Environmental pollutants and the epidemiology of cancer.

Cancer etiology involves the interplay of genetic and environmental factors. Striking geographic differences and changes in cancer incidence over time have led epidemiologists to infer that probably the major etiologic component is environmental. Recent experiences with vinyl chloride, kepone, and polybrominated biphenyl illustrate the problems involved in epidemiologic studies of proven or suspected environmental carcinogens. While epidemiologic studies will continue to be an essential means for monitoring potential human risks, the long latent periods involved in human carcinogenesis severely limit the usefulness of such approaches for disease prevention. While in vitro and animal test systems can never fully supplant human studies, they represent our only means for detecting potential carcinogenicity before human exposure has become widespread or long established.