, as the gradient increases. Even a 10% increase in the gradient may substantially increase metabolic heat production.

(v) The duration of physical activity : In harsh, hot & humid environment even well trained persons may suffer from adverse effect of hard physical activity if continued for more than half an hour unless adequate rest pauses are interspersed.

The type of clothing and adverse effects : There are three aspects, in relation to clothing, which determine the dissipation of metabolic heat, being produced in the body.

The ● insulation, measured in Clo units (8). The insulation should be, ideally, as low as possible in a hot environment.The ● permeability to moisture which should be as high as possible.Absorption of “ ● radiant energy” which is quite high for dark clothing.

Synthetic material has poor permeability and should be avoided. Similarly multilayered clothing, which ‘trap’ layers of still air between them tend to increase the insulation even if they have good permeability. Thus the correct approach would be to use light coloured loose fitting clothing, in one or two layers, and made of ‘breathable’ material as cotton.

Environmental FactorsWhile various attributes of the human host, as described earlier, play an important role in determining who will and will not ultimately get affected by heat illness, a major role in these health issues is played by the physical environment - the air temperature, humidity, air movement, and radiant heat from sun or other hot objects.

From the physical environment point of view, the major factor which emerge as determinants of heat illness are, the temperature of ambient air (usually determined by Dry Bulb Thermometer (DBT), the relative humidity (usually determined by using psychrometric charts, using the reading of both the

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DBT and the Wet Bulb Thermometer (WBT), the Mean Radiant Temperature (MRT) whose main source is either solar radiation or radiations from hot objects as furnaces, and which is usually determined by the Globe Thermometer (GT), and the speed of the air (usually determined by anemometers or specialized thermometer). Based on the permutation and combination of these parameters, certain indices of environmental heat illness have been developed. A brief description of these “thermal stress indices” is as follows :

(a) Effective Temperature : ET is defined as the subjective feeling of warmth (or cold) at a given temperature of air (DBT), when RH is 100%, the air is almost still (minimal air movement) and the subjects are ordinarily clothed. In general, when a person is at rest with a body metabolic heat production of 100 kcal/ hour, in an environment of 100% RH and minimal air movements, an air temperature (DBT) of 36°C is the ET and marks the upper limit of 4 hourly tolerance. If heat production increases, by strenuous activity to about 425 kcal/hour, under the same environmental conditions, a DBT of 31°C is the upper limit of ET for 4 hourly tolerance (14). For the outdoor setting, the preferred index is ‘Corrected Effective Temperature (CET)’, where Globe thermometer temperature (GT) is used in place of DBT.

(b) Oxford (syn - Wet-Dry - WD) Index : The Oxford Index is a simple and quite effective Index, based on DBT and WBT : WD Index = 0.85 WBT + 0.15 DBT.

(c) Wet Bulb Globe Temperature (WBGT) : WBGT index is the most commonly used index of thermal stress. It takes into account the effect of MRT (as measured through Globe Thermometer (GT) in addition to WBT and DBT as follows :

Outdoor WBGT = 0.7 WBT + 0.2 GT + 0.1 DBT

Indoor WBGT = 0.7 WBT + 0.3 GT

WBGT levels of 30°C and above indicate definite thermal stress and care needs to be exercised (15). From May to August, most of the Indian subcontinent (except the northern hilly areas) tends to have WBGT values of more than 30°C.

Prevention of Heat Related IllnessGovernmental as well as the public health functionaries cannot afford to ignore the potential dangers of sustained heat wave and should develop a contingency plan. Although heat stroke is amenable to medical treatment, control can best be achieved by applying the principles of public health surveillance, public education, outreach to vulnerable persons, availability of life saving first aid and enlistment of the help of the entire community can save lives (16). A structured approach towards prevention and control of Heat illnesses in communities consist of :

Public Health measures directed towards communities and ●large population groupsSpecific preventive measures directed towards individuals/ ●small groups identified to be at high risk of heat illnesses due to certain occupational characteristicsEarly detection and first aid. ●

Public Health Measures Directed Towards Communities and Large Population Groups : In tropical countries like India, millions of people among the general population are at

risk during the hot/humid months, especially when spells of heat wave strike. In such settings, heat related casualties may occur in large numbers in short duration, creating almost a disaster like situation and hence the need for public education, provision of preventive amenities at vantage points, and quick first aid. From the public health angle, the following aspects need to be addressed :

(i) Public education regarding preventive measures : Creating public awareness should be high on the list for the public health administrators. Full use of audio-visual and print mass media must be made during the onset of hot weather and also well before the expected heat wave. The messages should include the following aspects :

Do not venture out in the sun, especially between 10 am to ●4 pm unless the same is necessary.Avoid strenuous physical exertion between 10 am to 4 pm ●during the hot weather unless the same is necessary for reasons of occupation.Drink at least 4 to 5 litres of cool water in a day even if not ●feeling thirsty. If undertaking strenuous physical activities, drink a quarter to half litre of water after every half an hour, as long as strenuous activity continues.Do not wait for ‘thirst’ to develop. Keep drinking water ●regularly even if not thirsty.If exposure to sun is necessary, place a wet hand towel ●around your neck.Put on a wide - brimmed hat of light colour when going out. ●Simple caps as golf cap may not give enough protection.Put on sunglasses when going out in the sun. ●Apply a sun screen ointment with a Sun-Protection-Factor ●(SPF) of at least 15, which should be able to protect against both UVA and UVB rays, when going out in the sun.Avoid alcohol consumption during hot humid months. If ●consumption becomes necessary, keep the same within limits of less than 2 small drinks of hard liquor or one bottle of light beer per day.Keep children less than 5 years and elderly (aged 65 years ●and above) away from sun as far as possible.Never leave children (or pets) in a closed, parked car. Try ●and park your car in cool, shaded place.Use a car-sun visor to minimize the effect of direct radiant ●heat produced by the sun, to enter inside the parked car.Dress for hot, humid weather should be ‘breathable’ i.e. ●Loose fitting, light weight, light colored, preferably of cotton material and in one or two layers only.Carry a water bottle with cool drinking water whenever ●you go out in summer months.If you feel exhausted, confused or running out of memory/ ●consciousness, move to a shaded place, sit/lie down, drink cool water and seek help.

(ii) Provisions of basic preventive amenities at vantage points on a large scale basis, during high risk periods : There are four basic amenities which all public health managers must strive to provide to the general public during the hot weather or else, if some high risk activity as sports events or religious/social gatherings are likely. They are :

Cool drinking water at vantage points. ●Covered/shaded areas for taking rest pauses. ●

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Facilities for first aid in a way that they are early accessible ●to all, particularly the high risk groups.Public information system to make all aware about the ●facilities and the telephone numbers/addresses of key persons and first-aid facilities, who may be contacted during need.

(iii) Identification of high risk groups and enlistment of community support : Studies have revealed, there are certain high risk groups like agricultural workers, manual labourers, young children, old people those who are unable to care for themselves and those who form part of large social or religious gatherings/ festivals, are more vulnerable to the effects of heat. And enlistment of community support as part of voluntary services with outreach efforts towards these high groups can be of much utility in minimizing the public health impact of heat.

Public Health Surveillance, Early Warning Systems and Disaster Plan : The need to have a good epidemiological surveillance system for heat illnesses as well as various environment conditions that determine those illnesses need not be over emphasized. This should be established not only for specialized groups like Armed forces or industries but also for the general community as well. It is only through ongoing collection of data and monitoring of trends of occurrence of illness and environmental factors, that proper policy decisions on public health aspects of heat illnesses can be taken (3, 17, 18). An effective heat illness surveillance system must include reporting of all heat illness cases according to diagnostic categories, both for indoor and outdoor cases separately. It should have at the minimum, data related to time and place of exposure, as well as basic clinical data, besides including the antecedent/precipitating factors and personal risk factors. It should also have the essential meteorological data (WBT, DBT, GT) for various locations. The data should be analyzed in an ongoing manner and a ‘Heat and Health Early Warning System’ should be developed to issue early warnings and use of public health/preventive measures to the physician as well as to the general community. Simple warning criteria based on WBGT for outdoor exercises as running and cycling, for general public can be that, at the place where and time when an outdoor exercise or sports event is being planned, if WBGT index is more than 28°C, or else the WBT recording is more than 26.5°C, the event should not be held (17). If both, the Dry Bulb (DBT) readings and Relative Humidity (RH) levels are known, a rough guidance for outdoor physical exercise can be as shown in Table - 1. Note that these meteorological parameters should be recorded as near the place of outdoor exercise as possible.Specific Preventive Measures Directed Towards Individuals and Small Groups : Specific preventive measures directed towards individuals or specific high risk groups as industrial workers, military personnel, sports persons etc., are undertaken to achieve the following objectives :

Proper protective measures in the industries as isolation of ●furnaces, and spray of cold aerosols.Seeking shade and wind to the extent possible. ●Frequent rest pauses interspersed between phases of ●physical activity.

Table - 1

Dry Bulbs Temp. (DBT)°C

Relative Humidity (RH) levels (%)

Moderate risk High risk

29.5°C 100% -

32.2°C 70-99% -

35.0°C 50-70% >80%

37.8°C 40-50% 60-80%

40.6°C 20-40% 50-60%

43.3°C 10-30% 40-50%

46.1°C 10-20% 30-40%

48.9°C 1-10% 20-30%

(The interpretation of Table - 1 is as follows : for example if the outdoor DBT is 37°C and the RH is 48%, there is moderate risk of developing heat illness; if the RH at the same temperature is 65%, there is high risk.)

Putting on proper clothing of low insulation, low energy ●absorption and high permeability.Reducing the amount of exercise in terms of duration or ●intensity or both.Avoiding carrying of load or reducing the load. ●Acclimatization to heat and proper hydration. ●Avoidance of obesity, alcohol and other habit forming ●agents as cocaine, cannabis and caffeine.Avoidance of self medication. ●Avoiding physical activity and exposure to hot environment ●during febrile illness, until fully recovered.Ensuring proper sleep of 7 to 8 hours in the night and cooler ●parts of early morning. An afternoon rest in a shaded place may be of further protective value.Maintenance of general hygiene and sanitation, regular ●bath and care of skin, proper immunization and hygiene of food & water, to avoid GIT infections.Nutritious and palatable meals with plenty of drinking ●water.Treatment of skin conditions as prickly heat, psoriasis, sun ●burns etc.

Acclimatization to heat : Acclimatization to heat is a process of undertaking gradually increasing physical exercises in gradually increasing hot environment with a view to develop physiological changes, so that the individual, so acclimatized, is able to perform physical activities in the hot environment for which he/she has been acclimatized, with much less risk of suffering adverse effects of heat. The individuals to be acclimatized are subjected to physical exercise in a hot environment in which they are ultimately required to work. The schedule should be in a graded manner, starting with lower intensity of physical exercise for lesser duration (about an hour) in less hot environment. This is gradually increased, both in intensity and duration (about 90 -120 minutes) and to the required hot environment, by the 6th or 7th day and continuing thereafter for another 7 days. It takes about 10 to 14 days for status of acclimatization to be achieved. During the

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process of acclimatization, individuals should be encouraged to drink plenty of water/oral fluids and additional salt may be given with meals (not as salt tablets).

Maintenance of Hydration : During the process of acclimatization and also after acclimatization, it is imperative that adequate hydration be maintained, other wise the entire process of acclimatization will be negated. It needs to be noted, and explained that there is no substitute to adequate hydration even after full acclimatization since acclimatization itself works on the principle of increasing the sweating. One can acclimatize to physical work in heat but there is nothing like acclimatization to dehydration.

Persons should be encouraged (even, at times, forced or ordered) to keep drinking water regularly while working in hot environment, even when not thirsty. It must be explained clearly that thirst is quite a poor index of dehydration and should not be relied upon. Drinking only when thirsty will result in inadequate replacement of water losses and result in dehydration of more than 2% of body weight, which may be dangerous. The best fluid for drinking is cool, hygienic water. It would be worthwhile to drink half a litre of water, about an hour before starting physical activities in hot weather, as a ‘prehydration’ method and to negate any pre-existing water deficit. Thereafter every person should drink 300 to 350 ml water (equal to the usual steel tumbler) every half hourly, during the exercise, without waiting for thirst. In-fact, more frequent intakes of smaller amounts (250 ml i.e. one ordinary size glass tumbler every 20 minutes) may be even better. At the same time, care should be taken not to drink so much that it leads to abdominal distension.Adverse Effects of Environmental Heat & their Emergency Management

Heat Stroke (HS) : The classical clinical description of HS is the triad of hyperpyrexia (rectal temperature>40°C), CNS dysfunction and anhidrosis. Anhidrosis, however, is not a diagnostic requirement, since it may appear later when volume depletion is severe. Moreover, in cases which initially start as HE or cases of HS which occur among young people who have been exerting physically, the skin may be moist. Brain dysfunction is usually severe (coma, stupor or delirium), but may sometimes be subtle, manifesting as inappropriate behaviour or impaired judgment. In fact, any person who develops irrational or confused behavior following exposure to heat stress either with or without a history of physical exertion, should be treated as a potential HS patient. Other clinical features include evidence of dehydration, shock, convulsions and, sometimes, mild icterus. Two forms of HS are recognized, viz. the classical (CHS) and the exertional (EHS) form. It is important to recognize the clinical differences between the two forms (Box - 2).

Heat stroke should be considered as a possibility in any patient who presents with elevated body temperature and altered mental functions. Important and common diseases which need to be excluded are tropical infectious diseases like cerebral malaria, encephalitis and meningitis. The diagnosis of HS is usually one of exclusion and the typical history of exposure to hot environment during the immediate past is an indication towards heat stress hyperthermia. HS must be treated as a serious medical emergency. Delay in institution

of appropriate therapy by even few minutes may make all the difference between life and death. The treatment objectives are, firstly, rapid cooling to bring down the core temperature to below 39°C, reducing it by approximately 0.2°C per minute; secondly, rehydration and care of comatose patient; and, thirdly to support the organ system function. Cooling measures should be stopped once core temp falls below 39°C. The steps in management at first aid level, and at primary care/solo physician level are shown in Box - 3 and 4 respectively.

Heat Exhaustion (HE) : The features which differentiate HE from HS are that core temp is less than 40°C and there is no evidence of CNS dysfunction, though some patients may be anxious or irritable. The main features are feeling of exhaustion, nausea, headache or light headedness, features of dehydration, hypovolaemia (tachycardia, loss of skin turgor, dry mucous membranes and thirst) and syncope. Sweating is usually profuse and skin is moist. Rectal temperature is usually between 39°C to 40°C, though some patients may have a normal temperature. Urinary output is reduced and urine may be light to dark yellow in colour. Depending on how energetically the patient has been replacing either water or salt, two subtypes, viz. Water Depletion HE and Salt Depletion HE may occur. In water Depletion HE, as compared to Salt Depletion HE, vomiting and muscle cramps are not a prominent feature, while thirst is prominent, and serum Na+ is normal or raised. However, mostly a mixed picture, as described earlier is seen.

Treatment consists of shifting the patient to a cool, shaded and ventilated place. The clothing should be loosened, patient placed in recumbent position and feet should be elevated. If patient can drink, give one litre of water (or, preferably, “Oral Rehydration Solution” 1 packet dissolved in one litre water or else a solution of 2.5g common salt and 2.5g baking soda in 1 litre water) orally in about 30 min. Give a total of 2 litres in about one to one-and-a-half hours. Simultaneously, measures for cooling, as described under heat stroke, should be initiated. Keep monitoring rectal temp; if rectal temp goes beyond 39° C, the patient may be passing on to heat stroke and should be shifted to a medical facility for appropriate management.

Other Adverse Effects of Hot EnvironmentHeat Cramps : These manifest as spasms of muscles, especially lower extremity and shoulder, following heavy muscular exertion in hot environment, with associated intake of hypotonic oral fluids. Treatment consists of oral administration of 0.1% to 0.2% salt solution.

Box - 2

CHS EHS

Age group Elderly 15 to 45 years

Previous health statusUsually compromised

Healthy

Concurrent activity Sedentary Strenuous activity

H/o drug use Often present Usually present

Sweating Often absent Often present

Skin Dry Moist

Rhabdomyolysis Unusual May be severe

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Heat Tetany : Symptoms include carpopedal spasms and paraesthesiae following short exposures to excessively hot environment, leading to hyperventilation and respiratory alkalosis. Treatment consists of removing the patient to a cool environment and asking him to slow down the respiration.

Heat Syncope : This manifests as syncope following exposure to heat stress as a result of peripheral vasodilatation. One should exclude other serious causes of syncope. Treatment consists of removal of patient to cool environment and oral rehydration.

Heat Oedema : This presents with pitting oedema of hands and feet, usually in the elderly, following exposure to heat stress. Other causes of oedema should be excluded. Treatment consists of reassurance, elevation of affected limbs and, if required, compression bandage.

Prickly Heat (Lichen Tropicus, Milaria Rubra) : It manifests as erythematous, pruritic, maculopapular rash. If the condition is allowed to progress, extensive prickly heat that can progress to chronic dermatitis and superinfection can occur. Prevention consists of regular baths with cool water after gently scrubbing the skin and wearing loose, light weight clothing. Local application of calamine lotion or chlorhexidine lotion alongwith oral antihistamines is helpful.

SummaryThe term “heat stress” is applied to any degree of environmental heat that causes physiological thermoregulatory mechanisms to get activated. Humans are homoeothermic creatures whose physiology attempts to maintain a constant core body temperature of 37°C (range 36 to 38°C). For the purpose of thermoregulation, the human body can be conceived of having two “layers“ - an outer periphery or “shell” consisting of skin, subcutaneous tissue and muscles, and an inner “core” consisting of brain, heart and viscera.

Adverse effects of heat stress are an important cause of morbidity and mortality. In India, the central and northern plains, western deserts and tropical forest of North - East have environmental conditions causing heat stress during April to September. The high risk conditions include extremes of

age (<5 years or >65 years), pregnancy, workers in military, agricultural, construction & industrial settings, labourers, sports-persons and miners, those having poor physical fitness, lack of heat acclimatization, obesity, alcohol use, skin diseases, sleep deprivation, co-existing febrile illness, renal, thyroid, cardio-vascular and metabolic diseases, previous history of heat-illness & use of drugs or habit forming substances e.g. Phenothiazines, anti-cholinergics. Besides the factors mentioned, certain other Human (Host) Factors are implicated in causation of heat stress as gender, racial and genetic factors, physical activity, type of clothing, lack of concurrent hydration, floor of the residential building, urban rural differences & social and religious conglomeration. Environmental factors involved are temperature of ambient air, relative humidity, Mean Radiant Temperature (MRT) & air speed. Certain indices of environmental heat illness based on the permutation and combination of these parameters are Effective Temperature, Oxford (syn : Wet-Dry : WD) Index & Wet Bulb Globe Temperature (WBGT) index.

A structured approach towards prevention and control of heat illnesses in the community consist of Public Health measures directed towards communities and large populations groups, specific preventive measures directed towards high risk individuals/small groups & early detection and first aid.

In Public health measures directed towards communities and large population groups, the aspects that need to be addressed are public education on various preventive measures such as not venturing out in the sun, especially between 10 am to 4 pm during the hot weather, drinking at least 4 to 5 liters of cool water in a day even if not feeling thirsty; provisions of basic preventive amenities at vantage points on a large scale basis, during high risk periods; identification of high risk groups and enlistment of community support; and development of Public Health Surveillance, early warning systems and disaster plan.

Specific preventive measures directed towards individuals and small groups should be directed to high risk groups as industrial workers, military personnel, sports persons etc., to achieve the objectives of proper protective measures in the industries,

Box - 3 : Heat Stroke : First Aid

Record rectal temperature. If it is not possible to record rectal temp, record oral temp and add 0.5°C.

Try and move patient to a cooler, shaded place.

Remove the clothes.

Spray skin with water at 25 to 30°C or wrap the patient with a sheet soaked in water at 25-30°C.

Continue fanning manually or with an electrical fan.

Keep vigorously massaging the skin to prevent cutaneous vasoconstriction during cooling.

If available, place ice packs or towel soaked in cold water around the neck, axillae and groin.

Nurse in the comatose position; clear oral secretions.

Transport to the medical facility as an emergency.

Box - 4 : Heat Stroke Management at the Level of Solo-Physician or at Primary Health Care Level

Initiate measures outlined under first aid if not already initiated

Establish IV-line; take blood sample for investigations.

Start normal saline (or Ringer lactate) drip at 20-25°C. Give a challenge of 1 litre fluid in 15 to 30 minutes. Add other electrolytes such as K+, as guided by subsequent investigations.

If any evidence of seizures, give IV Diazepam 5-10mg over 10mts

If facilities are available, intubate the patient and initiate ventilatory support.

If rectal temp is not coming down or there is evidence of cerebral, hepatic or renal complications consider transferring the patient to a hospital with adequate facilities.

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seeking shade and wind to the extent possible, frequent rest pauses, proper clothing of low insulation, low energy absorption and high permeability, reduced physical exercise, avoiding carrying/reducing the load, heat acclimatization and proper hydration, avoidance of obesity, alcohol, habit forming agents, self medication, physical activity and exposure to hot environment during febrile illness; ensuring proper sleep of 7 to 8 hours in the night and cooler parts of early morning with an afternoon rest in a shaded place; maintenance of general hygiene and sanitation, regular bath and care of skin, proper immunization and hygiene of food & water, nutritious and palatable meals with plenty of drinking water, treatment of skin conditions.

Acclimatization to heat is the process of undertaking gradually increasing physical exercises in gradually increasing hot environment with a view to develop physiological changes, so that the individual is able to perform physical activities in the hot environment for which he/she has been acclimatized, with much less risk of suffering adverse effects of heat. It is in a graded manner, starting with lower intensity of physical exercise for lesser duration in less hot environment which is gradually increased, both in intensity and duration. The physiological changes consequent to acclimatization are increased sweating in response to exercise, lowered threshold for exercise induced sweating, lesser rise in heart rate and lesser rise of skin and rectal temperature in response to exercise, decreased amount of salt excretion in sweat, increased ability to sustain sweat production during prolonged exercise and redistribution of sweating from truncal region to the extremities.

Maintenance of hydration by drinking water regularly while working in hot environment, even when not thirsty is extremely important. Advise should be to drink 300 to 350 ml water (equal to the usual steel tumbler) every half hourly, during the exercise, without waiting for thirst.

Adverse effects of hot environment include Heat Stroke (HS) which is a triad of hyperpyrexia (rectal temperature >40°C), CNS dysfunction (usually severe) and anhidrosis. Other features include evidence of dehydration, shock, convulsions and mild icterus. Two forms of HS are recognized, viz. the Classical (CHS) and the Exertional (EHS) form. The treatment objectives are, firstly, rapid cooling to bring down the core temperature to below 39°C, reducing it by approx 0.2°C/min; secondly, rehydration and care of comatose; and, thirdly to support the organ system function. Heat Exhaustion (HE occurs when the core temp is less than 40°C with no evidence of CNS dysfunction. The main features are feeling of exhaustion, nausea, headache or light headedness, dehydration, hypovolaemia, syncope, profuse sweating and moist skin. Treatment consists of shifting the patient to a cool, shaded and ventilated place, loosening the clothing, recumbent position and feet elevation. If patient can drink, give one litre of water (or, preferably ORS) orally in about 30 min. Give a total of 2 litres in 1-1½ hours. Simultaneously, measures for cooling as under heat stroke, initiated. Other adverse effects of hot environment include heat cramps, heat tetany, heat syncope, heat oedema & prickly Heat.

Study ExercisesLong Question : Discuss the public health and community based preventive actions that you will adopt, as the District

health officer, for dealing with an expected heat wave that is likely to last for about 3 to 4 weeks, in the state of Punjab.

Short Notes : (1) Heat stroke versus heat exhaustion (2) Risk factors for adverse effects of hot environment (3) Thermal stress indices (4) Acclimatization to heat.

MCQs & Exercises1. For every additional kilogram of load being carried, how

much of additional heat will be produced, when walking at ordinary pace : (a) 1 kcal/hour (b) 2 kcal/hour (c) 3 kcal/hour (d) 4 kcal/hour.

2. All the following are important aspects which determine the dissipation of metabolic heat, in terms of the clothing being worn except : (a) Insulation (b) Radiance (c) Permeability (d) Absorption.

3. The commonest skin disease which interferes with sweat function thereby reducing heat tolerance is _________ .

4. Febrile illness, as a consequence of infection or following immunization, increases the ____________ of the body, as well as the heart rate.

5. During heat-wave conditions, the morbidity and mortality in urban areas tends to be higher as compared to rural areas due to ________ effect.

6. Globe Thermometer is used to measure : (a) Relative humidity (b) Ambient temp (c) Radiant heat (d) Air velocity.

7. Oxford Index is dependent on (a) DBT (b) WBT (c) DBT & WBT (d) None of the above.

8. Which is the most commonly used index of thermal stress (a) DBT (b) WBGT (c) WBT (d) Oxford.

9. A good sun screen ointment should have a Sun-Protection-Factor (SPF) of at least, to be able protect against both UVA and UVB rays, when going out in the sun : (a) 10 (b) 15 (c) 20 (d) 25.

10. Acclimatization to heat takes how many days? : (a) 2 - 6 days (b) 6 - 10 days (c) 10 - 14 days (d) 14 - 18 days.

11. Unit of measurement of insulation of clothing is ______ . 12. Anemometers are used to measure : (a) Relative humidity

(b) Ambient temp (c) Radiant heat (d) Air velocity.13. Which WBGT levels indicate definite thermal stress

and that care needs to be exercised : (a) 10°C - 20°C (b) 20°C - 30°C (c) 30°C & above (d) All are correct.

14. Drinking only when thirsty will result in inadequate replacement of water losses and dehydration due to loss of how much water as percentage of body weight : (a) <1% (b) 1% (c) 2% (d) >2%.

15. Heat stroke is a triad of hyperpyrexia (rectal temperature >40°C), CNS dysfunction and __________ .

Answers : (1) b; (2) b; (3) Prickly heat (Milaria Rubra); (4) Heat load; (5) Heat Island; (6) c; (7) c; (8) b; (9) b; (10) c; (11) Clo units; (12) d ; (13) c; (14) d; (15) Anhidrosis.

ReferencesSriramachari S. Heat hyperpyrexia; Time to act. Indian J Med Res 2004; 119 1. : vii - x.Mehta SR, Jaswal DS. Heat stroke. MJAFI 2003;59 : 140-3.2. Department of public health, Georgia. Georgia Epidemiology Report, vol (6), 3. 1996.Wyndham CH. Research in the human sciences in the Gold Mining Industries.. 4. Amer Indust Hyg Assoc Journal 1947; 35 : 113-36.. Klausen K, Dill DB, Phillips EE, McGregor D. Metabolic reactions to work in 5. desert. J Appl Physiol 1967;22 : 292-6.

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Rowell LB, Brengelmann GL, Murray JA, Kraning KK, Kusumi F. Human 6. metabolic responses to hyperthermia during mild to maximal exercise. J Appl Physiol 1969;26 : 395-402Gardner JW, Kark JA,Karnei K, et al. Risk factors predicting exertional heat 7. illnesses in male Marine Corps recruits. Med Sci Sports Exerc 1996;28 : 939-44.Gagge AP, Burlon AC, Bagett HC. A practical system for the description of 8. heat exchange of man with his environment.Science 1941; 94 : 928-30.Cadarette BS, Sawka MN, Tover MM, Pandolf KB. Aerobic fitness and the 9. hypohydration response to exercise-heat stress. Anat Space Environ Med 1984;14 : 194-8.Buskirk ER, Iampietro PF, Bass DE. Work performance after dehydration 10. : effects of physical conditioning and heat acclimatization. J Appl Physiol 1958;12 : 189-94.Sawka MN, Toner MM, Francesconi RP, Pandolf KB. Hypohydration and 11. exercise : effects of heat acclimation, gender and environment. J Appl Physiol 1983;55 : 1147-53.

Pandolf KB, Griffin TB, Munro EN, Goldman RF. Heat intolerance as a function 12. of Percent of body surface involved with Miliaria rubra. Am J Physiol 1980; 239 : R 233-R240.Leboneitz R, serdman DS, loar A, Shapiro Y,Epstein Y. Are psoriatic patient at 13. risk of heat tolerance? Br J Dermatol 1991;124 : 439-42.Goldman RF. Prediction of Human Heat Tolerance. In : Polinsbee et al eds. 14. Environmental stress. Academic press, New York., 1978.Yaglon CP, Minard D. Control of heat casualties at military training centres. 15. AMA Arch Ind Health 1957;16 : 302-16.Kellerman AL, Todd KH, et al. Killing heat. N Engl J Med 1996;335;126-7.16. Convertino VA, Armstrong LE, Coyle EF. American.college of sports medicine 17. American college of sports medicine position on heat and cold illness during distance running. Med sci sports exerc 1996;28 : 1Bruchnell MCM. Heat illness- A review of military experience. I JR Army Med 18. Corps 1996;142 : 34-42.

119 Public Health Aspects of Extreme Cold Environment

RajVir Bhalwar

Adverse effects of extremes of cold environment have been an important public health issue in the history of mankind (1, 2). Deleterious effects of extreme cold are inherent in the atmospheric environment at high altitude, but they also occur at low altitudes as in the Polar Regions. Even sub tropical areas like the plains of Northern India experience severe winters, where such illnesses do occur. Extreme cold conditions occur in India in the Himalayan, Sub - Himalayan and the northern Indian plains with cold waves and deaths being recorded every year. Over the 5-year period - 1999 to 2003, a total of 3,524 deaths due to cold exposure have been reported; the actual magnitude may be higher.

Human exposure to extreme cold produces significant physiologic and psychological challenges. Cold is considered as an important environmental stressor, in view of its serious consequences (3). The human body becomes even more susceptible to the adverse effects of cold when chronic exertional fatigue, sleep loss, and inadequate nutrition are also co-existent (4). Groups at particularly high risk include military personnel, agriculturists, mountaineers and persons engaging in adventure or winter sports. From socio - economic aspect, persons with low income, poor housing and inadequate clothing are at particularly high risk especially during the cold wave conditions. Extremes of age (<5yrs or >65yrs), physical exhaustion, pre - existent malnutrition or starvation, use of alcohol and underlying diseases (hypothyroidism, hypoadrenalism, diabetes and CV Disease) increase the risk.

Adverse Health Effects of ColdAdverse effects of cold environment can manifest as either

generalized effects (hypothermia) or local “tissue-freezing” effects as frost bite, or Non-Freezing Cold Injuries (NFCI) as trench foot and chilblains.

Generalised Hypothermia : The normal core (rectal) temperature of normal healthy human beings is 37 to 37.5°C. Early symptoms of generalised adverse effects of cold become apparent as the “core” (rectal) temp. drops below 36°C and are clearly evident once it is below 35°C. Depending on the core temp, hypothermia may be classified as borderline (36 to 35°C), mild (35 to 32°C), moderate (32 to 28°C) and severe (<28°C). One of the earliest symptoms of hypothermia is change in behaviour but, unfortunately, the victim is the last person to notice such changes himself. There are mild mood changes, lack of affect, apathy, uncoordinated movements, ataxia, confusion and decreased ability to sense cold.

Initially, there is tachycardia, tachypnoea & shivering which can be voluntarily controlled. However, as hypothermia becomes more severe, (32 to 35°C) there is bradycardia and decrease in respiratory rate. Higher reasoning becomes impaired; shivering becomes violent and cannot be stopped voluntarily. As the core temp falls below 32°C, shivering stops. Skin becomes blue and puffy. Patient becomes semiconscious and muscles start becoming rigid. Trismus is often present. There is marked bradycardia and lowering of respiratory rate. Cardiac dysrythmias are very common, especially atrial/ventriculalr fibrillation.

Once the core temp drops to 28°C or less, the patient is completely unconscious with severe bradycardia. Radial pulse may not be palpable and carotid pulse may reveal as low as 2 to 3 beats per mt. Respiratory rate is also reduced to 1 to 2 per min. Muscles become rigid and pupils dilated. At this stage the patient may appear dead but may not be so. Carotid pulse must be carefully palpated in all such cases.

Hypothermia should be treated as a medical emergency. Early recognition and institution of therapy may make all the difference between life and death. The basic principle of

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management is quick warming of the “core” without causing simultaneous vasodilation of the periphery, from the level of first aid till the most elaborately equipped critical care facility. The steps in management at the first aid level and at the primary care/ solo physician level are shown in Box - 1 & 2, respectively.Localized Effects of Cold

Frost Nip and Frostbite : Frost nip involves freezing of top layers of skin tissue. It is generally reversible and manifests as numbness and white, waxy or rubbery feeling of the affected skin but the deeper tissue is still soft. Frostbite is the more severe form and affects all layers of the skin and often the deeper tissue also. Frostbite is of four degrees, depending on the depth of the tissue involved. As an urgent first aid measure, remove any constrictive clothing or bands. Start local warming by placing the affected part in a warm water bath at 40-42°C. If nothing is available, place the affected part in the axillae or on the stomach of another healthy person. Analgesics and sedatives should be given for relief of pain. Initiate immunisation with tetanus toxoid and evacuate to a surgical facility at the earliest opportunity. If generalised hypothermia and local frost bite both are present, first treat the patient for generalized hypothermia. Local rewarming for frostbite should be undertaken only after core temp has returned to normal.

Non - Freezing Cold Injuries : These include chilblains and trench (immersion) foot, occurring due to prolonged exposure to cold environment with wet conditions. Chilblains manifest with initial pallor of affected area (usually fingers, toes, cheeks or earlobes) followed by erythema, pruritus and intense pain. Prevention by way of avoidance of exposure to cold and wet conditions among susceptible persons is the most important.

Otherwise, there is no specific treatment, though symptoms may be ameliorated by oral Nifedipine in some cases.

Trench foot is caused by prolonged exposure of feet to cold and wet conditions. The skin is reddened with tingling pain and itching. Gradually the skin becomes pale, mottled and finally dark purple, gray or blue. If the circulation remains impaired for more than a few hours, permanent damage to the affected part can occur. Treatment consists of gentle drying, elevation of the affected limb and keeping it at an environmental temperature of 18 to 22°C while keeping rest of the body warm. NSAIDS may be given for relief of pain. The patient should not walk on the affected limb till fully cured. Prevention is, once again, very important and consists of keeping the feet clean and dry, dabbing the feet with aluminium hydroxide powder thrice daily, and changing into dry socks and shoes at the earliest .

EpidemiologyEnvironmental Factors : The following are the major environmental factors which determine the severity of cold induced diseases :

Severity of Cold : Severity of atmospheric cold and its abrupt occurrence increases the liability of incidence of cold injuries among non-acclimatised, non-resident individuals.

Duration of Exposure : It is an important factor determining the final injury. About 10 hours of exposure to minus 10°C is needed to cause the cold injury, but may occur in shorter period of time, in intense cold.

Wind Movements : These hasten tissue cooling. The combination of ambient low temperature and wind movement is termed as the ‘Wind-chill factor’. The probability of cold climate to cause cold injuries is directly proportionate to the

Box - 1: Management At First Aid Level

Remove wet clothing only when patient has reached a warm, dry and sheltered environment and not in the open.

Immediately wrap the patient all around, including head, with warm clothes, blankets, quilts, sleeping bags - whatever insulatory material is available, even news papers or rags. Make an “insulatory wrap” of about 4 inches thickness all around the patient. Provide a wind and water proof outer most layer, as polythene sheets.

Make hot packs with warm water bottles covered with a cloth, or warm pads, at 42°C to 45°C, and apply them to axillae, groin and neck.

Do not warm the extremities at this juncture. Place arms and hands on the sides and not on the abdomen or in axillae.

Do not let patient do any physical activity. Treat as a “stretcher case”.

If patient can take orally give warm, sweetened tea or milk to provide “fuel”.

Do not massage the limbs.

Do not give alcohol or tobacco

Evacuate to a sheltered place preferably to a medical facility at the earliest.

Box - 2 : Management at Solo Physician/Primary Care Level

Check rectal temp and other vital parameters.

Quickly open up the insulatory layer, remove wet clothing (if not already removed at first aid level). Change patient to dry clothing.

Apply warm packs at axillae, groin and neck. Reapply the “insulatory layer” around the patient, as described under first aid.

Establish IV line and start 5% dextrose (or any other crystalloid) preferably warmed to 37 to 41°C. Initial fluid challenge should be 500 ml to 1 litre in half to 1 hour.

Start oxygen inhalations with face mask, 4 litres/min, preferably warm and humidified oxygen, if equipment is available.

If facility exists, pass an indwelling bladder catheter. Start monitoring urinary output.

Keep monitoring core temperature. The rectal thermometer should be inserted to at least 15 cm into rectum. If there is no increase in core temp despite rewarming efforts in more than an hour or else if patient is not shivering and unresponsive, consider evacuation to a well-equipped hospital. Evacuate as a stretcher case.

Institute CPR if carotid pulsations are absent.

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‘wind-chill’ factor rather than its temperature alone. Increased wind velocity, by increasing the ‘wind-chill’ factor, increases chances of generalised and localized injuries due to cold. For example, at 0°C ambient temperature, the conditions become equal to minus 18°C, if the wind is blowing at a speed of 40 km per hour.

Moisture : Moisture is a good thermal conductor and its presence in contact with the skin interferes with the natural insulating action of the sebaceous material on the skin. Wet clothing, either due to external wetting or internal wetting due to sweat, is therefore dangerous.

Hypoxia : High altitude hypoxia deprives the cardiac muscle of oxygen and thereby decreases the cardiac output, lowering the peripheral blood and oxygen tension and reducing the tissue oxygen saturation. Hypoxia also devitalises the capillary endothelium and increases exudation into tissues. All these increase the proneness of the extremities to get cold injuries; skin, being the least vital organ, suffers the most.

Clothing and shelter : An extremely important determinant of cold illnesses and their prevention is the adequacy of clothing and shelter in such weather. Clothing insulates the body from its surroundings. It can also cause radiant heat gain (mainly from solar radiations) as well as retard conductive and convective heat loss in cold climate. The index of thermal resistance of clothing is measured in ‘Clo’ units. To maintain a person in comfort, clothing with higher clo units will be required if metabolic heat production decreases, or ambient temperature decreases, or RH decreases, or air movement increases. At 0°C, persons undertaking light work or else complete rest, will need clothing 2.6 and 5.4 clo units respectively; at - 20°C these requirements will be 4 and 8.3 clo respectively. As a rough guideline, without wind penetration or air movement around the clothing, the Clo values for a given weight of clothes equals 35% of the clothing’s weight in Kg; e.g. wearing of total of 10 Kg clothing will produce Clo value of 3.5 Clo units, and will be reasonably good enough for a person doing very light work (1.5 MET) at an ambient air temperature of 0 degrees C, in a still air environment.Human (Host) Factors in cold illnesses

Age and Sex : People at extremes of age (less than 5 years or more than 65 years) are known to be more susceptible. Women seem to be protected possibly due to the increased subcutaneous fat. There is preliminary evidence from laboratory studies that dark skinned people may be more susceptible to adverse effects of cold as compared to whites.

Circulatory Stagnation : Local circulatory stagnation allows local temperature to be lowered, increases liability of exudation through the already damaged vascular endothelium and also deprives the tissues of nutrition and oxygen, thereby increasing devitalisation. This may be caused by forced immobility due to being pinned down in shelters or vehicles, or during conditions of prolonged bad weather. Tight fitting clothes, boots or socks may also cause constriction.

Physical Inactivity : It increases risk of cold injuries. Activity increases the metabolic heat production and is an important prophylaxis against cold injuries.

Nutrition : Adequate, or even increased, calorie intake is necessary to sustain the increased heat production and the increased work required to function in a cold environment (5). Vitamin A deficiency increases liability to infections especially of mucous membranes. Vitamin C deficiency increases capillary permeability and decreases healing power of tissues. The presence of adequate subcutaneous fat definitely increases the insulation and hence protects against cold (6, 7).

Poor Physical Health : Intercurrent /chronic diseases, convalescence and physical exhaustion decrease the general tissue vitality, physical activity and also power of acclimatisation, and hence increase the liability to cold injuries.

Poor Mental Health : Mental apathy, fatigue, fear and anxiety which are common in a cold climate, especially under hypoxic conditions at high altitude, cause neglect of precautions and increase in physical inertia, thereby increasing liability to cold injuries.

Local diseases : Local injury or skin infection predisposes the particular part to cold injuries.

Tobacco : Use of tobacco increases the risk of frost bite due to severe vasospasm induced by it and definitely aggravates the injury itself when once established.

Alcohol : Alcohol has been universally regarded as a very important and avoidable risk factor in cold illnesses. Its consumption, especially if followed by exposure to cold, or excessive physical activity or lethargy after alcohol consumption, increases risk of general hypothermia and also local cold injuries.

Cold Adaptation : Adaptation to cold, although not as good as acclimatisation to heat or high altitude, is nevertheless an important factor determining individual vulnerability to cold injuries.

Prevention of Cold IllnessesClothing : Special attention should be given to clothing in cold weather, in a scientific manner. In providing insulation from the cold, the mesh of the cloth fibres traps air that then becomes warm. Several layers of light clothing or garments lined with wool, fur, feathers or synthetic fabrics provide better insulation than a single, bulky layer. The clothing layer in contact with the skin should effectively “wick” moisture away from the body’s surface to the next insulating clothing layer for subsequent evaporation. Wool or synthetic (e.g. polypropylene) that insulate well, as well as dry quickly, serve this purpose. A woollen cap very effectively contributes to heat conservation since nearly a third (33%) of all body heat loss is from the head region alone. If clothing becomes wet either due to external moisture (snow or rains) or due to condensation form sweating, it looses as much as 90% of its insulating properties; this may actually start facilitating heat loss from the body rather than conserving heat. Hence, wet clothing should be changed at the earliest opportunity in cold environment.

