Nature and Sources of Pollutants

Air, water and soil have always been an admixture of chemicals. Some of these chemicals are capable of profound effects on living systems with which they come into contact. Plant and animal life has always depended on natural transformations continuously recycling high quantities of chemical substances through the biosphere. Man too has been exposed to and depended upon many of these environmental chemicals since time immemorial. Adaptive change has been necessary. However, a cognitive capability has distinguished man from other living things. This capability has permitted him to develop rapidly and to learn to use available surrounding resources both to improve the quality of his life and at times to jeopardize it. In the late 1940s and 1950s, destructive air pollution episodes occurred in the Meuse Valley, Donora, London, and New York. Thus, seeds of apprehension and fear of air pollution effects were sown. Such feelings were rekindled by The Silent Spring, the mercury problem, and others. It is my opinion that the doomsday approach (i.e., doomsday caused by environmental contamination per se) is wrong, and, by sane, sensible, and vigorous environmental control action we shall take care of the problems. Many requisites are necessary, one being an understanding of the nature and sources of pollutants. There are a number of ways to classify pollutants, such as by the medium polluted (air, water, or soil), the polluting chemical (organic, inorganic, etc.), the target organisms (people, plants, wildlife), the nature of effects (odors, respiratory irritants, carcinogens, eggshell thinning of birds exposed to "DDT"), or according to the sources (natural or man-made, intensive or extensive, etc.). See figure in PDF file