The ranking of chemicals for carcinogenic potency

A relatively new approach to assessing the carcinogenic hazard that chemicals pose to man involves the development of criteria by which carcinogens can be ranked regarding potency. Several such systems have been proposed which can be grouped into dose-dependent, mechanistic, and response-dependent classification systems. In this communication, examples of each type of classification system are described and the utility of these systems in assessing the carcinogenic hazard of chemicals is explored. Each of the classification systems which have been proposed has certain problems associated with it. However, in view of the potential utility of this approach, further efforts to develop a classification system for ranking carcinogens appear warranted. Such a system for ranking carcinogens could possibly be used in conjunction with low-dose extrapolation in the regulatory process. Once a carcinogen has been ranked for potency this ranking could influence the low-dose extrapolation model used in estimating the human risk associated with exposure to that carcinogen. The more potent the carcinogen, the more conservative the low-dose extrapolation model used.