Testing of chemicals for carcinogenic activities and some problems related to the assessment of carcinogenic risks to men.

It is recognized that many human cancers are influenced by environmental factors. Therefore, testing of chemicals for carcinogenic activities represents an important part of comprehensive toxicological examinations. Procedures to be employed in bioassays for carcinogenicity will be discussed. Short-term tests should be utilized as screening methods to select suspected chemicals which should or must be further tested in long-term animal experiments. Animal tests can predict carcinogenicity in man. Any substance which is shown conclusively to cause tumors in animals should be considered carcinogenic and therefore a potential hazard for man, but tests on experimental animals cannot provide irrefutable proof of the safety or carcinogenicity of a substance for the human species. Therefore, some of the problems related to the assessment of carcinogenic risks by chemicals will be discussed.