Chemicals with carcinogenic activity in the rodent liver; mechanistic evaluation of human risk.

A wide variety of chemicals, both naturally occurring and synthetic, have exhibited carcinogenic activity in rodent liver. Some are clearly DNA reactive whereas others produce only epigenetic effects. Hepatocarcinogens are categorized according to these properties and the characteristics of examples of both types are reviewed. DNA-reactive rodent hepatocarcinogens represent human cancer risk even at non-toxic exposures, whereas epigenetic agents pose either no risk because their effects are specific to rodents, or a risk only at high exposures at which they produce the same cellular effects in humans that are the basis for their carcinogenic activity in rodents.