Comparative mutagenicity of 2-methylpropene (isobutene), its epoxide 2-methyl-1,2-epoxypropane and propylene oxide in the in vitro micronucleus test using human lymphocytes.

2-Methylpropene (isobutene), a gaseous compound widely used in chemical industries, is metabolized to the epoxide 2-methyl-1,2-epoxypropane. The parent compound has previously been shown to be non-mutagenic in a modified Ames test, whereas the epoxide metabolite gave a positive result. In this study, both compounds have been tested in the in vitro micronucleus test using human lymphocytes. Propylene oxide, a well known mutagenic compound, served as a positive control. It was found that 2-methylpropene had no mutagenic effect, whereas its epoxide induced a statistically significant dose-dependent increase in the number of micronuclei. The effect observed was comparable with that obtained for propylene oxide.