Current status of experimental chemical carcinogenesis and its applications to human cancer risk.

The history of chemical carcinogenesis is a record of the observations of physicians and epidemiologists of the relation between the occurrence of uncommon cancers in humans and the exposures of those people to certain chemical agents. In parallel with some of these findings, experimental animal models were developed to imitate the findings in humans. From these experimental studies has been obtained most of the information we have about the mechanisms of chemical carcinogenesis. Many of the biochemical studies have focused on liver cancer which might be an inappropriate general model for chemically induced cancer, liver cancer being comparatively rare in humans. It is not known to what extent exposures to any particular chemical carcinogens are responsible for the major human cancers, and the agents responsible for most of them are not known. It is probable that many noncarcinogenic chemicals act as promotors of carcinogenesis, and among these alcohol can be included as in important contributor.