Short article on Air pollution
Increase in the concentration of gases (other than O,) and particulate solid waste in the air is called air pollution. It is caused due to industrilisation, automobile exhaust and burning of coal, petroleum, etc. These cause the accumulation of sulphur dioxide (SO,), smoke and suspended particles. Causes: Pollutants are produced by four major sources (1) automobiles and transporters (2) electric power plants (using petrol or coal) (3) industries, and (4) heating plants.
Air may contain pollutants of different sized particles and gases. Accordingly they are classified into many types.
(a) Coarser particles of over 200 |i in diameter like carbon particles and dust.
(b) Fine particles of less than 100 p in diameter like metallic dust, carbon particles, sulphates etc.
(c) Sulphur compounds
(e) Radioactive substances
(f) Oxygen compounds
Common air pollutants are sulphur dioxide and combustion gases.
Is produced as a result of coal, petrol and oil combustion. Sulphur dioxide does not remain as gas for a long time. Soon it reacts with moisture to form sulphuric acid. This is the cause of acid rain-fall in many advanced countries.
If there is a severe pollution it leads to bronchial asthama, vomitting, chest pain and causing death. This was reported in London (1952), New York and Tokyo in 1960 (Southwick 1976).
Sulphur dioxide causes acute and chronic injury to plant life leading to their death. Pines react by defoliation and reduced growth to SO2 pollution.
These are produced during combustion of petrol, diesel burning of coal in automobiles and other types of transport carriers (like ships and trains). Carbon monoxide and nitrogen oxide are produced during combustion of gasoline engines and coal burning.
Carbon monoxide is injurious to animal life. CO combines with haemoglobin (when inhaled) to form carboxyhaemoglobin which effects oxygen carrying capacity (blood poisioning). This is characterised by giddiness, lassitude and headache. When carboxyhaemoglobin content increases to 2 to 5%, nervous system becomes affected. In advanced conditions nausea, pressure in chest, heart palpitations and difficulty in breathing occur.
Nitrogen oxide is another important gas pollutant produced by the burning of petrol and other fossil fuels. In the atmosphere NO2 is reduced by ultraviolet light to nitrogen monoxide and atomic oxygen. Further, nitrogen monoxide reacts with ozone to form nitrogen dioxide and oxygen.
Sometimes atomic oxygen reacts with hydrocarbons like methane, ethane, toluene (originated from burning of petroleum products) and form reactive substances called radicles. These react with hydrocarbons, O2, etc. form O3 formaldehyde, aldehydes and peroxyacetyl nitrate (PAN). These are collectively called photochemical smog.
Effects on life:
NO2 produces brownish haze (thin mist) which causes nose and eye irritation and pulmonary discomfort. Ozone also has the same effect. PAN, O3 and NO2 damage chloroplasts, destroy the cells of leaves, and thus cause injury to plant life.
Lead is another air pollutant produce by the automobiles. Petroleum contains tetra ethyl lead which when burned enters into the atmosphere. Blood poisoning is caused when blood lead concentration is 80 milligram/ 100 gm of blood. It causes symptoms like anaemia, kidney diseases and convulsions. It is estimated that from 1954 to 1969 in New York 2018 persons were treated for leading poisoning and out of which 128 died.