US EPA

1,3-Butadiene has been shown to be an indirect mutage in bacteria. Two of its potential metabolites, 3,4- epoxybutene and diepoxybutane, are genotoxic in prokaryote as well as eukaryote test systems. Exposure of rodents to 1,3-butadiene results in ovarian tumors in mice and testicular tumors in rats, which offers suggestive evidence that 1,3-butadiene (or a motabolite of 1,3-butadiene) may reach the germ cells. There is also evidence that the dimer of 1,3-butadiene, 4-vinyl-1-cyclohexene, causes ovarian tumors in mice. The total body of evidence, including metabolism, mutagenicity and carcinogenicity data, suggests that 1,3-butadiene may present a genetic risk to humans. However, mutagenicity studies in mammalian test systems should be conducted to further characterize the mutagenic potential of 1,3-butadiene. On the basis of sufficient evidence from studies in two species of rodents, and inadequate epidemiologic data, 1,3-butadiene can be classified, according to EPA's Proposed Guidelines for Carcinogen Risk Assessment, as a 'probable' human carcinogen, Group B2. Using the classification scheme of the International Agency for Research on Cancer, 1,3-butadiene would be classified as a 'probable' human carcinogen, Group 2B.

Bayard, S., R. Beliles, A. Chiu, H. Gibb, AND B. Sadler. MUTAGENICITY AND CARCINOGENICITY ASSESSMENT OF 1,3-BUTADIENE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/8-85/004F (NTIS PB86125507).

See also PB85-181097.