Air pollution worldwide is a growing threat to human health and the natural environment. It may be described as contamination of the atmosphere by gaseous, liquid, solid wastes, or by products that can endanger human health and welfare of plants and animals, attack materials, and reduce visibility. Although some pollutants are released by natural sources like volcanoes, coniferous forests, and hot springs, the effect of this pollution is very small when compared to that caused by emissions from industrial sources, power and heat generation, waste disposal, and the operation of internal combustion engines. Fuel combustion is the largest contributor to air pollutant emissions, caused by man, with stationary and mobile sources both responsible. The air pollution problem is encountered outdoors as well as indoor.
Many people spend large portions of time indoors, as much as 80-90% of their lives. We work, study, eat, drink and sleep in enclosed environments where air circulation may be restricted.
For these reasons, some experts feel that more people suffer from the effects of indoor air pollution than outdoor pollution. There are many sources of indoor air pollution. Tobacco smoke, cooking and heating appliances, and vapors from building materials, paints; furniture, etc. cause pollution inside buildings. Radon is a natural radioactive gas released from the earth, and it can be found concentrated in basements in some parts of the United States. Pollution exposure at home and work is often greater than outdoors. Scientists estimate that indoor air pollutant levels are 25-62% greater than outside levels and can cause serious health problems.
Smog is a type of great outdoor pollution. It is caused by chemical reactions between pollutants obtained from different sources, mainly automobile exhaust and industrial emissions. Cities are often centers of these types of activities, and many suffer from the effects of...