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ENVIRONMENTAL EPIDEMIOLOGY: Volume 1
were enacted between 1952 and 1977 to control air and water pollution. Because of the Federal Water Pollution Control Act (1952), the Clean Air Act (1963), and the Clean Water Act (1977) surface water and ambient air were no longer considered acceptable outlets for the disposal of wastes. Consequently, industries and municipalities turned increasingly to the land for waste disposal. Contamination of groundwater and aquifers occurred where the waste dumps were poorly constructed or managed, or where wastes were disposed of improperly.
This chapter reviews evidence about some compounds commonly found at hazardous-waste sites that have been shown to cause adverse effects in humans exposed to these materials from consumption of domestic water. First it discusses studies of cancer risk posed by trihalomethanes (THMs) as an indicator of the sort of effects that can be anticipated from contamination of drinking water by such compounds. Then it assesses the relatively scanty literature on adverse effects that can be linked to the contamination of drinking water from toxic dump sites, including congenital anomalies, cancer, and other chronic diseases. As the importance of lead in drinking water is currently the subject of extensive analysis and regulatory attention, this chapter does not review this topic.
Epidemiologic evidence on the risk to health from contaminated water from hazardous-waste sites or other sources of contamination, such as pesticide runoff, has largely been derived from ecologic or descriptive studies, and therefore is seldom conclusive as to cause. The ecologic studies involving broad-scale comparisons of available data are unable to control for important confounding variables, such as smoking or other relevant exposures. Recent literature on the contamination of drinking water include a number of ecologic and case-control studies that evaluate the cancer risk of by-products of chlorination on human health (Jolley et al., 1990). Some chlorination by-products, particularly halogenated hydrocarbons or THMs, occur in greater quantities in drinking water if large amounts of organic matter are present (Burke et al., 1983). Two of these, chloroform and carbon tetrachloride, have been commonly found in the chemical mixtures at some toxic dump sites. Chloroform tends to be readily identified because it is more easily measured. Whether or not they, or other chemicals also present, increase the risk of cancer for exposed residents is unclear (Crump and Guess, 1982).
Several case-control studies based on examinations of death certificates have found an increased risk for cancers of the colon, rectum, bladder, breast, brain, and lung in persons who have consumed chlorinated drinking water (Velema, 1987). However the results have not always been consistent and causality cannot reliably be inferred.