heavy metals chromium - air pollution

8/22/2019 Heavy Metals Chromium - air pollution.

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HEAVYMETALS

INAIRPOLLUTION- CHROMIUM


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CONTENTS

APPEARANCE

DEFINITION

GENERAL PROPERTIES

SOURCES

NATURAL SOURCES OF CHROMIUM

HEALTH EFFECTS

ENVIRONMENTAL EFFECTS STANDARDS AND REGULATIONS

USES

APPLICATIONS


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APPEARANCE:

SILVERMETALLIC


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DEFINITION

Chromium is a hard steel-gray metal that is highly

resistant to oxidation, even at high temperatures.

It is the sixth most abundant element in the

earths crust, where it is combined with iron and

oxygen in the form of chromite ore.


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GENERALPROPERTIES

Name, symbol, numberChromium, Cr, 24

Atomic number 24

Atomic mass 51.996 g.mol-1

Density 7.19 g.cm-3at 20C

Melting point 1907 C

Boiling point 2672 C


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SOURCES

Chromium is a naturally occurring element found in rocks, animals,

plants, soil, and in volcanic dust and gases.

The most common forms are chromium(0), chromium(III), and

chromium(VI).

No taste or odor is associated with chromium compounds.

Chromium(III) occurs naturally in the environment and is an essential

nutrient.

Chromium(VI) and chromium(0) are generally produced by industrial

processes. The metal chromium, which is the chromium(0) form, is

used for making steel.

Chromium(VI) and chromium(III) are used for chrome plating, dyes

and pigments, leather tanning, and wood preserving.


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NATURALSOURCESOFCHROMIUM

It is a trace metal.

A trace metal is available in extremely small quantities, whichare present in animal and plant tissues.

Other trace metals include

Iron

Zinc

Copper

Nickel

CobaltVanadium

Arsenic

Molybdenum, and Selenium.


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SYMPTOMSOFCHROMIUMDEFICIENCY:

Anxiety,

Depression,

Irritability, Diabetes.


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FOODSOURCESOFCHROMIUMINCLUDE:

Whole grains,

Bread,

Brown rice,

Meat,

Mushrooms,

Green beans,

Brewers yeast, Beef, Beer, Chicken breast and

Fresh vegetables.


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CHROMIUM- CR

Chromium(III) is an essential nutrient for humans and

shortages may cause heart conditions, disruptions of

metabolisms and diabetes

But the uptake of too much chromium(III) can cause

health effects as well, for instance skin rashes


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CHROMIUM- CR

Chromium(VI) is harmful to human health, mainly forpeople who work in the steel and textile industry

People who smoke tobacco also have a higher chance

of exposure to chromium

Hexavalent ChromiumChromium (VI) is a species of

chromium that is forbidden to use in electrical &

electronic industry by RoHS Directive.


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HEALTH EFFECTS

When it is a compound in leather products, it can cause allergicreactions, such as skin rash

After breathing it in, chromium(VI) can cause nose irritations and

nosebleeds

Upset stomachs and ulcers

Respiratory problems

Weakened immune system

Kidney and liver damage

Alteration of genetic material

Lung cancer

Death


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ENVIRONMENTALEFFECTSOFCHROMIUM

Most of the chromium in air will eventually settle and end up

in waters or soils

Chromium in soils strongly attaches to soil particles and as aresult it will not move towards groundwater

In water chromium will absorb on sediment and become

immobile

Only a small part of the chromium that ends up in water will

eventually dissolve


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ENVIRONMENTALEFFECTSOFCHROMIUM

Chromium(III) is an essential element for organisms that

can disrupt the sugar metabolism and cause heart

conditions, when the daily dose is too low

Chromium(VI) is mainly toxic to organisms - it can alter

genetic materials and cause cancer


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ROUTESOFEXPOSUREFORCHROMIUM

The entry routes of chromium into the human body are

inhalation, ingestion, and dermal absorption.

Occupational exposure generally occurs throughinhalation and dermal contact, whereas the general

population is exposed most often by ingestion through

chromium content in soil, food, and water.


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ISATRISKOFEXPOSURETOCHROMIUM

Chromium is one of the most widely used industrial

metals.

