Drinking water and human cancer

The relatively low concentrations of the various natural and man-made contaminants of drinking water, together with the methodological problems of obtaining valid and complete exposure histories for individuals and of controlling for confounding factors, have made it difficult for epidemiological studies to detect and estimate risks of cancer. Nearly all studies to date, with some exceptions for the halogenated hydrocarbons, have been at the ecological level. For these and other reasons, quantitative risk assessment of the cancer risks due to this complex environmental exposure remains rudimentary. If, eventually, risks are assessed to be non-trivial, primary prevention could be sought by alternative choices of either methods of water treatment or of water sources. However, since we cannot eliminate all trace carcinogens from our environment, we need simultaneously to minimize both the exposures and the biological impact of such exposures. The latter will require studies of cancer chemoprevention, using biochemical and molecular epidemiological approaches.