chapter 15: how the environment affects our health
TRANSCRIPT
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Chapter 15: How the Environment Affects our Health
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Disease
• Disease is often due to an imbalance resulting from poor adjustment between the individual and the environment.– Continuum from state of health to disease– Gray zone in-between– As a result of exposure to chemicals in the
environment we may be in the midst of an epidemic of chronic disease.
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Disease
• Seldom have a one-cause- one-effect relationship w/ the environment
• Depends on several factors– Physical environment– Biological environment– Lifestyle
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Disease
• Chances of experiencing serious environmental health problems and disease depends on– The water we drink– The air we breathe– The soil we grow crops in– The rocks we build our homes on
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Disease
• Natural processes can release harmful materials into the soil, water or air.
• Lake Nyos in Cameroon, Africa– Experienced sudden release of carbon dioxide– Killed 1,800 people in near by town.
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Terminology
• Polluted environment – impure, dirty, or otherwise unclean.
• Pollution refers to the occurrence of unwanted change in the environment – introduction of harmful materials or the production of
harmful conditions.
• Contamination – similar to that of pollution – implies making something unfit for a particular use
through the introduction of undesirable materials
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Terminology
• Toxic refers to materials (pollutants) that are poisonous to people and other living things.– Toxicology is the science that studies chemicals
that are known to be or could be toxic.
• Carcinogen is a particular kind of toxin that increases the risk of cancer. – Most feared and regulated toxins in our society.
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Terminology
• Synergism– The interaction of different substances resulting
in a total effect greater than the sum of the effects of the separate substances.
– E.g. sulfur dioxide and coal dust
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Terminology
• Pollutants introduced into the enviro. at– Point sources, such as smokestacks, pipes
discharging into waterways, stream entering the ocean, or accidental spills.
– Area sources, (non point sources), which are more diffused over the land and include urban and agricultural runoff and mobile sources such as automobile exhaust.
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Measuring the Amount of Pollution
• How the amount or concentration of a particular pollutant or toxin present in the environment is reported varies widely.– E.g. waste water reported in millions of
gallons– Emissions of nitrogen oxides reported in
tons per year– Others given by a volume, mass of weight
• ppm, ppb, mg/kg or %
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Infectious Agents
• Infectious disease – Spread from the interactions between
individuals and food, water, air or soil.– Can travel globally via airplanes– New diseases emerging and previous ones
reemerging– Diseases that can be controlled by manipulating
the environment • classified as environmental health concerns
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Toxic Heavy Metals
• The major heavy metals that pose health hazards to people and ecosystems include:– mercury, lead, cadmium, nickel, gold,
platinum, silver, bismuth, arsenic, selenium, vanadium, chromium, and thallium.
• Each may be found in soil and water not contaminated by humans.
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Persistent Organic Pollutants
• POPs have several properties that define them:– They have a carbon-based molecular
structure, often containing highly reactive chlorine.
– Most are synthetic chemicals.– They do not easily break down in the
environment.
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Persistent Organic Pollutants
– They are polluting and toxic.– They are soluble in fat and likely to
accumulate in living tissue.– They occur in forms that allow them
to be transported by wind, water, and sediments for long distances.
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Hormonally Active Agents
• HAA are also POPs.
• Have potential to cause developmental and reproductive abnormalities in animals, including humans.– Include a wide variety of chemicals, herbicides,
pesticides, phthalates, and PCBs
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Radiation
• Nuclear radiation is linked to serious health problems– Including cancer
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Thermal Pollution
• Occurs when heat released into water or air produces undesirable effects.– Also called heat pollution– Sudden acute event or long term, chronic
release– Heated water released into rivers changes temp
and dissolved oxygen content• Thereby changing river’s species composition
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Thermal Pollution
• Heating river water changes natural conditions and disturbs the ecosystem– Fish spawning cycles may be disrupted– Fish may have heightened susceptibility to
disease.– Physical stress on fish– Easier pray– Change in type and availability of food
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Thermal Pollution
• Solutions to chronic thermal heating– Release of heat into air in cooling towers– Artificial lagoons– Used to heat buildings
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Particulates
• Small particles of dust released into the atmosphere by many natural processes and human activities.– Modern farming– Burning oil and coal– Dust storms– Volcanic eruptions
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Asbestos
• A term for several minerals that take the form of small, elongated particle or fibers.– Use contributed to fire prevention– Insulation
• Inhalation leads to asbestosis and cancer• 95% of asbestos now in use in US chrysolite
(white asbestos).– Not particularly harmful
• Another type crocidolite (blue asbestos)– Exposure can be very hazardous
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Electromagnetic Fields
• EMFs part of everyday urban life– electric motors, transmission lines and
appliances– Controversy as to whether they pose a health
risk– Children may be at greater risk
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Noise Pollution
• Unwanted sound
• Sound is a form of energy that travels as waves– We hear sounds when waves vibrate our
eardrum– Loudness a measure of intensity of energy– Measured in units of decibels
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Noise Pollution
• Environmental effects of noise depend on– Energy
– Pitch
– Frequency
– Time pattern
– Length of exposure
• Very loud noise can cause pain• Any sound above 80dB can cause hearing loss
– Rock concert 110dB
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Voluntary Exposure
• Sometimes referred to as exposure to personal pollutants.– Tobacco
• 30% of cancers tied to smoking
– Alcohol and other drugs• ½ of all deaths in automobiles accidents tied to
alcohol use by drivers
• Violent crimes, overdoses, chronic alcoholism
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General Effect s of Pollutants
• Almost every part of the human body is affected by one pollutant or another.
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Concept of Dose and Response
• Five centuries ago, the physician and alchemist Paracelsus wrote that “everything is poisonous, yet nothing is poisonous.”
• For Example– Selenium required in small amounts by living
things– May be toxic in high concentrations
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Concept of Dose and Response
• The effect of a chemical on an individual depends on the dose.– Dose response– Dose dependency can be represented by a
generalized dose response curve.
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Concept of Dose and Response
• Doses that are beneficial, harmful may differ widely for different organisms and are difficult to characterize.
• E.g. fluoride and dental health– Fluorine forms fluoride compounds that
prevent tooth decay and promote healthy bone structure.
– Toxic effects are noticed at concentrations of 6-7 ppm
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Tolerance
• The ability to resist or withstand stress resulting from exposure to a pollutant or harmful condition.– Result from behavioral, physiological,
or genetic adaptation.
• Behavioral tolerance- change in behavior– Learning to avoid traps
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Tolerance
• Physiological tolerance- the body of an individual adjusts to tolerate a higher level of pollutant.– Many mechanisms including detoxification
• the toxic chemical is converted to a nontoxic form
– Internal transport of the toxin to a part of the body where it is not harmful, such as fat cells.
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Tolerance
• Genetic tolerance- (adaptation) when some individuals in a population are naturally more resistant to a toxin than others.– Strains of mosquitoes resistance to DDT – Antibiotic resistance
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Acute and Chronic Effects
• Acute effect is one that occurs soon after exposure.– Usually to large amounts of a pollutant
• Chronic effect takes place over a long period– Often as a result of exposure to low levels of
pollutant
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Risk Assessment
• The process of determining potential adverse environmental health effects to people exposed to pollutants and potentially toxic materials.
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Risk Assessment
• Such an assessment generally includes four steps:– Identification of the hazard.– Dose–response assessment.– Exposure assessment.– Risk characterization.
• Risk assessment is difficult, costly, and controversial.
• Risk management integrates the assessment of risk with technical, legal, political, social, and economic issues.