Air pollution has been a public issue for decades and has been identified as having numerous health consequences. It has also spawned a good deal of effort to curb emissions from automobiles and factories and to maintain the forests and other natural entities which help preserve a good atmosphere. Air and water pollution have probably been the primary concerns which originally energized a number of groups in society to try to do something about the problem of pollution. Among the groups fighting to stop air pollution were the Sierra Club, the Audubon Society, scientific groups, Zero Population Growth, and other citizen-led groups. While no one was specifically agitating for pollution as such, business interests fought to prevent regulations they considered excessive and costly, such as regulations directed at reducing emissions from factories or calling for a redesign of automobiles to make them less polluting.
The question of what constitutes air pollution begins with a definition of what constitutes clean air. Even clean air contains many substances other than oxygen and nitrogen, its major constituents, including rare gases such as argon, neon, and helium, as well as ozone, carbon dioxide, radioactive materials from the earth, and various nitrogen and sulfur compounds. The air would also contain variable amounts of water vapor and many suspended solid particles and liquid substances. Suspended materials known as aerosols are defined as dust particles and condensation nuclei, the latter consisting of chloride salts, sulfuric and nitrous acids, phosphorous compounds, and many other chemical substances. These nuclei have an affinity for water and play an important role in the transformation of water vapor into fog, clouds, and precipitation (Miller and Miller, 1989, 4). When we refer to air pollution, we usually mean air pollutants resulting from human activity and thus something we believe we can cont
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