Several million workers worldwide are estimated to be

exposed to chromium compounds in an array of industries

such as ,

1) pigment production,

2) chrome plating,

3) stainless steel welding, and

4) leather tanning.


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WORKEREXPOSURE

Workers in industries that use chromium are at increased

risk of chromiums adverse health effects.

Those workers at greatest risk are those involved instainless steel welding, chromate production, chrome

plating, and chrome pigment industries, where exposure

is primarily to Cr (VI) via inhalation of aerosols.


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STANDARDSANDREGULATIONSFORCHROMIUM

The Occupational Safety and Health Administration (OSHA)

has established an 8-hour time-weighted average (TWA)

exposure limit of 5 micrograms of Cr(VI) per cubic meter of air

(5 g/m).

OSHAs standard is based upon the best evidence currently

available that at the previous for Cr(VI), workers face a

significant risk to material impairment of their health.

The evidence in the record for this rulemaking indicates that

workers exposed to Cr(VI) are at an increased risk of

developing lung cancer.


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STANDARDSANDREGULATIONSFORCHROMIUM

The final rule also contains ancillary provisions for worker

protection such as ,

requirements for exposure determination,

preferred exposure control methods,

respiratory protection,

protective clothing and equipment,

hygiene areas and practices,

medical surveillance,

record keeping, and


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TOXICITYOFHEXAVALENTCHROMIUM

Severe and often deadly pathological changes are associated with

excessive intake of Cr(VI) compounds.

Cr(VI) exerts toxic effects on biological systems.

It has been found that occupational exposure to hexavalent

chromium compounds leads to a variety of clinical problems.

Inhalation and retention of materials containing Cr(VI) can cause

perforation of the asthma, bronchitis, inflammation of the larynx and

increased incidence of bronchogenic carcinoma.

Skin contact of Cr(VI) compounds can induce skin allergies.


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TOXICITYOFHEXAVALENTCHROMIUM

Hexavalent chromium compounds are irritating and

corrosive when allowed to come in contact with skin, the

digestive system or lungs. Chromium trioxide (CrO3) is a

common toxic hexavalent chromium compound.

In fact, chromic baths used to soak and clean laboratory

glassware are very toxic and are a safety risk to use incommon laboratory situations.


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USESOFCHROMIUM

Chromium is resistant to ordinary corrosive agents at room

temperature, which explains its uses as an electro-plated,

protective coating.

It is also used in ferrous and nonferrous alloys, in refractories,

and in chemicals.

Ferrous alloys, mainly stainless steels, account for most of the

consumption.

These steels have a wide range of mechanical properties as

well as being corrosion and oxidation resistant.


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USESOFCHROMIUM

Cast irons may contain from 0.5% to 30% of Cr, which

provides harden ability enability, toughness and corrosion

and wear resistance.

Chromium is also widely used in nonferrous alloys

(nickel, iron-nickel, cobalt, aluminum, titanium and

copper).


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OTHERUSES

Chromium(III) oxide is a metal polish known as green rouge.

Chromic acid is a powerful oxidizing agent and is a useful compound

for cleaning laboratory glassware of any trace of organic compounds.

Sodium dichromate is sometimes used because of its higher solubility

(50 g/L versus 200 g/L respectively). The use of dichromate cleaning

solutions is now phased out due to the high toxicity and

environmental concerns.

Potassium dichromate is a chemical reagent,used as a titrating agent.

It is also used as a mordant (i.e., a fixing agent) for dyes in fabric.


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APPLICATIONS

The largest amount is consumed to manufacturepigments for use in paints and inks.

Other applications include leather tanning, metal

corrosion inhibition, drilling muds, textile dyes, catalysts,

wood and water treatment.

Chromite is used in the refractory industry to make bricks,

mortar, and ramming and gunning mixes.

Chromite enhances their thermal shock and slag

resistance, volume stability, and strength.


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ENVIRONMENTALISSUES

As chromium compounds were used in dyes and paintsand the tanning of leather, these compounds are often

found in soil and groundwater at abandoned industrial

sites, now needing environmental cleanup and

remediation per the treatment of brownfield land.

Primer paint containing hexavalent chromium is still

widely used for aerospace and automobile refinishing

applications.


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heavy metals chromium - air pollution

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