Introduction to Environmental Toxicology (पर्यावरण विषक्त्तता)

 Environmental Toxicology ( Contamination of Air, Water and Soil)

Air pollution 

Air pollution is the presence of one or more pollutants in the atmosphere such as dust, fumes, gas, mist, smoke etc. which are injurious to human, animal or plant life.

Major air Pollutants

Aerosol, Fog, Droplet, Dust, Fumes, Gases , Fly ash, Smoke etc.

Causes of contamination of air

1. Emissions like hydrocarbons, carbon monoxide etc. from motor vehicles.
2. Air pollutants released from various industrial units
3. Improper and extensive use of coal, kerosene oil etc. in household.
4. Improper sewage system leading to the entry of various microorganisms into the atmosphere.
5. Rotting and petrification of dead bodies or plants etc.
6. Uncontrolled use of pesticides, insecticides etc.
7. Excessive missile testing, nuclear power programmes etc.
8. Dust storms and eruptions etc are natural sources of air pollution.
Major effects of contamination of Air
1. The quality of air the man and animals breathe in has a direct effect on their health and well being. Contaminated air when inhaled, causes respiratory problems and ill health effects.
2. Carbon dioxide as a green house gas causes global warming resulting in increasing mean sea level, submerging fertile land and bringing famine leading to destruction of life.
3. Sulphurdiocide and nitrogen dioxide can bring acid rains which can upset the balance between various biotic and abiotic components of the biosphere.
4. CFCs, the chlorofluorocarbons can destroy the ozone layer spreading incurable diseases among human beings and animals.
Major diseases caused by contamination of air
Cough, Asthma, Tuberculosis, Lung cancer, Respiratory allergy etc.
Air pollution control
1. Air pollution can be controlled by lowering emission level from automobiles and trucks and switching to more ecofriendly commercial products.
2. Industries that produce hazardous air pollutants can install scrubbers or other devices on their smoke stacks to prevent pollutants entering the atmosphere. Planting large number of trees can prove to be good solution.
Water Pollution
Water pollution is any chemical physical or biological change in the quality of water that has harmful effect on any living thing that drinks, uses or kives in it.
Major water pollutants 
1. Organic pollutants eg. fats, oils, meat etc.
2. Inorganic pollutants eg. acids, salts, toxic metals etc.
3. Sediments of soil.
4. Radioactive materials that affect generations by altering DNA genetic structure.
Causes of contamination of water
i) Discharge of domestic, commercial, hospital, civil and industrial wastes into water bodies.
ii) Mixing of agricultural wastes like residues of pesticides, fertilizers, herbicides etc.with water.
iii) Discharge of radioactive materials and toxic substances like arsenic etc. from research labs in water.
Major effects of contamination of water
i) Bad and offensive taste, colour and odour of water.
ii) Unchecked growth of weeds/plants of aquatic flora and fauna.
iii) Decrease in population and species in polluted water.
Major Diseases caused by contamination of water
i) Due to hard water
Indigestion, Diarrhea, Anorexia
ii) Due to organisms
Fever, Diarrhea, Cholera, Hepatitis etc.
iii) Due to Parasites 
Amoebic dysentery, Hook worms etc.
Purification of contaminated water :
i) Physical method - a) Distillation
                                     b) Boiling
ii) Chemical method - a) Precipitation
                                    b) Disinfection
                                    c) Sterilization
iii) Fertilization - a) Slow sand filtration
                               b) Rapid mechanical filtration
                               c) Domestic filtration
For household use, contaminated water can also be purified by using chlorine, alum, iodine or potassium permanganate etc.
Soil Pollution
Soil pollution is the consequence of unhygienic habits, various agricultural practices and incorrect methods of disposal of solid and liquid wastes but can also result from atmospheric pollution.
Soil pollutants 
Inorganic toxic compounds, organic wastes, organic pesticides and radionuclides
The most dangerous metals causing soil pollution are cadmium, copper, nickel, zinc and molybedum etc.
Causes of contamination of soil 
1. Improper use of chemical such as fertilizers etc in agricultural practices.
2. Prolonged use of pesticides, herbicides, fungicides and nematocides etc.
3. Dumping of industrial wastes from the mining of coal, minerals etc. on land of domestic use.
4. Rupture of underground storage tanks.
5. Oil and fuel dumping
Major diseases caused by contamination of soil
Filariasis, food poisoning, Hepatitis, Dysentry, Encephalitis, Diarrhea, Asthma, sprue syndrome, cholera and congenital disorders etc.
Soil pollution control
Soil pollution can be prevented by -
1. Controlled use of chemicals such as fertilizers, pesticides, herbicides etc.
2. Proper dumping of waste material from mines and industries,
3. Proper storage of underground tanks.
4. Planting large number of trees.

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