ABSTRACT
Cancer is a leading cause of morbidity and mortality in the developed parts of the world and in many other regions [210,232]. The etiologies of most types of cancer are not known, but some are caused by exogenous chemicals, for example, lung cancer and cigarette smoke [210] and liver cancer and a¦atoxin B1 [210]. Accordingly, in the toxicological assessment of chemicals, testing for carcinogenic activity constitutes a critical component and is required under numerous governmental regulations or agreements (Table 25.1). A large database on the carcinogenic, or oncogenic, activities of chemicals in rodents has accrued [147,148,149,316] as a result of almost 100 years of basic research, as well as the output from national testing programs in several countries, particularly the United States and Japan, and regulatory studies conducted by the pharmaceutical, chemical, food, and cosmetic industries. In the United States, under the aegis initially of the National Cancer Institute (NCI) and subsequently the National Toxicology Program (NTP) [474], results of cancer bioassays in rodents,
chemicals [324], and further testing is ongoing.