Secondly, it must be ensured that while the clothing should provide adequate insulation (by way of adequate material and layers, as described above), it should, at the same time, allow for water vapour to escape through the clothing, if sweating occurs. If this does not happen and sweat accumulates near the

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skin layer, its condensation may become another hazardous situation, which was faced by the expeditions to Polar Regions. Hence, scope must be left to allow some layers to be removed if required, without exposing the body to cold. The basic rules for dressing in a cold climate are :

Keep the clothing clean otherwise the wicking / moisture ●repelling action will be compromised.Do not sweat unnecessarily; undertake activities in a way ●that sweating is kept to the minimum.Keep the clothing dry; wet clothing will grossly reduce the ●insulatory power.Dress in layers (as explained above). ●

It must be noted that clothing must be worn in sequence, with undergarments and thermal inners being the innermost layer, followed by shirt, trouser, sweaters, and finally the jackets/ thermal or feather coveralls. The fit of each item is very important; each item should be tried in its correct sequence. If clothing is too tight, it will restrict the blood flow and increase the predisposition to cold injury.

Boots : In cold weather when two pairs of socks are worn, boots become tight and this may compel the individual to discard them. Therefore, boots should be a loose fit, kept soft and water proof and every person should have an extra dry pair of socks and boots to change into, if feet get wet. One must remember never to sleep with boots on; before going to sleep, boots should be removed and dried.

Socks : A pair of thin nylon / polypropylene socks should form the inner layer, being worn next to the skin and the next layer should be the heavy woollen socks to absorb moisture. These should not be tight. Every person exposed to intense cold should wear extra pairs of woollen socks. Damp socks should be changed immediately.

Shelters : Shelter used in cold environment should be designed on the same basic principles of layering as for cold weather clothing. The tents should have a strong, tightly woven outer shell, which should be impervious to rain and snow. The inside liner is a lighter weight fabric and is hung to provide an air space along the outer shell. Ideally the tent should have a floor made of impervious material. If ever a stove is burnt inside the tent for heating purposes, the potential dangers of Carbon Monoxide (CO) poisoning and fire hazards is to be kept in mind. Arrangements for ventilation must be ensured in such circumstances.

Nutrition : Energy requirement in the cold environment is more due to higher metabolism. In general, for civilian population, who are also likely to be indulging in some sort of winter or mountain sports activities, the energy requirement may be 3000 to 3500 Kcal for women and 3500 to 4000 Kcal for men. Provision of adequate hot and appetising meals should be ensured. Vitamin C is also necessary for the cellular reformation, vascular endothelial integrity and as a steroid sparer. It may be given in the form of multivitamin tablets.

Exercise : Regular moderate exercise to keep up the circulation without causing any exhaustion or excessive sweating should be undertaken frequently. When climatic conditions do not permit movement in the open, static physical activity by frequent vigorous movements of limbs, movements of neck

and back, wriggling of toes and moving of fingers should be continuously practised. Face muscles should be wrinkled to keep up the circulation.

Venous Congestion : People should not sit for long periods cramped up in enclosed places or upon the railing with feet hanging down and especially over the edge of seats as this leads to venous congestion. Too tight clothing also causes venous stagnation.

Alcohol : Alcohol is best avoided when confronted with harsh, cold environment. In any case, it should never be consumed in excess over a short duration and none at all when one is likely to go out into cold environment.

Smoking : It is advisable not to smoke at all. Those who cannot avoid smoking should do so only in moderation. It should be definitely prohibited once the cold injury occurs.

Buddy System : For small parties on adventures / expeditions, it is always a good practice to have a “buddy system”, i.e. to pair up people and make them responsible to look after each other, by watching each other’s face and feet for observing any early tissue damage. Buddies also watch out for each other’s personal hygiene, nutrition, and behaviour so that any aberration is identified at the earliest and first aid is given.

General Personal hygiene : It should be maintained at the highest level. Besides ensuring local cleanliness and preventing infections, it will enhance the general feeling of well being, so essential in tough, cold environment. Proper bathing is preferred; however, even a basin of water for a sponge bath will help. When no water is available, simply rubbing the body, preferably with a wool rag, is worth the effort. It is recommended that such a procedure be followed weekly. Changing to clean or even airing of soiled socks and underwear periodically will help to maintain body cleanliness. At least two or three hot baths in a week in snowbound and cold environs are necessary. Bathing places should be sheltered from wind and snowfall. However, too frequent use of too much soap is not good as it removes the greasy sebaceous material and decreases insulation.

Foot Hygiene : The feet should be inspected before going to bed every night, for any swelling, ulcer or numbness. Wriggling the feet and toes before going to sleep and even within the boots, while walking, should be an inculcated habit. It is much better to make two partners responsible for inspecting each other’s feet. Feet must be washed with warm water, thoroughly dried and smeared with a little Vaseline, before sleeping. This helps prevent frost bite. An individual with ulcers and abrasions on the foot should not move around until they are healed. Talcum powder should be used before wearing socks in the morning to decrease dampness during exertion and reduce friction with socks.

Oral Hygiene : By daily cleaning the teeth with a piece of gauge or other cloth wrapped around a finger is an effective practice in the absence of toothbrush.

“Feel Good” : Keeping well is especially important when one is stranded. While physical fitness of the body decides survival, yet a positive mental attitude is just as important. Personal cleanliness, dry clothing, ventilated shelter without drought, a warm bed, and adequate recreational activities are helpful.

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Re-exposure : Persons who have once suffered from cold injury should be very careful when getting exposed to cold environment again.

Adaptation to Cold : Systematic acclimatisation to cold can be carried out by exposing newly inducted people to the atmospheric temperature of 0°C to 5°C for three or four hours a day for three consecutive weeks. During the first week people should be dressed in vest cotton, full sleeves flannel shirt, pullover, woollen trousers, woollen cap, gloves and boots with only one pair of woollen socks. Outside the exposure hours, people can put on the additional clothing as jackets, coveralls, etc. During the next two weeks, pullover is also removed, so that people stay in flannel shirt and trousers for 3 to 4 hours. The site selected for exposure should be sheltered from wind. If there is any wind or breeze, people should wear a thin nylon wind-cheater. Since physical exercise warms the body and hence impedes the acclimatisation process, during the hours of exposure, therefore, physical exercise should not be allowed; however, normal sedentary recreational work as reading, knitting, playing cards etc., which do not involve much physical activity, may be carried out. People should be assured that exposure to cold for cold acclimatisation will cause no harm. If any complaints like rhinitis, pharyngitis, fever, excessive shivering or cramps are noticed; the exposure should be discontinued for the day or until cured. It can be restarted and gradually increased day by day when the individual has recovered.

High Altitude Acclimatization : Often, cold environment co-exists with high altitude environment. Adverse effects of high altitude will worsen the physical and psychological adversities due to cold and vice-versa. Proper acclimatization to high altitude should be therefore undertaken, as described in the chapter on high altitude.

Early diagnosis, first aid and prompt treatment : These are aimed at prevention and arrest of tissue damage. Early detection and first aid would go a long way in prevention of further damage, in both generalised as well as local cold injury. The details have already been discussed earlier in this chapter.

Protection against Snow Blindness : Humans can make no natural adjustments to the reflection of bright sun from snow, ice, and water, even with an overcast sky. Dark glasses are, therefore, a must. One must not wait until eyes start hurting. If the glasses are lost, improvised eye protection, by either wearing a muffler or stockings over one eye through which one can barely see. Treat snow blindness by getting the victim to a dark place. Apply eye shades to both eyes. Cool compresses may help to relieve the pain. Time is the only cure for temporary snow blindness.

Protection against Sunburns : Sunburn can occur even at temperatures below freezing point especially at higher elevations. Sunlight reflected upwards from bright surfaces may rapidly burn the most tender spots, viz., lips, nostrils, upper portion of ears and eyelids. Sunburn also may occur on cloudy days. A strong wind makes the burn even more severe. Sunburn cream should be applied frequently to all exposed skin surfaces.

SummaryExtreme cold conditions occur in India in the Himalayan, Sub - Himalayan and the northern Indian plains with cold waves and deaths being recorded every year. Human exposure to extreme cold produces significant physiologic and psychological challenges. Groups at particularly high risk include military personnel, agriculturists, mountaineers and persons engaging in adventure or winter sports, low income groups with poor housing and inadequate clothing, extremes of age (<5yrs or >65yrs), physical exhaustion, pre - existent malnutrition or starvation, sleep loss, use of alcohol and underlying diseases. Environmental Factors as Severity of cold, duration of exposure, wind movements, moisture, hypoxia, clothing and shelter also play a significant role.

Adverse effects of cold environment manifests as either generalized effects (hypothermia) or local “tissue-freezing” effects as frost bite, or Non-Freezing Cold Injuries (NFCI) as trench foot and chilblains. Generalised Hypothermia, depending on the core temp, may be classified as borderline (36 to 35°C), mild (35 to 32°C), moderate (32 to 28°C) and severe (<28°C). Earliest symptoms are change in behaviour, mood, and lack of affect, apathy, uncoordinated movements, ataxia, confusion and decreased ability to sense cold. Tachycardia, tachypnoea & shivering occur initially followed by bradycardia, decreased respiratory rate, impaired reasoning & violent shivering, paradoxical undressing with stuporous gait as hypothermia becomes more severe (32 to 35°C). Below 32°C, shivering stops with blue, puffy skin, semiconsciousness, muscle rigidity, trismus, marked bradycardia, lowered respiratory rate & cardiac dysrythmias, especially atrial/ventriculalr fibrillation occurs. At 28°C or less, complete unconsciousness with severe bradycardia, reduced respiratory rate, muscle rigidity with dilated pupils is seen. Hypothermia should be treated as a medical emergency. Basic principle of management is quick warming of the “core” without causing simultaneous vasodilation of the periphery.

Frost nip involves freezing of top layers of skin tissue, is reversible and manifests as numbness and white, waxy or rubbery feeling of the affected skin. Frostbite is the more severe form affecting all layers of the skin involving the deeper tissue. It is of four degrees, depending on the depth of the tissue involved. As an urgent first aid measure, remove any constrictive clothing or bands, local warming by placing the affected part in a warm water bath at 40-42°C, analgesics, sedatives & Tetanus toxoid are to be administered. Evacuate to a surgical facility at the earliest. Non - Freezing Cold Injuries in the form of chilblains manifest with initial pallor of affected area followed by erythema, pruritus and intense pain. Prevention comprises of avoidance of exposure to cold and wet conditions. Trench foot is caused by prolonged exposure of feet to cold and wet conditions manifesting as reddened skin, tingling pain and itching. Gentle drying, elevation of the affected limb and keeping it at an environmental temperature of 18 to 22°C while keeping rest of the body warm along with NSAIDs is the treatment. Prevention consists of keeping the feet clean and dry, dabbing the feet with aluminium hydroxide powder thrice daily, and changing into dry socks and shoes at the earliest.

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Prevention of Cold Illnesses involves clean, dry & layered clothing; loose fit, soft & water proof boots, an extra dry pair of socks, inner thin nylon / polypropylene socks and outer heavy woollen socks with at least four pairs of woollen socks; strong, tightly woven impervious tents; provision of adequate hot and appetising meals ; regular moderate exercise, static physical activity by frequent vigorous movements of limbs, movements of neck and back, wriggling of toes and moving of fingers; not sitting for long periods cramped up in enclosed places or upon the railing with feet hanging down; avoiding smoking & alcohol; practice “buddy system”; personal hygiene including oral & foot hygiene; precautions on re-exposure; cold adaptation; high altitude acclimatization; early diagnosis, first aid and prompt treatment. In harsh, extreme cold climate, in the face of an emergency, survival techniques in the form of skills pertaining to shelter construction, first aid, map and chart orientation and sanitation should be a major element of preparation. Protection against Snow Blindness involves use of dark glasses. Treatment is by getting the victim to a dark place; apply eye shades to both eyes & cool compresses to relieve pain. Protection against sunburns should be practised by applying sunburn cream frequently to all exposed skin surfaces.

Study ExercisesLong Question : Forward a detailed plan of advise on preventive aspects as well as emergency first aid which you will give to a group of approximately 40 mountaineers who will be taking part in a national expedition to climb a mountain peak located at height of 25,000 feet.

Short Notes : (1) Acclimatization to cold (2) Principles of dressing for prevention of cold (3) First aid in hypothermia (4) First aid in frost bite.

MCQs & Exercises1. Age group which is most vulnerable to effects of cold is

(a) <5 yrs (b) 5-65 yrs (c) >65 yrs (d) a & b (e) a & c.2. Which of the following is a Non-Freezing Cold Injury

(NFCI) (a) Frost bite (b) Trench Foot (c) Hypothermia (d) Frost nip.

3. What is the Core body temp in Severe Hypothermia (a) <28°C (b) <29°C (c) <30°C (d) <31°C.

4. The normal core (rectal) temperature of normal healthy humans is : (a) 36 to 36.5°C (b) 36.5 to 37°C (c) 37 to 37.5°C (d) 37.5 to 38°C.

5. In________ , a person with hypothermia starts removing the clothes rather than putting on more clothes.

6. ECG shows _________ wave at the junction of QRS complex in Hypothermia.

7. The basic principle of management in Hypothermia is : (a) Quick warming of the “core” without causing simultaneous vasodilation of the periphery (b) Quick warming of the “periphery” (c) Quick warming of the “core” with simultaneous vasodilation of the periphery (d) None of the above.

8. In Frost bite, local warming is done by placing the affected part in a warm water bath at (a) 36 to 38°C (b) 38 to 40°C (c) 40 to 42°C (d) 42 to 44°C.

9. Treatment in Trench foot consists of keeping the affected part at what environmental temperature, while keeping rest of the body warm : (a) 14 to 18°C (b) 18 to 22°C (c) 22 to 26°C (d) 26 to 30°C.

10. About ____ hours of exposure to ____ °C is needed to cause cold injury. (a) 5 hours, minus 10°C (b) 10 hours, minus 10°C (c) 10 hours, to minus 5°C (d) 5 hours, minus 5°C.

11. The probability of cold climate to cause cold injuries is directly proportionate to the __________ rather than its temperature alone.

12. The index of thermal resistance of clothing is measured in __________ .

13. A woollen cap very effectively contributes to heat conservation since nearly ________ % of all body heat loss is from the head region alone : (a) 13% (b) 23% (c) 33% (d) 43%.

14. If clothing becomes wet either due to external moisture (snow or rains) or due to condensation from sweating, it loses what % of its insulating properties : (a) 60% (b) 70% (c) 80% (d) 90%.

15. Energy requirement in the cold environment is _____ Kcal for women and ____ Kcal for men : (a) 2000 to 2500 , 2500 to 3000 (b) 2500 to 3000 , 3000 to 3500 (c) 3000 to 3500, 3500 to 4000 (d) 3500 to 4000 , 4000 to 4500.

Answers : (1) e; (2) b; (3) a; (4) c; (5) Paradoxical undressing; (6) ‘J’ (Osborn); (7) a; (8) c; (9) b; (10) b; (11) ‘wind-chill’ factor; (12) ‘Clo’units; (13) c; (14) d; (15) c.

ReferencesThe Persian Expedition. Warner R (Trans). London : Penguin Books; 1972 1. : 175 - 217.The History of Rome from its Foundation. De Selincourt (Trans). London : 2. Penguin Books; 1965 : 52 - 62.Toner MM, McArdle WD. Human thermoregulatory responses to acute cold 3. stress with special reference to water immersion. In Fregly MJ, Blatteis CM (eds). Handbook of Physiology, Section 4 : Environmental Physiology, Vol 1. New York : Oxford University Press; 1996.Young AJ. Exertional fatigue, sleep loss, and negative energy balance increase 4. susceptibility to hypothermia. J Appl Physiol 1998; 85 : 1210.Burton AC, Edholm OG. Man in a Cold Environment.Arnold (Publishers), 5. London. 1st Ed 1955.Keighley JH, Steele G. The functional and design requirements of clothing. 6. Alpine Journal 1981; 86 : 138 - 45.Adam JM, Goldsmith R. Cold Climate. In : “Explorative Medicine”. Wright 7. (Publishers), Bristol. 1st Ed 1965.Edholm OG, Bacharach AL (Eds). The Physiology of Human Survival. 8. Academic Press, New York. 1st Ed 1965.World wide website address “http : //www.coolantarctica.com”9. World wide website address http : //www.wikipedia.org10.

Further Suggested ReadingBhalwar R, Banerjee PK , Bhaumik G, Gambhir RPS, Nangpal S, Bajaj R. 1. Cold Environment. In : Anand AC, et al (eds). Text Book of Environmental Emergencies. Published by Dept of Internal Medicine, Armed Forces Medical College Pune. 1st Ed 2005 : 64-85; 89-93. (A Comprehensive text on epidemiology, clinical features and management of adverse effects of cold environment).Nagpal BM, Sharma R. Cold injuries : the chill within. Med Jr Armed Forces 2. India 2004; 60 : 165-171 (Practical guidelines on clinical features and management of cold stress disorders).Auerbach P (ed) : Wilderness Medicine : Management of Wilderness 3. and Environmental Emergencies. Mosby Year Book, St Louis, Missouri 2001. (Detailed text on management of adverse effects of hot and cold environment).

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120Health Hazards at Mountains (High Altitude Terrestrial Environment)

RajVir Bhalwar

High Altitude illness is a collective term for the syndromes that can affect unacclimatised travellers, shortly after ascent to high altitude (1). The term “unacclimatised travellers” also includes the native highlanders who are re-inducted into high altitude after a sojourn to lower altitude or if they move to a still higher altitude from the normal place of stay in high altitude. The term “high altitude illness” encompasses the syndromes of Acute Mountain Sickness (AMS), High Altitude Cerebral Oedema (HACO) and High Altitude Pulmonary Oedema (HAPO) (1).

With the present body of knowledge, there does not seem to be any clear cut demarcation as to the height above sea level that constitutes “High Altitude (HA)”. The general opinion varies and is dependant on the altitude at which definite manifestation of high altitude illness are likely to occur in a noteworthy proportion of the subjects. Generally, an altitude of 2700 m (9000 feet) and above defines high altitude, with increasing grades of high altitude as 2700 to 3600 m, 3601 to 4500m and 4501 to 5400m. Altitudes above 5400 m in are often referred to as “extreme high altitude” wherein permanent successful acclimatization becomes very difficult. However, the above levels cannot be sacrosanct boundaries; in fact high altitude illness is being increasingly recognised at “moderate” altitudes of 2200 to 2500m (2)

Around 140 million people over the globe live permanently at altitudes of over 2500 m (3) and approximately another 40 million enter high altitude area every year for reasons of occupation, sporting or recreation. Miners in South America go for work to altitudes as high as 6000 m, while Indian soldiers are deployed at even higher altitudes. Persons who are at a definitely increased risk of being affected by high altitude illness include Native highlanders who re-enter high altitude after stay at lower altitudes; Mountaineers; Soldiers; Trekkers; Adventurers; Miners at high altitude; and, Pilgrims and porters (4, 5).

The High Altitude EnvironmentEffects of high altitude are encountered among visitors to high altitude terrestrial environments and in high altitude aviation. The environmental conditions at high altitudes which influence physiological processes are : the lowered atmospheric pressure and partial pressure of oxygen, lowered temperature and humidity, increased intensity of sunshine and cosmic electrical conditions and the isolation under monotonous mountain conditions. The chief hazards on health, however arise from the low atmospheric pressure, coupled with low partial pressure of O2 in the alveolar air leading to low oxygen tension in the blood and low ambient temperature, all of which worsen as the altitude increases. The main problem with high altitude terrestrial environment is, in fact, the declining atmospheric pressure. For instance, the atmospheric pressure which is 760

mm Hg at sea level drops down to only approx. 500 mm Hg at around 11000 feet above Mean Sea Level (MSL). Now, as we know from a very basic law of physics (Boyle’s Law) that the partial pressure of a mixture of gasses is equal to the sum of the partial pressure (pp) of these gasses; and the partial pressure of these individual gasses is proportional to their concentration in the gaseous mixture. For all practical purposes, air is mainly a mixture of Nitrogen (N) and Oxygen (O) in the proportion of 80% and 20% respectively. Thus the pp of N will be four fifth and that of O will be one-fifth that of the atmospheric pressure at a given location. Hence, at sea level, where the atmospheric pressure is 760 mm Hg, the partial pressure of ‘N’ is 4/5 of 760 i.e. approx 608 and that of ‘O’ is approx. 152 mmHg.

Now as the atmospheric pressure drops with ascent from sea level (by very roughly, 25 mm Hg for every 1,000 feet ascent), hence at 11,000 feet it would be approx. 500 mm Hg; and, by Boyle’s law, at this height, the partial pressure of Nitrogen would be (4/5 of 500) i.e. 400 mm and that of Oxygen will be 100 mm Hg. It is this progressive decline in partial pressure of oxygen in ambient air (commonly referred to as “thinning or air” or, “rarefied air’) that results in reduction of alveolar oxygen pressure, with all the resultant pathological issues of high altitude. Thus, though the concentration of oxygen in atmospheric air at high altitude is still one-fifth, the net result because of such reduction of partial pressure of oxygen is as if there was a lack of Oxygen in the air. Thus, at around 11,000 feet, the effect is as if oxygen in the air were 13.8% instead of 21% normally seen at sea level. The details are depicted in the Table - 1. This is the basic environmental issue that triggers a massive cascade of physiological responses, intended to be protective, once a human being is inducted into high altitude.

Table - 1 : Altitude, pressure, temperature, oxygen partial pressure and percentage

AltitudePressure (mm Hg)

Oxygen Partial pressure (mm Hg)

Equivalent Oxygen

percentageFeetMeters

(mm Hg)

0 0 760.0 159.2 20.96

9,000 2,743 543.2 113.8 14.96

12,000 3,658 483.2 101.2 13.31

15,000 4,572 428.8 90.5 11.81

18,000 5,486 379.4 79.5 10.45

20,000 6,096 349.2 73.1 9.61

Physiological Adaptation : The lowered atmospheric oxygen partial pressure at high altitude causes alveolar and arterial hypoxia leading to tissue hypoxia. As described earlier, the oxygen partial pressure in alveoli is decreased at high altitude and hence, to compensate for this, circulatory and haemopoietic adjustments are made by the body physiology. There is increased frequency of respiratory and cardiac rhythm. Finally the increased amplitude of respiratory and cardiac movements gradually occurs. Interstitial fluid is diverted to the vascular compartment which alters the haemodynamics and cause hypervolaemia, thereby overloading the pulmonary circulatory system and cardiac function. These mechanisms are usually

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uneventful and insensible up to about 2500 to 3000 m; however, above that height when pronounced physiological mechanisms are called to action, the symptoms of ‘early mountain sickness’ which in reality are the symptoms of ‘rapid acclimatization’, become manifest. If acclimatization is inadequate, or if it breaks down, or if the ascent to higher altitude is too rapid, the essentially beneficial adaptive responses become aberrant and the disease processes occur.

The common acute high altitude syndromes are Acute Mountain Sickness (AMS) and High Altitude Pulmonary Oedema (HAPO). Less commonly, High Altitude Cerebral Oedema (HACO), a cerebral syndrome may occur at sudden induction into very high altitudes of 4500 mtrs and above. Chronic Pulmonary Hypertension is a rare syndrome occurring after prolonged residence at high altitude areas.

Acute Mountain Sickness (AMS) : The latent period of AMS (time elapsing from entry into high altitude to onset of first symptom) is usually 6 to 12 hours. Sojourns to high altitude which last for less than 6 hours are not likely to be associated with AMS. AMS is quite uncommon below the altitudes of 2000 m. The incidence of AMS has been quite variable in different studies and primarily depends on the altitude reached, the rate (speed) of ascent to high altitude and physical exertion after entry into high altitude, besides other variables. Various workers have observed incidence of as low as 6% to as high as more than 60% (6 - 11).

High Altitude Pulmonary Oedema (HAPO) : The incidence of HAPO has been found to be quite variable, between 0.5% to 5%, as reported by various workers. Any person irrespective of age, gender or race, who enters into a high altitude terrestrial environment, is at risk of HAPO, including native highlanders who enter into high altitude after a stay at lowlands. However, certain groups seem to be at a higher risk due to Socio-behavioral or occupational reasons. These include soldiers, mountaineers trekkers, adventurers, mountain-sports persons, miners working at high altitude, porters, and land pilgrims to high altitude shrines. Most of the epidemiological studies indicate that the ‘latent period’ or ‘induction time” (period elapsing from entry into high altitude to the onset of first manifestation of HAPO) is usually between 6 to 96 hours, though rare cases can occur as late as ten days also. Onset beyond this range is quite uncommon (12 - 16). Therefore, it is logical to conclude that the period of first 72 hours following induction into high altitude seems to be important, with the initial 48 hours being most crucial for enforcing preventive measures regarding acclimatization, especially avoidance of any physical activity (except for self-care activities of a routine nature).

Risk Factors for AMS and HAPO : The major risk factors for both, AMS and HAPO are :

Physical exercise soon after induction into high altitude: Physical exercise even of moderate intensity, undertaken within 72 hours of arrival into high altitude is an important determinant and is almost universally upheld by all experts. The risk has been observed in nearly all the studies, at various places in the world, and the estimates show a strong and significant association. Thus, the association fulfils the required epidemiological parameters of strength of association,

temporality, consistency, dose response and plausibility. However, it is noteworthy that physical exercise is not an ‘essential’ determinant, since the condition can occur even among persons who have not exerted/are asleep/are at rest, especially if ascent to high altitude has been rapid, as by air.

Lack of Acclimatization : AMS and HAPO commonly affect subjects who have not properly acclimatized themselves to high altitude environment soon after arrival. Acclimatization is a gradual process by which the body physiology gets adjusted to high altitude environment.

Altitude of ascent : The “critical altitude” at which the risk of developing AMS or HAPO is very high has been reported as 3000 m in the Himalayas, 3600 m in the Andes and somewhat lower (2600m) in the Rocky mountains. This is not to be confused with the definition of “high altitude” which is generally taken as > 2500 mtrs. AMS can however, occur even at lower altitudes of 2500 mtrs.

Rate of ascent : Epidemiological studies have clearly shown that the speed with which an individual reaches high altitude, especially into a crucial altitude of 3000m and above, seem to be an important determinant in causing high altitude illness. Observations have shown that both among soldiers as well as tourists who move to high altitude areas by air, ascending almost 3000m (or even more) within less than an hour, the incidence rates are much higher when compared to the same location being reached by road transport over 3 to 4 days. The slow ascent by road over a few days may allow some acclimatization.

Prevention of Adverse Effects of High AltitudeIndividual tolerance to hypoxia varies and has no correlation with physical fitness in its ordinary sense. Complacency or bravado which in itself is one of the symptoms of hypoxia, encourages excessive physical activities without proper and adequate acclimatization. Rapid ascent without acclimatization followed by physical activity increases the risk of effects of hypoxia.

Acclimatization : In general, acclimatization should be undertaken whenever a person reaches an altitude of 2500 metres or above, though a night spent at moderate altitude of 1500 to 2500 m before ascent to high altitude, is likely to further aid in acclimatization process.

Acclimatization is undertaken by 1 to 2 days of complete rest (allowing for only daily activities of living), followed by gradually increasing physical effort for next 2 to 4 days at a particular level of high altitude. This process should be repeated for every 1000 mtrs gain in altitude, i.e. after the person reaches another stage of stay in high altitude which is 1000 metres higher than the previous level at which he / she had acclimatised, another similar round of acclimatization (of 2 days of complete rest followed by 3 to 4 days of gradually increasing physical activity) should be undertaken for each such 1000 metres gain in altitude.

While negotiating high altitude areas, gradual ascent, thereby giving time for acclimatization to develop, is the key strategy in prevention. In general, at altitude greater than 3000 m, each

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night should be spent at an altitude of not more than 300 m above the previous night, with a rest day after every 2 to 3 days (i.e. after every 1000 m of ascent). In certain situations, as tourists coming for mountaineering, this rate of ascent may be considered to be slow and unrealistic and may be modified so that the altitude difference between two consecutive “sleeping sites” should not be more than 600 m per day.

All recommendations emphasise “sleeping altitude” which means that it is permissible to ascend more than the recommended daily rate as long as descent is made for sleeping, i.e. the time tested maxim of “climb/work high but sleep low”.

Visitors to high altitude areas also need to be educated that the actual pathophysiological changes at high altitude take 6 to 24 hours to gradually develop and hence they may not get any symptom during initial 6 to 8 hours or even during first day; however, they should not take this as an immunity from adverse effects of high altitude. Many serious cases have occurred because tourists started exerting on the first or second day because they did not have any symptoms.

Chemoprophylaxis : Acetazolamide orally, for three days before induction into high altitude areas has been recommended by some authorities as it may help in reducing the occurrence or severity of AMS / HAPO, but evidence from RCTs is still not available.

Other Measures : Environmental cold is generally present at high altitude areas and care should be taken to adopt preventive measures, as explained in the previous chapter. Ensuring adequate intake of fluids by mouth and avoidance of tobacco and alcohol is also desirable.

Physical performance at High altitude : It needs to be noted that even after complete and successful acclimatization, the capability to perform any given exercise or physical task will be reduced at high altitude in comparison to lower altitudes. This was clearly evident during Mexico Olympics of 1968, held at an altitude of 2300m wherein most of the world class athletes experienced as much as 13% reduction in their performance. Leaving aside the world class sports persons, evidence suggests that for normal, healthy and properly acclimatized subjects, the physical capability will be just about 70 to 75% at an altitude of 3100 m (Compared to capability at sea level altitude) and would be about 50 to 60 % at 4000 m. Care should be taken, therefore, by all persons moving to high altitude, to make realistic readjustment in their expectations regarding task performance.

SummaryHigh Altitude illness is a collective term for the syndromes that can affect unacclimatised travellers, shortly after ascent & encompasses the syndromes of Acute Mountain Sickness (AMS), High Altitude Cerebral Oedema (HACO) and High Altitude Pulmonary Oedema (HAPO). High altitude (HA) is defined as an altitude of 2700 m (9000 feet) and above, with increasing grades. Altitudes above 5400 m are referred to as “extreme high altitude”. High risk groups are the native highlanders who re-enter HA after stay at lower altitudes, mountaineers, soldiers, trekkers, adventurers, miners, pilgrims and porters.

Health hazards in HA arise from the low atmospheric pressure,

with low partial pressure of O2 in the alveolar air leading to low oxygen tension in the blood and low ambient temperature. Progressive decline in partial pressure of oxygen results in reduction of alveolar oxygen pressure. Physiological Adaptation at HA involves lowered atmospheric oxygen partial pressure causing alveolar and arterial hypoxia leading to tissue hypoxia which is uneventful and insensible up to 2500 to 3000 m & above that height, symptoms of ‘early mountain sickness’ which are the symptoms of ‘rapid acclimatization’ appear. The common acute high altitude syndromes are AMS with a latent period of 6 -12 hours & uncommon at <2000 m, incidence varies between 6% - 60% & depends on the altitude reached, rate of ascent and physical exertion after entry into HA; HAPO with an incidence between 0.5% - 5% with certain groups at a higher risk due to socio-behavioural or occupational reasons, latent period being 6 - 96 hours, with the initial 48 hrs being most crucial for enforcing preventive measures regarding acclimatization.

Risk Factors for AMS & HAPO include physical exercise soon after induction, lack of acclimatization, altitude (higher the altitude more the risk) & fast speed of ascent. Prevention of adverse effects requires avoidance of complacency or bravado, acclimatization as per the recommendations with gradual ascent being the key strategy in prevention, not having an altitude difference of more than 600 m / day between two consecutive “sleeping sites”, chemoprophylaxis with Acetazolamide orally X 3 days before induction & other measures such as ensuring adequate intake of oral fluids, avoidance of tobacco & alcohol and precautions against environmental cold. Physical performance at HA is reduced. Care should be taken to make realistic readjustment in the expectations regarding task performance.

Study ExercisesShort Notes : (1) Acclimatization to high altitude (2) Acute mountain sickness (3) High altitude pulmonary oedema (4) Lake Louise criteria

MCQs & Exercises1. The term “unacclimatised travellers” also includes the

native highlanders who are re-inducted into high altitude after a sojourn to lower altitude (True/false)

2. “High altitude illness” encompasses the syndromes of all except : (a) Acute Mountain Sickness (AMS) (b) High Altitude Cerebral Oedema (HACO) (c) High Altitude Pulmonary Oedema (HAPO) (d) Cold stroke.

3. Altitude of _________ defines high altitude & Altitudes of _________ are often referred to as “extreme high altitude.

4. Globally, how many people live permanently at altitudes of over 2500 m : (a) 10 million (b) 40 million (c) 100 million (d) 140 million.

5. The environmental conditions at high altitudes which influence physiological processes are all except : (a) Lowered atmospheric pressure (b) High partial pressure of oxygen (c) lowered temperature and humidity (d) increased intensity of sunshine.

6. The adverse effects of environmental cold occurring at high altitude, as compared to when they occur at plains are not aggravated due to atmospheric and tissue hypoxia (True/false)

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7. Progressive decline in partial pressure of oxygen in ambient air is commonly referred to as ________ .

8. What is the partial pressure of oxygen (in mm Hg) at an alt of 3600m, where atmospheric pressure is about 485 mm Hg & equivalent O2% being 13.5% ? (a) 91.2 (b) 101.2 (c) 201.2 (d) 301.2 .

9. What is the latent period of AMS (time elapsing from entry into high altitude to onset of first symptom) : (a) 3 to 6 hours (b) 6 to 12 hours (c) 12 to 18 hours (d) 18 to 24 hours.

10. What is the usual incidence of HAPO ? : (a) 0.5% to 1% (b) 0.5% to 3% (c) 0.5% to 4% (d) 0.5% to 5%.

11. Which period is most crucial for enforcing preventive measures regarding acclimatization? (a) Initial 4 hours (b) Initial 14 hours (c) Initial 24hours (d) Initial 48 hours.

12. The “critical altitude” above which the risk of developing AMS or HAPO is very high in the Himalayas is (a)1000 m (b) 2000 m (c) 3000 m (d) 4000 m.

13. The process of Acclimatization should be repeated for every ___________ mtrs gain in altitude : (a) 100 (b) 500 (c) 1000 (d) 1500.

14. Altitude difference between two consecutive “sleeping sites” should not be more than : (a) 200 m per day (b) 400 m per day (c) 600 m per day (d) 800 m per day.

15. Which drug is recommended for Chemoprophylaxis three days before induction into high altitude areas (a) Acetazolamide (b) Furosamde (c) Doxycycline (d) Paracetamol.

Answers : (1) True; (2) d; (3) 2700 m (9000 feet), above 5400 m; (4) d; (5) b; (6) False; (7) Thinning of air” or “rarefied air’; (8) b; (9) b; (10) d; (11) d; (12) c; (13) c; (14) c; (15) a.

ReferencesBasnyat B, Murdoch DR. High Altitude Illness. Lancet 2003; 361 : 1967-74.1.

Gabry AL, Ledoux X, Mozzi Conacci M, Martin C. High Altitude Pulmonary 2. Oedema at moderate altitude (below 2400m, 7870feet) : a series of 52 patients. Chest 2003; 123 : 49-53World Health Statistics Annual 1995. WHO Geneva 1996.3. Basnyat B, Subedi D,Stafggs J, et al. Disoriented and ataxic pilgrims : an 4. epidemiological study of acute mountain sickness and high altitude cerebral oedema at a sacred lake at 4300 m in the Nepal Himalayas. Wilderness Environ Med 2000; 11 : 89-73.Basnyat B, Litch JA. Medical Problems of porters and trekkers in Nepal 5. Himalayas. Wilderness Environ Med 1997; 6 : 78-81.Hackett PH, Rennie D. Rales, peripheral oedema, retinal haemorrhaages and 6. acute mountain sickness. Am J Med 1979; 67 : 214-8.Maggiorini M, Buhler B, Walter M, Oelz O. Prevalence of acute mountain 7. sickness in the Swiss Alps. BMJ 1990; 301 : 853-5.Hongiman B, Thesis MK,Koziol-Melain J, et al. Acute mountain sickness in 8. general tourist population at moderate altitude. Ann Intern Med 1993; 118 : 587-92.Murdoch D. Altitude illness among tourists flying to 3740 meters elevation 9. in Nepal Himalayas. J Travel Med 1995; 2 : 253-6.Gaillard S, Dillasanta P, Loutan L, Kaysen B. Awareness, prevalence, medrea 10. use and risk factors of acute mountain sickness in tourists trekking around Annapurina in Nepal : a 12-years follow up. http : //www. Google. com. Accessed on 24 June 2005.Basnyat B, Savand GK, Zafren K. Trends in the workload of the high altitude 11. aid posts in the Nepal Himalayas. J Travel Med 1999; 6 : 217-22.Menon ND. High Altitude Pulmonary Oedema : a clinical study. N Eng J Med 12. 1965; 273 : 66-73.Bhalwar R, Singh R, Ahuja RC, Mishra RP. Vested case control analysis of the 13. risk factors for high altitude pulmonary oedema. Med J Armed Forces India 1995; 51 : 189-93.Hultgaon HN, Spickard W, Hellreigel K, Houston CS. High altitude pulmonary 14. oedema. Medicine 1961; 40 : 289-313.Singh I, Kapila CC Khanna PK, Nanda RB, Rao BDP. High altitude pulmonary 15. oedema. Lancet 1965; 1 : 229-34.Kleiner JP, Nelson WP. High altitude pulmonary oedema- a rare disease? 16. JAMA 1975; 234 : 491-5.

Further Suggested ReadingHeath D, Willliams DR. Man at High altitude : The pathophysiology of 1. Acclimatization and Adaptation. London, Churchill Livingstone. 2nd Ed 1981.Bhalwar R. Prevention of adverse effects of high altitude. In : Anand Ac, 2. et al (eds) Text Book of Environmental Emergencies. Armed Forces Medical College, Pune, Dept. of Internal medicine. 1st ed, 2005.

121 Water Supply

Sunil Agrawal

Water constitutes one of the important physical environments of man and has a direct bearing on his health. Water is a prime natural resource, a basic human need and a precious national asset. Water is important to man and therefore, WHO refers to “control of water supplies to ensure that they are pure and wholesome as one of the primary objectives of environmental sanitation”. Water is essential for drinking, cooking, bathing and washing, laundering, ablution, domestic sanitation, domestic animals and industries.

Safe and Wholesome water : Drinking water should be safe as well as wholesome. Water is termed safe when it does not harm

the consumer even when ingested over prolonged periods. Safe and wholesome water thus, must be(a) Free of pathogenic organisms(b) Free from harmful chemical substances(c) Acceptable to taste and appearance(d) Usable for domestic purposesWater Requirements : The supply of water must be satisfactory in quality and adequate in quantity, readily available to the user, relatively cheap, and easily disposed after it has served its purposes. The Environmental Hygiene Committee in the code of basic requirements of water supply, drainage and sanitation along with National Building Code recommends minimum of 135 lit per capita per day (lpcd) for residences with full flush system for excreta disposal. The recommended values for domestic and non domestic purpose are given in Table-1.

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Table - 1 : Recommended Per Capita Water Supply Levels For Designing Schemes (1)

S No

Classification of towns/cities

Recommended maximum

water supply levels (lpcd)

1 Communities where water is provided through public stand posts

40

2 Towns provided with piped water supply but without sewerage system

70

3 Cities provided with piped water supply where sewerage system is existing

135

4 Metropolitan and mega cities provided with piped water supply where sewerage system is existing

150

Sources of WaterRain Water : Rainwater is used as a direct source on islands, such as Bermuda, where the rain is collected and led into cisterns to serve as the only available water supply. Catchment areas for direct capture of rainwater are also useful for individual households as in South West USA or small communities as in Gibraltar where paved catchments are used. Rain water is usually soft, plumbosolvent and mildly acidic due to its reaction with carbon dioxide in the atmosphere to form carbonic acid. Physically it is clear, bright and sparkling. Bacteriologically, rain water from clean surroundings is free from pathogenic agents.

