IDENTIFICATION OF THE PRINCIPAL HUMAN CELL MUTAGEN IN AN ORGANIC EXTRACT OF A MUTAGENIC SEDIMENT

Organic extracts of sediments from a pond in eastern Massachusetts, which were previously shown to be mutagenic to human cells, have been analyzed to determine the identity of the principal mutagens. By using bioassay-directed fractionation methods, the mutagenicity of a sediment extract was entirely resolved into two subfractions (subfractions 3 and 4), which together comprised 9% by weight of the whole extract. Analysis by highperformance liquid chromatographic separation with UV-vis spectrometric detection revealed the presence of polycyclic aromatic hydrocarbons (PAH) in each of these subfractions. Of the total PAH measured, 94% (by weight) was present in subfraction 3, and 6% was present in subfraction 4. All of the PAH identified were tested for mutagenicity in human cells; however, only one compound, benzo[a]pyrene (B[a]P), was mutagenic at the concentration present in the original sediment extract. The results of experiments with subfraction 3 indicate that at low doses as much as 50 % of the mutagenicity was accounted for by B[a]P, while at high doses mutagenicity reached a maximum, indicating that a necessary step (or steps) in the mutagenesis process was inhibited. Knowledge of the principal mutagen in the pond's sediments can be used to assess the human health risks and to guide policy to mitigate exposure.