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. Outdoor air pollution gets the most attention, but more recently, there has been much attention given to interior air pollution from a variety of sources, including the pollution from outdoors, radon in cellars, and various structural materials and coverings which may cause allergic reactions in some people.
Most air pollution is emitted from the exhausts of automobiles or from the burning of fossil fuels by industry. 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 n...