2,2-dimethyloxirane

Endpoint summary

Additional information

Ames test

In a reverse gene mutation assay according to OECD TG 471 (BASF AG, 1989) identified as key study, Salmonella typhimurium strains TA1537, TA98, and TA100 were exposed to 0, 20, 100, 500, 2500 and 5000 µg/plate and Salmonella typhimurium strain TA1535 to 0, 2000, 3000, 4000, 5000 and 6000 µg/plate 2,2-dimethyloxirane (vehicle: DMSO) in the presence and absence of mammalian metabolic activation (S9-mix). No precipitation of the test substance was found with and without S9-mix. A bacteriotoxic effect was observed in test strain TA 1537 without S9-mix at 2500 µg and 5000 µg/plate. An increase in the number of positive wells (his+ revertants) was not observed either without S9-mix or after the addition of a metabolizing system in case of the test strains TA1537, TA98, and TA100. The test substance was weakly mutagenic in case of the test strain TA1535. The positive controls induced the appropriate responses in the corresponding strains. Thus, 2,2-dimethyloxirane was regarded as mutagenic in the Ames test (Salmonella typhimurium reverse mutation assay) under the given experimental conditions.

In a supporting study Cornet et al. (1992) performed detailed investigations by using a modified Ames test (incubation method for volatile genotoxins). The Salmonella typhimurium strains TA100, TA102 and TA1535 were exposed to concentrations of 2,2-dimethyloxirane up to 75000 ppm in the absence of S9 and up to 20000-40000 ppm in the presence of S9. 2,2-dimethyloxirane was mutagenic in all the strains tested, as demonstrated by a clear dose-response relationship. Test strain TA1535 seems to be most sensitive to the test substance compared with the other bacterial strains studied. For this strain, the mutagenic activity of 2,2-dimethyloxirane decreased significantly in the presence of S9 mix.

 

In vitro micronucleus test

In a reliable study of Jorritsma et al. (1995) 2-methyl-1,2-epoxypropane was tested in the ‚in vitro’ micronucleus test using human lymphocytes without metabolic activation system (S9-mix) at concentrations of 5000 ppm. It was found that 2-methyl-1,2-epoxypropane (= 2,2-dimethyloxirane) induced a statistically significant dose-dependent increase in the number of micronuclei.

Short description of key information:
The test substance was tested positive in the Ames test and in the in vitro micronucleus test.

Endpoint Conclusion: Adverse effect observed (positive)

Justification for classification or non-classification

2,2 -Dimethyloxirane was positive in the Ames test and in vitro micronucleus test with human lymphocytes. No in vivo data are available. For precautionary reasons, 2,2 -dimethyloxirane is classified for genetic toxicity (H341) according to Regulation 1272/2008/EC.