Surface water : It usually originates from rain water. It includes rivers, streams, upland reservoirs and lakes. Surface water is moderately soft and prone to contamination from human and animal sources. The extent of contamination at a particular time and place will depend upon the proportion of pollution to the amount of water available, from the feeding streams, upstreams or springs, the extent of stagnation or outflow over a given time and the extent of natural self purification. Surface water sources include Lakes and ponds; Impounding reservoirs; Rivers; irrigation canals; Sea water; and, Waste water reclamation.

a) Lakes and ponds : The water is more uniform in quality than water from flowing streams. Lakes are increasingly becoming vulnerable to pollution as they are quite accessible for human activities. Long storage permits self purification, sedimentation, oxidation of organic matter, and a tremendous drop in bacterial count. If there is proper cleanliness and sanitation in catchment area, then the stored water may not require any treatment other than disinfection. The concentration of pollution increases as water evaporates. The degree of self purification is negligible and the amount of pollution added to it each day is unpredictable. Therefore, water from fresh water lakes, which are properly protected, fenced and patrolled is generally pure and can be made potable whereas that from a pond is never recommended for human consumption. Unfortunately, it constitutes one of the main sources of water supply in the rural areas of this country. The improvement can be achieved

by applying the basic techniques of modifying a part of the pond into a filter bed. The filtered water is then drawn into gravity fed well and finally chlorinated before supply.

b) Impounding Reservoirs : These are the collections of water harnessed in the impounding reservoirs by constructing earth, concrete or masonry dams across at convenient places in the valleys in the mountainous regions. These collections are relatively pure in general but may get polluted due to grazing of animals and human activity. Impounding reservoirs are subject to same conditions as natural lakes and ponds. While top layers of water are prone to develop algae, the bottom layers of water may be high in turbidity, carbon dioxide, iron, manganese and, on occasions, hydrogen sulphide.

c) Rivers and Streams : These are natural drainage channels of the land. The quality of river water depends upon the geological strata through which it has travelled, the seasons of the year, and the amount of pollution that has occurred during its course. Generally, it is moderately hard but some river waters are brackish and may get contaminated while traversing long distances from sewage and other waste discharge from habitations located along their course. Other sources of pollution are the industrial effluents, carcasses and human dead bodies. The inadequacy of traditional methods of water treatment to tackle gross river water pollution may be indicated by the outbreaks of viral hepatitis in New Delhi in 1955-56, when there were 30,000 cases. In wet periods, the water in rivers and streams may be low in dissolved solids content but often of a high turbidity. In dry periods, river flows are low and the load of dissolved solids is less diluted.

d) Sea Water : Sea water is huge and plentiful source of water but it is difficult to economically extract water of potable quality because it contains 3.5% of salts in solution. Offshore waters of the oceans and seas have a very high salt concentration and hence are unfit for consumption. Desalting or demineralising process involves separation of salt and water from saline waters. The most appropriate method for desalination of sea water is thermal distillation as done in Middle East and the West Indies. Several different processes, including electrodialysis, reverse osmosis, and direct-freeze evaporation, have been developed for this purpose.

Underground water : Rain water percolating in the ground and reaching permeable layers in the zone of saturation constitutes ground water source. Underground Water (Fig. - 1) is of major importance to civilization, because it is the largest reserve of drinkable water in regions where humans can live. Underground reservoirs have the following major advantages: (a) Bacterially, groundwater is much better then surface

waters(b) They do not lose water through evaporation(c) Their quality is not so likely to be affected by natural,

urban or industrial pollution as surface water.(d) They do not require expropriation of large areas of land.(e) They may be located nearer to the points of use than are

surface impoundments.Generally, ground waters are clear and colourless but are harder than the surface waters of the region in which they occur. Although groundwater is a renewable resource, reserves are replenished relatively slowly. Because groundwater is recharged

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and flows so slowly, once polluted it will remain contaminated for extended periods. Contamination arises from leaking underground storage tanks, poorly designed industrial waste ponds, and seepage from the deep-well injection of hazardous wastes into underground geologic formations. Almost all highly industrialized areas in our country have contaminated their groundwater due to industrial wastes and agricultural run-offs (CPCB, 1994). Even all the villages too, do not have access to safe water. A “problem village” is defined as one where no source of safe water is available within a distance of 1. 6 km or where water is available at a depth of more than 15 meters or where water source has excess salinity, iron, fluorides and other toxic elements or where water is exposed to the risk of cholera and guinea worm.

Fig. - 1 : Underground Water

A

A

BB

C

C

D

(A) Impermeable layers (e.g. Clay) (B) Land springs (C) Shallow wells (D) Deep wells (E) Superficial water table (F) Deep water table

Springs : Springs are due to the emergence of groundwater to the surface. Springs can be ‘shallow springs’ and ‘deep springs’ depending upon whether the water comes from the superficial or the deep water tables. Deep springs can be turned into well like reservoirs by building parapets around them.

Wells : The subsurface sources include springs, wells and galleries. Wells can be classified according to construction process as Dug wells, Bored wells, and step wells. Alternatively, they can be classified depending on the depth and the layer of water table as shallow wells, deep wells and artesian wells.

Shallow Wells : These tap the ‘superficial water table’ i. e. the water table above the first impervious layer of the earth. They are of utility in abstracting limited quantity of water which usually goes dry in summers. The quality of water depends upon the geological formation and the degree of pollution by seepage from the adjacent area, which is unpredictable. Shallow wells are, therefore, inferior to deep wells as sources of water for human consumption as they are prone for contamination. The Cholera outbreaks in Delhi in 1988 were due to contamination of shallow wells.

Shallow well can be made sanitary by deepening the bottom, installing a handpump with screen and then filling the well with coarse sand upto water level; clay is then put over sand till it reaches a little above the surface level and then left for consolidation. When the material used for filling is consolidated a platform and drainage may be constructed.

Deep Wells : These tap the deep water table lying between the two impermeable strata and their yield is constant. Because of longer travel of groundwater to reach previous layers below the top impermeable layers, deep wells yield a safer supply than shallow wells. An ideal deep well is the one which is sunk to a sufficient depth below the first impermeable geological stratum, well stained with stones or bricks set in cement concrete provided with a covered parapet with a coping or sloped platform around and fitted with a pump. The depth of water should be sufficient to ensure an adequate quantity and sedimentation. The differences between shallow and deep wells is given in Table - 2.

Table - 2 : Difference between Shallow and deep well

S No

Shallow well Deep well

1 Definition Water from above first impermeable strata

Water from above second impermeable strata or impervious layer

2 Chemical quality

Moderately hard Much hard

3 Bacteriological quality

Fair but prone for contamination

Good

4 Yield 1 gpm 100 gpm

Artesian wells : Artesian groundwater is groundwater, that is, by an overlying impervious layer, prevented from rising to its free water table level, and therefore is under pressure. The name is derived from French Artesian of Artois, a province where such wells were first drilled in modern times. Artesian wells are not common in India.

Sanitary Well : A properly located, well constructed and protected against contamination, yielding safe water supply is known as Sanitary Well. Sanitary well can be constructed as :

a) Location : located at least 50 ft away from likely source of contamination on the higher ground but not more than 100 mt from consumers.

b) Lining : lining of the well is built by bricks or stones in cement upto a depth of about 20 ft. This lining is carried 2-3 ft above the ground level inside the parapet.

c) Parapet : Wall around well upto a height of 60-90 cm above the ground with lining inside.

d) Platform : There should be 2-3 ft wide cemented platform around parapet with sloping outwards.

e) Drain : A cemented drain is made around platform to drain storm water and spilled water to the main drain or soakage pit which should be constructed away from cone of filtration of well.

f) Covering : The top of the well should be covered with some gap for aeration and ventilation. The gaps should be such that impurities cannot go inside.

g) Handpump : A manual or electric pump should be connected to draw water hygienically.

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h) Consumer Responsibility : Strict cleanliness should be enforced in the near vicinity of the well, personal ablutions, animal droppings, washing of clothes and animals, bathing etc should be prohibited.

i) Water stagnation : Water should not be allowed to stagnate near well to prevent breeding of mosquitoes.

j) Quality : The physical, chemical and bacteriological quality of water should conform to the acceptable standards of quality of safe and wholesome water in rural settings.

Water Sources - Selection and Protection : In order to expect a safe and wholesome water for human consumption, the proper source and site should be selected keeping in view the liability and degree of pollution and its dilution, power of self purification, daily yield, duration for which available, wholesomeness of water, and the approach to the area. The area all around the source and delivery point should then be protected against pollution by fencing and prohibiting entry of animals and unauthorized persons. The activities like defecation, bathing and washing should not be allowed even in near vicinity of the area (catchment area). Water from streams and lakes should be drawn from the upstream side of the township and as far from the banks as possible and pumped into the treatment tanks. Personnel attending to the water treatment/distribution should be protected against typhoid and other infectious diseases and medically inspected.

Health Hazards Due to Impure WaterHealth may be affected either directly by consuming contaminated water or indirectly through food chain and also by use of water for recreational, agricultural, trade and other purposes. The health hazards of water pollution may be classified as Biological, Chemical and Radiological. The diseases related to water supply and caused by biological agents of disease are summarised in Table - 3.

Water Purification Comprehensive details of water treatment processes in settings of small scale communities, as well as large scale community supplies are laid down in standard publications (1, 4-6). Reference No. 1 is generally accepted as a standard reference by various Public / civil engineering agencies in our country.

Medical Officers dealing with water supply systems are advised to refer to these manuals.

Purification of Water on a Large Scale The aim of water purification is to produce and maintain water that is hygienically safe, aesthetically attractive and palatable, in an economical manner. The testing of water quality should not be restricted to treatment facilities but to be extended to the point of consumer use.

Conventional treatment of water includes prechlorination, aeration, flocculation (rapid and slow mixing) and sedimentation, rapid gravity filtration and post chlorination to render water safe for consumption. First few steps of water treatment are also called as Clarification which removes suspended matter and later disinfection kills pathogenic organisms. Disinfection without clarification may be practiced if water is beyond any doubt free of pollution and is visibly clear, or under extreme urgency. For example, ground water may need no treatment, other than disinfection. Surface water which tends to be turbid and polluted requires extensive treatment. The components of a typical water purification system comprise one or all of the following measures, viz., (a) Pretreatment, (b) Filtration and (c) Disinfection

Pretreatment : The sub-steps included in pre-treatment are Storage, Coagulation, Rapid Mixing, Flocculation, and Sedimentation. The details are described as follows.

(a) Storage : Even when water appears very clear, clarification should be insisted upon particularly for surface water. Minute particles of suspended organic matter which usually give lodgment to microbes particularly the viruses are not usually destroyed by the usual dosage of chlorine. Efficient clarification, therefore, eliminates besides the suspended matter, harmful organisms, cysts, ova, mollusc and Cyclops, and thus reduces the chlorine demand of water. The two methods available for clarification are sedimentation and filtration. Filtration is superior to sedimentation provided that the suspended matter is not too dense. Sedimentation requires more time (several hours) than filtration and the amount of water that can be dealt with is limited by the size of tanks available. Sedimentation less efficiently eliminates ova and cysts than filtration. However, efficient sedimentation prior to filtration definitely results in

Table - 3 : Classification of Water related diseases (3)

Category Diseases

Water borne diseases : Caused by the ingestion of water contaminated by human or animal faeces or urine containing pathogenic bacteria or viruses.

Cholera, typhoid, amoebic and bacillary dysentery, viral hepatitis, leptospirosis, giardiasis.

Water washed diseases : Diseases due to lack of water. Poor personal hygiene favours spread.

Scabies, skin sepsis & ulcers, yaws, trachoma, conjunctivitis, flea-, lice-, and tick- borne diseases, in addition to the majority of water borne diseases which are also water washed

Water based diseases : Caused by parasites found in intermediate organisms living in water. Infecting agents spread by contact or ingestion of water. An essential part of life cycle of agent takes place in aquatic animal eg snails, Cyclops etc

Schistosomiasis, dracunculiasis and some other helminths

Water related diseases : Transmitted by insect vectors which breed in water

Yellow fever, dengue, encephalitides, filariasis, malaria, onchocerciasis, trypanosomiasis, sleeping sickness

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a better final clarity of water, and relieves the filters of the clogging debris.

Sedimentation is carried out by allowing water to stand in concrete, masonry or canvas tanks over a variable period from 2 to 6 hours for settling the coarse suspended matter. This process can be hastened and improved in quality by coagulation and flocculation, which precipitates particulate and colloidal matter. The coagulation and flocculation are greatly influenced by physical and chemical forces such as electrical charges on particles, exchange capacity, particle size and concentration, pH and water temperature, electrolyte concentration and mixing.

(b) Coagulation : Coagulation describes the effect produced by the addition of a chemical to a colloidal dispersion, resulting in particle destabilisation. Operationally, this is achieved by the addition of alum and its rapid mixing for obtaining uniform dispersion of the chemical. The chemical coagulants employed are pure aluminium sulphate Al2(SO4)3 (alum) or more commonly alumino ferric, which is an impure form of alum containing about 1 percent of ferric sulphate. Both salts are readily soluble in water and forms aluminium hydroxide which engulfs and precipitates with it the minute particles of suspended matter. The optimum reaction for rapid and efficient sedimentation is at pH 7, at which the addition of 35 g of alum or aluminoferric per 1000 l will rapidly clarify any turbid water. If water is exceptionally turbid, as much as 70 g per 1000 l may have to be used. Finely divided clay, fuller’s earth, bentonites and activated carbon are commonly used materials used as Coagulant aids which improves or accelerates the quick forming, dense and rapid settling flocs.

(c) Rapid Mixing : Rapid mixing is an operation by which the coagulant is rapidly and uniformly dispersed throughout the volume of water, to create a more or less homogenous system. Water is agitated violently and the chemical is injected in the most turbulent zone. Generally large sludge volumes are produced with alum which requires frequent desludging operations at the treatment plants causing increased wastage of water. There is also the possibility of aluminium carry over in water treated with alum. High levels of aluminium in potable water are reported to cause Alzheimer’s disease, a form of senility. However at present there is no clear evidence to suggest a link between aluminium and Alzheimer’s disease (Cole, 1990). Poly aluminium chloride (PAC) has been developed as an alternative coagulant for alum by an Indian manufacturer. PAC hydrolyzes with great ease as compared to alum, emitting polyhydroxides with long molecular chains and greater electrical charge in the solution, thus contributing to maximize the physical action of the flocculation. Better coagulation is obtained with PAC as compared to alum at medium and high turbidity waters. Floc formation with PAC is quite rapid. The sludge produced by PAC is more compact than that produced by alum.

(d) Flocculation : Flocculation is the process of gentle and prolonged stirring of coagulated water in the flocculation chamber for the purpose of forming settle able particles (flocs) from destabilised colloidal sized particles through the aggregation of the minute particles. After coagulation, the individual floc particles are easily observed by the naked eye, being of the order of 1-2 mm in diameter. In practice, the velocities in flocculation tanks vary from 1 m/s at the entrance,

decreasing to about 0. 2 m/s near the outlet, with a retention time of 30 minutes. Slow mixing is the hydrodynamic process which brings the particles to collide and then agglomerate resulting in the formation of large and readily settle able flocs of aluminium hydroxide. These can be subsequently removed in settling tanks and filters. The mechanical type of flocculator is widely used in which paddles rotate at 2 to 4 rpm. In actual practice this quantity of alum or aluminoferric brings the natural alkalinity of the vast majority of waters down to a pH of 7 and no other treatment is required.

(e) Sedimentation : Sedimentation is the separation of suspended particles from water by gravitational settling down. The coagulated water is now led into sedimentation tanks where it is detained for periods ranging from 2-6 hrs, where the flocculant precipitate settles down in the tank together with impurities and bacteria. The precipitate or sludge which settles at the bottom is removed from time to time without disturbing the operation of the tank. For very turbid water sedimentation may be better carried out in two stages; initial settling of the bulk of the coarse debris followed by chemical flocculation. Leading the flow of water through long tortuous broad channels at slow velocity and storage in large reservoirs before its entry into the sedimentation tanks helps to achieve better sedimentation. This also exposes water to the natural purifying effects of the sun’s rays and fresh air, and the biological effect of minute aquatic fauna and flora. These processes render the water highly suitable for filtration and bring down the bacterial content of water considerably.Filtration

Filtration is a process for separating suspended and colloidal impurities from water by passage through a porous media. Filtration, with or without pre-treatment, has been employed for treatment of water to effectively remove turbidity. It is almost universally adopted in a large scale purifying process of water in municipal, cantonment, garrison or base areas where permanent water works exist. Storage and sedimentation, with or without flocculation depending upon the quality of water, almost always precede the process of filtration. Filters are slow and rapid sand filters and mechanical filters. Mechanical filters are used in small, more sophisticated water plants and also in the water tank trucks and trailers. Sand, coal, crushed coconut shell, diatomaceous earth and powdered or granular activated carbon have been used as filter media but sand filters have been most widely used as sand is widely available, cheap and effective in removing impurities. The driving force to overcome the fractional resistance encountered by the flowing water can be either the force of gravity or applied pressure force. The filters are accordingly referred to as gravity filters (Paterson’s filter) and pressure filters (Candys filter). Depending on flow rates the filters are classified as : (i) Biological or slow sand filters, and (ii) Mechanical or rapid sand filters

Slow Sand or Biological Filters

Slow sand filters were first used for treatment of water in 1804 in Scotland and subsequently in London. Then there use spread out throughout the world. These are large masonry tanks 2. 5 m - 4 m deep rectangular or circular, containing sand supported on gravel and the water is passed through them slowly from above downwards. As the filter plants need extensive tracts

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of land these are usually situated on the outskirts of town located on the bank of a river. To avoid choking of the media preliminary sedimentation and clarification is necessary.

Filter Bed : The filter beds are usually rectangular in shape, arranged side by side in rows and may be either open on top or covered. Each bed usually covers an area from one tenth of an acre to one acre land. The filter bed consists of(a) Supernatant water layer - 1-1.5 mt(b) A bed of filter medium - sand bed 1-1.2 mt.; graded gravel

0.3-0.5 mt.(c) An underdrainage system - 0.16 mt(d) Set of control valves and appurtenancesThe supernatant provides the driving force or constant head for the water to overcome the resistance of filter bed and provides waiting period of some hours for the raw water to undergo sedimentation, oxidation and particle agglomeration. A layer of graded gravel of about 30 - 50 cm thickness is placed over the perforated pipes. Above the gravel is the sand bed having a thickness of about 1-1.2 m. The sand grains have an effective diameter between 0.2-0.3 mm. The underdrainage system which is about 16 cm in depth, consists of porous or perforated pipes which serves the dual purpose of providing an outlet for filtered water as well as supporting the filter media above. A system of control valves facilitates the regulation of filter rate and adjustment of water level in the filter. An important component of the regulation system is the “V-notch” or “venturimeter” which measures the flow of water or bed resistance or loss of head.

In a slow sand filter, water is subject to various purifying influences as it percolates through the sand bed. Impurities are removed by combination of straining, sedimentation, bio-chemical and biological processes. Shortly after the start of filtration, slow sand filter acts primarily biologically by forming a slimy ‘zoogleal’ layer also known as ‘Vital Layer’ or ‘Schumutzdecke’ on the sand bed. This layer is slimy and gelatinous and consist of thread like algae and biological organisms like plankton, diatoms and other minute plants and protozoa. They feed on the organic matter and convert it into simple harmless substances. The vital layer which is also the heart of the filter removes organic matter, holds back bacteria & oxidises ammonical nitrogen into nitrates & helps in yielding, bacteria free water. Till the vital layer of the filter bed is fully formed (called ripening of bed), the filtrate is run to waste.

Filter cleaning : After several months of running of the filter, the bed resistance increases necessitating cleaning. When the filter has attained the maximum permissible head-loss, it is taken out for service for cleaning. The inlet is closed and the supernatant is drained out, then water level is lowered 10-15 cm below the top of sand bed by opening the valves. Without allowing the bed to dry up, the filter is cleaned manually by removing the top layer of 2-3 cm of sand along with the filter skin. This is done manually by scraping the vital layer. After several years of operation when the thickness of the sand bed reduces to about 0.4 to 0.8 m, it is necessary to make up the sand depth to the original level. The plant is to be closed down and a new bed is to be constructed.

Mechanism of Action of Slow Sand Filters : In a slow sand

filter, due to the fine grain size, the pores of the filter-bed are small. The filter is capable of reducing the Esch. Coli content and the total bacteria count. It will remove protozoa such as E. histolytica and helminths such as S. haematobium and A. lumbricoides. Trouble free operation is only possible when the average turbidity of the raw water is less than 5 nephelometric turbidity units (NTU) with occasional peak values below 20 NTU permissible. Removal of impurities is brought about by different processes such as :(a) Straining(b) Sedimentation(c) Adsorption(d) Biochemical and microbial actionsIn straining, suspended particles that are too large to pass through the pores are retained at the surface or top layer of the filter. In the upper part of the filter-bed, sedimentation of fine suspended solids also takes place. Settling efficiency is very high due to the large surface area (10,000 to 20,000 sq. m per cu. m of the filter sand) and slow rate of filtration. The rate of filtration of water lies between 0.1 to 0.4 m3/hour/sq mt of sand bed surface.

Advantages of slow sand filter

1. Simple to construct and operate.

2. The cost of construction is cheap.

3. The quality of filtered water is very high.

4. Preferred for rural or small community water supplies.

Performance standards for slow sand filter

1. The filtrate should be clear with a turbidity of 1 NTU or less.

2. The filtrate should be free from colour.

3. When raw water turbidity is around 30 NTU, the filter runs should normally be not less then 6 to 8 weeks, with the filter head not exceeding 0.6 mt.

4. The initial loss of head should not exceed 5 cm.

Rapid Sand Filters

In 1885, the first rapid sand filter was installed in USA, and since then they are popular worldwide. These are of two types ‘gravity type’ (Paterson’s filter) and the ‘pressure type’ (Candy’s filter). While the former is usually used in large installations, the latter is used in smaller installations such as swimming pools. The various steps in the working of a gravity type rapid sand filter are shown in Fig. - 1.

Filter Bed : The filter bed is a watertight rectangular chamber with a surface area of about 90 m2. The depth of the sand bed is usually one meter having sand particles whose sizes are bigger than the ones used in slow sand filters. The filter bed consists of :(a) Supernatant water layer - 1-1.5 mt(b) A bed of filter medium - sand bed 1-1.2 mt,; graded gravel

0.3-0.5 mt.(c) An underdrainage system - 0.16 mt(d) Set of control valves and appurtenances

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Below the sand bed is a layer of graded gravel of about 40 cm thickness. The ‘effective size’ of the sand particles is between 0.4-0.7 mm. The under drainage is below the graded gravel layer which collects the filtered water.

Filtration : The alum floc makes a tough slimy layer (chemical) over the sand bed, which acts mechanically. Oxidation of ammonia also takes place during the passage of water through the filters. In this system there is no time wasted for ripening of the bed. The rate of filtration in a rapid sand filter is about 100 times faster than of slow sand filter. The rate of filtration is 5-15 m3/m2/hour. When the bed gets clogged after use for a day or so, it is cleaned by back washing by reversing the flow of filtered water.

Filter Cleaning : Rapid sand filters need frequent washing daily or weekly, depending upon the loss of head. The process of cleaning the filter bed is called Backwashing, in which water or compressed air is passed in the reverse direction or below upwards to dislodge the impurities and loosen the sand bed. The backwash rates of 42-54 m3/m2/hour is used to clean filters. The washing is stopped when clear sand is visible or wash water is clear. After backwashing, the filter bed is put to use immediately and not after 24 hours or so as is required for the formation of biological film in a slow sand filter.

Advantages of rapid sand Filter

1. Rapid sand filter can deal with raw water directly.

2. The filter beds occupy less space.

3. Filtration is rapid, 40-50 times that of slow sand filter.

4. The washing of filter bed is easy.

Performance standards for rapid sand filters

1. The filtrate should be clear with a turbidity of 1NTU or less.

2. The filtrate should be free from colour.

3. The filter runs should normally be not less then 24 hours, with the loss of filter head not exceeding 2 mt.

4. The wash water consumption should not exceed 2% of the quantity filtered in between washing.

Disinfection

For purification of water after pre-treatment and filtration, the disinfection of water is carried out. The need for disinfection

to prevent water borne diseases and its inclusion as one of the water treatment processes is considered necessary. Disinfection of water means making it fit for drinking by destroying all pathogenic organisms that may be present in it. Broadly, modern disinfection processes include : 1. Physical methods such as thermal treatment and ultrasonic

waves.2. Chemicals including oxidising chemicals such as chlorine

and its compounds, bromine, iodine, ozone, metals like silver etc

3. Radiation.Chlorination : In water treatment or purification practise, the term disinfection is synonymous with chlorination. Disinfection of water is therefore, usually carried out by the use of chlorine who fulfils all the criteria’s of good disinfectant. Gaseous chlorine is greenish yellow in colour and is 2.5 times heavier then air. Under pressure, it is a liquid with an amber colour, oily nature and approximately 15 times as heavy as water. Chlorine gas is powerful irritant to lungs and eyes with odour threshold of 3.5 ppm by volume. The safety limit for a working environment is 1 ppm of chlorine in air by volume for an exposure period of 8 hours. When chlorine is added to water it forms hydrochloric acid and hypochlorous acid. Hypochlorous acid further dissociates into hydrogen ions (H+) and hypochlorite ions (OCl-).

Cl2+H2O=HCl + HOCl.

HOCl = H++ OCl-

The reaction is reversible. The disinfection action of chlorine is mainly by hypochlorous acid and partly by hypochlorite ion. Chlorine acts best when pH of water is around 7 because of predominance of hypochlorous acid. Fortunately most waters in India have a pH between 6 to 7.5. However sporing organisms, protozoal cysts, helminth ova, molluscs, cyclops and cercariae are not affected by the usual dosage. Organic matter or reducing salts deviate chlorine which results in uncertainty of its action.

Chlorine Demand : Chlorine and chlorine compounds by virtue of their oxidising power can be consumed by a variety of inorganic and organic materials present in water before any disinfection is achieved. It is therefore, essential to provide sufficient time and dose of chlorine to satisfy the various chemical reactions and leave some amount of unreacted chlorine as residual either in the form of free or combined chlorine adequate for killing the pathogenic organisms. The recommended concentration of free

Fig. - 1 : Rapid sand Filtration Plant

MixingChamber

FlocculationChamber

ChlorineAlum

Rive

r

Consumer

SedimentationTank Filters Clean

Water

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chlorine is 0. 5 mg/L for one hour. The difference between the amount of chlorine added to water and the amount of residual chlorine after a specified contact period (usually 60 minutes), at a given temperature and pH of water is defined as ‘chlorine demand’.

Breakpoint chlorination : The point at which the free residual chlorine appears after the entire combined chlorine residual has been completely destroyed is referred to as breakpoint and the corresponding dosage is the breakpoint dosage. The point at which chlorine demand of water is met is called ‘breakpoint chlorination’. If chlorine is added further, it only increases free chlorine. Breakpoint chlorination achieves the same results as superchlorination in a rational manner and can therefore be construed as controlled superchlorination.

A high chlorine dose creates unpleasant chlorinous taste in water. Initial high dose of chlorine application or the uncertain chlorine content of the unstable bleaching powder used may result in excessive chlorine application. Free chlorine in the strength of 0.5 ppm in water is imperceptible; but over 0.5 ppm the chlorine taste becomes faintly noticeable; whilst above 1 ppm a definite chlorine odour and taste are apparent.

Dosage of Chlorine : Under conditions assuring efficient clarity of water, 30 min of contact with the ‘disinfecting dose’, freedom from chlorinous taste and presence of 0.2 to 0.5 ppm of free chlorine is considered adequate to achieve health safety.

Superchlorination : Under worse conditions or in the presence of actual or potential danger of outbreak of intestinal infections or when water is heavily polluted or fluctuate rapidly in quality, large doses of chlorine is added to the water called ‘Superchlorination’. The dose of chlorine may be as high as 10-15 mg/L with contact periods of 10-30 minutes. Decolourisation should be carried out before consumption of water. The sporing organisms like the welchii group, the protozoal cysts like those of E. histolytica, helminth ova, molluscs, cercariae and viruses of infectious hepatitis and poliomyelitis in water require a higher concentration of chlorine maintained over a long time for disinfection.

Methods of Chlorine Application : Chlorine can be applied to water by three methods : 1) By the addition of a weak solution prepared from bleaching

powder, HTH etc. for disinfecting small to medium quantities of water. It is simple, does not require electricity and relatively safe but instability of bleaching powder, its hygroscopic nature and low percentage of available chlorine makes it difficult to reach desired levels of free chlorine.

2) By the addition of weak solution of chlorine prepared by electrolysing a solution of brine which requires deployment of electrochlorinators which is still an emerging technology.

3) By the addition of chlorine, either in gaseous form or in form of solution made by dissolving gaseous chlorine in small auxiliary flow of water, the chlorine gas being obtained from pressurised chlorine containers.

Chlorine Gas : In the modern water works application of gaseous or liquid chlorine with the help of mechanical injector called ‘Chloronomes’ is the method of choice. Since chlorine

gas is an irritant to the eyes and poisonous, it should be applied only through chlorinating equipment called Patersons Chloronome. In this process the charging of the water supply with chlorine, ascertaining persistence of free chlorine content are all carried out automatically. By ensuring 0.5 ppm of free chlorine at the treatment plant and if the delivery of water is not delayed for more than 6 hours, generally results in 0.2 ppm of free chlorine at consumers end. If quantity of water to be treated is more than 500,000 litres per day, chlorine gas has been found to be the most economical.

Chloramination : Chloramines are loose compounds of chlorine with ammonia. They impart less chlorinous taste in water and give a more persistent type of residual chlorine. This prolonged residuum confers the power of long resistance to contamination during the flow of water through the pipe system and hence may be advantageously used in large urban water plants where the pipeline runs for several million meters. Their drawback is that they have slower and inferior action than chlorine.

Bleaching Powder : Bleaching powder is used for disinfection of water in small water supplies having capacity upto 0.5 mld and rural areas. Bleaching powder is a variable mixture of calcium hydroxide, calcium chloride and calcium hypochlorite also known as chlorinated lime (CaOCl). It was first introduced for sterilization of water by Horrocks in 1914. When it is mixed with water, the calcium hypochlorite decomposes into calcium chloride and chlorine. It is a white amorphous powder with pungent smell of chlorine. When freshly made it contains about 33 percent of available chlorine. It is, however, very unstable and its chlorine is readily set free by the action of moisture, CO

2, heat, light, and possibly even by continued vibration sustained during long journeys. Bleaching powder is also difficult to introduce in accurate doses into large quantities of water, leading to further error in the dosage and finally to taste trouble. Bleaching powder is stored in corrosion free air tight containers made of wood, ceramic or plastics and kept away from sunlight. Bleaching powder is generally made into a thin slurry with the water and the supernatant is applied to water.

Water Sterilising Powder (WSP) : Bleaching powder is considerably improved in its keeping quality by the addition to quicklime in the proportion of 80 : 20 when it is known as water sterilising powder. Its available chlorine should not be less than 25 percent. WSP is usually used for disinfection of water under field service conditions. It is supplied in packs of 50 g, 100g, ¼ kg, ½ kg, 1 kg and 25 kg. WSP is soluble in about twenty times its weight of water, yielding an insoluble precipitate consisting mostly of Calcium Hydroxide Ca (OH), silica etc. This settles quickly, if too thick a paste is not made; otherwise a gelatinizing action takes place and great difficulty in settling is encountered. It is not necessary or desirable to grind or break up the lumps thoroughly and too much agitation is detrimental to prompt settling. 500 g of WSP mixed with 5 : 1 water contains approximately 2.5 percent available chlorine if the powder is of 25 percent strength. Chlorine solution can maintain its strength for weeks if properly corked in brown bottles.

Hypochlorites : The chemicals used are Sodium Hypochlorite and Calcium Hypochlorite which can have 60-70% available chlorine. Calcium hypochlorite can be fed either in the dry or

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solution form, while sodium hypochlorite is fed as solution. Corrosion resistant materials such as ceramics, glass, plastic or special rubber should be used while handling hypochlorite solutions.

Agents Other than Chlorine : Broadly there are three main types of disinfectants other than chlorine : 1. Physical agents including heat2. Chemical agents such as ozone, halogens3. Radiations of various types such as Ultraviolet rays,

Gamma rays and X-rays.Heat : Boiling of water can disinfect it but it cannot be used to disinfect large scale supplies. It can be used in emergency for individual or household drinking water.

Ozone : It is a powerful oxidizing agent. It removes undesirable odour, taste, colour and organic matter. It even inactivates viruses in a few seconds and hence can be used most advantageously for destruction of enteropathogenic viruses. Since ozone decomposes and disappears within short time there is no residual germicidal effect. Hence, a minimal dose of chlorine may be added to the ozonised water before distribution. In this combined treatment, the two methods complement each other. The ozone dosage required for potable water treatment varies from 0.2 to 1.5 mg per litre. Ozonisation of water is presently practiced in the advanced countries. The combination of ozone for pretreatment while providing some disinfection, to be followed by chlorination, has become a popular sequence in Europe and is beginning to be used in USA to reduce the level of trihalomethanes in finished water. Some disadvantages of ozone treatment are : 1. Its high cost of production.2. Inability to provide residual protection against

recontamination.3. Its onsite generation due to unstability.Ultraviolet Irradiation : UV radiation may kill a cell, retard its growth, change its heredity by gene mutation. Wavelength region from 2500-2650 Angstrom units is recommended for maximum destruction of cells.

A mercury vapour arc lamp emitting invisible light of 2537 Angstrom units applied to water by a low pressure mercury lamp constructed of quartz or special glass which is transparent and produces a narrow band of radiation energy, is a useful method of disinfection used in the Soviet Union. The advantages of UV radiation are that exposure is for short periods, no foreign matter is actually introduced and no taste and odour produced. Overexposure does not result in harmful effects.

Other Halogens : Halogens are oxidising agents and agents like fluorine, iodine, bromine can also be used for disinfection. In view of the formation of organochlorine compounds by chlorine which are either known or suspected carcinogens, many chlorine alternatives such as bromine and iodine substances are receiving renewed interest. These substances for the present, however, do not seem to be a viable alternative to chlorine.

Tests for Chlorination : Before disinfecting any source of water the chlorine demand of the water source should be calculated, this will give adequate disinfection and a desired level of free chlorine. The test used for calculation of chlorine

demand of water is called Horrock’s Test. The object of this test is to determine the quantity of the particular sample of WSP required to sterilize any particular sample of water. The test is carried out by means of the ‘case water testing sterilization’ (Horrock’s Box). The Horrock’s box contains :- six white cups of 200 ml capacity each- one black cup of 240 ml capacity;- two metal scoops, each of which holds 2 g of WSP when

filled level with the brim;- a bottle of stock cadmium iodide-starch solution;- a bottle containing 85 ml of 50 percent glacial acetic acid;- 25 sodium thiosulphate tablets 100 mg each;- seven glass stirring rods.- one pipette- two droppersThe test should be carried out while the water receptacle is being filled with clarified water (7).

Procedure : A standard solution of the particular sample of WSP is prepared in the black cup. First a thin paste with one level scoopful of the WSP and a little clarified water is made and then gradually more water is added up to the mark on the inside of the cup and the mixture is stirred with a clean glass rod. The lime in suspension gradually settles down. This is known as stock solution or mother solution. The six white cups are then filled with clarified water to within half a centimetre from its top. Drops of the standard WSP stock solution from the black cup are added to each of the white cups by the pipette, so that the first cup receives one drop; the second cup receives two drops and so on serially increasing until finally the sixth cup receives six drops. One drop represents one part of chlorine in a million parts of water when added to the white cupful of water. The pipette must be held vertical when delivering the drops. The contents of each cup are stirred with a clean stirring separate rod, starting at the first cup, and allowed to stand for half an hour, shading them from sunlight. After that time three drops of the starch-cadmium iodide indicator solution are added to each cup from the drop bottle/dropper and stirred with a clean stirring separate rod. Some of the cups will show a blue colour. This indicates the presence of free residual chlorine.

The serial number of the cup showing definite blue colour indicates the number of scoopfuls of the particular sample of water sterilizing powder required to sterilize 455 L of water and to leave 1 ppm of free chlorine after chlorine demand of that sample of water is satisfied during half an hour contact with chlorine.

For example, if cups 3, 4, 5 and 6 show a definite blue colour, then three scoopfuls of WSP are required to sterilize 455-500 L of the particular water sample and leave I ppm residual free chlorine after half an hour contact. If superchlorination is indicated one more scoopful of WSP per 500 L of water is required to be added. This will give 2 ppm of free chlorine in water after 15 min contact. In the example given above a total of 4 scoopfuls of WSP per 500L will be needed for superchlorination. The WSP used for chlorination or superchlorination should be from the same tin from which the WSP for Horrock’s test was used.

An indicator solution can be made by preparing a uniform paste of 1.5 g of starch in 25 ml of distilled water and then adding

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it slowly to 75 ml of boiling distilled water while continually stirring it, and boiling for subsequent 15 min. After cooling, 7.5 g of cadmium iodide is added to the mixture and dissolved by shaking. In an emergency potassium iodide may be used if cadmium iodide is not available. The solution should be stored in a well-corked dark brown bottle in a dark and cool place. The keeping quality of the solution is enhanced by the addition of 1ml formalin to this solution.

Tests for Adequacy of Chlorination : Adequate control must be kept on chlorination by a regular examination of the treated water to make sure that the requisite amount of free chlorine has persisted in the water for the requisite time. This can be done by means of starch-iodide, thiosulphate with starch-iodide, orthotoluidine, orthotoluidine arsenite or neutral red.

Orthotoluidine (OT) Test : This is the most commonly used test in public health practice. It is carried out with the ‘Comparator type of apparatus’ (Lovibond Comparator) indicates chlorine below 1 ppm. The test was developed in 1918 and it uses analytical grade O-tolidine, dissolved in 10% solution of hydrochloric acid. 0.1 ml of orthotoluidine solution is added to 1 ml of water in a standard glass cell or tube. The yellow colour, which develops, is matched against tinted glass discs. The immediate (flash) reading within 10 seconds shows the free chlorine and that taken after 5 min (delayed) gives the combined content of chloramines and free chlorine. OT reacts with free chlorine instantaneously but reacts more slowly with combined chlorine. In the absence of the Comparator, the appearance of intensity of yellow colour can give rough estimate of amount of free chlorine present.

Orthotoluidine Arsenite Test (OTA) : It is a modification of OT test. Certain interfering substances such as nitrates, iron, manganese etc which when present in water also gives yellow colour with orthotoluidine. The OTA reagent overcomes this drawback and hence gives better determination of free and combined chlorine separately.

Colour Test : Fill a white cup with chlorinated water to be tested and stir into it 10 drops of fresh cadmium-iodide-starch indicator solution. If there is one or more parts of free chlorine in million parts of water a blue colour will appear. In this test the residual chlorine replaces iodine and combines with cadmium radical; iodine so released combines with starch and turns it blue.

Determination of Chlorine Content in WSP : A rough and ready field test can be carried out by the use of the Horrock’s Box. A WSP solution is made by mixing one level scoopful of the WSP powder to be tested in the black cupful of clarified water. One scoopful of this solution is mixed with a scoopful of cadmium-iodide indicator solution in a white cup and a tablet of acid sodium bisulphate is added to it. The 0.05 percent neutralising reagent is prepared by dissolving a 100 mg tablet of sodium thiosulphate in a white cupful of water. Scoopfuls of this solution are added to the blue mixture of indicator-WSP solution and stirred. The number of scoopful of the thiosulphate solution added until the blue colour first disappears indicates the percentage of chlorine in the WSP under test.

Purification of Water on a Small Scale (Households and small groups of people)

Boiling : It is very effective and kills all bacteria, viruses, spores, cysts and ova when the water is boiled for 5 to 10 min called “rolling boil”. It also removes temporary hardness by driving off CO2 and precipitating the calcium carbonate. The taste of water is, however, altered. Boiled water has also no residual protection against subsequent contamination and hence care to be taken to avoid contamination during storage.

Chemical Disinfection : It may be carried out with either chlorine solution, bleaching powder, WSP, perchloron, chlorine tablets, high test hypochlorite or iodine solution. The chlorine tablets manufactured by the National Environmental Engineering and Research Institute, Nagpur (NEERI) are about 15 times more potent than ordinary halogen tablets and are available in the market. A single tablet of 0.5 g is sufficient to disinfect 20 l of water. The tablets are mostly used while travelling or by soldiers during march or field areas. Potassium permanganate is no longer recommended, as it is not a satisfactory water disinfecting agent although it is a powerful oxidizing agent. It has other drawbacks such as alteration of colour, smell and taste of water.

Filtration : It is done through ceramic filters such as Pasteur Chamberland, Berkefeld and Katadyn filters. The essential part of a filter is the candle, which is made of unglazed porcelain in Pasteur Chamberland type, and of Kieselgurh in Berkefeld type. The surface of the candle in Katadyn filter is coated with a sliver catalyst. The bacteria coming in contact with filter candle get killed by the oligodynamic action of silver ions. Filter candles are liable to be clogged. These are to be cleaned by scrubbing with a hard brush under running water. The candles should be boiled at least once a week. Relatively clean water should be used with ceramic filters. Filter candles, however, removes bacteria but do not remove filter-passing viruses. Most of the household filters available in market work on electricity on principles of disinfection by UV radiation.

Disinfection of Wells : It is sometimes necessary on a large scale during epidemics of cholera and other gastro-intestinal infections. Chlorination with bleaching powder is the most effective and cheapest method for this purpose. The quantum of water in the well is first worked out and the amount of WSP required is then estimated by Horrock’s test. The required quantity of WSP is then made into a thin paste with little water in a bucket. The bucket is filled three-fourth with water stirring all the time. About 5 to 10 min time is allowed for the chalk to settle down. The supernatant clear solution is then transferred to another bucket and the chalk is discarded. The bucket containing the clear chlorine solution is lowered into the well and the well water agitated by lowering and drawing the bucket several times. After half an hour’s contact, orthotoluidine test is carried out. If fresh residual chlorine is less than 0.5 mg/l, additional quantities of WSP will have to be added. During epidemics, wells should be disinfected every day. Steps in well disinfection are :

a) Find the volume of water in a well by formula

(3.14 x d2 X h x 1000) ÷ 4

(Where d = diameter of well, h = depth of water column)

Or, find out by following formula (measurements of depth and diameter are in metres)

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Circular well : Depth of water x square of diameter x 785 = liters of water in the well.

