The genetic toxicology of Gene-Tox non-carcinogens

The Gene-Tox Program has identified 61 chemicals that have been tested in chronic rodent carcinogenesis bioassays and found to be inactive. The genetic toxicology data of these 61 non-carcinogens is reviewed and summarized. A large proportion of these chemicals have been tested to a limited extent in genetic toxicity bioassays: 32 in 2 tests or less. Of the remaining 29 chemicals, 28% have been tested in 9 or more tests which encompass a range of genetic endpoints: gene mutation, chromosomal effects, other genetic endpoints, and cell transformation. The genetic toxicity of 12 chemicals with sufficient data is discussed in detail: benzoin, caffeine caprolactam, ethanol, halothane, hycanthone methanesulfonate, malathion, maleic hydrazide, methotrexate, 1-naphthylamine, 4-nitro-o-phenylenediamine, and p-phenylenediamine. A new technique for the evaluation of multiple test data, the "genetic activity profile", has been applied to 6 of these chemicals, allowing the qualitative and quantitative information to be compared collectively. In the evaluation of the genotoxicity effects of these non-carcinogens, a number of discrepancies between the results from genetic toxicity bioassays and chronic rodent bioassays have been uncovered. These discrepancies are discussed in light of current knowledge on the strengths and weaknesses of both genetic toxicity bioassays and chronic rodent bioassays.