Effects of Air Pollution. Air is needed for breathing by humans, other land organisms and many aquatic organisms. Its pollution can, thus, affect human health as well as human wealth (domestic animals, crops). It also spoils materials such as buildings, clothes, metals. It affects climate too. Air problems include offensive odours, noxious fumes, corrosive gases, smoke, dust, hazy atmosphere, soiling of clothes and household articles, and pollution of food. Air pollution also causes diseases.
Air pollution is more serious man water pollution. Whereas water pollution may remain localised, air pollution may quickly spread over wide areas.
Air pollution has become a serious problem in the big, congested, industrialized cities with heavy rush of vehicular traffic. The magnitude of air pollution is revealed by a recent estimate that about 630 tonnes of pollutants am daily added to the air in Kolkata and its suburbs from over 2,000 industrial units, over 1.5 lakh motor vehicles, 2 thermal plants, and many steam engines, slips and aeroplanes.
1. Effect on Humans. The effect of particulate pollutants depends on the size of the particles. Particles larger than 2 `mum` are trapped in nasal hair and bronchial mucus, whence they are passed out. Smaller particles reach the lung alveoli with inhaled air. Here they may be engulfed by phagocytes or absorbed into the blood and prove harmful.
(i) Air-borne organic materials, such as spores, pollen, bacteria, fungi, fur, feathers, produce allergic reactions, bronchial asthma, emphysema, tuberculosis and lung cancer.
(ii) Dust, smoke, and smog cause bronchitis, asthma and lung diseases. People living near thermal plants often contract these troubles. Soot and tobacco smoke are carcinogenic (cancer causing). Cotton dust, asbestos fibres, stone particles causes lung fibrosis. The latter also affects the coal miners and flour mill workers.
(iii) The effect of gaseous pollutants depends upon their solubility in water, which allows their diffusion into the tissues.
(a) Sulphur dioxide causes drying of the mouth, sore throat and eye irritation. It may damage the tissues by forming sulphuric acid.
(b) Sulphur trioxide, nitrogen oxides and carbon monoxide combine with haemoglobin of the blood and reduce its oxygen-carrying capacity. Nitrogen oxide impairs the working of lungs by causing accumulation of water in the air spaces.
(c) Peroxyacyl nitrate causes irritation of eyes and throat and respiratory diseases (bronchitis, lung cancer).
(d) Hydrocarbons cause cancer.
(e)Carbon dioxide causes headache and nausea .
(f) Lead affects central nervous system and distorts red blood corpuscles.
(g)PCBs damage liver and central nervous system , impair vision and change skin pigmentation.
2. Effect on Animals. Domestic animals in and around industrial areas are affected by air pollutants just like humans, Ingestion of fluorine compounds deposited from the air on fodder causes fluorosis (excessive calcification of bones and teeth), which leads to lameness, frequent diarrhoea and loss of weight. Microbes cause diseases in animals also.
3. Effect on Plants. Sulphur dioxide causes chlorosis, plasmolysis, membrane damage, metabolic inhibition and death. It does a great harm to forest trees. Fluorides and PAN damage leafy vegetables such as spinach and lettuce. Ozone and hydrocarbons cause premature yellowing and fall of leaves and flower buds, and decolouration and curling of sepals. Nitrogen oxides reduce yield of crops. Dust, smoke and smog reduce sunlight and form a thin layer on the leaves, thereby retarding photosynthesis. Microbes cause diseases in plants too.
Air pollution kills lichens, the hardy organisms. Death of lichens is a sure indicator of air pollution.
4. Effect on Materials. Acid rain and photochemical oxidants adversely affect buildings, metals, clothes, paper and marble. Many industrial units have been shifted to save the precious marble monument, the Taj Mahal at Agra. Acid rains pollute soil and water sources also. Silver and lead paints are decolourised by hydrogen sulphide.
5. Change in Climate. Carbon dioxide content of the air is increasing due to deforestation and combustion in industries, automobiles and aeroplanes, and is likely to become double by 2020. This increase is affecting the atmospheric composition and balance of gases, which are among the factors that control earth.s climate. Increase of carbon dioxide may cause rise in atmospheric temperature, producing what is called the green house effect. A rise of global temperature by more than 2 or 3 degrees may melt glaciers and polar ice. This will cause rise in ocean level and consequent flooding of coastal towns and submersion of islands. Rainfall pattern may also change, affecting agricultural output.
Aerosols deplete the ozone layer in the stratosphere. Thinning of ozone layer would permit more of the harmful ultraviolet rays to reach the earth. This may cause sunburn, blindness and inactivation of proteins, RNA, DNA and plant pigments.
6. Aesthetic Loss. Dust and smoke in the air do not allow a clear view of nature.s beauty. Foul odours emitted by industries, automobiles, dirty drains, and garbage heaps in cities are a great nuisance.