Rectangular : Depth of water x length x breadth x 1000 = liters of water in the well.b) Find the amount of bleaching powder required for

disinfection by Horrock’s test.c) Dissolve bleaching powder in waterd) Delivery of chlorine solution into the well.e) Contact periodf) OTA test

Water Quality Standards and CriteriaThe WHO has published in 1993 vol 1 and in 1996 vol 2 of second edition of Guidelines for Drinking water quality on various parameters for drinking water quality to be used by different countries in making their own standards. They are laid down in standard references (8, 9, 10, 11) and should be referred to as and when required. The methods of examination of water are also given in details in the publications of ICMR (12). In brief the standards are as follows1. Acceptability Aspects.2. Microbiological Aspects3. Chemical Aspects.4. Radiological Aspects.Acceptability Aspects The drinking water should not only be safe but also pleasing in appearance, taste and colour. Wholesomeness and acceptability of drinking water is determined by the following factors :

Turbidity : Turbidity should be less than 5 NTU and before chlorination should be < 1 NTU. Turbidity above 5 NTU, becomes unacceptable to the consumer. Turbidity indicates incomplete treatment of water and also interferes with disinfection of the water.

Colour : The acceptable limit for colour in drinking water is 15 true colour units (TCU). Colouration of water may be due to presence of organic matter such as peat, metals like iron and manganese or due to industrial wastes.

Taste and Odour : Even though no guideline limit values have been laid down, any water with significant degree of taste and odour is unacceptable to the user. Taste and odour may be due to mineral matter, presence of organic matter and occasionally due to excessive residual chlorine in treated waters.

Total Dissolved Solids (TDS) : The amount of TDS in water has an important effect on its taste. Water with very low concentrations of TDS, such as the rain water is not relished by the consumer because of the flat, insipid taste. The palatability of waters with TDS levels below 600 mg/litre is considered to be good and those above 1200 mg/litre become unpalatable and objectionable due to scale formation in pipes, heaters and household appliances. The guideline value for TDS is to be below 1000 mg/litre.

pH : The guideline value for pH of water is 6.5 to 8.5. Water with pH levels below this range may corrode pipelines, resulting in increased levels of certain chemical substances, such as lead, in water. At pH levels above this range, the efficiency of the disinfectant action of chlorine is reduced.

Hardness : Depending on the interaction of other factors, such as pH, water with hardness above 200 mg/litre may cause scale deposition in the distribution system and may result in excessive soap consumption. On the other hand, water with a hardness of less than 100 mg/litre has a low buffer capacity and is corrosive for water pipes. For domestic use the amount of hardness of water should not be more than 300 ppm. For laundries and boilers the softer the water the better it is.

Dissolved Oxygen : Even though no health based guideline value has been laid down, depletion of dissolved oxygen content in water encourages microbial reduction of nitrates and sulphates to nitrites and sulphides respectively, with consequent odour problems.

Ammonia : Ammonia in water is an indicator of possible bacterial, sewage and animal waste pollution. It may be present in a non-ionised or ionised form. The guideline value is 1.5 mg/litre. Ammonia may be free (F), saline(S), or Albuminoid (Alb). If both types of ammonia are low i.e. F and S are 0.05 ppm or less and Alb. 0.1 ppm or less, the water is probably good. If both types of ammonia are higher than the above figures then the water is bad.

Chlorides : The guideline value for chloride is 250 mg/litre even though the maximum permissible level is kept at 600 mg/litre. Other indications of pollution will also help in arriving at conclusions.

Iron : A trace of iron is almost always present in water. Iron upto 0.3 mg/L is acceptable. Above that it causes constipation, colic and results in the colouration of vegetables while cooking and staining of linen.

Microbiological Aspectsa. Standards of Bacterial Quality : The primary bacterial indicator recommended are coliform group of organisms, whereas supplementary indicator organisms are faecal streptococci, sulphite reducing clostridia etc.

Coliform Organisms : It includes all aerobic and facultative anaerobic, gram negative, non sporing, motile and non motile rods capable of fermenting lactose at 35-37 deg. C in less than 48 hrs. The coliform group includes both faecal and non faecal organisms. e.g. Faecal group is E Coli and non faecal group is Klebsiella aerogenes. The coliform organisms are chosen as indicators of faecal pollution in water because : a. Coliform organisms are present constantly in the human

intestines but they are foreign to potable waters and hence their presence in water indicates faecal contamination.

b. They are easily detected by culture methods.c. They survive longer than other pathogens.d. The coliform organisms have greater resistance to the

forces of natural purification.Faecal Streptococci : In doubtful cases, the finding of faecal streptococci is regarded as important confirmatory evidence of recent faecal pollution of water. Streptococci are highly resistant to drying and may be valuable for routine control testing after laying new mains or repairs in distribution systems or for detecting pollution by surface run off to ground or surface waters.

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Cl perfringes : The spores of Cl perfringes survive longer time and resist chlorination at the doses normally used for disinfection. Their presence in water, in absence of other organisms indicates the faecal contamination occurred at some remote time.

Bacteriological Standards - Treated Water : Ideally, all samples taken from the distribution system should be free from coliform organisms. In practice this standard is not always attainable and the following standard for water collected in the distribution system is therefore recommended throughout any year : 95 percent of samples should not contain E Coli coliform organisms in 100 ml water sample taken during that 12 month period; no consecutive samples should contain coliform organisms in 100 ml of water samples.

Bacteriological Standards - Individual or Small Community Supplies : The standards outlined above may not be attainable in the case of waters from wells and springs. In these waters, the coliform count should be less than 10 per 100 ml. Persistent failure to achieve this particularly if E Coli is repeatedly found calls for rejection of water supply.

b. Standards of Viral Quality : As stated earlier, water free of faecal coliform need not necessarily be free of viruses. Enteroviruses, reoviruses and adeno-virus have all been detected in water. As per WHO standards not more than one plaque forming unit (PFU) per liter of water is considered potable. There should also be complete absence of enteropathogenic viruses and faecal bacteriophages. Ozone has been shown to be most effective viral disinfectant.

Chemical AspectsThese indicators are of two types, viz., inorganic constituents and organic constituents.

a. Inorganic Constituents : The details are shown in Table-4.b. Organic Constituents

Polynuclear Aromatic Hydrocarbons (PAHs) : Most of the PAHs identified in the environment are from combustion and pyrolysis processes. The main source of human exposure to poly aromatic hydrocarbons is via food with drinking water contributing only minor amounts. Some of these are know to be carcinogenic. Their concentration, in general should not exceed 0.2 g / L.

Pesticides : Chlorinated hydrocarbons and their derivatives, herbicides, soil insecticides and pesticides that leach out from the soil are of importance in connection with water quality. The recommended guideline value for human beings are given in Table - 5.

Table - 5 : Guidelines for Chlorinated Hydrocarbons for Humans

Pesticides Upper limit of concentration (microgram/lit)

Aldrin/dieldrin 0.03

Chlordane 0.2

DDT 2

Hexachlorobenzene 1

Lindane 2

Methoxychlor 20

Pentachlorophenol 9

Radioactive Substances The effects of radiation exposure are called ‘Somatic’ if they manifest in exposed individual, and called ‘Hereditary’ if they affect the descendents. There is an increasing hazard of pollution of water supplies by radioactive substances. Malignant diseases are the most important delayed somatic effect. The radioactivity of water is measured in picocuries per liter (pCi/l). The WHO has proposed the following limits of radioactivity as acceptable :

Gross alpha activity 3 pCi/l. ●Gross beta activity 30 pCi/l. ●

Surveillance of Drinking Water QualityDrinking-water supply surveillance is “the continuous and vigilant public health assessment and review of the safety and acceptability of drinking-water supplies” (WHO, 1976). This surveillance contributes to the protection of public health by promoting improvement of the quality, quantity, accessibility, coverage, affordability and continuity of water supplies (known as service indicators) and is complementary to the quality control function of the drinking-water supplier. The following are the component steps for establishing a water quality surveillance system :

Table - 4 : Inorganic chemicals of health significance in drinking water

Constituents Recommended maximum limit of concentration (mg/lit)

Antimony 0.005

Arsenic 0.01

Barium 0.7

Boron 0.3

Cadmium 0.003

Chromium 0.05

Copper 2

Cyanide 0.07

Fluoride 1.5

Lead 0.01

Manganese 0.5

Mercury 0.001

Molybdenum 0.07

Nickel 0.02

Nitrate 50

Nitrite 3

Selenium 0.01

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a. Sanitary SurveyA sanitary survey is an on-site inspection and evaluation by a qualified person of all the conditions, devices, and practices in the water supply system which pose a danger to the health and well being of the water consumer. The hygiene inspection of the source, surroundings and site of water supply is carried out by making a plan and following it systematically. The site for obtaining water for human consumption from the selected source should also be properly examined before final selection. No bacteriological or chemical examination can take the place of a sanitary survey as the pollution is often intermittent and may escape the laboratory testing.

Sanitary Surveys should be undertaken when :

A new source is contemplated ●Laboratory analysis indicates hazard to health ●An outbreak of waterborne disease occurs in the area ●To interpret bacteriological, chemical and physical ●analyses of samplesWhen any change takes place that can affect the water ●system, e.g. industries coming up in watershed andAlso on a regular basis depending on size and available ●staff and resources and population / area under coverage. Majority of samples should be from problem areas, i.e. those with poor results in the past, low pressure zones, areas with high leakage, densely populated areas with inadequate sewerage, dead ends on pipelines, areas far away from waterworks etc.

b. Sampling Sampling of water should be done with strict aseptic precautions. It should be carried out by competent and trained personnel in accordance with the methods and frequency of sampling prescribed in the WHO guidelines for drinking water quality.

c. Bacteriological Surveillance The World Health Organization (WHO) recommends the measurement of E Coli in drinking water samples as the best indicator of water quality. The WHO guideline for potable water is less than one E Coli per 100 ml of drinking water (World Health Organization 1998). The following tests are conducted for bacteriological surveillance of drinking water :

Presumptive Coliform Test : The available methods are

Multiple Tube Method : This test is based on estimating the Most Probable Number (MPN) of coliform organisms in 100 ml of water. The test is carried out by inoculating measured quantities of the sample water (0.1, 1.0, 10, 50 ml) into tubes of McConkey’s Lactose Bile salt Broth with bromocresol purple as an indicator. If the samples can’t be inoculated on the spot then, they should be packed in ice and sent expeditiously to the laboratory. Bottles containing McConkey’s broth, the sample of water and a small inverted tube are incubated for 24 to 48 h at 37°C. The multiplication of the faecal organisms present in water under test produces acid and gas. From the number of tubes showing acid (as shown by the pink colour of the mixture) and gas, as seen in the inverted tubes, an estimate of the MPN of coliform group of organisms per 100 ml water

is ascertained from the standard tables. The estimates are therefore ‘presumptive’ and not actually existing. Details of the procedure are given by Cheesbrough (13).

Membrane Filtration Technique : In some countries membrane filter technique is used as a standard procedure to test for the presence of coliform organisms. A measured value of the water sample is filtered through a membrane made of cellulose ester. Bacteria present in water are retained on the surface of the membrane. The membrane is then directly inoculated face upwards on suitable media at appropriate temperature. Within 20 h the colonies grow and can be counted (13).

Faecal Streptococci and Cl. perfringens Detection : The significance of these two tests have been discussed earlier. Their presence provides useful confirmatory evidence of the faecal pollution of water.

Colony Count : The colony count on nutrient agar at 37ºC and 22ºC provide an estimate of the general bacterial content of water. A single count is of little value, but counts from the same source at frequent intervals are of considerable value. A sudden increase in the count serves as the earliest indicator of contamination and hence this test is gainfully used in the public water works. The recommended plate counts are given in Table - 6.

Table - 6

Water at consumer end

Plate count after 2 days at 37°C

Plate count after 3 days at 22°C

Disinfected 0 20

Not disinfected 10 100

Plate count on yeast extract agar at 22°C for 7 days is even a better indicator due to the absence of chlorine residue when there is uninhibited bacterial growth.

Colilert Method : Colilert is a recently available method to determine the MPN of coliforms. Colilert uses defined substrate technology to detect and quantify total coliforms and E Coli from water samples. Colilert is simpler to use, allows greater output and requires less time to standardize than standard methods. Colilert is an acceptable method to measure the presence and quantity of coliforms in water samples in a developing country setting (14).

Organic matterData on the level of organic matter in treated water provide an indication of the potential for the regrowth of heterotrophic bacteria (including pseudomonads and aeromonads) in reservoirs and distribution systems. Organic matter can be measured as Total Organic Carbon (TOC), Biochemical Oxygen Demand (BOD) or Chemical Oxygen Demand (COD). BOD is primarily used with wastewaters and polluted surface waters, and TOC is the only parameter applicable to drinking water. Measurement of these three parameters requires basic laboratory facilities and adequately trained personnel.

Hardness of WaterHardness of water may be defined as its soap destroying power. Hardness is undesirable because it wastes soap, retards washing, causes encrustation of the water carrying system and

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heating utensils resulting in wastage of fuel and even explosion of boilers (1, 4 - 7). Vegetables cooked in very hard water may be less digestible. It reduces the life of fabrics also. Hardness is of two types :

Temporary or carbonate Hardness : ● It is due to Calcium bicarbonate or Magnesium bicarbonatePermanent or non carbonate Hardness : ● It is due to Calcium sulphate, Magnesium sulphate, Chlorides and nitrates of calcium and magnesium or else Iron, manganese and aluminium compounds

Hardness is expressed in terms of milli-equivalents per litre (mEq/L). One mEq/L of hardness producing ion is equal to 50 mg (CaCO3) (50 ppm) in one litre of water. The four grades of describing hardness are : Soft water : <1 mEq / L (<50 mg/L); Moderately Hard : 1-3 (50 - 150 mg/L); Hard Water : 3-6 (150-300 mg/L); Very Hard Water : >6 (>300 mg/L). Softening of water is recommended when hardness exceeds 3 m Eq/L.

Drinking water should be moderately hard. It has been observed that in some localities supplied with soft drinking water showed a significantly higher prevalence of either arteriosclerotic heart disease, degenerative heart disease, hypertension, sudden death of cardiovascular origin, or a combination of these. However, it is based on purely circumstantial evidence and further studies are in progress to establish the association.

The methods of removal of hardness are briefly stated as below:

Temporary Hardness : This can be removed by boiling, addition of lime, addition of sodium carbonate or by permutit process.

Permanent Hardness : This can be removed by addition of sodium carbonate or by base exchange process.

Fluoridation of WaterFluorine is naturally present in water supplies. Its removal is necessary when the concentration in drinking water is more than 1.5 ppm. The optimum concentration in countries like India where people consume a lot of water should be between 0.5 to 0.8 ppm. Fluoride concentration over 1.5 ppm causes dental fluorosis. A still higher concentration causes skeletal fluorosis. People in the States of Rajasthan and Punjab are presently facing this problem of water supply. The excess quantity of fluoride in water may be removed by ‘Nalgonda technique’. On the other hand if fluoride content of water is less than 0. 5 ppm then it is associated with dental caries. The term ‘Flouridation’ has been given to the process of supplementing the natural fluoride content of potable waters to the point of optimum concentration.

Detection of Poisons in WaterWater is the most vital source of all kinds of life on this planet. There is every possibility of sabotage of the drinking water source by the enemy/militants. It must be ensured that water is free from poisons before it is declared potable. Testing of poison in drinking water requires elaborate laboratory facilities, which are not possible in remote areas. A set of Kit has been developed by DRDE Gwalior and marketed by Hindustan Metal Industries, Nai Sarak, Gwalior-1(MP) keeping in view the above requirement and facilitated testing of most commonly present poisons, sulphur mustard, nerve agent and microbial

contaminations. The kit is housed in aluminium container having shoulder strap to carry for field use. The kit is provided with the reagents/material, sufficient for testing poisons 50 times.

Sanitation of Swimming PoolA swimming pool is an artificial structure where water volume per swimmer is relatively small. The recommended area is 2.2 sq m (24 sq ft) per swimmer. The water is thus exposed to contamination by ammoniacal and other organic substances as well as organisms from skin, nasopharynx and other orifices of the swimmer. The health hazards associated with swimming in these pools are usually fungal, viral and bacterial infections of the skin, eye, ear, nose, throat and upper respiratory tract, intestinal tract and so on. Proper maintenance of pools is, therefore, of vital importance. General guidelines on sanitation of swimming pool are being given in subsequent paragraphs. Further details are available in standard texts (15).

A continuous inflow or a daily change of water, though ideal, is usually not feasible. The modern pools are equipped with continuous filtration and chlorination system. The “fill and empty” system is also encountered. Considerable attention is thus necessary to ensure that water is maintained continuously in a pure state in such pools. If the water is turbid provision for sedimentation in a separate settling tank may become inescapable. The water must be renewed at least once a week and 10-15 percent of the water should be replaced by a fresh daily inflow. When the pool is emptied, the floor and the sides should be thoroughly scrubbed and lime washed. Addition of copper sulphate 2g per 1000 l once a week will prevent algal growth and accumulation of slime.

Chlorination is carried out by injecting gaseous chlorine by the use of chloronome. Continuous maintenance of 1 ppm of free residual chlorine provides adequate protection against bacterial and viral agents. When chloronomes are not installed or not functioning, the required amount of WSP as calculated by Horrock’s test is first made into a thin mixture and distributed evenly over the surface of water. The water is then stirred with paddles. Subsequently, each day until the next filling, half that amount of WSP should be added half an hour before the swimming time. Tests for free residual chlorine is to be carried out daily half an hour after adding WSP. It will be ideal to keep the pH of water between 7.4 to 7.8 as irritation of eyes due to chloramine formation will be minimum. In a swimming pool the process of chlorination preferred is ‘breakpoint’ chlorination. When chlorine is added to water it immediately forms chloramines with ammonia, which is always present. The process continues till all the ammonia present is used up and the concentration of chloramines reaches its peak. Chloramines are, however unstable and react with excess free chlorine present in water and get oxidized completely to nitrogen and thus water contains no longer any free chlorine. Break point is said to have been reached when water no longer gives ‘flash’ reaction of free chlorine. Any further addition of chlorine hereafter causes a proportionate rise in the residual free chlorine, which acts as efficient germicidal agent. The bacteriological quality of swimming pool water should reach as nearly as possible the standard of drinking water. The test should be carried out weekly.

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Water Supply in Emergencies and DisastersThe following is a list of hygiene practices that protect health in disasters and emergencies.

People’s ability to achieve these protective actions depends on the availability of material resources, such as adequate clean water, soap, toilets, etc. and personal resources, such as time and energy. The details are shown in Table - 7.

The International Drinking Water Supply and Sanitation Decade 1981-1990 (16, 17)The ‘Decade’ was launched at a special meeting of the United Nations General Assembly on 10 November 1980 following the recommendation of the UN Water Conference at Mardel Plata in 1977. The priority given by the above conference to the provision of safe water supply and sanitation was influenced by the joint report of WHO and World Bank which showed that in 1975 some 1230 million people were still without safe water supplies and 1350 million people had lack of adequate sanitation facilities. Among the rural populations of developing countries, only 22 percent had access to reasonable safe water and only 15 per cent had facilities for excreta disposal. The Mardel Plata action plan also urged the individual countries to establish goals for 1990, which match the global target of the Decade. In India, under the International Drinking Water Supply and Sanitation Program the laid down target was 100 percent safe water supply, in both urban and rural areas. As per available reports, till 1994-95, 85 percent of the target has been achieved.

Targets of the Decade (1991-2000) : The targets were fixed by the Indian Government for the decade as

100% urban and rural supply ●50% urban sanitation ●25% rural sanitation ●

The Guinea worm eradication programme was linked with this decade. In 1986 the National drinking water Mission (NDWM) popularly unknown as Technical Mission was launched in order to provide scientific and cost effective content to the centrally sponsored Accelerate Rural water supply programme. In 1987 the National Water Policy was announced that has given high priority to drinking water.

Eleventh Five Year Plan (2005-2012) in Relation to Safe Water SupplyPast Programmes and Outlays : Government of India’s major intervention in water sector started in 1972-73 through Accelerated Rural Water Supply Programme (ARWSP) for assisting States/UTs to accelerate the coverage of drinking water supply. In 1986, the entire programme was given a mission approach with the launch of the Technology Mission on Drinking Water and Related Water Management. This Technology Mission was later renamed as Rajiv Gandhi National Drinking Water Mission (RGNDWM) in 1991-92. In 1999, Department of Drinking Water Supply (DDWS) was formed under the Ministry of Rural Development (MoRD) to give emphasis on rural water supply as well as on sanitation. In the same year, new initiatives in water sector had been initiated through Sector Reform Project, later scaled up as Swajaldhara in 2002.

An investment of about Rs.72,600 crores has been made (under both State and Central Plans) from the beginning of the planned era of development in rural water supply sector. This investment has helped to create assets of hand pumps, public stand posts, mini-piped water supply schemes and multi village schemes in the country under the Rural Water Supply Programme.

The Swajaldhara programme was launched in 2002-03. The programme involves a community contribution of 10% of the

Table - 7 : Water Safety

At the source

Water for drinking is collected from the cleanest possible source. If necessary, a distinction is made between water for drinking and water for other uses, such as bathing, laundry, watering animals.

Water sources are protected from faecal contamination by fencing (to keep animals away), and by siting latrines or defecation fields at least 10 - 30 metres away, depending on ground conditions.

Collection, storage and use of water at household level

Water is collected and stored in clean, covered containers. Water is taken from the storage container with a clean, long-handled dipper or through a tap placed slightly above the bottom container.

Efforts are made not to waste water.

Use of water If there is a risk that water is not safe, it is filtered and/or chlorinated or boiled.

Water for making food or drinks for young children is boiled.

Personal Hygiene

Water for washing If possible, plenty of water is used for washing. Clothing is laundered regularly.

The most readily-available water is used for personal and domestic hygiene.

Hand-washing All family members wash their hands regularly : after defecating; after cleaning a child who has defecated and disposing of the stool; before preparing food; before eating; before feeding a child.

Adults or older children wash the hands of young children.Note : To make water safe for drinking, it should be brought to a vigorous rolling boil. If boiling or chlorination are not possible at household level, then low-turbidity water may be disinfected by exposing it to bright sunlight for at least one day (Reed 1997).

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project cost to instill a sense of owner ship among the people and also to take over the O&M of the schemes constructed under the programme. The Centre provides 90% of the project cost as grant. The proportion of population covered till now is shown in Table - 8.

Table - 8 : Percentage of population covered with Water Supply Facilities

YearUrban Population

(million)Percentage of Population

Covered with Water Supply

1981 152 78

1991 217 84

2001 285 89

2004 308 (Projected) 91

Eleventh Five Year Plan Targets for Rural Water Supply : To “Provide clean drinking water for all by 2009 and ensure that there are no slip-backs by the end of the Eleventh Plan” is one of the monitorable targets of Eleventh Five Year Plan. Under Bharat Nirman Programme it is proposed to provide safe drinking water to all habitations. The Government is also committed to provide 100% coverage of water supply to rural schools. The ARWSP includes school water supply also. Accelerated Rural Water Supply Programme has provision of water supply to existing schools; the new schools are covered under other programmes like Sarva Shiksha Abhiyan of Ministry of Human Resources Development.

Strategies during the Eleventh Five Year Plan : In order to achieve 100 per cent coverage of clean water and sanitation in rural areas, rural sanitation programme will be linked with the National Rural Health Mission. Efforts will be made to launch a Sarva Swasthya Abhiayan in the county that will cover the primary health care, safe drinking water and sanitation in urban areas. The strategies include :

Convergence of health care, hygiene, sanitation and ●drinking water at the village levelParticipation of stake holders at all levels, from planning, ●design and location to implementation and management of the projectsInstitution water quality monitoring and surveillance ●systems by involving PRIs, community, NGOs and other civil society organizationsIncreased attention to IEC campaign ●

Local Participation

Involvement of the community in the monitoring of the water supply works is recommended. Department of Drinking Water Supply has initiated monitoring of the water quality under the National Rural Drinking Water Quality Monitoring and Surveillance Programme under which the Gram Panchayat/Village Water and Sanitation Committee provided with user friendly field test kits for testing both bacteriological and chemical contaminants followed by testing of the samples at district and state level laboratories. Such initiatives need to be extended to the other regular programmes under the Accelerated Rural Water Supply Programme also.

Recommended Outlays for Eleventh Five Year Plan : The full coverage of rural drinking water supply is to be achieved by March 2009 and 100 % sanitation coverage by the end of Eleventh Plan (2012) with mass awareness and Nirmal Gram Puraskar. The Eleventh Plan Central sector GBS is Rs.41,826 crore (at 2006-07 prices) and Rs.47,306 crore (at current prices) and this provision will draw matching provision in the State Plan to the tune of Rs. 49,000 crore. Thus the total outlays in the Eleventh Five Year Plan for Rural Water Supply & Sanitation sector would be close to Rs. 1,00,000 crore. The total outlay for Urban Water Supply and Sanitation sector would be Rs. 75,000 crore.

SummaryFor drinking water to be wholesome it should not present a risk of infection, or contain unacceptable concentrations of chemicals hazardous to health and should be aesthetically acceptable to the consumer. The infectious risks associated with drinking water are primarily those posed by faecal pollution, and their control depends on being able to assess the risks from any water source and to apply suitable treatment to eliminate the identified risks. Rather than trying to detect the presence of pathogens, at which time the consumer is being exposed to possible infection, it is practice to look for organisms, while not pathogens themselves, that show the presence of faecal pollution and therefore the potential for the presence of pathogens.

It is also important to be able to check on the effectiveness of treatment processes at eliminating any pathogens that might have been present in the untreated source, and ‘indicator’ organisms fulfil that role. Treatment should be able to eliminate all non-sporing bacteria and enteric viruses and the less restricted the parameter chosen the more suitable it should be. Water quality can deteriorate in distribution due to ingress or regrowth and measures of regrowth potential are described.

Study ExercisesMCQs1. Which of the following is considered an adequate water

supply/head/day in urban areas (a) 50-100 L (b) 100-150 L (c) 150-200 L (d) 200-250 L

2. Purest water in nature is from (a) Lakes (b) Springs (c) Rains (d) Ponds.

3. Salt concentration in sea water is (a) 1.5% (b) 2% (c) 3.5% (d) 5%.

4. Ground water has the following advantages : (a) Likely to be free from pathogenic organisms (b) Usually requires no treatment (c) Supply is likely to be certain even during dry season (d) Likely to be hard.

5. Guinea worm disease was a health problem where there were : (a) Dug wells (b) Artesian wells (c) Tube wells (d) Step wells.

6. Which one of the following is not a waterborne disease : (a) Kala azar (b) Poliomyelitis (c) Giardiasis (d) Roundworm

7. The vital layer of the slow sand filter is also known as : (a) Superficial layer (b) Sand bed layer (c) Schmutzdecke (d) Chemical layer.

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8. The disinfecting action of chlorine is mainly due to (a) Chloride atom (b) Hypochlrous acid (c) Chloride ion (d) Hypochlorite ion.

9. Action of chlorine is maximum when water pH is around (a) 3 (b) 5 (c) 7 (d) 9.

10. Chlorination does not affect in normal doses (a) Salmonella (b) Polio (c) Shigella (d) HIV.

Answers : (1) b; (2) c; (3) c; (4) d; (5) d; (6) a; (7) c; (8) b; (9) c; (10) b.

ReferencesGovt of India, Ministry of Urban Development, Central Public Health and 1. Environmental Engineering Organisation. Manual of water supply and treatment. New Delhi, 3rd Ed, 1999.C K Varshney. Eutrophication in book Water pollution and management. 2. Wiley eastern limited, 1991; 12-17L Fewtrell, J Bartram. Water Quality : guidelines, standards and health : 3. assessment of risk and risk management for water related infectious disease. WHO, Geneva 2002Wagner EG, Lanoix JN. Water supplies for rural areas and small communities. 4. World Health Organisation Publications WHO, Geneva, 1959.Fair GM, Geyer J, Okun DA. Elements of water supply and waste water 5. disposal. John Wiley and Sons, New York. 1st Ed 1971.Cox CR, Operation and Control of water treatment processes. World Health 6. Organisation, WHO Geneva, 1964.Bhattacharya JK. BN Ghosh ‘s treatise on hygiene and public health. Scientific 7. Publishing Co, Calcutta 15th Ed 1970. Section VI (water) : 37 94.World Health Organisation. Guidelines for drinking water quality. Volume 8. 3 : surveillance and control of community supplies. WHO, Geneva, 2nd Ed 1997.

World Health Organisation. Guidelines for drinking water quality. Volume 1 9. : Recommendations. WHO, Geneva, 1993.World Health Organisation. Guidelines for drinking water quality. Volume 2 10. : Health criteria and other supporting information.Govt of India, Indian Council of Medical Research. Manual of standards of 11. quality for drinking water. ICMR Report No.44, 1975.Govt of India, Indian Council of Medical Research. Manual of methods for 12. the examination of water, sewage and industrial wastes. ICMR, New Delhi, 1963.Cheesbrough M. Medical Laboratory Manual for tropical countries.Volume 13. II. ELBS, Butter Worth Hienemann and Tropical Health Technology. 1st Ed 1984, reprint 1993 ; p 212 20.Macy, J.T., Dunne, E.F., Angoran-Benie, B., Kameln-Tano, Y., Kouadio, 14. L., Djai, K.A., & Luby, S.P. Comparison of two methods for evaluating the quality of stored drinking water in Abidjan, Cote d’Ivoire, and review of other comparisons in the literature. Journal of Water and HealthVol 3 No 3 2005; p 221-228.Dunham GC. Military Preventive Medicine Military Service Publishing 15. company Phildelphia USA. 3rd Ed. Chapter VII : Sanitation of swimming pools : p 375 408.World Health Organisation. Drinking water and Sanitation decade, 1981 16. 1990 : A way to Health. WHO, Geneva, 1981.The United Nations. United Nations Development Programme. International 17. Drinking water Supply and Sanitation Decade. 1, UN Plaza, New York, NY 10017, USA.

Further Suggested Reading : Govt of India, Ministry of Urban Development, Central Public Health and 1. Environmental Engineering Organisation. Manual of water supply and treatment. New Delhi, 3rd Ed, 1999.

122 Excreta Disposal

Rajul K Gupta

Disposal of human excreta assumes greater importance than any other waste. The methods of disposal can be classified as follows :

(a) Insanitary Methods : These include open defecation and conservancy system.

(b) Sanitary Methods : These are further subdivided into two methods, depending whether sewerage (water carriage system) is available or not, as follows :

Unsewered Areas : The methods include trench latrine, dug ●well or bore hole latrine, water seal latrines, septic tanks, aqua privies and chemical closets.Sewered areas : The system in these areas includes the ●standard sewerage system.

Sanitation Barrier : The sanitation control which aims at interruption of transmission of the disease agent from the reservoir to the new host can be achieved at several levels such as segregation of excreta and wastes, protection of water supply, protection of food and drinks, control of flies and the

practice of personal hygiene. The most effective measure out of all these would be segregation of excreta and arrangement for its proper disposal so that the disease agents do not get a chance to reach the new host. The sanitation barrier (Fig. 1) in the simplest way can be provided by a sanitary latrine and a disposal pit.

Fig. - 1: Sanitation Barrier

Protected Host

Excreta

WaterFingers

Flies

Soil

FoodSani

tatio

nba

rrie

r

Excreta Disposal in Non-Sewered AreasOpen defecation fields In some cultures, defecating in the open is preferred to using a latrine. Open defecation can never be accepted as a satisfactory system of excreta disposal but it might be inevitable in certain circumstances. In these situations, open defecation areas

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should be clearly demarcated rather than littering the entire area. The principles of hygiene must be kept in mind (as discussed below) and the method must be followed for as short a period as possible. Open defecation may be the only option (for a displaced population in disaster) in the initial phase and might work well for 24 to 48 hrs, provided appropriate facilities of open defecation areas are set up and the following aspects are carefully considered. The community must be encouraged to use better alternatives as soon as the latrines are ready for use.Locationa) It should be located as centrally as possible to the people

who are going to use it (within 50-100 m or 1 minute walking distance, of shelters if possible) but away from public buildings or roads.

b) It has to be located at least 30m, preferably 50m from water sources or food storage/preparation areas. The fields where crops are grown should not be used for this purpose.

c) It is preferable to have adequate space and vegetation to allow people to find an appropriate defecation space so that there is enough privacy.

d) The field should be surrounded by a drain so that surface water cannot enter it and to prevent any runoff from the field contaminating other areas.

e) The field should be on land sloping away from the camp and surface water sources and downhill of settlements. Consideration should be given to the direction of prevailing winds, to reduce the nuisance caused by odour. Areas subject to flooding or containing running water should be avoided. The soil should be easy to dig so that faeces can be buried.

Setting up : As a first measure, it may be necessary to make temporary open defecation fields by just marking off areas with tape. Defecation areas or fields may be surrounded by screening/ plastic /canvas sheeting. Segregated sites for each sex are desirable.Usage a) Attendants will need to be recruited and provided with

training to encourage correct use and hand-washing.b) Users need to be encouraged to use one strip of land at a

time and the strip furthest away from the entrance. Used areas must be clearly marked.

c) Users should cover the faeces with soil.d) Provide anal-cleansing materials (water in small pots /

mugs) and methods for their safe disposal.e) People must wash their hands afterwards. A 200 lit plastic

barrel or a large bucket fitted with tap can be situated at the entrance of the area for hand-washing. Soap or ash should also be provided for effective hand washing. If soap or ash is not available, a barrel can be filled with 0.05% chlorine solution. This can be made by adding half a tablespoon (7.5g) of High Test Hypochlorite HTH (70% active chlorine) granules, or 15g of bleaching powder (approx 35% active chlorine), to 10lit of water.

Service Type Latrines (Conservancy System)In the conservancy system, night soil is removed by a human agency using a bucket. Night soil is transported in buckets

on the head or in night soil carts manually to a disposal site. Disposal may be done through dumping, composting or burial by shallow trenching. This is totally unacceptable not only considering human dignity but is not acceptable through hygiene point of view either. It is filthy and insanitary. Night soil lying at home awaiting disposal stinks and attracts flies. The collection, transport and disposal of night soil, all perpetuate the infection cycle. Absence of manpower for this job puts the system to a halt.

It was recommended by the Environmental Hygiene Committee, in 1949, that service areas must be replaced by sanitary latrines. The founder of Sulabh International, Dr B Dubey, also took up the issue in a big way. He showed the way forward by almost revolutionizing the sewage disposal to eliminate human carriage of night soil and installing low cost sanitary latrines instead.

Shallow Trench Latrines Shallow trench latrines are trenches 20-30cm (about a foot) wide and 15-30cm (about ½ -1 foot) deep. The dimensions can however vary. The trench field can be divided into strips 1.5m wide with access paths. Trenches are dug in parallel with an interval of at least 60 cm in between two trenches. The earth removed should be neatly piled at its head end which could be used to cover the excreta by each user, and subsequently to fill the trench. The issue of privacy is also important. Plastic sheeting, bamboo-mat etc. can be used to make ‘walls’ (Fig.-2). The trench is used by squatting astride it, with a foot on either side and not both feet on the same side. After defecation the excreta must be covered by earth with a scoop.

Advantages : It is rapid to implement. Faeces can be covered easily with soil.

Constraints : Limited privacy, short life and requirement of considerable space are some of the constraints. Fly breeding occurs if excreta is not covered with earth.

Deep Trench Latrines Deep trench latrines could be an appropriate short term solution to the immediate requirements of a displaced community or for camps of a longer duration(1, 2). While they are much more hygienic than the Shallow Trenches and can be used for a relatively prolonged period but at the same time more manpower, tools and materials are required to set them up. The recommended maximum length of trench is 6m, providing six cubicles. Trenches should be 0.8m -1m wide and 2m - 2.75m deep. (Fig. - 3). A deep trench latrine of the above dimensions (80 cm to 100 cm wide by 2 m to 2.75 m deep) which is 3.75 m long can be used by 100 people for few months. One must work on a minimum standard of at least one ‘toilet seat’ for every 20 persons (1,3).

Advantages : It is cheap and quick to construct; no water is needed for operation. It is easily understood by the community.

Constraints : Unsuitable where water-table is high, soil is too unstable to dig or ground is very rocky; often odour problems; cleaning and maintenance of communal trench latrines are often poorly done by users.

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Fig. - 2 : Shallow trench latrines (1)

Image courtesy of WEDC. © Ken Chatterton

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Fig. - 3 : Deep Trench Latrine (1)

Image courtesy of WEDC. © Ken Chatterton

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Improvised Deep Trench Latrine An improvisation of Deep Trench Latrine may be carried out by placing the seats fitted with modified water closets, 1.5m in front of the long edge of the trench. As many as 3 to 5 Indian type water closet seats of plastic / fiber glass / chinaware are fitted to enable maximum number of people use it simultaneously. The seats are fitted with a water seal (bend pipe) which is connected to a pipe leading into the trench. Small quantity of water (2.5 to 3 liters) is sufficient to flush the seats after each use. The excreta is flushed through sewage pipes into the trench. This type of latrine, therefore, is more hygienic and acceptable. It is similar in principle to the hand flushed water seal latrine. The water seal prevents access to flies by sealing off the night soil and escape of foul gases (4). A storm water drain dug all around prevents rainwater from entering the trenches.

Simple Pit Latrines (Dug Well Latrine)Simple pit latrines are simple and quick to construct and generally inexpensive. The pit should be as deep as possible (at least 2m in depth) and covered by a latrine slab. If the soil is loose, at least the top 1m of the pit should be lined to prevent collapse. This should be firmly supported on all sides and raised above the surrounding ground level to prevent surface water entering the pit. A squat or drop-hole is provided in the slab which allows excreta to fall directly into the pit-this can be covered with a removable lid to minimize flies and odour. The

superstructure can be made from materials available locally.

The advantages are that it is cheap; quick to construct; no water needed for operation. However, the constraints are that it is unsuitable where water-table is high, soil is too unstable to dig or ground is very rocky; often odour problems (Fig. - 4).

Improvised Pit Latrine (The Ventilated Improved Pit Latrine)This latrine is an improved pit latrine designed to minimize odour and flies. A vent pipe covered with a gauze mesh or fly-proof netting extending at least 0.5m above the superstructure roof is incorporated into the design to remove odorous gases and prevent flies entering and trap any flies trying to leave. Air should be able to flow freely through the squat hole and vent pipe; therefore no drop-hole cover is required. The superstructure interior is kept reasonably dark to deter flies, but there should be a gap, usually above the door, to allow air to enter (Fig. - 5).

Advantages : Reduced odour & flies and good results.

Constraints : Difficult and expensive and time consuming to construct properly; dark interior may deter young children from use; does not deter mosquitoes.

Borehole LatrinesEmergency demands quick work. A borehole latrine fulfills this requirement. It can be constructed very rapidly if an auger or

a drilling rig is available. Borehole latrines are most appropriate in situations where a large number of latrines must be constructed rapidly, and where pits are difficult to excavate, either because of ground conditions or the lack of a labour force.

Dimensions : The borehole has a typical diameter of 400mm and a depth of 5-10m. At least the top 0.5m should be lined (Fig. - 6).

Advantages : The borehole can be excavated quickly; suitable in hard ground conditions and appropriate where only a small workforce is available.

Constraints : Drilling equipment is required; there is a greater risk of groundwater pollution due to greater depth than pit latrines; lifespan is short; sides are liable to be fouled, causing odour and attracting flies; and there is a high likelihood of blockages. This option should only be considered in extreme

Fig. - 4 : Simple pit latrine (1)

Image courtesy of WEDC. © Rod Shaw

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conditions when pit excavation is not possible. A hole 300mm (1 foot) in diameter and 5 metres deep should last for (a family of) five people for two years.

Pour-Flush Latrines (Water Seal Latrines) Pour-flush (hand flush or water seal) latrine is a very hygienic mode of excreta disposal. It functions on the principle of a ‘water seal’. Water acts as a hygienic seal and helps remove excreta to a wet or dry disposal system. The simplest pour-flush latrines use a latrine pan incorporating a shallow U-bend which retains the water (water seal). After defecation, a few litres of water must be thrown into the bowl in order to flush the excreta into the pit or sewerage system below. Pour-flush latrines may be constructed directly above a pit or may be offset whereby the waste travels through a discharge pipe to a pit or septic-tank (Fig. - 7).

Dimensions : The amount of water required to flush the system will depend on the type and size of the water-seal construction. A 90mm (3”) U-bend normally requires 2-3 litres to flush effectively, while a 120mm (4”) U-bend generally requires 4-5 litres to flush. These quantities are significantly less than the amount required to flush most western water-closet toilets which may use as much as 15 litres per flush.

Advantages : Lack of odour; relatively less water is used up. It is ideal where water is used for anal-cleansing; easy to clean; off-set design does not require a self-supporting latrine slab.

Constraints : Solid anal-cleansing materials may cause blockages; more expensive than simple pit latrines.

Variants : Several designs have been tried and are in use. Noteworthy of these are those made by Planning Research and Action Institute (PRAI), Lucknow and by Research cum Action Project (RCA), Ministry of Health. The RCA latrine is widely in

use.

Design of a RCA Latrine : The RCA latrine comprises of a squatting plate, made of an impervious material like cement-concrete. This is easy to clean and maintain. Raised footsteps are included in the squatting plate. There is a pan directly underneath the squatting plate. The pan receives the night soil. Pan is connected to the trap, which is a bent pipe. The trap holds water and serves as a water seal. The depth of the water seal is 2 cm (Fig. - 7C). It prevents access to flies and avoids release of odour. The trap is connected to the pit (which could be a dug well), through a connecting pipe. When the pit fills up another one can be dug up and pipe may be accordingly shifted. The pit can also be made directly underneath the pan; in that case there is no requirement of the connecting pipe. An appropriate superstructure can be made.

