Air pollution by Particulates:
Particulates constitute the third category of air pollutants. These are mostly fine carbon particles (less than 0.002 mm in diameter) formed by the combustion of fossil fuels. They remain suspended in the air, where they absorb other substances such as lead, hydrocarbonssulphur and nitrogen oxides. These particles enter the lungs during breathing and increases the chances of lung cancer, and other respiratory diseases.
Diesel automobiles and trucks emit between 30 and 100 times more carbon particles than other vehicles. Asbestos is also an air pollutant in the form of particles that enter the atmosphere from asbestos mining andmilling operations and from the manufacture, disposal and use of asbestos containing products such as insulation devices. Asbestosis, a cancerous disease caused by deposition oasbestos in the lungs, is widely prevalent among the people working with this material. Several miners are known to have died in Singhbhum, Bihar due to this disease. Recently, this disease has been classified as a killer disease under the Factories Act.
Silicosis, another cancerous disease caused by deposition of silica in the lungs, is prevalentamong the people working in the mining, potteries, foundries, stone cutting and finishing, and glass manufacturing industries. It is also a fatal disease.
The air in most of the urban areas in India has a very high level of particulates. In fact, an unpleasant haze of dust and smoke particles has become almost an integral part of our urbaenvironment. For example in cities like Delhi and Bombay, during rush hours in the mornings or evenings, it becomes difficult to breathe if you are caught for long at traffic crossings. There is so much of vehicular exhaust fumes. One of the most harmful pollutants is sulphur dioxide.
It is a compound containing sulphuand oxygen and is produced when fossil fuels contaminated by sulphur are burned. Sulphurdioxide has a sharp odour and irritates the respiratory tissues. It also reacts with water, oxygen and other materials in air to form sulphur containing acids.
The acids also become attached to particles in the air, When, inhaled, such particles are veiy corrosive to lung tissue. Sulphur dioxide also adversely affects the plants and reduces their growth. Steel getscorroded 2 to 4 times faster in sulphur-laden air. Sulphur dioxide also corrodes other metalslike zinc as well as building stone. Oxides of nitrogen are also major primary air pollutants. As a result of a variety of combinations of nitrogen and oxygen, a number of compounds, oxides of nitrogen, are formed. The primary source of nitrogen oxides is automobile engines. Oxides of nitrogen react with other compounds to produce photochemical smog which we will describe now.