Quantitative integration of the Salmonella microsuspension assay with supercritical fluid extraction of model airborne vapor-phase mutagens

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Abstract

Vapor-phase mutagens are potentially a major class of toxic contaminants in ambient and indoor air. These compounds are not routinely analyzed due to a lack of an established integrated methodology to quantitatively trap, extract and test the compounds in a bioassay. In a previous report, we emphasized the trapping of volatile and semi-volatile mutagens and the extraction of these compounds using supercritical carbon dioxide (CO2). In the present study, we discuss the use of a bioassay for the quantitation of the model mutagens, ethylene dibromide (EDB) and 4-nitrobiphenyl (4-NB), trapped from an airstream. The compounds EDB and 4-NB were released into a controlled airstream, trapped on XAD-4 adsorbent, and were extracted using supercritical CO2. The extract was tested in a microsuspension modification of the Ames Salmonella/microsome test adapted for volatile compounds. Linear dose-response relationships were obtained for supercritical CO2-extracted EDB using tester strain TA100 (±S9) and for 4-NB using tester strains TA98 and TA100 (−S9). Standard dose-response curves with known amounts of the compounds were also determined for comparison with measured amounts of the model compounds collected in an airstream. The gas chromatographic (GC)- and bioassay-determined quantities of EDB and 4-NB were highly correlated, accurate and precise. For example, bioassay-determined EDB concentrations were within 10% of the GC-determined concentrations. Our results demonstrate that the integrated methodology for vapor-phase mutagens developed in this study would be useful for quantitative analysis of these and related airborne vapor-phase mutagenic compounds.

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The information and views presented in this paper are those of the authors and not necessarily those of the California Air Resources Board.

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