It is easy to maintain the latrine. Latrine is hand flushed by

Fig. - 6 : Borehole latrine (1)

0.5m

Depth5- 1

0m

(Depending

onwater

table)

Pipe lining(Greater length may berequired in unstableformations)

Cover Slab

Typical diameter400 mm

Solid accumulation

Image courtesy of WEDC. © Rod Shaw

Fig. - 5 : Ventilated Improved Pit (VIP) Latrine (1)

Image courtesy of WEDC. © Rod Shaw

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Fig. - 7 : Pour-flush latrines (1)

Image courtesy of WEDC. © Rod Shaw

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pouring 1 to 2 lit of water every time the latrine is used. The squatting plate should also be washed clean every day.

Certain modifications can be undertaken for more efficient functioning. A pre-fabricated Indian type of commercially available squatting plate made of china clay can be used instead of a concrete one. This would be most hygienic. Secondly, rather than using a ‘dug-pit’ for disposal of night soil, a septic tank can be built. One will have to incur extra cost on these modifications but these would make the latrine close to an ideal system.

Septic TankSeptic tank is an ideal system for hygienic final disposal of excreta in the absence of a central sewerage system. Excreta from many pour-flush latrines can be discharged into a septic-tank. A septic-tank is designed to collect and treat excreta and toilet wastewater. Its use is likely to be appropriate where the volume of wastewater produced is too large for disposal in pit latrines, and water-borne sewerage is uneconomic or unaffordable. Septic-tanks are, therefore, particularly suited to systems involving high water use, especially where water is used for flushing and anal-cleansing. However, they are difficult to manage for very large populations and are best suited to single households or a group of households or institutions such as hospitals or schools. The efficiency of a septic tank system is inferior to the sewage works but is much cheaper, quicker and easier to provide and maintain than sewage works.

Design and Construction : Septic tank consists of an underground concrete tank usually double chambered. A tank with more than two chambers is expensive and has no additional advantage. Even a single chambered tank has been found satisfactory for a small installation. The latrines should preferably be grouped together with one or more tanks placed close to a group. The sewers leading from the latrines to the tanks should have manholes at every 100m and at every change of direction. Two or more medium sized tanks arranged in parallel instead of one large tank are preferable as these facilitate removal of sludge without disturbing the functioning of the system.

The capacity of the tank should be at the scale of 20-30 gallons per user with a minimum size of 3mx3m (500 gallons). It may be 1.5 to 2m deep. The entire length of the tank should provide a minimum air space of 30 cm above the liquid level. The septic tank is covered by a concrete slab with a manhole in it. The aeration chamber should be ventilated by one or more shafts, the opening of which should be screened with wire-gauze. The inlet and exit pipes to the tank should be trapped. The effluent may be disposed into a soak-well (Fig. - 8).

Functioning : The septic tank functions by the biological process of anaerobic and aerobic digestion. The crude sewage on entry to the anaerobic chamber is allowed to stand for 2 to 3 days and is acted upon by the anaerobic microorganisms. A colloidal solution is formed which is only partially digested and hence has an offensive smell. The complete oxidation and mineralization of the colloidal matter is carried out by the aerobic micro-organisms in the aerobic chamber. Though most of the pathogens, after having undergone aerobic treatment, die but the cysts and ova of the intestinal parasites survive.

The effluent loses most of its offensive smell. The minerals are absorbed from the soil by the plants. The use of ordinary household soap in normal amounts is unlikely to affect the digestion process of a septic tank.

Maintenance : The operation and maintenance of a septic tank is simple. To commission a septic tank it has to be first filled with water and then seeded with a bucketful of sludge from another tank. Not less than 25 lit of water per day per user must enter the tank. Use of soap water and chemicals should be avoided. Sludge from the tank is to be bailed out once in a year or two. The tank cover or roof, which usually consists of one or more concrete slabs, must be strong enough to withstand any load that will be imposed. Removable cover slabs should be provided over the inlet and outlet. Circular covers, rather than rectangular ones, have the advantage that they cannot fall into the tank when removed.

Routine inspection is necessary to check whether desludging is needed, and to ensure that there are no blockages at the inlet or outlet. A simple rule is to desludge when solids occupy between one-half and two-thirds of the total depth between the water level and bottom of the water tank. The most satisfactory method of sludge removal is by vacuum cleaner.

Communal Aqua-Privies An aqua-privy is a latrine constructed directly above a septic-tank. Aqua-privies are appropriate where pit latrines are unacceptable. The amount of water required for flushing is much smaller than for a septic-tank due to the location of the tank. It helps to exclude odours from the superstructure.

Advantages : Reduced odour; ideal where water is used for anal-cleansing; easy to clean.

Constraints : Increased quantity of water required; solid anal-cleansing materials may cause blockages; more expensive and difficult to construct than simple pit latrines.

Minimum standards : Not more than four families per latrine.

Sulabh Shauchalaya The concept of Sulabh Shauchalaya was introduced by Dr B Dubey. He modified the standard hand flush latrine to suit rural Indian community. It consists of a specially designed pan and a water seal trap. It is connected to a pit 3x3x3 feet. Minimal water is needed in the process. The excreta gets decomposed to manure in the pit. Sulabh International also maintains a chain of Sulabh Shauchalayas, community latrine, across the country. This provides clean and sanitary toilets to the users at a minimal cost. These are also maintained by the Sulabh International society.

Chemical ToiletsChemical toilets are sanitation units that consist of a squatting pan placed above a water-tight excreta-holding tank, which usually contains a chemical solution (formaldehyde, etc) to aid digestion and reduce odour. This is contained in a single prefabricated plastic unit with a lockable door. These can be adopted as temporary solutions where pit latrines or septic-tanks are unsuitable or unacceptable, as in aircrafts or trains. The initial charge of chemical is adequate for 40 to 160 uses.

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Fig. - 8 : Septic tank (1)

Image courtesy of WEDC. © Ken Chatterton

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Uses : These are used in aircrafts and as a short term measure in disasters, etc.

Advantages : Portable; hygienic; minimized odour; can be mobilized rapidly.

Constraints : High cost; unsustainable for long periods; regular servicing and emptying required.

Water carriage systemThe water carriage system is useful for large residential and commercial. The human excreta and waste water are carried away by a network of underground pipes called sewers to the ultimate disposal site. Obviously this is the method of choice for urban areas having piped water supply (5). In India the water carriage system was used for the first time in Calcutta in 1867. But even today, unfortunately not more than 20 percent of the urban areas in India can boast of this method of sewage disposal. In large cities this is the ideal system of sewage disposal.

Laying down such a system is infrastructure and capital intensive. It amounts to digging up lanes and by-lanes. Skilled manpower is a must to establish the system. Piped water supply is mandatory to run the system. On - going maintenance has to be done to keep the pipes going. Importance of sewerage system was realized during floods at Mumbai in the year 2005 when heavy rains lashed Mumbai. The water carriage system being inadequate, ill maintained and choked, couldn’t cope up with the excessive rain water and caused flash floods. This had drastically disrupted life in the commercial capital of India leading to heavy economic losses and outbreak of Leptospirosis.

Classification There could be two types of sewerage systems, the combined and the separate systems. The combined system carries both sewage and storm water in the same sewage line. In the separate system, however, the surface water is not admitted into the sewers. The latter is the system of choice.

Components The water carriage system consists of house hold sanitary fittings, house sewers, street sewers and sewer appurtenances.

(a) Household Sanitary Fittings : These include water closets, urinals, washbasins, bathtubs along with their plumbing systems.

(b) Soil Pipes : These are pipelines, which carry excreta from the water closets to the house drain. They are fitted with outlet ventilators for the escape of foul gases and hence are placed outside along rear walls of the houses and are carried above the roof tops.

(c) House Drains : It is an underground iron or stoneware pipe usually of 10 cm diameter and is laid in the courtyard 15 cm below the ground level on a bed of cement concrete mix with sufficient gradient towards the public sewer. It carries away the discharges from the household sanitary fittings to the street sewers.

(d) Public Sewer : It is a network of underground pipelines varying in diameter from 22 cm to 3 m for carriage of sewage from domestic, industrial and commercial areas to the place

of final disposal. While laying the pipelines sufficient gradient is to be ensured for self-cleansing velocity of sewage. This velocity varies from 60 cm to 90 cm per second.

(e) Sewer Appurtenances : These are manholes and traps installed in the sewerage system :

(i) Manholes : Manholes are the openings built in sewers for the purposes of repairs and cleaning. They are placed wherever there is change in the direction of sewers, at the junction of two or more sewers and at a distance of 100 meters in the long, straight run of the sewers. Workers entering manholes are at a risk of gas poisoning and asphyxiation; so due precautions must be taken while entering them.

(ii) Traps : Traps are devices designed to prevent entry of foul gases inside the house and to remove sand, grit, grease etc. from sewage. Traps are placed at three points (1) under the water closet, (2) at the junction of the house drain and the street sewer and (3) where the surface water enters the sewers. There are several designs of traps. The simplest one is a bent pipe containing water as a seal (Fig. - 7C). The water seal in a trap is the distance between the highest level of water in the trap and the lowest point of the trap’s concave upper surface.

Composition of SewageSewage contains 99.9 percent water and 0.1 percent solids, which are partly organic and partly inorganic. Sewage teems with living organisms, some of which may be pathogenic. The strength of the sewage may be expressed in terms of biochemical oxygen demand, chemical oxygen demand and suspended solids.

Biochemical Oxygen Demand (BOD)It is defined as the amount of oxygen absorbed by a sample of sewage during a specified period, generally 5 days at a specified temperature, usually 20°C for aerobic digestion. This is the most important test carried out on sewage. Sewage with a BOD value of 300 mg/l (300 ppm) or above is termed as strong while that of 100 mg/l (100 ppm) or below is termed weak.

Chemical Oxygen Demand (COD) Chemical oxygen demand is the amount of oxygen required to oxidize the organic matter by use of dichromate in an acid solution and to convert it to carbon dioxide and water. The value of COD is always higher than the BOD because many organic substances can be oxidized chemically but not biologically. Commonly, BOD is used to test the strength of untreated and treated municipal and biodegradable industrial waste waters. COD is used to test the strength of wastewater that is either non biodegradable or contains compounds that inhibit activities of microorganisms.

Suspended solidsIf the suspended solids are 100 mg/l or more, it is termed strong.

Sewage PurificationThe aim of sewage treatment is to convert an offensive and potentially dangerous mixture into an inoffensive effluent and sludge which can be disposed off safely and without causing nuisance into river, sea or on land. The conversion of complex organic matter in the sewage to simpler substances takes

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place by two processes, viz aerobic and anaerobic. The aerobic method requires a continuous supply of free dissolved oxygen for the aerobic microorganisms to break the organic matter into simpler substances such as carbon dioxide, ammonia, water, nitrite, nitrate, sulphate etc. The anaerobic process is more effective where the sewage is highly concentrated and contains plenty of solids. Hence, this method is usually gainfully utilized for digestion of sludge in sewage works. The end products of anaerobic decomposition are methane, ammonia, carbon dioxide, hydrogen etc.

Sewage Treatment Plant : The sewage treatment undergoes through many stages. These can be conveniently divided into Primary, secondary and tertiary treatment stages.

Primary treatment : The first stage is the physical treatment ●to remove solids (from the liquid). This physical treatment is often referred to as primary treatment. Secondary treatment : The primary treatment is followed ●by biological treatment brought about by aerobic and anaerobic bacteria.Tertiary treatment : Treatment rendered in addition to the ●conventional secondary treatment for improving further the quality of effluent is termed ‘tertiary treatment’ or advanced waste treatment process. The sludge is also given treatment for stabilization and dewatering. Chemical treatment by the addition of coagulants may be used to assist sedimentation and sludge treatment. Flow diagram of a modern sewage treatment plant is shown in (Fig. - 9).

Primary Treatment(a) Screening : It is the first step in the sewage treatment for removing the larger solids. The raw sewage is passed through bar-screens with openings of 8 to 10 cm between the bars placed across the inflow channels. The screenings can be manually raked from the screens and buried.

(b) Grit Removal : Combined sewerage systems carry grit from roads or other debris from general sullage and fine granular

inorganic material. This material which otherwise causes heavy wear in pumps and tends to settle out and cause difficulty in later treatment processes must be removed in grit chambers and channels. The sewage is allowed to flow in a channel at a controlled velocity of about 30 cm/s, which is slow enough for the heavy non-organic solids to settle down but fast enough to carry the lighter organic solids forward. The grit is removed periodically, washed free of organic matter and dumped on waste land for reclamation or to fill excavations and quarries without causing nuisance.

(c) Primary Sedimentation : It is the third step to remove as much of the organic solids as possible from the liquid sewage. The same principles as those for the treatment of water are employed. Sedimentation tanks may be rectangular with a horizontal flow, hopper-shaped with vertical flow, or circular with radial centrifugal flow. Slow moving paddles to encourage flocculation of solids and increased settling velocities may be incorporated. The sewage is retained in sedimentation tanks for 4 to 12 hours. The process removes 50-60 percent of the suspended solids and about 40 percent of the BOD of the sewage. The settled sludge is removed by mechanical scrapers to hoppers from which it is drawn off either continuously or at frequent intervals to prevent it from becoming septic. The sewage is then treated biologically.

Secondary TreatmentThe secondary or biological treatment of sewage essentially involves the oxidation of suspended and dissolved organic matter by aerobic bacteria. Carbonaceous matter is converted to carbon dioxide and water, and nitrogenous material to ammonia, nitrites, and nitrates. Fungi, algae, ciliate protozoa, insects and worms supplement the bacterial digestion. The main processes employed for biological treatment are as under:

(a) Percolating or Trickling Filters : The effluent from the primary sedimentation tanks is brought into the percolating filter through a central pipe. The effluent is sprinkled uniformly

Fig. 9 : Flow Diagram of Modern Sewage Treatment Plant.

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on the surface of the bed by a revolving device. This device is nothing but an assembly of pipes with rows of multiple holes in them (spraying nozzles). The rotating pipes sprinkle a thin layer of effluent on the surface of the filter. This effluent then trickles down the filter. The percolating filter consists of beds 1.5 to 2 m in depth, made of stone, cinders, slag, brick pieces or other impervious material generally from 3 to 8 cm in size. The beds are usually circular. A slimy ‘zoogleal’ film of aerobic bacteria and other organisms develops on the surface of the stones. In trickling downward through the bed, the sewage donates its organic content to the vital zoogleal film for its nutrition and in return receives soluble organic salts produced by oxidation. Access of air through the filter is essential for the zoogleal fauna to oxidize the organic matter. A competent percolating filter plant reduces the BOD of the raw sewage by 85 to 95 percent. Percolation is followed by final settling into secondary sedimentation or humus tanks to remove the particles of the zoogleal matter and innocuous debris (Fig. - 10).

b) Activated Sludge Process : Activated sludge process is an alternative to the percolating or trickling filter method described above.

Principle : The principle is to add sufficient quantity of sludge obtained from the final settlement tank (called ‘activated sludge’ or return sludge) to sewage that is to be treated (the effluent from the primary sedimentation tank). Activated sludge contains active aerobic bacteria vital for decomposition of sewage. This mixture (called the ‘mixed liquor’) is mechanically aerated in an aeration tank to facilitate bacterial decomposition. In the presence of ample oxygen the aerobic bacteria utilize the raw sewage and convert it into stabilized, odourless compounds.

Process : The process requires air supply and thorough mixing which brings about an intimate contact of the organic solids with oxygen and aerobic bacteria. First the effluent from the primary sedimentation tank is mixed for an hour or two with the activated sludge returned from the final sedimentation tank to form the ‘mixed liquor’. Now the oxygenation of this mixed liquor is carried out for 4 to 6 hours by one or more of these methods : (i) Diffused Air System : Compressed air is blown through

porous plates, domes or pipes fixed at the bottom of aeration channels (Fig. - 11).

(ii) Simplex Surface Aeration : Motor driven propellers are used

Fig. - 10 : Diagrammatic section of a percolating Filter for biological treatment of sewage

Fig. - 11 : Conventional Activated Sludge Process

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to mix and break up the sewage into fine spray, bring it in contact with air and induce circulation in hopper bottomed chambers.

The plant : The plant consists of a long channel or a series of chambers through which the sewage passes while aeration process proceeds. The aeration is followed by settling in tanks. The sludge is removed and the clear purified final effluent flows out for safe discharge. Most of this activated sludge is returned to be mixed with the sewage from the primary settling tanks as described above. Thus there is a continuous circulation of activated sludge within the system.

The activated sludge method is a more efficient than trickling filter method. Activated sludge plant occupies one tenth of the space occupied by a trickling filter and is also faster. This however is costlier to install and run. It is best suited for large towns.

Following secondary treatment, there are two types of substances that are left, viz., the semisolid sludge and the watery effluent. These two products are dealt in the following ways :

Sludge TreatmentThe sludge from primary or final sedimentation tanks contains 90 to 95 percent water. This high water content needs to be reduced for converting the sludge to a solid condition in which it may be used or disposed off harmlessly. Anaerobic digestion is the most preferred sludge treatment method. The sludge is pumped daily into enclosed digestion tanks. With anaerobic fermentation a gas comprising of about 70 percent methane and 30 percent carbon dioxide is produced. This sludge gas is a valuable fuel. It can be used to generate the entire power needed for running the activated sludge plant. Power is used for pumping, air compression, electricity generation, and heating on the plant. The surplus gas may be compressed and used as vehicle fuel or cooking.

For most effective digestion and gas production, the digesters are heated to about 32ºC. Digestion converts much of the organic solids to gas and soluble matter, and so reduces the quantity of solids to be handled eventually. Digested sludge is a black liquid with a tarry odour and is more amenable to subsequent dewatering than undigested sludge. Apart from digestion, the main object of sludge treatment is to de-water it so that it can be handled as relatively compact, moist solid rather than as a much greater volume of liquid with a low solid content. The following processes are used for dewatering the sludge and may be applied to either raw or digested sludge.

a) Air drying : Liquid sludge, after digestion, is placed on sand beds for air drying. Percolation into the sand and evaporation are the chief processes involved in the dewatering process. Air drying requires dry, relatively warm weather for greatest efficiency, and some plants have a green-house like structure to shelter the sand beds. The semisolid sludge, which is left, is lifted manually or mechanically. Dried sludge in most cases is used as a soil conditioner; sometimes it is used as a fertilizer.

b) Lagooning : Sludge is stored in open basin, a few meters deep to allow settlement of solids. Clarified liquid may be drawn off, and the solids are eventually dug out.

Sewage sludge contains useful nitrogen and phosphorus, and although rather deficient in potassium, it forms a moderately good fertilizer. Undigested primary sludge and undigested activated sludge are easier to apply to land, and their humus content improves the soil. In suitable circumstances sewage sludge may be composted with municipal refuse. Where sludge cannot be used either as a fertilizer or for composting, or, in a few cases, for recovery of by-products, it is usually tipped for land reclamation, dumped at sea, or incinerated.

Disposal of Effluent The effluent after treatment is usually discharged on land or into water bodies.

a) Disposal on Land : If suitable land is available the effluent can be used gainfully for irrigation purposes. Over the past few decades, there has been a considerable revival of interest in the use of wastewater for crop irrigation in arid and semiarid regions owing to the scarcity of alternative water supply and the need to increase food production. Reuse of treated effluent for the irrigation of crops and urban ‘green spaces’ (such as parks and golf courses) has expanded significantly in many countries.

Risks in sewage farming : Enteric viruses appear to be particularly persistent in sewage, under natural conditions. Sewage farming or spread of treated effluent on farms is still used in many countries, particularly those having low rainfall and high temperatures. Enteric viruses have been found in raw sewage in concentrations of 1-10 per ml in various countries. Thus the risk of transmission of infections through sewage farming remains alive. The risk increases if the sewage had not been treated adequately, prior to its discharge for sewage farming.

(b) Disposal by Dilution : Discharging the effluent into bodies of water such as rivers, streams, lakes and sea for the purpose of dilution and oxidation of the impurities by the dissolved oxygen in water is termed as “disposal by dilution”. The BOD content of the effluent and diluting capacity of the bodies of water are the important considerations before discharging effluent into the water body. Since river water is used for drinking, effluent must be adequately treated before discharging. Lately industrial waste and chemicals are being dumped into the sewage, which poses a threat to people’s health, when the effluent is eventually discharged into rivers. The aquatic flora and fauna is also adversely affected.

Oxidation pondOxidation pond is also known as the “Redox Pond, Sewage Lagoon and Waste Stabilization Pond”. It is probably the cheapest method of satisfactory sewage disposal. It is an open shallow pool up to 5 feet deep with an inlet and outlet. The presence of algae, bacteria decomposing organic matter and sunlight are mandatory for the functioning of oxidation pond. Bacteria oxidize sewage to carbon dioxide, ammonia and water. The algae, with the help of sunlight utilize carbon dioxide, water and other organic substances for its growth. Algae releases oxygen during photosynthesis, which is used by bacteria. So the pond works as an aerobic system during the sunlight hours, and anaerobically during the dark (night) hours, especially in the lower layers (Fig. - 12). The effluent can be used for farming

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or can be discharged into rivers after suitable treatment. If the pond runs well, it is an accepted method for sewage disposal in small communities.

Fig. - 12 : Oxidation Pond

Oxidation Ditch/Aerated Lagoon (6)This process used in oxidation ditch or aerated lagoon utilizes mechanical rotors for extended aeration and thus minimizes the requirement of land area. The land requirement in this method is barely one tenth of oxidation pond. During primary sedimentation itself, a reduction of 30-40% in the number of coliforms is obtained (as against 90% and 95% in other biological treatment processes). On stabilization with a 30-day retention, coliforms reduce to 99 - 99.9%. Most other vegetative bacterial pathogens also appear to be removed in the same proportion as coliforms. Certain helminthic eggs may be effectively removed by primary sedimentation and even more effectively by stabilization pond treatment of 5-7 days duration; viruses are less effectively removed. Coagulation and filtration remove 98 to 99.9% of viruses.

Ponds have the advantage of providing a fairly high degree of treatment at relatively low cost, with minimal requirement of equipment or skilled operators.

Biolatrine (Biogas plant)The biolatrine is an example of ‘appropriate technology’. It not only takes care of the sewage in an efficient manner, the gas obtained as a by-product is utilized for cooking. Moreover the digested substrate may be utilized as fertilizer (18 - 20). It functions on the principle of anaerobic degradation of excreta. The main focus is however mostly on sanitary aspects, i.e. clean toilets with low maintenance demand, rather than high gas productivity.

Design : Biolatrines are designed as integrated fixed-dome biogas plants, where up to 6 latrines can be installed around a dome. The main advantage of biolatrines is that they are generally run without water (except for the start-up phase) thus substantially reducing water demand and related costs. The urine will provide sufficient liquid for the substrate to be able to flow. The toilet chamber is connected to a vent pipe corresponding to those of the VIP latrine. The soil conditions is a consideration and should allow effluent and slurry

absorption.

Usage : A biolatrine may only be an appropriate if at least 25 people are connected to its use. The excreta of 25 people will produce an average of about 1 m³ of biogas per day (40 l per person a day), representing the approximate cooking energy demand of one household. For institutions with 500 or more people, the produced biogas may supply sufficient energy for a canteen. Application may occur for institutions like schools, prisons, religious centres, or for public facilities like markets. In Ralegaon Siddhi (Dist. Ahemednagar), Maharashtra community latrines have been connected to biogas plants. Biogas produced is being distributed to houses for cooking purposes.

Disposal of Animal ExcretaAnimal excreta is also required to be disposed off in a sanitary manner. It might not directly cause disease but it carries enormous potential for fly breeding. It can be managed by disposing it in biogas plants, sanitary land fill or composting (disposal along with biodegradable solid waste).

a) Disposal in Biogas Plant (Gobar Gas Plant) : In view of the increasing energy crisis, this method is gaining rapid popularity, particularly in countries having large cattle population. In this method the dung gets anaerobically converted into good quality manure under hygienic conditions and there is also generous liberation of biogas energy.

The digester is partly an underground masonry tank with an incomplete partition in the middle. It has an inlet and an outlet pipe. Dung mixed with water in equal proportion is put inside through the inlet. In the plant, excreta is often mixed with straw or other vegetable waste, and equal quantity of water is added to make slurry which is fed to the inlet side of the chamber. Effluent slurry is removed after retention time of 30-50 days. Biogas production is greater at higher temperatures. This gas can be used as fuel in the kitchen, for running engines, lighting and other purposes. A biogas plant is inexpensive, simple in construction, easy to handle and can be made locally from indigenous materials.

(b) Composting : It is often carried out in conjunction with solid waste and night soil. Chapter on solid waste disposal can be referred to for details.

SummaryEffective and hygienic disposal of excreta is called for not only as a social need but as a health need as well. Many diseases like cholera, typhoid, dysentery, diarrhoea, hookworm, roundworms, poliomyelitis, hepatitis etc can be transmitted through fingers, flies, food, fomites and water contaminated by excreta.

There are various methods of sewage disposal. While open defecation might still be a preferred method in many rural areas, it remains the most unsatisfactory one. It can only be resorted to in the eventuality of a disaster when the population is displaced and has to be accommodated in a relief camp for a short duration. The conservancy system (carrying excreta manually to the disposal site), is also a detesting method and is fortunately waning. In the areas where there is no sewage system, simple pit latrines (dug well latrine), bore hole can be used. But the pour flush latrine is the ideal one as it contains

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an eater seal. PRI and RCA types are its modifications that are in use.

Septic tank is a suitable method of final disposal of night soil. Trench latrines (deep and shallow) can be used for camps for short durations. Chemical closets are also used for short duration use.

Water carriage system is the ideal system of sewage disposal and is used in large cities. Networks of pipes from households connect to a labyrinth of underground sewage pipes to the final disposal site, i.e. the sewage treatment plant. Biological and mechanical processes break down the sewage into innocuous products that can be discharged safely into land or water bodies.

Other methods of sewage disposal are the oxidation pond and oxidation ditch. Biogas plant is also one method. Animal excreta can be disposed off through a Gobar gas plant or composting.

Study ExercisesLong Questions : (1) Enumerate the diseases that can be caused by poor disposal of sewage. Describe one method for the disposal of sewage in a village at a family level (2) What do you mean by secondary treatment of sewage ? Describe the activated sludge process in detail.

Short Notes : (a) Oxidation pond (b) Sanitation barrier (c) Water seal (d) Trickling filter (e) Gobar gas

MCQs1. The depth of the water seal is : (a) 2 cm (b) 2” inches (c) 20

inches (d) 20 cm2. Septic tank uses (a) Aerobic digestion (b) Anaerobic

digestion (c) Both (d) None3. Which is not a method of secondary treatment of sewage

(a) Trickling filter method (b) Activated sludge method (c) Screening (d) Sludge treatment

4. In immediate aftermath of disaster, displaced population can use this method (a) Open defecation (b) Water carriage system (c) Biogas method (d) Communal aqua privy.

5. Oxidation pond works on : (a) Aerobic principle during night and anaerobic during day (b) Aerobic principle during day and anaerobic during night (c) Aerobic in both day and night (d) Anaerobic in both day and night

Match the following

Population group with most suitable method

of sewage disposal

Population group Most suitable method of sewage disposal

6. Joint family in a village (a) Trench latrine

7. Large city (b) Septic tank

8. Group of 20 households (c) Water carriage system

9. Temporary camp (d) Pour flush latrine

10. Family in a town (e) Biogas plant

Answers : (1) a; (2) c; (3) c; (4) a; (5) b; (6) e; (7) c ; (8) b; (9) a; (10) d.

ReferencesHarvey P. Excreta Disposal in Emergencies : A Field Manual. Loughborough 1. University, Leicestershire, UK 2007.Public Health and Preventive Medicine for the Indian Armed Forces. Dept of 2. Community Medicine, AFMC, Pune. 2008.Veer, T. de Beyond Sphere : Integral Quality System for Operation of Water 3. and Sanitation Programs in Camps. draft report Leiden, 1998.Jaitawat SS, Khajuria RK, Adhau R, Singh A. Improved method of human 4. excreta disposal in field area. MJAFI 2004; 60 (3); 273-5.Conway JB. Water Quality Managemany, In Maxcy Rosenau Last. Public 5. Health and Preventive Medicine (Ed : Wallace RB, Prentice Hall Int Inc.National Environment Engineering Research Institute (NEERI), Nagpur 6. India. Waste Stabilization ponds : Design, construction and operation in India. (Ed. Arcenala SJ). 1st ed, 1970.The Sphere Project : Human charter and minimum standards in disaster 7. response. Geneva. 2004.Field Operations Guide For Disaster Assessment and Response US Agency for 8. International Development Version 4.0; 2005.

123 Disposal of Solid Wastes

Kunal Chatterjee

Solid wastes include rubbish or materials that are not economically useful, present in solid, liquid or gaseous form, which originate from a wide range of human operations, such as industry, commerce, transport, agriculture, medicine and domestic activities. It contains food waste, demolition products, dead animals, manure and other discarded material but should not contain nightsoil.

Waste produced by human activities is increasing in most parts of the World. The output depends on the degree of urbanisation, dietary habits, lifestyles and living standards. In most of the countries the per capita daily solid waste produced is between 0.25 to 2.5 Kg. Majority of this waste is diverted towards recycling in developing countries, while in the developed countries sophisticated methods are used to dispose the ever increasing waste generated (Solid wastes disposal in all the countries is done through landfill). With the rise in urbanisation, land areas available for filling are getting lesser and lesser. The alternate methods of disposal such as burning or incineration are neither cost effective nor environment friendly. Toxic products from wastes disposed in

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landfill sites increasingly leach into groundwater or cause the generation of explosive methane gas. These waste materials are also attractive to cockroaches, flies and rodents and hence need early and effective disposal.

Environmental impact of solid waste disposal : Solid wastes, if allowed to accumulate and not disposed off properly have a tendency to cause the following impacts :

Contamination of ground water by leachate generated by ●waste dumpSurface water contamination by run-off from the dump ●Waste decomposes and favours fly breeding, attracts ●rodents and pestsIt is aesthetically unpleasant and generates foul odour ●Generation of inflammable gas such methane and green ●house gases inside the waste dumpBird menace on the dump, which affect the flight of ●aircraftTransmission of disease through pests, stray animals and ●cattle

Classification of Solid wastes : A thorough knowledge of quantity, composition and type of waste is essential to plan effective disposal. Solid wastes could be of different types such as :

(a) Refuse could be generated from street sweepings, markets, stable litter comprising of animal droppings and left-over feeds, industrial refuse ranging from inert to toxic and explosive compounds and commercial refuse from retail stores, hotels, warehouses and offices.

(b) Rubbish a general term applied to solid wastes originating in houses, commercial establishments and institutions, excluding garbage and ash. It includes paper, clothing, bits of wood, metal, glass, dust and dirt.

(c) Ash is the residue from burning of wood, coal, charcoal, coke and other combustible materials used for cooking and heating purposes in domestic, commercial and industrial establishments. Ashes consist of a fine powdery residue, cinders often mixed with small pieces of metal and glass.

(d) Garbage is a term used to describe animal and vegetable wastes resulting from the handling, storage, sale, preparation, cooking and serving of food. It contains organic matter, which decomposes to emit foul odour and hence requires urgent disposal.

Plastics and their role in waste disposal: Plastics are organic polymeric materials that can be transformed into desired shapes by different industrial processes. These may contain natural elements such as natural rubber, cellulose or synthetic elements such as polythene or nylon. Plastics have excellent thermal and electrical insulation properties and good resistance to acids, alkalis and solvents. Plastics are widely used in commercial and industrial sectors such as packaging industry, building, motor manufacturing and consumer goods industry. However these plastics are not easily destroyed during waste management processes and are poorly biodegradable. Moreover the chlorinated plastics emit toxic gases when thermally treated. Plastics are known to clog or choke water lines, sewers or storm water drainage systems. They are easily blown by wind and litter the areas near waste dumps thereby

being aesthetically unappealing

Solid Waste ManagementThe activities associated with the management of solid wastes in a community from the point of generation to its disposal revolves around the following functional elements (a) waste generation (b) waste handling (c) sorting, storage and processing at source (d) collection (e) sorting, processing and transformation and (f) disposal (Fig. - 1). These elements are relevant to all manner of solid waste disposal be it from urban localities, slums, rural areas or after any calamitous event in an area. In the latter event the urgency to dispose off the waste material is extreme. The waste material in a post disaster situation depends on the type of disaster, which has occurred. It could range from household goods to building material and in extreme situations include human and/or animal bodies.

Fig. - 1 : Activities Associated with Solid Waste Management

Sorting,processing &

transformationof solid waste

Waste generation

Waste handling,sorting, storage andprocessing at source

Collection

Transfer &transport

Disposal

Solid Waste Disposal in an Urban AreaUrban areas include cities and towns and have a higher density of population by virtue of which the quantity of solid wastes generated is very high. Besides this there are people from different professions, socio-economic status, ethnic and cultural backgrounds living in varied accommodations in these areas. They thus produce equally diverse kinds of waste material from their domestic, commercial and industrial professions/establishments. Composition of solid wastes changes from place to place even in the same country due to this heterogeneity.

Major constituent of waste is putrescible organic matter with the balance of the content comprising of metal, glass, ceramics, plastics, textiles, dirt and wood in proportions depending on the local factors. Studies have shown that while the quantity of paper waste increases with the rise in income of the countries, the density, moisture content and proportion of food waste is

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more in the waste generated in low income countries.

Studies conducted by National Environmental Engineering Research Institute, Nagpur have shown that in India out of the wastes generated, the biodegradable fraction is very high due to the habit of using plenty of fresh vegetables in food preparation. It demands frequent removal of waste from the collection points. The proportion of ash and fine earth content in the waste are also high due to the inclusion of the street sweepings, drain silt and construction and demolition debris in it. The most ideal arrangement for collection of solid waste in an urban area would be door-to-door collection of waste material by a team of waste handlers. However this is not practicable in all places in the cities especially in the urban slums.

Waste Management Plan(a) Sorting : This indicates ‘separation and storage of individual constituents of the waste materials’. Sorting helps in removing the material, which needs to be recycled and ensures that the hazardous wastes are handled separately. It assists in minimising the waste and ensures reduction in landfill space for final disposal. Sorting could be carried out at household level, at the municipal bin, central sorting facility, waste processing site or the landfill site. At the household level sorting is carried out by the inmates. Traditionally, items such as newspapers, used bottles, jars, old clothes, strong plastic bags are not mixed with everyday household wastes. These are reused or sold at a later date to informal recycling trade middlemen or the ‘kabariwallah’. Garden wastes from houses gets mixed with the municipal waste, there being no separate mechanism for its disposal. At the next stage of sorting at the municipal bin the ragpickers take over and collect waste material of use to them such as plastics mostly water bottles, paper, rags, metal cans and rubber items to resell or recycle them. This business continues at the landfill site where the pickings include small metal pieces, plastic bags or any item considered to be of economic value. Thus at the primary level an intensive sorting is carried out. The recovered material thereafter reaches the next level of sorting where the informal recycling trade middlemen sort out all metals, plastics and all types of paper. The salvaged items out of the waste is purchased by the wholesale dealer, who does more sorting, since he is the final link in the chain before the recycling factory. The balance of waste material is disposed off in the landfill. After sorting the waste is divided into the following streams :

Dry recyclables ●Construction and demolition waste ●Biodegradable waste ●Bulky waste ●Hazardous waste ●Mixed wastes ●

Sorting could be carried out manually or by semi-mechanised or fully mechanised systems. The manual system employs handpicking of waste for reuse, which is followed in most cities in developing countries, by the ragpickers and the informal recycling trade middlemen, while in the semi-mechanised system the waste material is placed on a conveyor belt and then hand-picked off the belt, for reuse. The mechanised system involves size reduction of waste through shredders and crushers followed by screening, density and magnetic

separation of waste followed by its compaction by balers and crushers.

(b) Storage : This is the first essential step in management of solid wastes. Every household, shop, industry, commercial centre or establishment generates waste that it needs to be stored safely prior to giving it for collection. Presently such establishments and institutions do not maintain receptacles of adequate size for storage of waste as a result of which the solid waste lies overflowing the bins or littering the streets causing public nuisance. In some instances the waste generated is simply thrown out to the streets for the municipal sweeper to sweep it up. Wastes of the recyclable variety are mixed with organic waste and not sorted out or at worst the wastes may be thrown into the municipal sewers or drains, which end up blocking them and obstructing the flow of water in them.

It is therefore essential at first to educate the people to store waste at source, dispose waste as per directions of the local bodies and effectively participate in the activities of local authorities to keep the cities clean. The type and size of waste bins need to be described to households, shops, offices, institutions, hotels, vegetable & fish/meat markets, street vendors, marriage halls, construction sites and health care establishments. It needs to be emphasised that the recyclable wastes should be kept separate from the organic matter capable of decomposition. The food/ biodegradable waste should be stored in a non-corrosive container with lid. Building associations, communities and commercial complexes must keep central waste storage bins of adequate capacity to ensure that they hold the wastes generated till the time they are cleared by the waste lorries. Construction and demolition wastes should not be dumped on the streets, public spaces, footpaths and pavements.

(c) Collection of waste : The next essential step in waste management is primary collection of waste matter. This ensures that the waste from the source is collected regularly such that it is not disposed in the streets, drains or water bodies.

Doorstep collection of waste from households, shops and establishments is insignificant in the urban areas and wherever it is introduced through private sweepers or departmentally, the system does not synchronise further with the facility of waste storage depots and transportation of waste. This results in its indiscriminate disposal in public places.

Waste collection measures : A daily waste collection service should be provided to all sources of generation for collection of putrescible organic waste from the doorstep because of the hot climatic conditions of the country. Recyclable material can be collected at longer intervals as this waste does not normally decay and need not be collected daily. Domestic hazardous waste is produced occasionally hence needs to be collected less frequently and could be disposed off by the community in central bins kept for the purpose.

Collections could be made from doorstep or at the community level by hand carts/ tricycles or motorised vehicles. The hand carts or tricycles should have detachable containers of 30 to 40 litres capacity, made of sturdy material, with a handle at the top and a rim at the bottom for easy handling. Similarly the community bin carrier or the bin lorry should have the capacity to carry 40 containers from a central point in the communities

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or slums to the place of final disposal.

Waste storage depots (secondary) : Wastes collected from the source could be temporarily stored at depots till the time they are taken to the final disposal site. At present most municipal areas have cement-concrete-cylindrical bins, masonry bins, metal rings or open sites for storage of wastes. Improper storage at the bins or littering of waste gives an unsightly appearance and also attracts rodents, pests and animals that further spread the litter or could carry diseases from the decomposing matter.

Temporary waste storage depots, which synchronize with primary collection and transportation system, are required to be located at suitable sites in a municipal area. Large metal containers, which are covered, could be placed at specific points. These places should have concrete or asphalt flooring. The waste material could thereafter be transported at regular intervals by Lorries having mechanised equipment to lift and load the bins to take them to the final disposal sites.

(d) Disposal of solid waste : Solid waste disposal in developing countries is mostly carried out by filling up land sites. In India this nature of disposal accounts for most of the municipal refuse. This is followed by incineration and to a very minimal extent by composting. The choice of disposal method depends on the economic considerations, availability of land, local labour and circumstances. Some of the technologies in use in these countries include sanitary landfill, incineration, composting, biogas plant, Effective Microorganisms technology and salvaging.

Dumping : The refuse collected from the cities and municipal areas are dumped in the low-lying areas or open tracts of lands, usually by the roadside. This process, though not a correct method of disposal of solid waste, is nevertheless practised in many cities in the country and in certain locations in a particular municipal area limit. The city of Kolkata in India practises the method of dumping of municipal solid wastes after its sorting. Some of the reclaimed lands, where refuse is dumped, are also given thereafter for cultivation.

This method has the disadvantage of lying in the open ground thereby being dispersed by the wind to nearby places, attracting rodents, insects and birds causing a risk of transmission of diseases and encouraging breeding of flies. Besides this the

open waste dump lying on the roadside emits foul odours and is an aesthetic nuisance. The urban areas thereafter resort to burn these wastes to reduce their bulk, thereby causing air pollution. The malodourous fumes and the toxic gases, which are emitted due to burning of wastes such as plastics and other materials, are spread in the direction of wind movement. Besides, these dumps are accessible to animals and scavengers or ragpickers since these areas are usually not made secure from ingress of these elements. The drainage from these dumps contributes to the pollution of surface and ground and the soil around.

Dumping of waste disposal should be outrightly discouraged as an unsanitary practice. Only dumping of demolition materials could be permitted in low lying areas outside the cities or municipalities (Fig. - 2).

Landfill : Landfill (Controlled tipping) is a method of selecting depressed areas or creating artificial trenches where waste matter is thrown and compacted with a layer of earth on top of it. This method is suitable if adequate land is available, within the economic range of the waste source. The modern day landfill is utilised for disposal of wastes two to three times a week and differs from dumping in that if properly carried out it reduces the nuisance of foul odour, menace of flies, rodents and animals. It also prevents any dispersal of the waste matter and is protected from scavengers. Soil, water and air pollution is avoided and the reclaimed land could be utilised for growth of vegetation or parks after a period of time (Fig. - 3).

