Air pollution

1. Pollution of the air by certain industrial processes, particularly by burning of coal, has been a concern for many years. However, it was not until thousands died because of air pollution, in such cities as London in the 1950s, that the first steps were taken to reduce the poisons that were routinely being emitted into the air we breathe. Two major sources of harmful emissions became the targets for initial action: utilities and industries, and motor vehicles. Steps were first taken to clean up smokestack emissions around power plants and industrial complexes. Attention was then focused on the sulfur oxides emitted from utility, commercial, and industrial stacks. At the same time devices were developed to cut back on emissions from motor vehicles.

2. Air quality management is a complex undertaking. It is complicated by the nature of air, and by the gases that are commonly considered its basic components. It is further complicated by the continual chemical changes that take place in the air as it moves from one location to another and by atmospheric forces.

3. Special understanding of city air pollution is needed because of great potential health hazards. Sources of pollution are more abundant in major cities than in small towns or rural areas. Often there are coal-fired power plants nearby; schools, universities, hospitals, and other institutions often burn oil as their heat source; industries use fossil fuels as a vital part of industrial processes; each individual home, burning oil, gas, or wood, adds to the pollution entering the city's air.

4. There are many other sources of pollution: motor vehicles, construc­tion activities, dust generated in the city and from agricultural activi­ties nearby, and thousands of vaporized chemicals, some of them toxic and hazardous.

5. Each year millions of dollars are spent to reduce the amount of pol­lution emitted into the atmosphere. Some control devices are already used to reduce emissions from smokestacks and automobile exhausts. However, even tighter controls may be needed in the future. It is an endless battle, one that is essential to safeguard human health and the natural environment.

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Where are control devices already used?

Контрольная работа № 5

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