Common pollutants of air
Carbon dioxide content of air has increased by 20% during the last century. Carbon dioxide causes nausea and headache. It’s increase in the air may cause greenhouse effect, rise in the atmospheric temperature. This may melt the polar ice resulting in rise in level of oceans and flooding of coastal regions.
It is a very poisonous gas and is produced by incomplete combustion of fuel. If inhaled. it combines with hemoglobin and reduces its oxygen-carrying capacity. This leads to laziness, reduced vision and death.
Oxides of Nitrogen
Oxides of Sulphur
SO2 and SO3 are produced by burning of coal and petroleum and are harmful to buildings, clothing, plants and animals. High concentration of SO2 causes chlorosis (yellowing of leaves), plasmolysis, damage to mucous membrane and metabolic inhibition. SO2 and SO3 react with water to form Sulphuric and sulphurous acids. These may precipitate as rain or snow producing acid rain or acid precipitation.
These are unburnt discharges from incomplete combustion of fuel in automobiles. These form PAN with nitrogen oxides, which is highly toxic.
Industries and automobiles release fine solid and liquid particles into the air. Fly ash and soot from burning of coal, metal dust containing lead, chromium, nickel, cadmium, zinc and mercury from metallurgical processes; cotton dust from textile mills; and pesticides sprayed on crops are examples of particulate pollutants in the air. These are injurious to respiratory tract.
Aerosols are chemicals released in the air in vapour form. These include fluorocarbon (carbon compound having fluorine) present in emissions from the Jet aeroplanes. Aerosols deplete the ozone layer. Thinning of ozone layer results in more harmful ultraviolet rays reaching the earth, which are harmful to skin, and can lead to skin cancer also.
These are released by nuclear explosions and explosives. These are extremely harmful for health.
Rocks, soils and. minerals containing fluorides release an extremely toxic gas called hydrogen fluoride on heating. This gas is highly injurious to livestock and cattle.