Site selection : The site selection for a landfill is carried out away from habitation. A hollow low lying area is usually selected such as an abandoned quarry, depression in land or swampy area, which is not a source of rain water harvesting or natural aquifer for a municipal area. If such land area is not available, as an alternative to this, trenches are dug in an open and flat area with the help of dozers. Some of the points which should be remembered while selecting a site for landfill are :

Waste site should not be subject to flooding easily ●Deep sands with shallow water tables should be avoided, ●to prevent seepage of toxic wastes into the drinking waterFractured limestone soils, humid areas or wetlands with ●easy percolation should be avoided.Soil with pH 6.5 or above should be chosen such that the ●

Fig. - 2 : Dumping Fig. - 3 : Landfill

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metals such as cadmium, mercury, lead, chromium and copper are less soluble in the subsoil water and reduce the chance of pollution.

Sites

(a) Trenches - where long trenches of 2 to 3 m depth and 4 to 12 m width are dug and the refuse is compacted and covered with excavated earth. It is estimated that an acre of flat land area would be required for ten thousand population.

(b) Ramps or slopes - where moderately sloping lands are selected and soil is excavated for compacting purposes. The waste dump should be prevented from damage by rain water and thus upland drainage should be diverted.

(c) Unused areas - such as disused quarries, pits and land depressions wherein the solid waste is packed and consolidated in uniform layers using mechanised equipment.

Process of disposal : The refuse or solid waste is collected and deposited in these sites using bulldozers or crawler type tractor. In trenches the filling takes place from the farthest end. Each layer is upto 2 to 2.5 m deep. At the end of the day or as per the desired frequency the top of the refuse is layered with earth of at least 30 cms thick using mechanised equipment and evenly levelled. The mass is covered with clinkers and fast growing shrubs. Over a period of time due to physical, chemical and biological processes in the buried waste matter, heat is generated and anaerobic decomposition of the organic matter takes place, which also destroys pathogens. Thereafter the process cools down and the waste is converted into an innocuous mass by the end of six months of burial. The land could thereafter be used as a green belt or parks could be developed on it.

Notable features: The trenches could also be lined and the filled could be contoured to minimise pollution of soil nearby. Methane gas is generated during the decomposition of solid waste, which is explosive in nature. This land should therefore not be used for construction purposes. Vents could be created in the topsoil cover to release this gas. Dumping of bulky goods such as household equipment should be avoided. These goods could be recycled or incinerated. The method has a drawback that it requires soil cover, which has to be made available at all landfill sites.

Composting : It is a method where in the combined disposal of solid waste is carried out alongwith stable litter, night soil and sludge. Compost is humus like material, which is generated due to the breakdown of organic matter under bacterial action, and is rich manure. Thus the final product of degradation in composting has a recyclable component and the compost could be sold at a price to agriculturists. Composting uses aerobic method of digestion (Fig. - 4).

Pre-treatment : The refuse or solid waste is pre-sorted to remove materials that could be recycled or have salvage value or those ones, which cannot be composted. It is thereafter ground to reduce the waste particle size and this improves the efficiency of decomposition process.

Methods

(a) Bangalore method : It was evolved under the auspices of Indian Council of Agricultural Research at the Indian Institute of Science, Bangalore. It is also known as the hot fermentation

process due to the generation of heat in the process to decompose the waste.

In this method long trenches are dug each with a depth of 1 m and width of 1.5-2.5 m. Greater depths is not recommended since they delay the process of decomposition and therefore decrease its effectiveness. The refuse is then placed in the trench at the bottom making a layer of about 15 cms thick. Over this a layer of nightsoil is put to a depth of 5 cms. In this manner alternate layers of solid waste and nightsoil are layered one above the other till the heap rises 30 cms above the ground level. The top layer is recommended to be of refuse of about 25 cms thickness. Thereafter the heap is covered with excavated earth firm enough to not allow a person’s legs to sink in the heap while walking.

Fig. - 4 : Composting

Process : The fermentation process begins in a week’s time with generation of considerable amount of heat, which stays for 2 to 3 weeks. The organic mass is decomposed and pathogenic microorganisms are destroyed in the process, which is completed in 4 to 6 months. Gases such as ammonia, methane, carbon dioxide and nitrogen produced in the process are released into the atmosphere. The resultant manure is well-decomposed, odourless, innocuous material of high manurial value. The soluble material produced may leach into the underlying or surrounding soil or ground water.

(b) Mechanical composting : It is a process in which the compost is manufactured in a short period of time with use of waste materials and night soil. A sorting is done in the initial stages and items such as rags, bone and metal pieces and glass, which are likely to interfere with grinding operation, are removed. The waste matter is then pulverised by mechanised equipment and thereafter mixed with night soil or sludge in a rotating machine. This mixture is then incubated under controlled conditions of pH, temperature and aeration. The compost is ready in 4 to 6 weeks time as humus like material with a total nitrogen, phosphorus and potassium content of 1 to 3 percent. The product thereafter is cured, blended with additives, bagged and marketed.

(c) Vermicomposting : It is a method of disposal of kitchen and

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plate wastes, which serves the dual purpose of disposing off the garbage as well as proving eco-friendly. Here a suitable area is chosen which is bound by a 2 to 3 feet high brick wall and few hundred earthworms are introduced in it. The waste is dumped in this area and water is sprinkled daily on this dump. The waste matter is broken down by the worms and compost, which could be used as bio-fertiliser, is produced in 2 to 3 months.

The process does not generate any explosive gases or leachate and can be used in agriculture and organic farming. It enriches the soil due to the deep burrowing worms and bacteria in the organic matter. The process could generate green areas and is used in small scale disposal of waste matter.

Notable features : The process of vermicomposting has the advantage of dual disposal of nightsoil and solid waste in a manner that the end product could be reused as organically rich manure. However the process needs training of manpower who are required to handle the mixing and incubation of night soil with refuse and may generate hesitation on their part to be involved in the process.

Effective Microorganisms (EM) Technology : This is a modern eco-friendly technology consisting of use of friendly microorganisms such as phototropic bacteria, lactic acid bacteria, Actinomyces and yeasts. These microorganisms are added to kitchen wastes in specially designed drums. The wastes are converted into compost, which can thereafter be utilised as manure. The EM solutions available commercially are classified into EM 1 and EM 2 categories depending on their shelf life, which varies from 30 days in the latter to 6 months in the former. EM technology also has the advantage of keeping the drains clean by decomposing the sewage and suppressing its bacterial content.

Incineration : This is a process of disposal of solid waste material by thermal technology and has gained popularity in several developed countries. The incinerators use heat recovery process and also have air pollution controls. Incineration is also chosen in those places where suitable land mass is not available. Many industrialised countries are practising this method under strictly controlled environment, with appropriate training to the waste handlers. Waste generated in hospital premises is disposed off in this manner in most countries.

Incineration of waste material is not a useful method for India because of the fair proportion of ash, which is contained in it. The ash contained in the refuse makes its combustion difficult. Hence pre-treatment of the waste material is required, which is expensive and requires heavy infrastructural outlay. Besides this incineration involves wastage of precious bio-fuels and deprives the communities of much needed manure.

Solid Waste Disposal in an Urban SlumUrban slums comprise a congregation of temporary or semi-permanent structures, which are constructed by the new settlers in an urban area, due to lack of proper housing facilities and in most instances by illegal occupation of land. These settlements usually house people from low socio-economic strata, who are poorly educated and as a consequence show a lack of awareness regarding the hygiene and sanitation issues especially related to solid waste management.

The houses in slums are constructed in rows with a narrow path in between them. The storm drainage system is usually rudimentary and temporarily constructed. The slum dwellers use common toilets and bathing facilities, where the waste water or night soil is connected to the sewers or in certain instances to the larger storm water drains. Disposal of solid wastes in the slums has the following peculiarities :

Quantity of waste generated is lesser as compared to other ●areas in the urban locality.Solid wastes mostly comprise of used bottles, tins, plastics ●and ashes, since most of the salvageable items are recycled.Animal manure and feeds are a significant part of solid ●wastes from slums since small farm animals co-habit with humans.Vegetable peels and kitchen wastes are discarded in large ●quantities while the food product packages are not usually a part of the waste matter.Slums localities in the various cities also have small-scale ●or cottage industries, which generate waste materials. Sometimes these industries give rise to hazardous or toxic chemicals such as from the dyeing and tanning industries. Some industries are also engaged in recycling of goods salvaged from the refuse bins. Hence the wastes from these places need to be disposed off properly.There is no existing system of door-to-door collection of ●waste items. The people in the slum community deposit their garbage in the public bins located centrally.The roads/paths in the slums are narrow, hence the refuse ●lorries are unable to negotiate the paths and therefore the waste bins are placed at fewer points.The wastes from these bins require more frequent emptying ●to prevent waste matter to spill over in the ground below and create nuisance.Adequate sorting of the wastes take place in the bins ●located in the slum localities, hence the remaining waste meant for final disposal is non-recyclable matter.

Waste DisposalWaste disposal in slums in carried out in the same manner as the solid waste, which is disposed from the rest of the municipal locality. The waste bins are placed at the pre-determined points and the community is made aware of the place. The wastes are collected at these sites from the households and these are thereafter taken to the disposal area. Sorting of the wastes is carried out by the rag-pickers at the municipal bins and the recyclable material salvaged by them is sold to informal middlemen. The second stage of sorting by the rag-pickers is carried out at the municipal waste disposal area. The remaining wastes comprise of non-recyclable material, which is easily decomposed by the processes such as sanitary landfill, composting or incineration or any modern day technology discussed in the previous paragraphs.

Solid Waste Disposal in Rural AreasRural areas comprise of villages and some temporary nomadic settlements or camps. In the last census conducted in 2001 the rural population in India comprised more than 70% of the total population of the country. The rural economy is primarily

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agrarian with the population engaged in cultivating crops or vegetables for selling in the market and for consumption, depending on the nature of farming practised in the area or economic need. Some rural areas also practise poultry farming, fish farming or apiculture. The farm work is steadily becoming mechanised in most parts of the country with machines sowing and harvesting crops throughout the year. As a result of this large amounts of unused parts of the crops or vegetables are generated as wastes, which require regular disposal. Some of the rural areas also have small-scale industries, which produce solid wastes or liquid chemical wastes. These also require disposal in an appropriate manner.

The community residing in the villages comprise of a large population who belong to the lower socio-economic strata. The levels of literacy are lower compared to cities and the health status indicators of morbidity, mortality and natality compare unfavourably with the urban areas. The density of population is lesser in villages, while more number of families live jointly, with all of its members contributing to the family occupation.

Waste generated in the rural areas is lesser in quantity compared to urban wastes. It consists primarily of organic matter from the households or the rural industry such as vegetable peels, crop wastes, manure, fodder, animal feeds, ash and lesser quantities of tins, bottles or paper unless there is a particular industry located in the rural area. Majority of the recyclable wastes are salvaged before disposal to be used in households.

Current disposal methods : In the rural areas at present there is no system of organised collection and disposal of refuse, which is temporarily deposited in a pit or a bin to be disposed later by burning or dumping outside the village or is thrown around indiscriminately. The waste ends up polluting the nearby soil, water and air and at times hazardous wastes from small industries could be harmful to the human life. The local self-governing bodies or the Panchayati Raj Institutions are responsible for maintenance of hygiene and sanitation in the rural areas and they influence the methods of waste disposal.

Methods of disposal(a) Manure pits : This method of waste disposal could be practised by the individual households in the rural areas. Pits could be dug near the house and the wastes such as kitchen wastes, cattle dung, fodder or animal feeds, leaves could be thrown into them. The wastes should be covered by earth at the end of each day and reused the next day. Two such pits could be dug simultaneously of 1 to 1.5 m and used one at a time. When one pit is filled up it is covered with a top layer of soil and compacted. In 5 to 6 months time, the wastes are decomposed and converted into manure, which could be returned to the fields.

(b) Burial : Burial method of disposal is suitable for disposal of refuse of the village or small settlements. This could be undertaken in an area if sufficient land is available. The method is similar to sanitary landfill and the involves digging a trench 2 m deep and 1.5 m wide in which the refuse from the village or camp is deposited and at the end of the day the refuse is covered with 20 to 30 cms of earth. The disposal continues in this manner till the time the level in the trench is 40 cms from ground level, when the trench is filled and compacted and

a new trench is dug out. The waste matter is decomposed in 4 to 6 months time when it can be taken out and used as manure in the fields. A trench of this size and 1 m long would suffice for 200 persons for a week. The length of the trench could be varied depending on the requirements of the rural area. The method of burial needs to be practised in the correct manner to avoid any rodent or pest nuisance.

(c) Biogas plant : The animal excreta generated in the rural areas are fairly large in quantity and could be utilised to generate bio-fuels and thus be recycled (Fig. - 5). In the rural areas this excreta is mixed with straw to make dung cakes which are used as fuel for cooking purposes.

Fig. - 5 : Bio-gas Plant

Animal excreta also carry an enormous potential of fly breeding and thus its sanitary disposal is required. This could be achieved by disposing them in bio-gas plants or through landfills or by composting. Details of biogas plant have already been discussed in the chapter on excreta disposal.

Solid Waste Disposal in Post Disaster SituationsDisasters produce solid wastes in large amounts. Natural or man-made disasters produce debris comprising of soil, building material and green waste such as trees and shrubs. The type and quantity of the waste depends upon the type and magnitude of the disaster. Most of the times the destruction created in the wake of the disasters are of such magnitude that it overwhelms the capacity of the affected community to dispose off the debris.

Solid Wastes during DisastersThese wastes are mostly in the form of debris, which stands for ‘the remains of anything that is broken down or destroyed’. Hurricanes leave behind debris made of construction materials, damaged buildings, sediments, green waste and personal property. Earthquakes generate sediment from landslides besides building materials and personal property; the waste material due to fires and explosions may increase the ash and toxic waste contents in the debris. Floods notoriously produce

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mud, sediment and sandbags beside the rubble of dismantled houses. The household goods damaged due to inundations are disposed off by the communities. Fire debris also includes charred remains of vehicles, wood, ash and metal objects. In addition to all this, there could be bio-hazardous and radiation wastes due to manmade disasters, which need specialised disposal techniques. Disasters also tend to take a heavy toll of human and animal lives and thus disposal of dead bodies or animal carcasses has to be carried out on priority after identification of the bodies. Post disaster wastes also include the wastes from relief material, which arrives in bulk at the disaster affected sites and have a potential to cause aesthetic nuisance.

Managing Disaster Debris or Solid WastesThe management of solid wastes after disaster situations must be based on the existing regulations in a community and it must be consulted on all occasions. The cycle of waste management comprising of collection, storage, staging, recycling, disposal, hazardous waste identification and handling, administration and dissemination of information to the public needs to be adhered to ensure efficient disposal of waste matter.

Planning for disposal : Post disaster situations require additional quantity of specialised equipment and supplies such as saws, portable generators, vehicle repair equipment and water storage arrangements. It is important to pre-select temporary debris storage and processing sites at a convenient place to allow the collection crews to reduce travel time when transferring debris to processing or disposal facilities. These sites should be accessible to heavy equipment with low impact on the environment and adjacent housing areas.

Waste management : After the disposal of the dead bodies and the carcasses in a hygienic manner, the task that needs to be carried out next on priority is to dispose off organic matter first. This comprises food wastes, animal feeds, plants and trees, soil, decomposable household goods, waste from the relief materials and manure. The existing methods of sanitary landfill, composting or incineration could be used for this purpose. Equipment are needed to quickly prepare the area for disposal of refuse. Incinerators, which are not damaged, could serve as the best method of early disposal of solid waste in a post-disaster situation.

Large bulk of disaster generated waste matter comprises of building rubble and damaged infrastructure. This could first be removed to a temporary storage site and thereafter be disposed off by landfill, filling up land depressions or for road construction or levelling, after suitable grinding and breaking down to pieces of desirable size. Care should be taken to ensure that no hazardous waste matter is included in this waste bulk. Broken trees, poles, metal roofs, sandbags, cables, packing material from relief goods, which are salvaged, could thereafter be disposed off by selling or reusing them to construct the infrastructure in the affected area.

The local authorities should establish communication strategies to coordinate with the affected communities in implementing disaster plans. Staffing patterns should be improved and they should be trained to handle increased number of telephone calls and requests concerning waste removal. Additional staff would

be required to train and monitor debris collection contractors, enforce disposal restrictions and help solve implementation problems.

Legal Framework : The following acts and rules govern the disposal of solid wastes in India, published by the Ministry of Environment and Forests, which is the nodal Central Govt ministry responsible for the proper disposal of solid wastes : (a) Environment (Protection) Act 1986(b) Bio-Medical Waste (Management and Handling) Rules

1998(c) Municipal Wastes (Management & Handling) Rules 1999

SummarySolid wastes include rubbish or materials that are not economically useful, present in solid, liquid or gaseous form, which originate from a wide range of human operations, such as industry, commerce, transport, agriculture, medicine and domestic activities. It contains food waste, demolition products, dead animals, manure and other discarded material but should not contain nightsoil. The output depends on the degree of urbanisation, dietary habits, lifestyles and living standards. In most of the countries the per capita daily solid waste produced is between 0.25 to 2.5 kg.

Solid wastes, if allowed to accumulate and not disposed off properly have a tendency to contaminate drinking water sources, favour fly breeding, attract rodents and pests, generate foul odour and inflammable gases and transmit various diseases. Solid wastes could be of different types such as Refuse generated from street sweepings and markets, Rubbish originating in households excluding garbage and ash, Ash which is residue from burning of wood or coal and Garbage including animal and vegetable wastes

The management of solid wastes in a community include (a) waste generation (b) waste handling (c) sorting, storage and processing at source (d) collection (e) sorting, processing and transformation and (f) disposal.

Urban areas produce diverse kinds of waste material from their domestic, commercial and industrial professions/establishments. Sorting could be carried out at household level, at the community refuse collection site or the landfill site. It segregates the different types of wastes. Collection of wastes could be made by waste handlers at household level, shops and small establishments, while at the community level it could be carried out by hand carts/ tricycles or motorised vehicles equipped with detachable containers of 30 to 40 litres capacity. Wastes collected from the source could be temporarily stored in cement-concrete-cylindrical bins or masonry bins till the time they are taken for final disposal. The waste material could thereafter be transported at regular intervals by Lorries having mechanised equipment to lift and load the bins to take them to the final disposal sites. Final disposal of solid waste is carried out by sanitary landfill, incineration, composting, biogas plant or Effective Microorganisms technology.

Waste disposal in urban slums, is carried out in the same manner as the rest of the municipal locality though the type and quantity of waste generated is slightly different. Waste generated in the rural areas is lesser in quantity and

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consists primarily of organic matter from the households or rural industry. The local self-governing bodies or Panchayati Raj Institutions are responsible for maintenance of hygiene and sanitation in the rural areas. The main methods of waste disposal here are manure pits, burial, biogas plants and other technologies such as composting and incineration. Solid wastes during disasters are mostly produced in the form of debris, dead bodies or animal carcasses and wastes from relief material. The management of solid wastes after disaster situations must be based on the existing requirements of the affected community. Additional quantity of specialised equipment and supplies such as saws, portable generators, vehicle repair equipment and water storage arrangements are required in these situations.

Community participation is the key to ensure success in the implementation of solid waste disposal. To ensure that community participation is optimum, strong and sustained Information, Education and Communication programme needs to be adopted. The acts and rules governing the disposal of solid wastes in India, published by the Ministry of Environment and Forests are Environment (Protection) Act 1986, Bio-Medical Waste (Management and Handling) Rules 1998 and Municipal Wastes (Management & Handling) Rules 1999.

Study Exercises : Long Questions : Enumerate the health hazards due to improper Solid waste disposal and describe the methods for solid waste disposal in an Urban area.

Short notes : (1) Solid waste disposal in an Urban Slum (2) Solid waste disposal in a rural area (3) Sanitary landfill (4) Incineration (5) Composting

MCQs : 1. Waste paper is an example of (a) Refuse (b) Rubbish

(c) Garbage (d) none2. A method of selecting depressed areas or creating artificial

trenches where waste matter is thrown and compacted with a layer of earth on top of it is (a) Manure pit (b) Controlled tipping (c) Burial (d) Dumping

3. Bangalore method of Composting is a type of (a) Aerobic (b) Anaerobic (c) both (d) none

4. Bangalore method of refuse disposal is not recommended for population above (a) 100,000 (b) 200,000 (c) 300,000 (d) 400,000

5. Dual disposal of nightsoil and solid waste is seen in (a) Manure pit (b) Controlled tipping (c) Composting (d) Sanitary landfill

6. The method of solid waste disposal which is not ideal/feasible for rural setup is (a) Manure pit (b) Biogas plant (c) Burial (d) Mechanical composting

Answers : (1) b; (2) b; (3) b; (4) a; (5) c; (6) d.

124 Management of Biomedical Wastes

Kunal Chatterjee

Biomedical waste could be defined as “any solid, fluid or liquid waste, including its container and any intermediate product, which is generated during the diagnosis, treatment or immunisation of human beings or animals, in research pertaining thereto, or in the production or testing of biologicals and the animal waste from slaughter houses or any other like establishments”. As per the Biomedical waste (management and handling) rules 1998, under the Environment Protection Act of India, proper management of biomedical waste is a statutory requirement and these rules have been elaborated in the Gazette notification of the Ministry of Environment and Forests, Govt of India dated 20 Jul 1998.

Majority of the waste generated in a health care establishment is non-hazardous waste of general nature. It is comparable to domestic waste and is produced due to administrative and house-keeping functions of these establishments. Almost four-

fifths of hospital wastes comprise this category of general waste. The rest 20 percent of health-care waste is hazardous and could be infectious, toxic or radioactive and cause significant risk to the health of community members.

How do we Classify Biomedical Waste?The Ministry of Environment and Forests of the Govt of India, in exercise of its powers conferred under the Environment Protection Act 1986, have categorised these biomedical wastes for the purpose of safe disposal, as given in the Table -1.

Quantity of Biomedical Waste Generated in Health Care SettingsThe quantity of waste generated in a hospital would direct its waste management policy and is dependent upon the type of hospital and the health problems, hospital policies and practices followed and the nature of patient care provided in them. The reports available from developed countries indicate that this quantity is equal to 1 to 5 kg/bed/day with variations among countries, hospitals and specialities. In India, from the data available from regional or local studies, it is presumed that most hospitals generate roughly upto 1 to 2 kg/bed/day of biomedical waste. This quantity varies between Government

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and private health care establishments. Most studies in India also inform that the waste generated contains less disposable material like rubber tubes, plastics etc. Most of the waste generated in a hospital (around 85%) is non-hazardous, while 10% are infective including sharps and pathological waste and the remaining 5% are non-infectious but hazardous such as chemical, pharmaceutical or radioactive wastes.

Principles of Control of Hazards of Biomedical Waste in Health Care EstablishmentsThe biomedical wastes generated in a health care setting could be rendered safe by following certain principles of infection control as described : (a) Each institution should develop its own biowaste

management policy and ensure that the health care workers are adequately trained to handle biological waste.

(b) Measures such as universal safety precautions, hand washing and proper segregation of waste material should be encouraged.

(c) Rationale patient management policy should be followed and admissions restricted to those for whom it is felt absolutely necessary, to reduce incidence of hospital acquired infections.

(e) Proper house-keeping is essential and the hospital premises should be kept clean and well-ventilated.

(f) Use of disinfectants should be rationalised.Steps in the Management of Biomedical WasteThe biomedical waste generated in a health care establishment is required to be disposed in an appropriate manner to prevent health hazard to the health care providers and the general community. As a pre-requisite to a good hospital waste management plan, it is essential to ensure the availability of safe and reliable supply of water, sanitation facilities, maintenance of cleanliness and demarcation of vital areas that need stricter sterility norms. After ensuring the availability of these basic facilities, the steps discussed below should be followed for management of biomedical waste :

(a) Survey of waste generated : A survey of waste generated in a health care establishment determines the quantity, type and source of waste generation inside the premises. It also

finds out the level of disinfection in a hospital and gives an insight to the disposal practices being followed by the hospital staff. In this manner proper attention could be given to dispose of all categories of waste safely with least harm to the environment and also provide specific training to providers to correct improper waste disposal practices.

(b) Segregation of hospital waste : Segregation could be defined as ‘separation of different types of wastes by sorting’. It denotes the process where wastes of different types, hazardous nature and consistency are separated such that special attention could be given to their disposal. This ensures that the associated risks and the costs of handling the relatively smaller quantities of infectious and hazardous wastes are kept minimal. Accordingly, the non-hazardous waste, which is of general nature and disposed off with municipal garbage, could be dealt with less harm to health care providers and waste handlers. Therefore the best course of action is to segregate the wastes into various categories at the source/point of generation itself. This activity is best undertaken by the ‘generator’ of the biowaste that is the health care provider himself. The waste categories need to be segregated as per the categories described earlier. This categorisation should be displayed at such locations that most of the people i.e. patients, providers and attendants benefit from it. It would be of more benefit to prepare these instructions in the local languages.

(c) Collection & Categorisation of waste : This step in the waste management integrates into segregation of biomedical wastes. The wastes generated need to be collected in proper containers such as sputum mugs, urinals, plastic containers for sharps and so on. It is a good practice to colour code the containers holding different types of hospital waste (Table-2).

In such instances where the detailed colour coding system is not feasible on account of low level of training among the waste handlers it is preferred to use at least three colour codes for ease of understanding. These are -

Green for general waste (non infectious) ●Red for infectious waste (microbiological, anatomical, ●pathological and soiled linen)Yellow for sharps, plastics and disposables ●

Table - 1 : Classification of Biomedical Wastes

Waste category

Waste Class

Cat. No. 1 Human Anatomical Wastes

Cat. No. 2 Animal Wastes

Cat. No. 3 Microbiology and Biotechnology wastes

Cat. No. 4 Waste Sharps

Cat. No. 5 Discarded medicines and Cytotoxic drugs

Cat. No. 6 Soiled wastes include items contaminated with blood, body fluids such as cotton, dressings, linen, beddings etc.

Cat. No. 7 Solid wastes i.e. waste generated from disposable items other than sharps such as tubings, catheters, IV sets.

Cat. No. 8 Liquid wastes

Cat. No. 9 Incineration ash is generated of any biomedical waste.

Cat. No. 10 Chemical wastes

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Table - 2 : Colour coding and type of containers for disposal of Biomedical waste

Waste category

Type of Containers Colour code

Category 1 Plastic bags Yellow

Category 2 Plastic bags Yellow

Category 3Plastic bags/ disinfected container

Yellow/Red

Category 4Puncture proof plastic containers

Blue

Category 5 Plastic bags Black

Category 6Plastic bags/ disinfected containers

Yellow/Red

Category 7Disinfected containers/ puncture proof containers

Red/Blue/White

Category 8 Not applicable Not applicable

Category 9 Plastic bags Black

Category 10 Plastic bags (for solids) Black

Besides this colour coding, the categories of waste to be disposed should also be mentioned on the containers. If reusable bins/containers are used then they should be cleaned/disinfected properly before being used again. The containers should be of the correct size to hold the desired quantity of waste and devoid of sharp edges for ease of handling. The colour coded containers need to be located at the point of generation of wastes to ensure proper segregation at the source itself.

(d) Storage of waste : It means the ‘holding of biomedical waste for such period of time, at the end of which waste is treated and disposed of.’ The wastes, which are generated in a health care establishment, should ideally be disposed off immediately. However if there is a chance that the waste needs to be stored at some place as per hospital policy, then the place should be safe from tampering and access to rag-pickers. In most instances it is seen that the wastes are stored near the municipal dump pending final disposal and generally the hospitals shake their responsibility off it. This happens more often when the waste disposal is outsourced to a contractor and creates a potentially hazardous situation, due to unscrupulous elements picking up these wastes and recycling them. It is thus absolutely essential that no biomedical waste is stored at any place where it is generated, beyond a period of 48 hours. During the storage period the waste must not be allowed to decay or putrefy.

The storage containers should have the following characteristics -

They should be made of sturdy, hard plastic or metal and ●should be leak proof and puncture proof.They should be of adequate size to avoid overflow with a ●secure lid and handle and should be colour coded.They should not be easily destroyable by rodents & should ●have smooth, rounded surfaces to hold plastic bags.Plastic bags should be large, sturdy and leak proof with ●no tears. They should line the complete storage bin from

inside and some portion should be outside.In case the wastes need ●to be incinerated along with plastic bag then the bags should be made of non-chlorinated plastics, to avoid environmental pollution.Bags should be colour ●coded, labelled and marked with a biohazard symbol (Fig. -1).The storage containers holding sharps, besides being leak ●proof, should also contain appropriate disinfectants such as sodium hypochlorite solution.

Storage area The storage area should be earmarked and protected from ●all sides. It should have a clear warning sign and accessible to only authorised persons.The facility should have adequate storage space for at least ●two days with a robust construction and proper drainage system.Radioactive wastes should be disposed off separately, in a ●demarcated area and labelled properly.The timings of waste collection should be fixed for specific ●areas and all the containers should be regularly cleaned and disinfected before reuse.

Biohazard symbol should be used as label on all containers and vehicles meant for storage and transportation of waste.

(e) Transportation of waste : Transportation is the vital link between the site of waste generation and the final disposal point. It involves movement of the waste generated from the source to interim storage site and its final disposal as per its category. While being transported, it should be secured from the public as well as waste handlers, who have inadequate knowledge of the waste and could be exposed to unnecessary risks. The vehicle used for transportation should be able to achieve the task with minimal effort, spillage or disturbance to the waste. Usually the health care establishments utilise push carts, waste trolleys and wheelbarrows to transport waste inside the hospital premises. Outside the hospital cycle rickshaw or waste van/lorry is used to transport the biomedical waste to its final site of disposal. It should be ensured that the transport used is of robust construction, has adequate space, is leak proof and covered. It should also not allow the mixing of hazardous and non-hazardous waste materials and the frequency and timings of transport should be informed to all sites of generation of waste in a health care establishment. The hospital authorities should keep proper documentation of the frequency of waste transportation.

(f) Technologies for waste treatment : Biomedical waste is treated before its final disposal to reduce its bulk and make it free from pathogenic organisms. Treatment changes the physical, chemical or biological characteristics or composition to render the waste non-hazardous to health and environment. The different types of waste treatment technologies are chemical

Fig. - 1 : Biohazard symbol

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disinfection technology, thermal technology, mechanical technologies and irradiation technology. These are described as follows :

(i) Chemical disinfection Technology : It uses chemicals to destroy pathogenic organisms from any inanimate object. Generally the infectious wastes generated in a health care establishment are treated with this method. This method is used to treat the following wastes (Table - 3).

Sharps contaminated with blood and body fluids ●Instruments, equipment that are used to cut, pierce or enter ●the natural orifices like needles, syringes and endoscopesContaminated floors, surfaces, clothes, beds, beddings, ●enamel, crockery and bed pansWet mopping of intensive care units, operation theatres, ●wards and patient waiting areas.

Table - 3 : Recommended concentration/dilution of Chemical disinfectants

DisinfectantsContaminated

condition

Grossly contaminated

condition

Sodium hypochlorite 5% available chlorine as liquid bleach

20 ml/L 200 ml/L

Calcium hypochlorite 70% available chlorine

1.4 gm/L 7.0 gm/L

Sodium dichloro-isocyanurate powder

1.7 gm/L 8.5 gm/L

Chloramine 20% available chlorine

20 gm/L 20 gm/L

Tincture of Iodine/Povidone Iodine

2.5% 2.5%

Ethyl alcohol 70% 70%

Isopropyl alcohol 70% 70%

Glutaraldehyde 2% 2.5% 2.5%

Formaldehyde 40% 5% 10%

Savlon 5% 10%

Dettol 4.8% v/v 4% 10%

Cresol 2.5% 5%

Notes : The choice of disinfectants would depend on factors such as effectiveness, availability and the cost considerations. A contact period of 30 minutes is required for effective disinfection by the disinfectants. Plastics, rubbers and metals could be treated by chemical disinfection, but not all instruments/ waste should be treated in this manner. Some of the waste materials require further disposal after chemical disinfection such as blood, secretions, excreta and body fluids, which have been spilled. It should also be ensured that the wastes, which are to be incinerated, are cleaned of chemical disinfectants, especially halogen compounds to avoid environmental pollution.

(ii) Thermal technology : It uses heat to decontaminate instruments and equipment and the temperatures in this process may rise to extremely high levels. Most of the microbes are destroyed at temperatures below 100°C. Thermal technologies could be broadly classified into two groups depending upon the range of temperatures used in the process. There are the low heat systems operating at temperatures below 150°C and high heat systems where temperatures could go upto 5000°C. The

former uses steam or hot water while the latter uses plasma torches or combustion pyrrolysis to destroy the waste material. Thermal technologies include autoclave, hydroclave, microwave and incinerators.

Autoclave : This is a low heat process in steam at high temperatures is brought into contact with microorganisms for a specified period of time, to disinfect the waste matter completely. Autoclaves are used for sterilisation of reusable medical instruments, microbiology cultures and stock solutions (Fig. -2). The autoclaves used for biomedical waste management are of the following types :

Gravity displacement type - where air is pushed out of the ●autoclave by steam under pressure. This system operates at temperatures of 121°C and has a cycle time of approximately 60 - 90 minutes. The material to be sterilised is packed inside and the steam needs to penetrate into the waste wads to ensure effective sterilisation. The system has its disadvantage that there may be pockets of air left within the waste layers, which may reduce the temperatures attained inside thus reducing efficiency of the system.Prevacuum type - here vacuum pumps are utilised to ●evacuate the air in the chamber of autoclave and steam under pressure is pushed in, which is able to penetrate the waste material more thoroughly. This technology thus reduces the cycle time to approximately 30 - 60 minutes and the temperatures attained are upto 132°C.

Fig. - 2 : Autoclave

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Infectious wastes and bags are placed in the sealed chamber and exposed to the steam at required temperature and for a specified holding time. The wastes are reduced in volume minimally and the contaminating organisms are destroyed after the holding time period. The treatment process is monitored by placing spores of Bacillus stearothermophillus at the centre of waste load and checked.

Notes : The process has the advantage of having low operating costs, with minimal or non-toxic liquid or air emissions. However the waste volume is not completely reduced and certain categories of wastes such as cytotoxic or pathological wastes cannot be treated through this method. Moreover at times malodorous fumes are generated which need to be controlled. This method could be combined with shredding, grinding or compacting to reduce the volume of the waste material substantially.

Hydroclave : This is a steam sterilisation technology in which the steam is used as an indirect heating source thus allowing total dehydration of waste material.

Fig. - 3 : Hydroclave

The hydroclave (Fig. - 3) essentially comprises of a double-walled cylindrical container, which is horizontally mounted and has doors at the top and bottom for loading and unloading waste matter. In addition it has mixing arms inside the container that rotate to fragment the waste material. When steam is introduced into the outer jacket/wall it transmits heat rapidly into the wet waste inside the inner chamber. The waste matter is continuously subjected to tumbling motion by the motor mounted mixing arms whereby it produces its own steam and the pressure inside the chamber begins to rise. More steam is introduced from without to achieve the desired temperature and pressure. The holding time for waste is 15 minutes at 132°C or 30 minutes at 121°C. This continuous mixing ensures dehydration of the waste material and almost total dryness can be achieved inside the chamber. The organic components of the waste are hydrolysed and the waste matter is reduced by weight and volume. It has a mechanism of self-unloading after the treatment cycle, by opening the bottom door and reversing the rotation of the mixing arms. The mechanism has the advantage

of not requiring any pre-treatment of waste and complete dehydration of waste is achieved. The reduction in volume and weight makes it easy for final disposal of biomedical waste and the capital costs are low. However this mechanism also gives out malodorous fumes and certain pathological and cytotoxic wastes cannot be treated with this method.

Microwave : This low heat system uses microwaves to heat up the waste material from inside, unlike the external heat given in autoclave and hydroclave. Microwaves are electromagnetic waves that lie between the 300 to 300,000 mega hertz range in the electromagnetic radiation spectrum. They are able to penetrate materials and create vibrations in all the dipole molecules such as water in the waste materials. This vibration generates friction, which in turn produces heat to disinfect the waste material (Fig. - 4).

Fig. - 4 : Microwave

The waste matter is loaded manually on to a bucket hoist, which loads it into a sealed unit with a shredder, where the waste alongwith its bag is shredded and thereafter moistened with steam. This is then moved continuously by a screw auger, which is heated by series of microwave generators. The heat produced at 95 - 100°C for a holding period of 25 minutes kills all microorganisms without decomposing the material. Emissions are thus reduced and the air inside the microwave is passed through filter to eliminate potentially hazardous airborne pathogens. Wastes such as tubings, needles, syringes are rendered harmless and reduced in volume by 80%. These could then be used as landfill.

Notes : The process of microwave treatment renders waste matter acceptable for landfill. The water emissions are negligible; however air emissions are somewhat odorous. It requires a shredder for pre-treatment of waste and the microwaves are unable to penetrate large objects such as amputated limbs and specimens, which are part of anatomical wastes. The operational costs are high and skilled operators

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are required.

Incinerator : Incineration is a high heat system process of burning combustible solids at a very high temperature in a furnace. It employs combustion of waste material in stages, followed by cleaning of the flue gas through a number of pollution control devices. The end product is devoid of infectious organisms and organic compounds of waste, which is aesthetically acceptable (Fig. - 5).

Fig. - 5 : Incinerator

Classification : Incinerators are classified into different types depending on the type of fuel consumed, stages of incineration process and mechanism of action. Based on the type of fuel consumed the division could be -

Conventional incinerator using wood/charcoal ●Electrical incinerator ●Oil fired incinerator using some electricity and diesel oil ●

Currently the incinerators used are mostly of oil fired variety. This is almost maintenance free, quick to operate and almost smoke free. The incinerators could also be divided into stage I, II & III depending on the incineration process. Stage I involves thermally combusting the waste at temperatures above 800°C in a refractory lined heated chamber. This stage of combustion generates some volatile chemicals. The stage II incinerator is made of special refractory material and uses excess additional air to raise the temperature inside it to 1050 - 1100°C. This destroys the pathogenic organisms alongwith all chemicals/volatiles produced during stage I including harmful gaseous by products like dioxins and furans. Stage III incinerator uses venturi scrubbers, fabric filters, activated carbon and packed bed towers to eliminate polluting gases such as carbon monoxide, HCl, oxides of nitrogen and heavy metals such as mercury.

The hospital wastes that can be incinerated are : Surgical, autopsy and obstetrical wastes containing human ●or animal tissues.Dialysis, contaminated ward waste and isolation room ●waste.Blood and its products and microbiological wastes. ●

Notes : All materials of infectious nature are destroyed by incineration. The volume and mass of the waste material is reduced upto 80 - 95% thus ensuring safe final disposal. No pre-treatment such as shredding is required. However incineration process could give rise to air emissions of toxic materials such as particulate matter, acid gases, dioxins and furans. High operational costs and level of skill to operate the system is required. Certain radioactive wastes and aerosols containers cannot be incinerated.

(iii) Mechanical Technology : This technology is generally used to change the physical form and characteristic to enable ease of handling of the waste. This technology involves pulverising, compacting or shredding of waste matter to reduce its volume and weight. However this technology cannot be used of its own as final means of waste treatment, but has to be combined with other technologies especially thermal technology. Typically, these processes are carried out either before or after the waste has been decontaminated and are as under :

Compaction : Compacting is carried out by a hydraulic ram against a hard surface. Infectious content of waste is not reduced, while the possibility of formation of aerosols of infected matter and spillage of liquids does exist. Also, the process destroys the integrity of containers and requires skills to operate and maintain machines.

Grinding and shredding : Waste material is broken down into smaller particles under negative pressure to avoid any spillage outside the chamber. This method is used as a pre-treatment before technologies such as microwave and reduces the waste volume and renders it unrecognisable.

Pulverisation : This method consists of putting the waste in a hopper and mixed with large volume of water and bleach solution. The waste is torn to shreds and then fed to an ultra high speed hammer mill with large spin blades which pulverise the matter into small, safe particles. The solids and liquids are then separated and disposed off.

(iv) Irradiation technology : This involves exposing the waste matter to ultraviolet or ionising radiation in an enclosed chamber. Decontamination occurs when nucleic acids in the living cells are irradiated. The time of exposure, directness and level of relative humidity in the waste matter determines the efficiency of the procedure. The wastes are reduced by 20% in volume and the disinfected remains could thereafter be mechanically broken down and disposed off in landfill sites. The advantage with this technology is that energy input is minimal and it is used to treat items, which cannot be heated. The emissions are low however trained operators are required for this operation. The wastes need further treatment by another technology prior to disposal. Source of radiation also needs to be properly disposed off after its decay.

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How to select a treatment technology : The health care establishments have to establish a fine balance between optimum use of consumable material/ disposables and selection of appropriate waste treatment technology. This selection would depend on the categories of waste generated, type of equipment/technologies available on-site and off-site and the appropriateness of the selected technology for a particular waste matter. Disinfection efficiency, automated system, reduction of waste volume/ weight and recovery of recyclable products should be primarily considered. The selected technologies should have minimal polluting effect, discharges and emissions should be low and operational and fuel costs must be low. Usually incineration and autoclaving are the most widely used technologies, the former for anatomical wastes and latter for other infectious wastes, which are not incinerable.(g) Final disposal methods

General non hazardous wastes : These could be disposed off by landfilling at sites away from water sources and dwelling units and covered with suitable cover material. The site should be delimited with secure fences and sign postings. The sites could be trenches, sloping terrains or abandoned quarries. Mechanised equipment could be used for spreading the waste and trimming the top soil. Composting using night soil along with the biowaste could be used in trenches and vermiculture methods for garbage from kitchen and cafeteria could also be used. Large quantities of general wastes could be disposed using technologies, which convert the biodegradable wastes into fuel pellets, incinerable matter or biogas.

