Various chemical pollutants, such as nitrates, nitrites, fluorides, arsenic, mercury, selenium, lead, boron, cadmium, copper, nickel, detergents, biocides, polychlorinated biphenyls, polynuclear aromatic hydrocarbons and other carcinogens, radionuclides, etc., (see WHO, 1971), can cause various kinds of physiological and metabolic disturbance and diseases in man and domestic animals. Fluoride pollution is now a serious problem in many districts of Rajasthan, where excess fluoride in water adversely affects the health of the humans: many villagers have aged prematurely or become hunchbacks. Recent studies have shown that persistent exposures to even low levels of environmental chemicals can sometime induce mutagenic, teratogenic or carcinogenic effects on various organisms. Airborne mutagens or carcinogens can enter the body through the respiratory tract and can cause delayed effects, sometime after several years or even in the next generation.
Mutations can be caused not only by ionizing radiations but also by certain chemicals. Many of the drugs and other chemicals being used by civilized man these days are potentially or actually mutagenic and have been demonstrated to be so in microorganisms and insects; and also, in some cases, in mammals. Such mutagens may cause cell death, may induce chromosomal abnormalities which may be transmitted to progeny with deleterious effects, or may induce gene mutations which can constitute a potential hazard for future generations.
Several sea birds are grossly affected by oil pollution. Oiled birds cannot fly. Oil pollution has resulted in declines in the population sizes of razorbills, puffins, scoters and other birds, but certain other birds, e.
g., gulls, stormy petrels and cormorants have not been so affected. When fishes become trapped in an oil polluted area, they are adversely affected. Their gills become clogged with oil. Some sessile invertebrates have surprisingly been found to be unaffected by oil pollution. The seaweed Macrocystis also seems to be unaffected (or even stimulated) following an oil spillage; however, another plant, Zostera, disappears after a spillage (see Atlas and Bartha, 1973).