American Chemical Society, Environmental Science and Technology, 3(49), p. 1787-1796, 2015
DOI: 10.1021/es504465f
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This study employed an in vitro version of the lacZ transgenic rodent mutation assay to assess the mutagenicity of non-polar neutral and semi-polar aromatic soil fractions from ten PAH-contaminated sites, and evaluated the assumption of dose additivity that is routinely employed to calculate the risk posed by PAH mixtures. Significant mutagenic activity was detected in all non-polar neutral fractions, and 8 of 10 semi-polar aromatic fractions (non-polar > semi-polar). Mutagenic activity of synthetic PAH mixtures that mimic the PAH content of the soils (i.e., 5-PAH or 16-PAH mix) were greater than that of the PAH-containing soil fractions, with 5-PAH mix > 16-PAH-mix. Predictions of mutagenic activity, calculated as the sum of the contributions from the mutagenic mixture components, were all within two-fold of the observed activity of the non-polar neutral fractions, with one exception. Observed differences in mutagenic activity are likely the result of dynamic metabolic processes, involving a complex interplay of AhR agonsim and saturation of metabolic machinery by competitive inhibition of mixture components. The presence of hitherto unidentified polar compounds present in PAH-contaminated soils may also contribute to overall hazard; however, these compounds are generally not included in current contaminated site risk assessment protocols.