Liquid wastes : Liquid wastes from kitchens, cafeteria and laundry should be treated with a chemical disinfectant followed by neutralisation with reagent. The waste should thereafter be discharged into the sewerage system. In places with no sewerage system, the treated liquid wastes could be drained into soakage pits or waste stabilisation ponds.

Human anatomical wastes : These should be incinerated and thereafter the ash can be sent to landfill sites.

Sharps : These have the maximum chances of causing injuries due to mishandling and hence need precaution and care during disposal. They are stored in puncture proof containers in disinfectant solutions (e.g. plastic bread boxes), at the site of generation. Major portion of the sharps are needles, which can be cut by needle cutter and contained in 1% bleach solution or destroyed by needle destroyer. Some of the precautions in handling sharps are :

The health workers employed in the hospital should be ●vaccinated against Hepatitis BInfectious waste handlers should wear heavy duty gloves ●while dealing with waste matterRecapping of needles should be discouraged. Sharps should ●not be carelessly put at place of work.

After this treatment the residual waste could be sent to a landfill for disposal.

Microbiology waste : This is disposed by autoclave, hydroclave, microwave or incineration. The residue could be used in specialised landfills.

Infectious solid waste : This is treated by an appropriate thermal technology method and disposed off as general waste.

Chemical waste : Chemical waste of non hazardous nature could be disposed off as general wastes or recycled/ reused. Hazardous waste should be treated and discharged into sewers after dilution or incineration.

Radioactive waste : These are generated in the Nuclear medicine, Radiotherapy or Radiology departments need to be disposed according to guidelines laid down by the Bhabha Atomic Research Centre, India. Checks also need to be carried out in these establishments for radiation emission, use of protective gears and maintenance of equipment. The solid wastes are disposed by concentration and storage, while liquids by dilution and dispersal.

Pressurised containers : These should be disposed off alongwith general waste, in special landfills.

Administrative issuesEffective hospital waste management is possible when all the components of an organisation are well trained, aware and actively supportive of the programme.

Waste Management PolicyAll health care establishments should have a comprehensive waste care management policy. The hospital administrators, safety and infection control committees and departments such as nursing, housekeeping, laboratories and maintenance need to be more involved in the waste management activity. The general hospital waste management policy should serve as a mission statement, to inform regulatory and other agencies how the hospital’s waste is managed. It should give an overview of the programme while the different departments need to prepare their specific procedures.

The hospital/health care establishment waste management policy should be in consonance with the existing guidelines on the subject by the regulating authority, i.e. the Biomedical Waste (Management and Handling) Rules, 1998 of the Ministry of Environment and Forests, Govt of India and should cover the following aspects : (a) A background survey and evaluation of waste generated

should be conducted prior to implementation of waste management policy guidelines. Suitable places for placement of equipment should be identified and equipment, materials and supplies procured based on the requirement.

(b) A Hospital Waste Management Committee could be created, especially in large hospitals. Its members could be Head of hospital, Infection Control committee members/their representatives, Heads of certain Departments, Chief of nursing staff and representatives from ancillary and support services.

(c) In smaller hospitals a nodal officer could be identified as in-charge hospital waste management. Key members from the hospital could be designated to assist the nodal officer in discharge of his/her duties.

(d) The role and functions of each of the member of the hospital waste management committee should be clearly and lucidly defined. Periodic meetings could be held of the functionaries to ascertain the progress of implementation of policy, hear suggestions and discuss any change of plans.

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(e) The steps of waste management for the hospital/ health care establishment alongwith the actions of the various departments should be clearly described in the policy.

(f) Training of staff on the issues related to hospital wastes and generating awareness regarding the vision and mission of the establishment are critical to the success of the programme.

(g) Supervision of waste handlers and periodic reinforcement of training is required for efficient and safe management of hospital wastes.

SummaryBiomedical waste is defined as “any solid, fluid or liquid waste, including its container and any intermediate product, which is generated during the diagnosis, treatment or immunisation of human beings or animals, in research pertaining thereto, or in the production or testing of biologicals and the animal waste from slaughter houses or any other like establishments”. If it is not handled or disposed with proper care, it could be potentially hazardous and have significant public health consequences. Most of the wastes generated in a hospital (around 85%) are non-hazardous, while 10% are infective including sharps and pathological waste and the remaining 5% are non-infectious but hazardous such as chemical, pharmaceutical or radioactive wastes. The quantity of waste generated in a hospital in developed countries is 1 to 5 kg/bed/day with variations among countries, hospitals and specialities and in India; it is upto1 to 2 kg/bed/day. As per the Biomedical waste (Management and Handling) rules 1998, under the Environment Protection Act of India, proper management of biomedical waste is a statutory requirement and these rules have been elaborated in the Gazette notification of the Ministry of Environment and Forests, Govt of India dated 20 Jul 1998.

As per WHO, the biomedical wastes could be classified into eight categories on the basis of the type of waste and the risk of transmission of infectious material in them. They are General waste (domestic), Pathological, radioactive, Chemical, Infectious, Pharmaceutical wastes, Sharps and pressurised containers.

The biomedical wastes generated in a health care setting could be rendered safe by following certain principles of infection control like developing policies for bio-waste management as well as rationale patient management; by taking measures such as universal safety precautions, hand washing and use

of disinfectants and most importantly by reduction and proper segregation of wastes. The important steps to be followed for management of biomedical waste are survey of wastes generated; segregation of the hospital wastes at the source itself; collection & categorisation of waste into colour coded containers; storage of wastes for short period of time till the time of transportation in proper containers and in earmarked areas, displaying the biohazard symbol; transportation of waste to the final disposal point in proper vehicles by earmarked staff with protective gear; treatment of waste before its final disposal to reduce its bulk and make it free from pathogenic organisms by chemical disinfection, thermal technology (like autoclave, microwave, UV, IR and incinerators), mechanical technology or by irradiation and final disposal of the waste by incineration or by disposing off in a secured landfill.

Study ExercisesLong Question : Describe the procedure of Biomedical waste management in a 100 bedded hospital / health care setting.

Short Notes : (1) Biomedical waste categorisation (2) Segregation of Waste (3) Final Disposal of Biomedical wastes (4) Incineration (5) Hazards of Biomedical waste

MCQs1. The percentage of Biomedical waste generated in a

hospital which is non-hazardous is (a) 85% (b) 50% (c) 25% (d) 15%

2. The quantity of waste generated in a hospital in developed countries is (in kg/bed/day) (a) 10-15 (b) 5-10 (c) 1-5 (d) >30

3. According to the categories of bio-medical waste, waste sharps come under which category? (a) 3 (b) 4 (c) 5 (d) 6

4. According to the categories of bio-medical waste liquid waste comes under which category? (a) 8 (b) 7 (c) 5 (d) 6

5. According to the categories of bio-medical waste incineration ash comes under which category? (a) 8 (b) 7 (c) 9 (d) 10

6. The recommended treatment option for disposal of bio-med wastes with colour-coding of Black is (a) Secured Landfill (b) Incineration (c) Chemical Disinfection (d) None

7. Category of bio-med wastes that is not colour-coded as Black (a) 5 (b) 8 (c) 9 (d) 10

Answers : (1)a; (2)c; (3)b; (4)a; (5)c; (6)a; (7)b.

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125 Public Health Aspects of Housing and Ventilation

Kunal Chatterjee

House, as per the New Oxford Dictionary, is defined as a building for human habitation, especially one that is lived in by a family or a small group of people and consists of a ground floor and one or more upper storeys. Housing is described as houses and flats considered collectively. For the purpose of public health aspects, housing would also include adjacent walks, paths, streets, open space, shops, utilities, health centres, schools and administrative services. The density of population in an area, number of persons per room and physical condition of the dwellings are also considered when the effect of housing on the health of a community is taken.

The last two centuries have seen a rapid rise in industrial economies in the World with consequent changes in the distribution of population resulting from migrations, movements, establishment of new settlements and temporary camps in different countries. The increase in number of people results in increase in demands on the local civic amenities. Public health infrastructure in cities is unable to cope with this rise alongside the natural rise in the population residing in it. Population movements thus result in overcrowding, uncontrolled settlements and poor environmental conditions in the urban areas.

Housing Conditions in the WorldDeveloping Countries : Most of the developing countries have a problem of overcrowding and the living conditions are inadequate, forcing the urban dwellers into periurban slums. Cities in Southern and south-eastern Asia, African continent and Latin America variously have deplorable living conditions in these slums, which lack the basic housing and sanitation facilities. As a result of these conditions compounded by malnutrition, lack of education and inadequate medical and social services, communicable diseases become the predominant cause of morbidity. The plight of the vulnerable groups in these slums such as the children, elderly and women is terrible with the health care indicators grossly unsatisfactory. Infant mortality rates are high, high crime rates and other malevolent behaviour are often seen in the community and children may be abandoned by the parents due to poverty. These places are also the ideal grounds for breeding social unrest.

Developed Nations : In the recent decades the numbers of people without adequate shelter have increased even in the developed or relatively affluent countries. Rising economic costs of living, unemployment, inflation of commodity prices have created hard times for people in these countries and forced them out of their homes. The developed countries and their public health departments have to increasingly spend on the creating shelters and provide for such people. When these social safety nets are broken or wilt under pressure of increasing destitute population, the vulnerable people suffer the most and are turned homeless. These nations also have a problem of migrants or refugees pouring in from neighbouring

countries thereby affecting the already groaning public health infrastructure. As a consequence to this, a rise in mental health problems, substance abuse, alcoholism and crimes is noticed. Rising land prices and the need to provide accommodation for all its dwellers have also seen a proliferation of high-rise, high-density apartments. These create problems such as tensions attributable to living too close to neighbours, inadequate playing space for children and poor civic services in these areas.

Displaced Populations : The refugee population and the internally displaced people live in temporary settlements in developing countries. They depend on civic services of the nearby areas, which are themselves below par. Countries in Asia, Latin America and Africa are home to millions of refugees who have arrived due to displacement resulting from natural calamities, civil strife or wars. Their housing conditions are worse than periurban slums with inadequate health services, precarious supplies and poor record of safety and security of these people. The refugee population are often threatened by hostilities and suffer from various communicable diseases prevalent in poor camp living conditions. The children and vulnerable people exhibit signs of malnutrition and stress disorders due to trauma of displacement.

Housing StandardsHousing standards vary from country to country and are not confined to merely calculating the per capita space and floor space. Socio-economic characteristics such as family income, family size, composition, living standards, and cultural factors are also taken into consideration in determining housing standards. The Environmental Hygiene Committee has established minimum standards required to be maintained by building regulations in India, of which the important ones are:

Site - elevated, not subject to flooding, away from vector breeding places and nuisance, soil should be dry and safe for founding the structure. Subsoil water should be below 10 feet.

Set back - as open space around house with no obstruction to lighting and ventilation

Floor - pucca, impermeable, easily washable, smooth and free of cracks and crevices and damp-proof.

Walls - reasonably strong, low heat capacity, not easily damaged and should not harbour rats or vermin

Roof - height not less than 10 feet with low heat transmittance coefficient

Rooms - at least two with the number increasing according to family size

Floor area - should be 100 sq. ft for one person and at least 120 sq ft for more than one person

Cubic space - at least 500 c.ft per capita; optimum is 1000 c.ft.

Windows - at least 2 windows per living room if the room is not provided mechanical ventilation and artificial lighting, placed at a height of not more than 3 feet above ground, window area should be 1/5th of floor area.

Lighting - daylight factor exceeding 1% over half floor area.

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Kitchen - should be separate for every dwelling, protected against dust and smoke, provided with storage space, water supply, drainage and adequately lighted.

Sanitary privy - in every house and readily accessible.

Garbage and refuse - should be removed daily and sanitarily disposed.

Bathing and washing facilities - should be exclusive to the house.

Water supply - should be safe and adequate.

Rural Housing Standards : At least two living rooms, ample verandah space, built up area should not exceed one-third total area, separate kitchen with paved sink or platform for washing utensils, sanitary latrine in the house, sanitary well or tube well within quarter mile of house, cattle sheds at least 25 feet from dwelling houses and adequate arrangement for disposal of waste water, refuse and garbage.

Housing Standards for Displaced Populations : Temporary shelter in existing buildings should be provided to people as per the following guidelines :

People living on beds or mats should have minimum of 3.5 ●sq. m of floor area or 10 cu m of air space.Beds or mats separated by a minimum distance of 0.75 ●m.Buildings should have emergency exits and fire escapes ●and people educated in fire safety drills.One wash basin provided for every 10 people, separate ●benches for men and women.One shower head is needed for every 50 people in temperate ●climates and one for every 30 people in hot climates.Water flushed toilets may be made available in existing ●buildings. Outside latrines should be located within 50 m of the building, but at least 20 m away from kitchen, dining hall and water supply.One refuse bin of capacity 50-100 litres with tightly fitting ●lid should be provided for every 12-15 people.

The guidelines for those people who are housed in tents or makeshift shelters are as below :

Site should be located above flood level and away from ●excessive vegetationCamps should not hold more than 10000-12000 people. ●Drainage ditches should be constructed to drain rain water ●away from shelters and storage areas. Stagnant water collections should be drained or filled up.Shelters should be arranged in rows of 10-12 on both ●sides of road, at least 2 m away from road edges. The road should be at least 10 m wide for easy access of vehicles and distance between tent pegs should be 8 m.Tents or prefabricated units could be used as shelters. ●Where plastic sheets are used, one piece 4 metres by 6-7 metres should be provided to one household.No one should have to walk more than 500 m to water ●point and there should be at least one water point for every 250 people.At least one toilet should be provided per 20 people with ●separate provisions for men and women. Requirement of children and elderly should be accordingly catered for suitably.

Accommodation arrangements should be separately catered ●for children, with provision for adults to stay with them. These children may be disoriented and frightened and may have special nutritional needs, which should be adequately looked after. Feeding and nutrition rehabilitation units for special needs should be provided with up to 15-30 litres of potable water per bed per day.

Housing and the Governmental policy : In India the National Family Health Survey (NFHS) collects data on housing condition of people. The data from NFHS 3 shows that only about 26% of rural India lives in pucca houses, with only 28% having access to piped drinking water and 26% have access to toilet facilities. While housing is a state subject but the Union Govt formulates policy for housing especially pertaining to weaker sections, and the schemes are implemented at the state level. A separate Ministry of Works and Housing has been created as early as 1952 to implement the Government Housing Programmes. These programmes comprise of the public sector housing for governmental employees and social housing schemes for low and middle income groups.

States have established statutory housing boards for promoting various housing schemes. The National Housing Policy is enunciated in the national five year plans and the eighth and subsequent plans consist of creating an enabling environment for housing activity by eliminating various constraints and providing special assistance to the disadvantaged groups including the rural and the urban poor, the scheduled castes and tribes, physically handicapped, widows and single women.

VentilationThe ability of an individual to comfortably accommodate himself in a house depends upon numerous factors in the physical environment of which an important one is the ventilation provided in his living and working area. The dictionary meaning of ventilation is ‘intentional movement of air from outside a building to inside’. Adequate ventilation improves comfort levels of an inhabitant. However an excess of ventilation may result in discomfort due to cooling of the indoor air temperature, which is a not desirable, particularly in cold and dry or damp area in the country. Ventilation is one of the most important factors for maintaining acceptable indoor air quality in a building.

Ventilation does not merely mean flow of air in a room or replacement of vitiated air inside the room by fresh air being blown from the windows, doors or ventilators. It also implies control of the quality of air flowing inside the room by modifying the temperature, humidity and purity to provide an environment, which is thermally controlled and comfortable, gives a sense of well-being and reduces the risk of transmission of airborne diseases.

Ventilation air : The air used to provide acceptable indoor air quality is called as ventilation air. It removes the bad odours from inside building spaces due to presence of humans/ animals. This air is delivered either naturally or by means of mechanical ventilation and these means could increase or decrease the temperature of air or change its moisture content depending on the requirement inside the building. The rate at which outdoor air replaces indoor air is described as ‘air

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exchange rate’. When this rate is low, the pollutant levels in an environment increase.

Ventilation standards : These standards have largely been fixed on the area and amount of ventilation air required to achieve a sense of freshness in a room and remove body odours. These standards are described as :

(a) Floor space : This describes the product of the length and breadth of the room and is considered an important parameter for ventilation. The optimum floor space requirements per person vary from 50 to 100 feet.

(b) Cubic space of area : This has been used in the past and earlier prescriptions were of a fresh air supply of 3000 cu feet of air per person per hour. Since the products of respiration tend to accumulate in the lower levels, hence higher heights of rooms, beyond 12 feet, are ineffective from the point of view of ventilation and are not taken into account for establishing these standards. Current standards consider 1000 to 1200 cu feet per person per hour to be sufficient for generating comfort.

(c) Air change : It is a better standard for ventilation than cubic space requirement. If the cooling power of air arising out of adequate air changes is satisfactory, then even with a dip in the oxygen content of air upto 18 percent no deleterious effects would occur on human physiology. The recommended number of air changes in living room should be 2 to 3 in an hour, while in work rooms and assemblies the air changes could be 4 to 6 per hour. Higher changes could result in creation of air drought, which could reduce the comfort levels and hence should be avoided.Types of ventilation

Infiltration : In infiltration the outdoor air flows into the house through openings, joints and cracks in walls, floors, ceilings and around windows and doors. Commercial buildings and sometimes residential areas are kept under slightly positive pressure relative to the outdoors to reduce infiltration. This helps in moisture management and humidity control inside the rooms.

Natural ventilation : This occurs when the air in a space is changed with outdoor air without the use of mechanical systems such as fans or circulators. Natural ventilation is mostly achieved through operable windows but could also be achieved through temperature and pressure difference between spaces. In this method of ventilation reliance is placed on the forces of nature such as wind, ambient temperature and air pressure. These are best utilised by proper location of windows, doors, ventilators and skylights. There are two types of natural ventilation occurring in buildings as described below :

(a) Wind driven ventilation : Pressures generated by wind are usually high and majority of the buildings rely mostly on this method. When wind blows through a room it is termed as ‘perflation’ and on its tail end it generates a suction effect known as ‘aspiration’. These phenomena are seen when the doors and windows face each other and provide cross ventilation. The air has a capability to diffuse through narrow openings and spaces and thus may ventilate the rooms in addition to passage through the doors and windows.

The impact of wind on a building affects ventilation and

infiltration rates through it and the associated heat losses and gains. It creates areas of positive pressure on the windward side of the building and negative pressure on the leeward side and the sides of the building. Thus the shape of the building is crucial in creating wind pressures that will drive air flow through its apertures. Simple building shapes improve the ventilation while complex shapes create more turbulent air flows.

Wind driven ventilation has several benefits. Being a naturally occurring force it is readily available, economic to implement, could be controlled by users and achieves great magnitude and effectiveness. However it is limited by its unpredictability in speed and directions, which vary constantly; the air quality is not controlled and could introduce pollutants inside a room and may create draughts and discomfort.

(b) Stack driven ventilation : When there is temperature difference between two adjoining volumes of air, the warmer air will have lower density and be more buoyant and thus will rise above the cold air, creating an upward stream. In a house, such kind of effect, known as ‘stack effect’ happens in a fire place in a forced/active manner, while it occurs passively in spaces without direct access to outdoors. To have optimum ventilation due to stack effect in a building, the inside and outside air temperatures must be different, such that the warmer indoor air rises and escapes the building through the higher apertures, while colder, denser air from the exterior enters the buildings through lower level openings. The greater this temperature difference the greater the stack effect.

This kind of ventilation does not rely on wind but can take place in hot, summer days also; the air flow is relatively stable with a greater control in choosing the areas of air intake. However it is limited due to lower magnitude of ventilation, reliance on temperature differences, restrictions to the ventilation due to building designs and possibility of introducing polluted external air inside the room. Such type of ventilation is generally used in mills, boiler rooms, warehouses and industrial plants.

Natural ventilation can be an effective means when both the wind driven and stack ventilation can be used to augment each other’s effect in an optimal manner. However its chief drawback is that it is not possible to regulate the velocity of incoming air or adjust its temperature and humidity.

Mechanical ventilation : This kind of ventilation is used where natural ventilation does not improve the indoor air quality or increases the chance of bringing contaminants inside the building. Such ventilation systems are usually established in places with high humidity to remove the excess moisture from ventilation air. Commonest forms of mechanical ventilation are:

(a) Ceiling fans, table or floor fans : These are used to circulate air within a room for the purpose of reducing the perceived temperature, because of evaporation of perspiration from the skin of occupants. These fans do not introduce outside air inside the room, hence do not provide ventilation in the strictest sense. Air-coolers are used in hot & dry conditions in the developing countries and are quite popular in India. They comprise of a chamber whose walls are made of straw, which is kept cool by pouring water on to the walls and evaporation

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of water due to the warm air outside. A cool environment is thus created inside the chamber and a fan kept in this chamber blows cool air inside the room.

(b) Use of exhausts : Here the indoor air is extracted out with the help of mechanically driven fans. These are used in combination with the doors and windows since exhaustion of air outside the room creates a vacuum and this needs to be replaced by fresh air, which enters the room through windows, doors and other inlets. Exhausts are useful in industries especially where excess heat is generated. In residential areas they are placed in kitchens and bathrooms for extricating smoke or odours. Usually exhausts are placed near the roof to extricate hot air, which rises up in a room. The exhaust blades should be cleaned & well maintained to ensure their long life.

(c) Plenum ventilation : This is a process where air is blown inside a room by the use of fans and it enters through ducts. This kind of ventilation creates a positive air pressure inside the room. When this mechanism is combined with exhaust mechanism it creates ‘balanced ventilation’. Such kind of plenum ventilation is also being used, alongwith air-conditioners, to supply air inside the building such that fresh air is circulated to leave out the odours and pollutants.

(d) Air conditioning : It is a system, which provides a combination of cooling, ventilation and control of humidity for a building where it is installed. The system has a refrigerant providing cooling through a ‘refrigeration cycle’. This cycle comprises of four elements to provide the cooling effect. A compressor provides compression for the system. This causes the cooling refrigerant vapour to heat up. Next a condenser cools the vapour by exchanging its heat with outside air and the vapour condenses into a fluid. The condensed fluid enters the next element called as evaporator-dehumidifier where in the pressure drops and fluid evaporates and in the process draws heat from the surroundings, thus cooling it. The vapour is then returned to the compressor and pushed inside the room by a fan. Since the evaporator operates at a temperature below dew-point, moisture is collected at this end, which falls into a pan and is removed by a pipe outside.

Air conditioners are installed inside the residential areas or commercial complexes as either stand-alone systems or a part of central air-conditioning systems. Central air-conditioning system should be installed at the time of construction, since they are difficult to retrofit or install in a building, which was not designed to receive it, due to the large ducts needed to carry the air to the specific areas. These ducts must be carefully maintained to prevent growth of pathogenic bacteria in them. Another system of air-conditioning gaining popularity in residential areas and smaller commercial buildings is the split air-conditioning where the fan coils are connected to remoter condenser unit using piping instead of ducts.

Demand controlled ventilation : This is another technique of ventilation, which reduces the energy consumption in a building, while maintaining adequate air quality. Here, instead of a fixed air replacement rate, carbon-dioxide sensors dispersed inside the building areas are used to control the ventilation rate dynamically, based on emissions of actual building occupants.

HVAC : HVAC stands for ‘Heating, Ventilation and Air-Conditioning’. This system is important in those places where humidity and temperature must be closely regulated while maintaining healthy and safe conditions inside buildings. These three terms are used in combination to ensure thermal comfort, accessible indoor quality and reasonable installation, operation and maintenance costs. HVAC systems determine the room air distribution i.e. how air is delivered to and removed from room spaces.

Ventilation requirements in different areas : Ventilation is used to remove unpleasant smells and excessive moisture, introduce outside air and to keep interior of a building air circulating to prevent stagnation of the interior air. Ventilation requirements vary from urban areas to rural areas and also post disaster situations. In urban areas the requirements differ between bungalows, high-rise buildings, slums and shanty settlements. The factors which determine the difference in ventilation are :

Type of buildings, bungalows, high rise buildings, ●temporary shelters, tents, camps, hutmentsSize of the buildings and the floor areas. ●Type of roof inside the buildings such as cement-concrete, ●thatch, mud, tins or indigenous material, presence of false ceilings etc.Locally prevalent wind directions ●Number of persons occupying the room ●Proximity to commercial or industrial areas ●Sanitation of the surrounding area ●Nature of work being carried out inside the buildings ●Geographical locations such as closeness to sea, large ●water bodies, hilly areas

In urban areas, due to rise in ambient temperatures in the day and obstruction to wind movement due to building constructions, the residents use mechanical cooling devices and air-conditioning systems. Similarly in commercial and industrial establishments a combination of natural and mechanical ventilations is being used. Energy efficient systems are utilised in large buildings and storage areas. Urban slums are overcrowded and do not have free air circulation in most places. The houses are constructed close by each other and numerous small scale industries develop within these settlements. Most of the slum dwellings have erratic power supply in the developing countries and hence the dwellers largely rely on natural ventilation or the use of fans, circulators or air-coolers.

In rural areas the houses are mostly single storied and well spread out and thus air circulation around houses is not obstructed. Overcrowding does not usually exist and there is natural ventilation in plenty and hence the dwellers rarely use fans or air-coolers. Natural ventilation is however not able to prevent the odours arising out of animals residing nearby houses and improper disposal of garbage and solid wastes.

In post-disaster situations, the displaced persons need to be accommodated in shelters and camps constructed or occupied temporarily. These places are usually overcrowded and require proper sleeping arrangements and disposal of wastes of the dwellers. The odours and insanitation generated due to this

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situation is compounded by the devastation caused by the calamity in the surroundings. There is usually a breakdown of power supply in the early days following the disaster. In such temporary shelters, arrangements should be made to ensure plenty of natural ventilation from the doors and windows and augmented by mechanical fans and coolers. However care must be taken to ensure that the air infiltration does not create a draught, especially in coastal areas and hills during cold or rainy weather conditions.

SummaryHousing is described as houses and flats considered collectively. For the purpose of public health aspects, housing would also include adjacent walks, paths, streets, open space, shops, utilities, health centres, schools and administrative services. The effect of housing conditions on the health of human beings varies with the type of community and the prevalent socio-political conditions in the country. It has been shown that the people who live in bad housing and poor environmental conditions in any area experience higher mortality rates and are generally less healthy than those who live in districts where housing is good. People living in houses with poor water supply and inadequate means of excreta disposal and fly control report higher incidence of diarrhoeal diseases. Poor domestic surroundings could result in breeding of disease vectors.

Rural housing has few characteristics like Inadequate drainage of standing water around dwellings, littering with artificial containers and water stagnation in fields, Improper solid waste disposal and the cohabitation of cattle and pet animals creating ideal grounds for transmission of communicable diseases among the rural inhabitants. The settlements, which house people undergoing a social and economic change, often from a rural to urban way of life, to integrate with the urban society, are termed as transitional housings. The transitional house dwellers are affected by rapid urbanisation in the towns and cities and their houses are converted into substandard dwelling units. These shanty towns need to be either replaced with good housing, which provide complete services or the current dwellers could be provided with alternate land areas at low costs to construct their own homes. This could generate a sense of integration among the dwellers with the urban areas and decrease the public health impact of their temporary settlements. During natural and civil disasters, governments and international agencies need to provide comprehensive services to cover the provision of shelter, sanitation, food, epidemiological surveillance and medical care for displaced populations.

Housing standards vary from country to country and are not confined to merely calculating the per capita space and floor space. Socio-economic characteristics such as family income, family size, composition, living standards and cultural factors are also taken into consideration in determining housing standards. The Environmental Hygiene Committee has established minimum standards required to be maintained by building regulations in India.

The data from NFHS 3 shows that only about 26% of rural India lives in pucca houses, with only 28% having access to piped drinking water and 26% have access to toilet facilities.

While housing is a state subject but the Union Govt formulates policy for housing especially pertaining to weaker sections, and the schemes are implemented at the state level. States have established statutory housing boards for promoting various housing schemes. The National Housing Policy is enunciated in the national five year plans and the eighth and subsequent plans consist of creating an enabling environment for housing activity by eliminating various constraints and providing special assistance to the disadvantaged groups including the rural and the urban poor, the scheduled castes and tribes, physically handicapped, widows and single women.

Ventilation does not merely mean flow of air in a room or replacement of vitiated air inside the room by fresh air being blown from the windows, doors or ventilators. It also implies control of the quality of air flowing inside the room by modifying the temperature, humidity and purity to provide an environment, which is thermally controlled and comfortable, giving a sense of well-being and reducing the risk of transmission of airborne diseases. Ventilation standards have largely been fixed on the area and amount of ventilation air required to achieve a sense of freshness in a room and remove body odours. The optimum floor space requirements per person vary from 50 to 100 feet and cubic space of 1000 to 1200 cu feet per person per hour. The recommended number of air changes in living room should be 2 to 3 in an hour, while in work rooms and assemblies the air changes could be 4 to 6 per hour. HVAC (Heating, ventilation and air-conditioning) is important in those places where humidity and temperature must be closely regulated while maintaining healthy and safe conditions inside buildings.

Study Exercises Long Question : Enumerate the effects of improper Housing conditions on Health. Discuss the standards laid down for Housing.

Short Notes : (1) Criteria for Healthful Housing (2) Public Health aspects of Rural Housing (3) Steps to be taken by Public Health authorities to provide Housing for displaced during disasters (4) Overcrowding (5) Transitional housing (6) Housing policy in India (7) Ventilation standards (8) HVAC

MCQs 1. As per the Housing standards recommended by The

Environmental Hygiene Committee, Subsoil water should be below (in feet) (a) 2 (b) 5 (c) 10 (d) 20

2. As per the Housing standards recommended by The Environmental Hygiene Committee, height of the roof should not be less than (in feet) (a) 2 (b) 5 (c) 10 (d) 20

3. The minimum Floor area in a house required for one person should be (a) 100 sq. ft (b) 200 (c) 250 (d) 50

4. The minimum Cubic space in a house required for one person should be (in Cu ft) (a) 100 (b) 200 (c) 250 (d) 500

5. In a House, window area should be _________ of floor area (a) 1/5th (b) 2/5th (c) 1/3rd (d)1/2

6. The recommended number of air changes in living room should be ______ (per Hour) (a) 1-2 (b) 2-3 (c) 3-4 (d)4-5

Answers : (1) c; (2) c; (3) a; (4) d; (5) a; (6) b.

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126Environmental Pollution : Air, Soil, Noise and Radiological Pollution

Leo S Vaz

Air PollutionClean air is considered to be a basic requirement of human health and well-being. However, air pollution continues to pose a significant threat to health worldwide. According to a WHO assessment of the burden of disease due to air pollution, more than 2 million premature deaths each year can be attributed to the effects of urban outdoor air pollution and indoor air pollution (caused by the burning of solid fuels). More than half of this disease burden is borne by the populations of developing countries. Source of major air pollutants and their effects on man are as mentioned in the Table - 1 and 2.

Indicators of air pollutionThe WHO Air quality guidelines are designed to offer global guidance on reducing the health impacts of air pollution. They recommend measurement of selected air pollutants, viz., particulate matter (PM), ozone (O3), nitrogen dioxide (NO2) and sulfur dioxide (SO2), applicable across all WHO regions. In addition, “smoke (soiling) index” and “coefficient of haze” are also commonly used indicators. In India, the Central Pollution Control Board through its National Air Quality Monitoring Programme monitors air quality in all major cities.

Particulate Matter : PM affects more people than any other pollutant. It consists of a complex mixture of solid and liquid particles of organic and inorganic substances suspended in the air. The particles are identified according to their aerodynamic diameter, as either PM10 (particles with an aerodynamic diameter smaller than 10 µm) or PM2.5 (aerodynamic diameter smaller than 2.5 µm). The latter are more dangerous since, when inhaled, they may reach the peripheral regions of the bronchioles, and interfere with gas exchange inside the lungs.

Table - 1 : Major Air Pollutants and their Health Hazards

Pollutant Source Pathological effects on man

Sulphur dioxide

Colourless gas produced by coal and oil combustion and certain industrial sources

Respiratory irritant, aggravates asthma and other lung and heart diseases, reduces lung function.

Nitrogen oxides

Brownish orange gas produced by motor vehicles and combustion at major industrial sources

Inhibits cilia action so that soot and dust penetrate far into the lungs.

Hydrogen sulphide

Refineries, chemical industries and bituminous fuels Causes nausea, irritates eyes and throat.

Carbon monoxide

Burning of coal, gasoline, motor exhausts Reduces oxygen carrying capacity of blood.

Hydrogen cyanide

Blast furnace, fumigation, chemical manufacturing, metal plating, etc.

Interferes with nerve cells, produces dry throat, indistinct vision, headache, etc.

AmmoniaExplosives, dye making, fertilizer plants and lacquers

Inflames upper respiratory passages.

Phosgene or carbonyl chloride

Chemical and dye makingInduces coughing, irritation and fatal pulmonary edema.

Aldehydes Thermal decomposition of oils, fats, or glycerols Irritate nasal and respiratory tracts

ArsinesProcesses involving metal or acids containing arsenic soldering

Damage red cells in blood, kidneys and cause jaundice

Suspended particles (ash, soot, smoke, etc.)

Solid or liquid particles produced by combustion and other processes at major industrial sources (e.g. steel mills, power plants, chemical plants, incinerators and almost every manufacturing process)

Respiratory irritants aggravate asthma and other lung and heart diseases (especially in combination with sulphur dioxide); many are known as carcinogens. Toxic gases and heavy metals absorb onto these particulates and are commonly carried deep into the lungs. Cause emphysema, eye irritation and possibly cancer

Lead Very small particles emitted from motor vehicles and smelters

Toxic to nervous and blood-forming systems, in high concentrations can cause brain organ damage.

Ozone A colourless gas formed from reactions between motor vehicle emissions and sunlight. It is the major component of smog

Respiratory irritant, aggravates asthma and other lung and heart diseases, impairs lung functions. Ozone is toxic to plants and corrodes materials.

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The guideline values (upper acceptable limits) are: PM ● 2.5 10 µg/m3 annual mean; 25 µg/m3 24-hour mean PM ● 10 20 µg/m3 annual mean; 50 µg/m3 24-hour mean

The major components of PM are sulfate, nitrates, ammonia, sodium chloride, carbon, mineral dust and water. Particles may be classified as primary or secondary, depending on how they are formed. Primary particles are emitted into the atmosphere through man-made (anthropogenic) and natural processes including combustion of fuels in vehicle engines or in households; industrial activities; erosion of road surfaces by road traffic and abrasion of brakes and tyres; and work in caves and mines. Secondary particles are also emitted largely from anthropogenic sources, but they are formed in the air, usually by chemical reactions between gaseous pollutants. Particles produced by outdoor sources (industry and traffic) penetrate easily into indoor spaces and add to the burden of PM emitted indoors.

Chronic exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as of lung cancer. In developing countries, exposure to pollutants from indoor combustion of solid fuels on open fires or traditional stoves increases the risk of acute lower respiratory infections and associated mortality among young children; indoor air pollution from solid fuel use is also a major risk factor for chronic obstructive pulmonary disease and lung cancer among adults.

Ozone (O3) : Ozone at ground level - not to be confused with the ozone layer in the upper atmosphere - is one of the major constituents of photochemical smog. It is formed by the reaction with sunlight (photochemical reaction) of pollutants such as nitrogen oxides (NOx) from vehicle and industry emissions and volatile organic compounds (VOCs) emitted by vehicles, solvents and industry. The highest levels of ozone pollution occur during periods of sunny weather. Excessive ozone in the air can have a marked effect on human health. It can cause breathing problems, trigger asthma, reduce lung function and cause lung diseases. Guidelines values for upper limits are: 100 µg/m3 (8-hour mean)

Nitrogen dioxide (NO2) : As an air pollutant, NO2 has several correlated activities: -(a) At short-term concentrations exceeding 200 µg/m3, it is

a toxic gas which causes significant inflammation of the airways.

(b) NO2 is the main source of nitrate aerosols, which form an important fraction of PM2.5 and, in the presence of ultraviolet light, of ozone.

The major sources of anthropogenic emissions of NO2 are combustion processes (heating, power generation, and engines in vehicles and ships). Epidemiological studies have shown that symptoms of bronchitis in asthmatic children increase in association with long-term exposure to NO2. Reduced lung function growth is also linked to NO2. The upper limits of guideline values are: 40 µg/m3 (annual mean) and 200 µg/m3 (1-hour mean).

Sulfur dioxide (SO2) : SO2 is a colourless gas with a sharp odour. It is produced from the burning of fossil fuels (coal and oil) and the smelting of mineral ores that contain sulfur. The main anthropogenic source of SO2 is the burning of sulfur-containing fossil fuels for domestic heating, power generation and motor vehicles. The use of tall chimneys at power stations has caused widespread dispersion of SO2 affecting populations located far away from the sources. In many developing countries, the usage of coal high in sulfur is increasing. SO2 can affect the respiratory system and the functions of the lungs, and causes irritation of the eyes. Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract. Hospital admissions for cardiac disease and mortality increase on days with higher SO2 levels. When SO2 combines with water, it forms sulfuric acid; this is the main component of acid rain which is a cause of deforestation. The upper limit of acceptable values are 20 µg/m3 (24-hour mean) and 500 µg/m3 (10-minute mean).

Prevention Public health recognizes air pollution as an important determinant of health, especially in developing countries. There

Table - 2 : Major natural and man-made pollutant sources.

Contaminant Man-made sources Natural sources

SO2 Fossil fuel combustion Volcanoes, reactions of biological emissions

H2S and organic sulphides, CO Chemical processes, sewage Auto exhaust, general combustion

Volcanoes, biological processes in soil and water, forest fires, photochemical reactions

NO, NO2 Combustion Biological processing in soil, lightning

NH3 Waste treatment, combustion Biological processes in soil

N2O Small amounts from combustion Biological processes in soil

CH4 Combustion, natural gas Biological process in soil and water.

Isoprene and terpenes None Biological plant Emission

Total non CH3 hydrocarbons Combustion Biological process in soil and vegetation

CO2 Combustion Biological processes

CH3CI Combustion Oceanic biological processes

HCl, Cl2 Combustion, Cl manufacturing Atmospheric reactions of NaCl volcanoes

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is significant inequality in the exposure to air pollution and related health risk; air pollution combines with other aspects of the social and physical environment to create a disproportional disease burden in less affluent parts of society. Exposure to air pollutants is largely beyond the control of individuals and requires action by public authorities at the national, regional and even international levels. The health sector can play a central role in leading a multisectoral approach to prevention of exposure to air pollution with support of other relevant sectors (transport, housing, energy production and industry). The major modes of prevention are:

(a) Containment : This prevents pollutants from entering the atmosphere. This can be carried out by engineering methods like enclosure, ventilation or air scrubbing & arresting of pollutants. The following dust control devices are generally used in industry :

(i) Dust collection systems : These are designed to handle heavy dust loads; a dust collector consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system, such as Cyclones, Electrostatic precipitators, and, Baghouses.

(ii) Scrubber systems : These are a diverse group of air pollution control devices that can be used to remove particulates and/or gases from industrial exhaust streams, such as Baffle spray scrubber, Cyclonic spray scrubber, Ejector venturi scrubber, Mechanically aided scrubber, Spray tower, and, Wet scrubber.

(b) Replacement or modernisation of equipment/process: This can result in decrease in pollution. e.g. Use of unleaded petrol.

(c) Zoning : During the planning process itself polluting industries are kept away from habitable locations.

(d) Regulatory Measures : The Air (Prevention and Control of Pollution) Act, 1981.

The objective of the Air (Prevention and Control of Pollution) Act, 1981 is to provide for the prevention, control and abatement of air pollution in India by the establishment of pollution control Boards at the Centre as well as State levels, and by conferring and assigning such Boards, powers and functions, with a view to implementing air pollution control measures. Details are discussed in the chapter on health legislations.

Greenhouse Gases and SocietyGreenhouse gases naturally blanket the Earth and keep it about 33°C warmer than it would be without these gases in the atmosphere. This is called the Greenhouse Effect. Over the past century, the Earth has increased in temperature by about 0.5°C and many scientists believe this is because of an increase in concentration of the main greenhouse gases: carbon dioxide (76%), methane (13%), nitrous oxide (6%), and fluorocarbons (5%). People are now calling this climate change over the past century the beginning of Global Warming. Fears are that if people keep producing such gases at increasing rates, the results will be negative in nature, such as more severe floods and droughts, increasing prevalence of insects, sea levels rising, and Earth’s precipitation may be redistributed. These changes to the environment will most likely cause negative effects on society, such as lower health and decreasing economic

development. However, some scientists argue that the global warming we are experiencing now is a natural phenomenon, and is part of Earth’s natural cycle. Presently, nobody can prove if either theory is correct, but one thing is certain; the world has been emitting greenhouse gases at extremely high rates and has shown only small signs of reducing emissions until the last few years. After the 1997 Kyoto Protocol, the world has finally taken the first step in reducing emissions.

