One of the formal definitions of air
pollution is asfollows – ‘The presence in the atmosphere of one or more contaminants
in suchquality and for such duration as is injurious, or tends to be injurious, tohuman health or welfare, animal or plant life.’ It is the contamination of airby the discharge of harmful substances. Air
pollution can cause health problemsand it can also damage the environment and property. It has caused thinning ofthe protective ozone layer of the atmosphere, which is leading to climatechange. Industries, vehicles, increase in the population, and urbanization aresome of the major factors responsible for air pollution. Dust storms in desertareas and smoke from forest fires and grass fires contribute to chemical andparticulate pollution of the air. The source of pollution may be in one countrybut the impact of pollution may be felt elsewhere. When released into the air,CFCs rise to the stratosphere, where they come in contact with few other gases,which leads to a reduction of the ozone layer that protects the earth from theharmful ultraviolet rays of the sun.Ozone occur naturally in the upper layers of the atmosphere. This importantgas shields the earth from the harmful ultraviolet rays of the sun. Vehiclesand industries are the major source of ground-level ozone emissions. Suspended particulate matter (SPM) consistsof solids in the air in the form of smoke, dust, and vapour that can remainsuspended for extended periods and is also the main source of haze whichreduces visibility. The finer of these particles, when breathed in can lodge inour lungs and cause lung damage and respiratory problems.Smog forms when heat and sunlight react with thesegases and fine particles in the air. It hampers visibility and harms theenvironment. In fact, in the early part of the 20th century,
heavy smog in someparts of Europe resulted in a decrease in the production of natural vitamin Dleading to a rise in the cases of rickets. In fact the word smog has beencoined from a combination of the words fog and smoke. The industrial revolution in the 19th century saw thebeginning of air pollution in Europe on a large scale and the presence of smogmainly in Britain. The industries and the households relied heavily on coal forheating and cooking. By the end of the 19th century, many people visited Londonto see the fog. In addition, the introduction of cleaner coals led to areduction in sulphur dioxide pollution. In the 1940s, severe smog began coveringthe city of Los Angeles in the USA.The term smog was first used in 1905 by Dr H A DesVoeux to describe the conditions of fog that had soot or smoke in it. Smog is acombination of various gases with water vapour and dust. A large part of thegases that form smog is produced when fuels are burnt. Smog forms when heat andsunlight react with these gases and fine particles in the air. Smog can affectoutlying suburbs and rural areas as well as big cities. Its occurrences areoften linked to heavy traffic, high temperatures, and calm winds. During thewinter, wind speeds are low and cause the smoke and fog to stagnate; hencepollution levels can increase near ground level. This keeps the pollution closeto the ground, right where people are breathing. It hampers visibility andharms the environment. Heavy smog is greatly decreases ultraviolet radiation. Infact, in the early part of the 20th century, heavy smog in some parts of Europeresulted in a decrease in the production of natural vitamin D leading to a risein the cases of rickets. Smog causes a misty haze similar to fog, but verydifferent in composition. In fact the word smog has been coined from acombination of the words fog and smoke. Smog refers to hazy air that causesdifficult breathing conditions.With the boom in population and industrial growth, theneed for power has increased manifold. Nearly 73% of India’s total installedpower generation capacity is thermal, of which 90% is coal-based generation,with diesel, wind, gas, and steam making up the rest. Thermal power generationthrough coal combustion produces minute particles of ash that causes seriousenvironmental problems. The 80-odd utility thermal power stations in India usebituminous coal and produce large quantities of fly ash. According to oneestimate, up to 150 million tonnes of fly ash will be produced in India in theyear 2000, primarily by thermal power plants and, to a lesser extent, by cementand steel plants and railways. This poses problems in the form of land use,health hazards, and environmental dangers. Both in disposal and in utilizationutmost care has to be taken to safeguard the interest of human life, wild life,and such other considerations. The prevalent practice is to dump fly ash onwastelands, and this has lain to waste thousands of hectares all over thecountry. To prevent the fly ash from getting airborne, the dumping sites haveto be constantly kept wet by sprinkling water over the area. The coal industryin USA spends millions of dollars on lining fly ash dumping grounds. But inIndia, these sites are not lined and it leads to seepage, contaminatinggroundwater and soil. It lowers soil fertility and contaminates surface andground water as it can leach into the subsoil. When fly ash gets into thenatural draining system, it results in siltation and clogs the system. It alsoreduces the pH balance and portability of water. Fly ash interferes with theprocess of photosynthesis of aquatic plants and thus disturbs the food chain. Besides,fly ash corrodes exposed metallic structures in its vicinity. ...