A procedure for the quantitative measurement of the mutagenicity of volatile liquids in the Ames Salmonella/microsome assay.

We have designed a closed, inert incubation system for testing the mutagenicity of volatile compounds. The containment properties of this system have been investigated using carbon-14 labelled 1,2-dibromoethane. The recovery of this solvent was about 95% following a 48-h incubation at 37 degrees. Using the Ames Salmonella/microsome mutagenicity assay we have determined the mutagenic potency of 10 common halogenated alkane solvents. Of these 10 compounds, only 1,2-dibromoethane and 1-bromo-2-chloroethane give positive results in the standard test procedure, whereas 7 of the 10 give positive results in the closed system. The specificity observed for reversion of the tester strains and the lack of any significant effect of added rat-liver "S9" fractions suggest that these haloalkanes are direct-acting "base-pair" type mutagens. The mutagenic potencies of the 7 positive compounds range from 0.001 revertants per nanomole for 1,2-dichloroethane to 0.172 revertants per nanomole for 1,2-dibromoethane. A minimum or threshold response level for each material has been calculated.