The “greenhouse effect” is the heating of the Earth due to the presence of greenhouse gases. It is named this way because of a similar effect produced by the glass panes of a greenhouse. Shorter-wavelength solar radiation from the sun passes through Earth’s atmosphere, and then is absorbed by the surface of the Earth, causing it to warm. Part of the absorbed energy is then re-radiated back to the atmosphere as long-wave infrared radiation. Little of this long-wave radiation escapes back into space; the radiation cannot pass through the greenhouse gases in the atmosphere. The greenhouse gases selectively transmit the infrared waves, trapping some and allowing some to pass through into space. The greenhouse gases absorb these waves and re-emits the waves downward, causing the lower atmosphere to warm. The diagram below explains the process of global warming and how greenhouse gases create the “greenhouse effect” (Fig. - 1).

Fig. - 1 : Greenhouse effect

Greenhouse Gases

Carbon-dioxide : It is a colorless, odorless non-flammable gas and is the most prominent Greenhouse gas in Earth’s atmosphere. It is recycled through the atmosphere by the process photosynthesis, which makes human life possible. Carbon-dioxide is emitted into the air as humans exhale, burn fossil fuels for energy, and deforest the planet. Every year humans add over 30 billion tons of carbon dioxide in the atmosphere by these processes. We use “fossil fuels” as coal, oil and natural gas to generate electricity, heat our homes, power our factories and run our cars. These fossil fuels contain carbon, and when they are burned, they combine with oxygen, forming carbon dioxide. Deforestation is another main producer of carbon dioxide. The causes of deforestation are logging for lumber,

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pulpwood, and fuel wood. Also contributing to deforestation is clearing new land for farming and pastures used for animals such as cows. Forests and wooded areas are natural carbon sinks. This means that as trees absorb carbon dioxide, and release oxygen, carbon is being put into trees. This process occurs naturally by photosynthesis, which occurs less and less as we cut and burn down trees. As the abundance of trees declines, less carbon dioxide can be recycled. As we burn them down, carbon is released into the air and the carbon bonds with oxygen to form carbon dioxide, adding to the greenhouse effect.

Methane : Methane is a colorless, odorless, flammable gas. It is formed when plants decay and where there is very little air. It is often called swamp gas because it is abundant around water and swamps. Bacteria that breakdown organic matter in wetlands and bacteria that are found in cows, sheep, goats, buffalo, termites, and camels produce methane naturally. Since 1750, methane has doubled, and could double again by 2050. Each year we add 350-500 million tons of methane to the air by raising livestock, coal mining, drilling for oil and natural gas, rice cultivation, and garbage sitting in landfills. It stays in the atmosphere for only 10 years, but traps 20 times more heat than carbon dioxide.

Nitrous Oxide: Nitrous oxide is another colorless greenhouse gas; however, it has a sweet odour. It is primarily used as an anesthetic because it deadens pain and for this characteristic is called laughing gas. This gas is released naturally from oceans and by bacteria in soils. Nitrous oxide gas risen by more than 15% since 1750. Each year we add 7-13 million tons into the atmosphere by using nitrogen based fertilizers, disposing of human and animal waste in sewage treatment plants, automobile exhaust, and other sources not yet identified. It is important to reduce emissions because the nitrous oxide we release today will still be trapped in the atmosphere 100 years from now. Nitrogen based fertilizer use has doubled in the past 15 years. These fertilizers provide nutrients for crops; however, when they breakdown in the soil, nitrous oxide is released into the atmosphere. In automobiles, nitrous oxide is released at a much lower rate than carbon dioxide, because there is more carbon in gasoline than nitrogen.

Fluorocarbons: Fluorocarbons are a general term for any group of synthetic organic compounds that contain fluorine and carbon. Many of these compounds, such as chlorofluorocarbons (CFCs), can be easily converted from gas to liquid or liquid to gas. Because of these properties, CFCs can be used in aerosol cans, refrigerators, and air conditioners. Studies showed that when CFCs are emitted into the atmosphere, they break down molecules in the Earth’s ozone layer. Since then, the use of CFCs has significantly decreased and they are banned from production in the United States. The substitutes for CFCs are hydrofluorocarbons (HFCs). HFCs do not harm or breakdown the ozone molecule, but they do trap heat in the atmosphere, making it a greenhouse gas, aiding in global warming. HFC’s are used in air conditioners and refrigerators. The way to reduce emissions of this gas is to be sure that in both devices the coolant is recycled and all leaks are properly fixed

There are many environmental problems coming from the

increase concentration of greenhouse gases in Earth’s atmosphere. Several signs indicate that we’ve begun changing Earth’s climate: increased water vapor in the atmosphere, glaciers and polar ice caps appear to be melting, floods and droughts are becoming more severe, and sea levels have risen, on average, between 4 and 10 inches since 1990. We are already beginning to see this (global warming) taking place - a lot more flooding, a lot more droughts. By 2100, we might get a 2 foot sea level rise, but the catch is levels might continue to rise 2 or 3 feet per century, for 1000 years. These rises in sea level can increase the salinity of freshwater throughout the world, and cause coastal lands to be washed under the ocean. Warmer water and increased humidity may encourage tropical cyclones, and changing wave patterns could produce more tidal waves and strong beach erosion on the coasts.

Increasing amounts of greenhouse gases in the atmosphere and global warming could also lead to more health concerns. A statement released from the Intergovernmental Panel on Climate Change (IPCC) said, “Climate change is likely to have wide-ranging and mostly adverse impacts on human health, with significant loss of life.” As temperatures increase towards the poles, similar to farmland, insects and other pests migrate towards Earth’s poles. This could lead to 50 to 80 million additional cases of Malaria annually, a 10-15% increase. Climate change is already a factor in terms of the distributions of malaria, dengue fever, and cholera.

The most obvious health effect is directly from the heat itself. With an increase in heat waves, there will be more people who will suffer from heatstroke, heart attacks and other ailments aggravated by the heat. Hot conditions could also cause smoke particles and noxious gases to linger in the air and accelerate chemical reactions that generate other pollutants. This leads to an increase in risk of respiratory diseases like bronchitis and asthma.

Energy and Greenhouse gases : The present ways of producing Energy i.e. fossil fuels, chiefly coal, oil and natural gas, now supply most of the world’s energy. Only a small amount comes from renewable sources, which do not release gases that trap heat in the atmosphere. If we could get more of our energy from renewable sources, we could reduce the amount of fossil fuels we burn. By the year 2050, renewable sources could provide forty percent of the energy needed in the world. Use of renewable energy can help both to slow global warming and to reduce air pollution. Hydro power, currently supplying only six percent of the world’s energy, is a renewable energy source. Energy is produced by hydraulic turbines that rotate with the force of rushing water (higher to lower elevation). It is one of the most clean and cheapest ways of producing energy, but it can also change the flow of rivers and increase sediment which kills fish. It is a large investment for developing countries. Denmark is currently the world leader in wind power.

These fossil fuels, coal, oil, and natural gas also emit greenhouse gases when burned. Coal emits high amounts of greenhouse gases, and the world may be supplied with enough of it to last over 100 years. Oil emits high amounts of greenhouse gases and also other types of air pollution harmful to the environment. The world’s oil supply is also estimated to

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last over 100 years. Natural Gas is the lowest of all fossil fuels in greenhouse gas emissions; supplies are projected to last over 100 years.

Kyoto Protocol : The Kyoto Protocol is an international agreement linked to the United Nations Framework Convention on Climate Change. The major feature of the Kyoto Protocol is that it sets binding targets for 37 industrialized countries and the European community for reducing greenhouse gas (GHG) emissions .These amount to an average of five per cent against 1990 levels over the five-year period 2008-2012. The major distinction between the Protocol and the Convention is that while the Convention encouraged industrialised countries to stabilize GHG emissions, the Protocol commits them to do so.

Recognizing that developed countries are principally responsible for the current high levels of GHG emissions in the atmosphere as a result of more than 150 years of industrial activity, the Protocol places a heavier burden on developed nations under the principle of “common but differentiated responsibilities.” The Kyoto Protocol was adopted in Kyoto, Japan, on 11 December 1997 and entered into force on 16 February 2005. 182 Parties of the Convention have ratified its Protocol to date. The detailed rules for the implementation of the Protocol were adopted at COP 7 in Marrakesh in 2001, and are called the “Marrakesh Accords.” Under the Treaty, countries must meet their targets primarily through national measures. However, the Kyoto Protocol offers them an additional means of meeting their targets by way of three market-based mechanisms.

Parties with commitments under the Kyoto Protocol have accepted targets for limiting or reducing emissions. These targets are expressed as levels of allowed emissions, or “assigned amounts”, over the 2008-2012 commitment period. Since carbon dioxide is the principal greenhouse gas, people speak simply of trading in carbon. Carbon is now tracked and traded like any other commodity. This is known as the “carbon market”.

The Kyoto Protocol is generally seen as an important first step towards a truly global emission reduction regime that will stabilize GHG emissions, and provides the essential architecture for any future international agreement on climate change. By the end of the first commitment period of the Kyoto Protocol in 2012, a new international framework needs to have been negotiated and ratified that can deliver the stringent emission reductions the Intergovernmental Panel on Climate Change (IPCC) has clearly indicated are needed.

Ozone Hole : For nearly a billion years, ozone molecules in the atmosphere have protected life on Earth from the effects of ultraviolet rays. The ozone layer resides in the stratosphere and surrounds the entire Earth. UV-B radiation (280- to 315- nanometer (nm) wavelength) from the Sun is partially absorbed in this layer. As a result, the amount of UV-B reaching Earth’s surface is greatly reduced. UV-A (315- to 400-nm wavelength) and other solar radiation are not strongly absorbed by the ozone layer. Human exposure to UV-B increases the risk of skin cancer, cataracts, and a suppressed immune system. UV-B exposure can also damage terrestrial plant life, single cell organisms, and aquatic ecosystems.

Fig. - 2 : Ultraviolet Rays

In the past 60 years or so human activity has contributed to the deterioration of the ozone layer. Only 10 or less of every million molecules of air are ozone. The majority of these ozone molecules reside in a layer between 10 and 40 kilometers (6 and 25 miles) above the Earth’s surface in the stratosphere. Each spring in the stratosphere over Antarctica (Spring in the southern hemisphere is from September through November.); atmospheric ozone is rapidly destroyed by chemical processes. As winter arrives, a vortex of winds develops around the pole and isolates the polar stratosphere. When temperatures drop below -78°C (-109°F), thin clouds form of ice, nitric acid, and sulphuric acid mixtures. Chemical reactions on the surfaces of ice crystals in the clouds release active forms of CFCs. Ozone depletion begins, and the ozone “hole” appears. In spring, temperatures begin to rise, the ice evaporates, and the ozone layer starts to recover. The ozone “hole” is really a reduction in concentrations of ozone high above the earth in the stratosphere. The ozone hole has steadily grown in size (up to 27 million sq. km.) and length of existence (from August through early December) over the past two decades. After a series of rigorous meetings and negotiations, the Montreal Protocol on Substances that Deplete the Ozone Layer was finally agreed upon on 16 September 1987 at the Headquarters of the International Civil Aviation Organization in Montreal.

The Montreal Protocol stipulates that the production and consumption of compounds that deplete ozone in the stratosphere such as chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform are to be phased out. Scientific theory and evidence suggest that, once emitted to the atmosphere, these compounds could significantly deplete the stratospheric ozone layer that shields the planet from damaging UV-B radiation. Man-made chlorines, primarily chlorofluorocarbons (CFCs), contribute to the thinning of the ozone layer and allow larger quantities of harmful ultraviolet rays to reach the earth. The Govt of India has come up Ozone Depleting Substances (Regulation) Rules 2000 under the Environmental Protection Act 1986 so as to control the production, emission and consumption of Ozone depleting substances.

The Bhopal Disaster : The Bhopal Gas Tragedy is a catastrophe that has no parallel in industrial history. In the early morning of December 3, 1984 a Union Carbide pesticide producing plant

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leaked a highly toxic cloud of methyl isocyanine onto the densely populated region of Bhopal, central India. The cause was the contamination of Methyl Isocyanine (MIC) storage tank No. 610 with water carrying catalytic material. Of the 800,000 people living in Bhopal at the time, 2,000 died immediately, 300,000 were diseased and as many as 8,000 have died since. The leak was caused by a series of mechanical and human errors. A series of studies made five years later showed that many of the survivors were still suffering from one or several of the following ailments: partial or complete blindness, gastrointestinal disorders, impaired immune systems, post traumatic stress disorders, and menstrual problems in women. A rise in spontaneous abortions, stillbirths, and offspring’s with genetic defects was also noted. Although Union Carbide denied liability, in 1989 the Indian Supreme court agreed to a settlement payment of $470 million by Union Carbide to the survivors of the disaster.

Noise PollutionThe word noise is derived from the Latin term nausea. It has been defined as unwanted sound. Noise can be described as sound without agreeable musical quality or as an unwanted or undesired sound. Thus noise can be taken as a group of loud, non harmonious sounds or vibrations that are unpleasant and irritating to ear. Sound, which pleases the listeners, is music and that which causes pain and annoyance is noise. Section 2 (a) of the Air (Prevention and Control of Pollution) Act, 1981 includes noise in the definition of ‘air pollutant’. Section 2(a) air pollution means any solid, liquid or gaseous substance including noise present in the atmosphere in such concentration as may be injurious to human beings or other living creatures or plants or property or environment.

Measurement : Loudness/intensity depends on amplitude of noise which is measured in decibels. The zero on a decibel scale is at the threshold of hearing, the lowest sound pressure that can be heard. 20 db is whisper, 40 db the noise in a quiet office. 60 db is normal conversation, 80 db is the level at which sound becomes physically painful. The human ear responds to perceived intensity of sound which is expressed in dB (A). Frequency is measured in Hertz which represents one wave per second. The normal human ear can bear frequencies from 20-20,000 Hz.

Sources of Noise Pollution : Noise pollution like other pollutants is also a by- product of industrialization, urbanizations and modern civilization. Broadly speaking, the noise pollution has two sources, i.e. industrial and non- industrial. The industrial source includes the noise from various industries and big machines working at a very high speed and high noise intensity. Non- industrial source of noise includes the noise created by transport/vehicular traffic and the neighborhood noise generated by various noise pollution can also be divided in the categories, namely, natural and manmade. Most leading noise sources will fall into the following categories: roads traffic, aircraft, railroads, construction, industry, noise in buildings (as furniture and plumbing), and consumer products (as household commodities as mixies, vacuum cleaners, etc.) and “recreational” (as loud music, discos, religious and social assemblages, etc.).

Harmful Effects : Noise exposure can cause two kinds of health effects on humans. These effects are non-auditory effects and auditory effects.

Non-auditory effects : These include stress, related physiological and behavioural effects, and safety concerns. It decreases the efficiency of a man Noise causes lack of concentration in people. Thus they have to give more time for completing a job. Noise Pollution has been considered to be a cause of elevated blood pressure, sleep disturbance, and decreased school performance. Noise exposure has also been known to induce tinnitus, hypertension, vasoconstriction and other cardiovascular impacts. Beyond these effects, elevated noise levels can create stress, increase workplace accident rates, and stimulate aggression and other anti-social behaviors.

Auditory Effects

(a) Acoustic trauma : Sudden hearing damage caused by short burst of extremely loud noise such as a gun shot or blasts.

(b) Tinnitus : Ringing or buzzing in the ear.

(c) Temporary hearing loss : Also known as temporary threshold shift (TTS) which occurs immediately after exposure to a high level of noise. There is gradual recovery when the affected person spends time in a quiet place. Complete recovery may take several hours.

(d) Permanent hearing loss : Permanent hearing loss, also known as permanent threshold shift (PTS), progresses constantly as noise exposure continues month after month and year after year. The hearing impairment is noticeable only when it is substantial enough to interfere with routine activities. At this stage, a permanent and irreversible hearing damage has occurred. Noise-induced hearing damage cannot be cured by medical treatment and worsens as noise exposure continues. When noise exposure stops, the person does not regain the lost hearing sensitivity. As the employee ages, hearing may worsen as age-related hearing loss or presbycusis adds to the existing noise-induced hearing loss.

Noise-induced hearing loss is a cumulative process, both level of noise and exposure time over a worker’s work history are important factors. At a given level, low-frequency noise (below 100 Hz) is less damaging compared to noise in the mid-frequencies (1000 - 3000 Hz). Noise-induced hearing loss occurs randomly in exposed persons. Some individuals are more susceptible to noise-induced hearing loss than others. In the initial stages, noise-induced hearing loss is most pronounced at 4000 Hz but it spreads over other frequencies as noise level and/or exposure time increases.

Noise affects the cochlea in the inner ear. That is why noise-induced hearing loss is sensory-neural type of hearing loss. Certain medications and diseases may also cause damage to the inner ear resulting in hearing loss as well. Generally, it is not possible to distinguish sensory-neural hearing loss caused by exposure to noise from sensory-neural hearing loss due to other causes. Medical judgment, in such cases, is based on the noise exposure history. Workers in noisy environments who are also exposed to vibration (e.g. from a jack hammer) may experience greater hearing loss than those exposed to the same level of noise but not to vibration. Noise-exposed workers who are also exposed to ototoxic chemicals (e.g. toluene, carbon

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disulfide) may suffer from more hearing impairment than those who have the same amount of noise exposure without any exposure to ototoxic chemicals.

Hearing loss is measured as threshold shift in dB units using an audiometer. The 0 dB threshold shift reading of the audiometer represents the average hearing threshold level of an average young adult with disease-free ears. The PTS (permanent threshold shift), as measured by audiometry, is dB level of sounds of different frequencies that are just barely audible to that individual.

Effect on animals : Noise can have a detrimental effect on animals by causing stress, increasing risk of mortality by changing the delicate balance in predator/prey detection and avoidance, and by interfering with their use of sounds in communication especially in relation to reproduction and in navigation.

Noise mitigationThis is a set of strategies to reduce noise pollution. The main areas of noise mitigation or abatement are transportation noise control, architectural design, and occupational noise control. Roadway noise and aircraft noise are the most pervasive sources of environmental noise worldwide, and remarkably little change has been effected in source control in these areas since the start of the problem, a possible exception being the development of the hybrid vehicle.

(a) Buildings : Multiple techniques have been developed to address interior sound levels, many of which are encouraged by local building codes; in the best case of project designs, planners are encouraged to work with design engineers to examine tradeoffs of roadway design and architectural design. These techniques include design of exterior walls, internal walls and floor/ceiling assemblies; moreover, there are a host of specialized means for dampening reverberation from special purpose rooms such as auditoriums, concert halls, dining areas and meeting rooms. Many of these techniques rely upon materials science applications of constructing sound baffles or using sound absorbing liners for interior spaces.

(b) Roadway noise : The most fertile area for roadway noise mitigation is in urban planning decisions, roadway design, noise barrier design, speed control, surface pavement selection and truck restrictions. Speed control is effective since the lowest sound emissions arise from vehicles moving smoothly at 30 to 60 km per hour. Noise barriers can be applicable for existing or planned surface transportation projects. They are probably the single most effective weapon in retrofitting an existing roadway, and commonly can reduce adjacent land use sound levels by ten decibels

(c) Aircrafts : The most promising forms of aircraft noise abatement is through land planning, flight operations restrictions and residential soundproofing. Flight restrictions can take the form of preferred runway use; departure flight path and slope; and time of day restrictions

(d) Industries : Industrial noise control is really a subset of interior architectural control of noise, with emphasis upon specific methods of sound isolation from industrial machinery and for protection of workers at their task stations. In the case of industrial equipment, the most common techniques for

noise protection of workers consist of shock mounting source equipment, creation of acrylic glass or other solid barriers, and provision of ear protection equipment. In certain cases the machinery itself can be re-designed to operate in a manner less prone to produce grating, grinding, frictional or other motions that induce sound emissions.

(e) Legal Control : Under Cr PC Section 133 the magisterial court have been empowered to issue order to remove or abate nuisance caused by noise pollution. Noise pollution can be penalized under I.P.C. Public Nuisance 268-295 relating to public health, safety, decency, morals. Action can also be taken under the Law of Torts as Noise pollution is considered a civil wrong. The Factories Act does not contain any specific provision for noise control. However, under the Third Schedule Sections 89 and 90 of the Act, noise induced hearing loss, is mentioned as notifiable disease. Similarly, under the Modal Rules, limits for noise exposure for work zone area have been prescribed. In Motor vehicle Act rules regarding use horns and any modification in engine are made.

Noise Pollution Control Rule 2000 under Environment Protection Act 1996Under this Act State governments shall take measures for abatement of noise including noise emanating from vehicular movement and ensure that the existing noise levels do not exceed the standards specified. An area not less than 100 m around hospitals, education institutions and courts may be declared as ‘silence area’ for the purpose of these rules. A loud speaker or a public address system shall not be used except after obtaining written permission from the authority and the same shall not be used at night, between 10 pm to 6 am.

Personal Protection Ear plugs and ear muffs are important appliances, particularly used in the industries, which can effectively reduce the level of noise by 15 to 30 decibels and their use must be encouraged wherever possible.

Soil PollutionSoil pollution comprises the pollution of soils with materials, mostly chemicals that are out of place or are present at concentrations higher than normal which may have adverse effects on humans or other organisms. It is difficult to define soil pollution exactly because different opinions exist on how to characterize a pollutant; while some consider the use of pesticides acceptable if their effect does not exceed the intended result, others do not consider any use of pesticides or even chemical fertilizers acceptable. However, soil pollution is also caused by means other than the direct addition of xenobiotic (man-made) chemicals such as agricultural runoff waters, industrial waste materials, acidic precipitates and radioactive fallout. Consequently, the atmosphere, bodies of water, and many soil environments have become polluted by a large variety of toxic compounds. Many of these compounds at high concentrations or following prolonged exposure have the potential to produce adverse effects in humans and other organisms: These include the danger of acute toxicity, mutagenesis (genetic changes), carcinogenesis, and teratogenesis (birth defects) for humans and other organisms.

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Some of these man-made toxic compounds are also resistant to physical, chemical, or biological degradation and thus represent an environmental burden of considerable magnitude.

Industrial Wastes : Industries are known to dispose of their pollution in pits, ponds of lagoons with little or no prior treatment. Leaking underground storage tanks compound the pollution of the soil. The most prominent chemical groups of organic contaminants are fuel hydrocarbons, polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorinated aromatic compounds, detergents and pesticides. Inorganic species include nitrates, phosphates and heavy metals such as cadmium, chromium and lead; inorganic acids; and radionuclides (radioactive substances). Among the sources of these contaminants are agricultural runoffs, acidic precipitates, and industrial waste materials.

Agricultural Wastes : Fertilizers, pesticides and other chemical like soil conditioners and fumigants used in agriculture may remain for long in the soil. Some of these may enter the food chain and cause health problems in the population. On the other hand, Cattle and poultry produce and wastes are biodegradable. However when these are not properly disposed it may cause a nuisance of smell and sight and facilitate breeding of flies.

Urban Community Wastes : Refuse and other solids wastes when not disposed of properly can result in pollution of the soil. Even practices like sanitary landfill if not carried out in a systemized manner may result in contamination of the soil. Defecation in the open in farms etc. result in contamination of the soil with various biological contaminants harbored by the host.

Radiological Wastes : Occur from atmospheric fallout of a nuclear explosion, which may travel distances due to air currents. Disposal of radioactive wastes if not carried out as per laid out norms is another source of pollution.

Control measures (a) Natural : Nature has an effective mode of controlling pollution. Most bacteria and viruses do not survive on the surface of the soil after exposure to sunlight. Rainwater also carries contaminants away from the source. Biological products which are below the upper surface of the soil are catabolised by the “Nitrogen Cycle”.

(b) Bioremediation : In-situ biodegradation involves the enhancement of naturally occurring microorganisms by artificially stimulating their numbers and activity. The microorganisms then assist in degrading the soil contaminants. A number of environmental, chemical and management factors affect the biodegradation of soil pollutants, including moisture content, pH, temperature, the microbial community that is present, and the availability of nutrients. These physical parameters can be influenced, thereby promoting the microorganisms’ ability to degrade chemical contaminants. Of all the decontamination methods bioremediation appears to be the least damaging and most environmentally acceptable technique.

(c) Soil Washing : For the removal and recovery of heavy metals various soil washing techniques have been developed including physical methods, such as attrition scrubbing and wet-screening, and chemical methods consisting of treatments

with organic and inorganic acids, bases, salts and chelating agents. The problem with these methods, however, is again that they generate secondary waste products that may require additional hazardous waste treatments.

(d) Engineering measures : Proper disposable of community wastes through composting, disposable in pits, sanitary landfills goes a long way in prevention of soil pollution. Industrial wastes should be properly treated prior to disposal. Non biodegradable products should be recycled or properly disposed. Farm wastes can be properly utilized by composting or used in biogas plants. The most common decontamination method for polluted soils is to remove the soil and deposit it in landfills or to incinerate it. These methods, however, often exchange one problem for another: land-filling merely confines the polluted soil while doing little to decontaminate it, and incineration removes toxic organic chemicals from the soil, but subsequently releases them into the air, in the process causing air pollution. Health education goes a long way in change of attitude of a community on oxygen defecation of disposal of agriculture wastes.

Radioactive PollutionRadioactive contamination is the uncontrolled distribution of radioactive material in a given environment. Radioactive contamination is typically the result of a spill or accident during the production or use of radionuclides (radioisotopes), an unstable nucleus which has excessive energy. Contamination may occur from radioactive gases, liquids or particles. For example, if a radionuclide used in nuclear medicine is accidentally spilled, the material could be spread by people as they walk around. Radioactive contamination may also be an inevitable result of certain processes, such as the release of radioactive xenon in nuclear fuel reprocessing. Nuclear fallout is the distribution of radioactive contamination by a nuclear explosion.

Ionising radiation : These are radioactive rays capable of penetrating tissues. These can be of two types;(a) Electromagnetic - X-rays and gamma rays(b) Corpuscular radiations - Alpha, beta particles & protonsAlpha particles are ten times more harmful than X-rays but have little penetrating force. Gamma rays & X-rays are deep penetrating in nature.

Non ionizing radiations : These are of higher wavelengths & cannot penetrate. The spectrum ranges from Ultraviolet radiation, visible light, infrared radiation, microwave & radio frequency.

Activity of radioactive material is measured in Becquerel which is 1 disintegration per second. This was earlier measured as Curies. Potency of radiation is measured with -

(a) Exposure : Number of ions exposed in a ml of air is called Roentgen. Current exposure SI unit is Coulomb/kg.

(b) Absorption : Amount of radioactive energy absorbed by a gram of tissue/material is called Rad. The SI unit currently used is Gray (1Gy = 100 rads).

(c) Dose equivalent : The degree of potential danger to health is measured in Rem which is a product of Rad and a modifying factor. The newer unit is the Sievert (1 Sievert=100 Rems).

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Hazards In practice there is no such thing as zero radioactivity. Not only is the entire world constantly bombarded by cosmic rays, but every living creature on earth contains significant quantities of carbon -14 and most (including humans) contains significant quantities of potassium-40. These tiny levels of radiation are not any more harmful than sunlight, but just as excessive quantities of sunlight can be dangerous, so too can excessive levels of radiation.

Low level contamination : The hazards to people and the environment from radioactive contamination depend on the nature of the radioactive contaminant, the level of contamination, and the extent of the spread of contamination. Low levels of radioactive contamination pose little risk, but can still be detected by radiation instrumentation. In the case of low-level contamination by isotopes with a short half-life, the best course of action may be to simply allow the material to naturally decay. Longer-lived isotopes should be cleaned up and properly disposed of, because even a very low level of radiation can be life-threatening, on long exposure. Therefore, whenever there’s any radiation in an area, many people take extreme caution when approaching such areas.

High level contamination : High levels of contamination may pose major risks to people and the environment. People can be exposed to potentially lethal radiation levels, both externally and internally, from the spread of contamination following an accident (or a deliberate initiation) involving large quantities of radioactive material. The biological effects of external exposure to radioactive contamination are generally the same as those from an external radiation source not involving radioactive materials, such as x-ray machines, and are dependent on the absorbed dose.

Biological effects : The biological effects of internally deposited radionuclides depend greatly on the activity and the bio-distribution and removal rates of the radionuclide, which in turn depends on its chemical form. The biological effects may also depend on the chemical toxicity of the deposited material, independent of its radioactivity. Some radionuclides may be generally distributed throughout the body and rapidly removed, as is the case with titrated water. Some radionuclides may target specific organs and have much lower removal rates. For instance, the thyroid gland takes up a large percentage of any iodine that enters the body. If large quantities of radioactive iodine are inhaled or ingested, the thyroid may be impaired or destroyed, while other tissues are affected to a lesser extent. Radioactive iodine is a common fission product; it was a major component of the radiation released from the Chernobyl disaster, leading to many cases of pediatric thyroid cancer and hypothyroidism. On the other hand, radioactive iodine is used in the diagnosis and treatment of many diseases of the thyroid precisely because of the thyroid’s selective uptake of iodine.

In general, the adverse effects on the human body may be acute or chronic (long term). Acute effects include acute radiation sickness. Chronic effects may manifest either as somatic effects or chromosomal effects which result in genetic abnormalities. The most important somatic effect is on haemopoietic system (leukaemias), cancers, particularly thyroid, and foetal

developmental abnormalities if mother is exposed during ante-natal period.

Means of contamination : Radioactive contamination can enter the body through ingestion, inhalation, absorption, or injection. For this reason, it is important to use personal protective equipment when working with radioactive materials. Radioactive contamination may also be ingested as the result of eating contaminated plants and animals or drinking contaminated water or milk from exposed animals. Following a major contamination incident, all potential pathways of internal exposure should be considered.

Effective protection : Effective protection can be given to workers in hazardous industries by provision of lead shields & lead rubber aprons. Exposed workers should wear TLD badge or dosimeters which show accumulated exposure to radiation. Periodic medical exam should also be carried out to monitor health of workers. Exposure to investigative radiology should be kept to the minimum, especially during pregnancy.

The Chernobyl disaster was a nuclear reactor accident in the Chernobyl Nuclear Power Plant in the Soviet Union on 26 April 1986. It was the worst nuclear power plant accident in history and the only instance so far of level 7 on the International Nuclear Event Scale, resulting in a severe release of radioactivity into the environment following a massive power excursion which destroyed the reactor. Two people died in the initial steam explosion, but most deaths from the accident were attributed to fallout. The plume drifted over extensive parts of the western Soviet Union, Eastern Europe, Western Europe, Northern Europe, and eastern North America. Large areas in Ukraine, Belarus, and Russia were badly contaminated, resulting in the evacuation and resettlement of over 336,000 people. According to official post-Soviet data, about 60% of the radioactive fallout landed in Belarus. The 2005 report prepared by the Chernobyl Forum, led by the International Atomic Energy Agency (IAEA) and World Health Organization (WHO), attributed 56 direct deaths (47 accident workers, and nine children with thyroid cancer), and estimated that there may be 4,000 extra cancer cases among the approximately 6,00,000 most highly exposed and 5,000 among the 6 million living nearby. Although the Chernobyl Exclusion Zone and certain limited areas will remain off limits, the majority of affected areas are now considered safe for settlement and economic activity.

Radioactive wastes are waste types containing radioactive chemical elements that do not have a practical purpose. They are sometimes the products of nuclear processes, such as nuclear fission. However, industries not directly connected to the nuclear industry can produce large quantities of radioactive waste. It has been estimated, for instance, that the past 20 years the oil-producing endeavors of the United States have accumulated eight million tons of radioactive wastes. The majority of radioactive waste is “low-level waste”, meaning it contains low levels of radioactivity per mass or volume. This type of waste often consists of used protective clothing, which is only slightly contaminated but still dangerous in case of radioactive contamination of a human body through ingestion, inhalation, absorption, or injection. The United States currently has at least 108 sites it currently designates as areas that are

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contaminated and unusable, sometimes many thousands of acres.

The issue of disposal methods for nuclear waste was one of the most pressing current problems the international nuclear industry faced when trying to establish a long term energy production plan.

Nuclear waste requires sophisticated treatment and management in order to successfully isolate it from interacting with the biosphere. This usually necessitates treatment, followed by a long-term management strategy involving storage, disposal or transformation of the waste into a non-toxic form.

Long-term storage of radioactive waste requires the stabilization of the waste into a form which will not react, nor degrade, for extended periods of time. One way to do this is through vitrification. It is also common for medium active wastes in the nuclear industry to be treated with ion exchange or other means to concentrate the radioactivity into a small volume. The much less radioactive bulk (after treatment) is often then discharged. For instance, it is possible to use a ferric hydroxide floc to remove radioactive metals from aqueous mixtures. After the radioisotopes are absorbed onto the ferric hydroxide, the resulting sludge can be placed in a metal drum before being mixed with cement to form a solid waste form.

High-level radioactive waste is stored temporarily in spent fuel pools and in dry cask storage facilities. This allows the shorter-lived isotopes to decay before further handling.

The process of selecting appropriate deep final repositories for high level waste and spent fuel is now under way in several countries with the first expected to be commissioned some time after 2010.

Storing high level nuclear waste above ground for a century or so is considered appropriate by many scientists. This allows for the material to be more easily observed and any problems detected and managed, while the decay over this time period significantly reduces the level of radioactivity and the associated harmful effects to the container material. Sea-based options for disposal of radioactive waste include burial beneath a stable abyssal plain, burial in a subduction zone that would slowly carry the waste downward into the Earth’s mantle, and burial beneath a remote natural or human-made island. Another option is to find applications of the isotopes in nuclear waste so as to re-use them. Already, caesium-137, strontium-90 and a few other isotopes are extracted for certain industrial applications such as food irradiation and radioisotope thermoelectric generators. While re-use does not eliminate the need to manage radioisotopes, it may reduce the quantity of waste produced.

SummaryAir Pollution : According to a WHO assessment of the burden of disease due to air pollution, more than 2 million premature deaths each year can be attributed to the effects of urban outdoor air pollution and indoor air pollution. Important pollutants are Sulphurdioxide, Nitrogen oxides, Hydrogen sulphide, Carbon monoxide, Hydrogen cyanide, Ammonia, Lead, Ozone etc and their main sources are mainly industries, motor vehicles, coal and oil combustion, Explosives, dye making, fertilizer plants

etc. The pathological effects on man are aggravation of asthma and other lung and heart diseases, reduction of oxygen carrying capacity of blood, damage kidneys, cause jaundice and also toxic to nervous system.

The WHO Air quality guidelines are designed to offer global guidance on reducing the health impacts of air pollution. They recommend measurement of selected air pollutants, viz. Particulate Matter (PM), Ozone (O3), Nitrogen dioxide (NO2) and Sulfur dioxide (SO2) applicable across all WHO regions. In addition, “smoke (soiling) index” and “coefficient of haze” are also commonly used indicators. In India the Central Pollution Control Board through its National Air Quality Monitoring Programme monitors air quality in all major cities.

Exposure to air pollutants is largely beyond the control of individuals and requires action by public authorities at the national, regional and even international levels. Intersectoral coordination is required with the health sector playing a central role. The major modes of prevention are Containment, dust control devices like Data collection systems, crubber systems, replacement or modernisation of equipment/process and Zoning. The objective of The Air (Prevention and Control of Pollution) Act, 1981 is to provide for the prevention, control and abatement of air pollution in India by the establishment of pollution control Boards at the Centre as well as State levels, and by conferring and assigning such Boards, powers and functions, with a view to implementing air pollution control measures.

Over the past century, the Earth has increased in temperature by about 0.5°C and many scientists believe this is because of an increase in concentration of the main greenhouse gases: carbon dioxide (76%), methane (13%), nitrous oxide (6%), and fluorocarbons (5%). This climate change might be the beginning of Global Warming. The “greenhouse effect” is the heating of the Earth due to the presence of greenhouse gases. The Kyoto Protocol, an international agreement linked to the United Nations Framework Convention on Climate Change sets binding targets for 37 industrialized countries and the European community for reducing Greenhouse Gas (GHG) emissions. In the past 60 years or so human activity has contributed to the deterioration of the ozone layer. When temperatures drop below -78°C (-109°F), thin clouds form of ice, nitric acid, and sulphuric acid mixtures and Chemical reactions on the surfaces of ice crystals in the clouds release active forms of CFCs. Ozone depletion begins, and the ozone “hole” appears. The Montreal Protocol stipulates that the production and consumption of compounds that deplete ozone in the stratosphere such as Chlorofluorocarbons (CFCs), halons, carbon tetrachloride and methyl chloroform are to be phased out. The Govt. of India has come up with Ozone Depleting Substances (Regulation) Rules 2000 under the Environmental Protection Act 1986 so as to control the production, emission and consumption of Ozone depleting substances. In the early morning of December 3, 1984 a Union Carbide pesticide producing plant leaked a highly toxic cloud of methyl isocyanate onto the densely populated region of Bhopal, leading to Bhopal Tragedy with 2,000 immediate deaths, 8000 subsequent deaths and 300,000 diseased.

Noise Pollution : Noise can be described as sound without agreeable musical quality or as an unwanted or undesired

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sound. Section 2 (a) of the Air (Prevention and Control of Pollution) Act, 1981 defines air pollution as any solid, liquid or gaseous substance including noise present in the atmosphere in such concentration as may be injurious to human beings or other living creatures or plants or property or environment. 60 db is normal conversation and 80 db is the level at which sound becomes physically painful. The normal human ear can bear frequencies from 20-20,000 Hz.

Broadly, the noise pollution has two sources, i.e. industrial and non- industrial. The industrial source includes the noise from various industries and Non- industrial source of noise includes the noise created by transport/vehicular traffic and the neighborhood noise. Noise exposure can cause non-auditory effects and auditory effects. Non-auditory effects include stress, related physiological and behavioural effects, and safety concerns. It decreases the efficiency of a man. Noise causes lack of concentration in people, elevates blood pressure, sleep disturbance, and decreased school performance. Noise exposure has also been known to induce tinnitus, hypertension, vasoconstriction and other cardiovascular impacts. Beyond these effects, elevated noise levels can create stress, increase workplace accident rates, and stimulate aggression and other anti-social behaviors. Auditory effects include: Acoustic trauma, Tinnitus, Temporary hearing loss, Permanent hearing loss.

Noise mitigation is a set of strategies to reduce noise pollution, which include transportation noise control; architectural design of Buildings, roads, aircrafts and industries; and occupational noise control. Noise pollution can be penalized under I.P.C. Public Nuisance 268-295 relating to public health, safety, decency, morals. Under Noise Pollution Control Rule 2000 under Environment Protection Act 1996 State governments shall take measures for abatement of noise including noise emanating from vehicular movement and ensure that the existing noise levels do not exceed the standards specified. Personal Protection by using Ear plugs and ear muffs is also important.

Soil Pollution : Soil pollution comprises the pollution of soils with materials, mostly chemicals that are out of place or are present at concentrations higher than normal which may have adverse effects on humans or other organisms. It is caused by agricultural runoff waters, industrial waste materials, acidic precipitates, and radioactive fallout. It leads to acute toxicity, mutagenesis (genetic changes), carcinogenesis and teratogenesis (birth defects) for humans and other organisms. Control measures include Bioremediation, Soil Washing, Engineering measures like Proper disposable of community wastes, Industrial and Agricultural wastes through composting, disposable in pits, sanitary landfills etc.

Radioactive Pollution : Radioactive contamination is the uncontrolled distribution of radioactive material in a given environment. Radioactive contamination is typically the result of a spill or accident during the production or use of radionuclides (radioisotopes). The adverse effects on the human body may be acute or chronic (long term). Acute effects include acute radiation sickness. Chronic effects may manifest either as somatic effects or chromosomal effects which result in genetic abnormalities. The most important somatic effect is on haemopoietic system (leukaemias), cancers particularly thyroid and foetal developmental abnormalities if mother is exposed during ante-natal period. Effective protection - Effective protection can be given to workers in hazardous industries by provision of lead shields & lead rubber aprons, TLD badge or dosimeters, Periodic medical exams. The Chernobyl disaster was a major nuclear reactor accident in the Chernobyl Nuclear Power Plant in the Soviet Union on 26 April 1986. Nuclear waste requires sophisticated treatment and management in order to successfully isolate it from interacting with the biosphere. This usually necessitates treatment, followed by a long-term management strategy involving storage, disposal or transformation of the waste into a non-toxic form.

Study ExercisesLong Questions : (1) Enumerate the Sources and Health Hazards of Air Pollution. Describe the measures for its prevention and control (2) Enumerate the Sources and Health Hazards of Noise Pollution. Describe the measures for its prevention and control

Short Notes : (1) Chernobyl disaster (2) Bhopal gas tragedy (3) Radioactive pollution (4) Soil pollution (5) Air pollution Indices (6) Global warming (7) Ozone Hole (8) Auditory effects of Noise pollution

MCQs1. The main greenhouse gas which is largely contributing

to Global warming is (a) Carbon dioxide (b) Methane (c) Nitrous oxide (d) Fluorocarbons

2. Kyoto Protocol is an international agreement which deals with (a) Radioactive pollution (b) Soil pollution (c) Emission of green house gases (d) Noise pollution

3. Bhopal Tragedy of 1984 was due to a toxic chemical called (a) Methyl cyanide (b) Methyl isocyanate (c) Methyl isochloride (d) none of the above

4. Soiling index is an index to measure (a) Radioactive pollution (b) Soil pollution (c) Air pollution (d) water pollution

5. The Chernobyl disaster was a major nuclear reactor accident in the Chernobyl Nuclear Power Plant in the Soviet Union occurred in the year (a) 1982 (b) 1986 (c) 1989 (d) 1990

Answers : (1) a; (2) c; (3) b; (4) c; (5) b.