[Methods of identifying carcinogenic factors in medication, food and cosmetics]

The removal of carconogenic factors would be a most efficient measure to prevent cancer. As far as known chemicals are concerned, every effort is made to avert them, or at least to reduce the exposure to such compounds, but is necessary to detect unknown chemicals, especially those, drugs and foodstuffs for example, to which large populations are exposed. Giving suspected chemicals to laboratory animals is a standard carcinogenicity test. Studies of the carcinogenicity of unknown chemicals in animals are time consuming, expensive and cumbersome. This is why other means of establishing carcinogenicity are sought for. Several rapid tests are available to-day to select suspected carcinogens. These methods aim primarily at determining with chemicals--at the cell or tissue level--certain changes that would appear essential to trigger the carcinogenic process, such as somatic mutations. Studies are used on the mutagenicity of chemicals for bacteria of the Salmonella type, for yeast and cultured mammalian cells, together with the induction of recessive lethal mutations in Drosophila and of the unscheduled repair synthesis of DNA and the transformation of mammalian cells in vitro. Although there is an unequivocal correlation between the activity of chemicals in such tests and their carcinogenicity, discrepancies are found. Thus, the in vivo tests on laboratory animals remain the most reliable method to determine carcinogenicity. Whereas direct extrapolation of experimental data to human pathology is impossible, the experimental evidence of the carcinogenicity of any chemical should allow us to draw constructive conclusions. We shall never be able to reject drugs which produce the expected results and cannot be replaced by other drugs. But we can must the drugs whose beneficial effects are not exceptional and which can be replaced by other chemicals. As for the chemicals used in food additives and cosmetics, and recognized as carcinogenic in animals, they should be totally given up. Any decision made should be based on animal studies.