ABSTRACT
Laboratory animals were employed to study biological phenomena long before cancer research was established as a branch of the biological sciences. The aim of a carcinogenicity study is to discover the potential of a particular chemical to increase the incidence of tumors in laboratory animals under strictly controlled exposure conditions. The oral route is appropriate for examining the carcinogenic activity of most substances ingested by humans. The test substance may be administered mixed with the diet or dissolved in drinking water to which the experimental animals are allowed unlimited or limited access. There is agreement among toxicologists that the route of administration should parallel as closely as possible human exposure. Substances that would normally come into contact with human skin are tested for carcinogenicity by topical application to the skin of mice. After decades of data accumulated from cancer bioassays in rats and mice, these experimental results can be qualitatively compared to the epidemological data available in humans.
