Genotoxicity assessment of wood-preserving waste contaminated soil and groundwater undergoing bioremediation

The goal of this study was to determine whether measurement of chemical endpoints alone accurately reflects the genotoxic risk posed by exposure to complex mixtures in media. Chemical analysis using GCMS, in vitro mutagenicity tests (Salmonella bioassay and E. coli prophage induction) and 32P-postlabeling for DNA adducts in vivo were used to investigate the genotoxic risk of wood-preserving waste contaminated soil and groundwater samples collected from a Superfund site. Chemical concentrations were used to determine the human health risk associated with exposure to contaminated soil. Contaminants of concern at the site included polycyclic aromatic hydrocarbons and pentachlorophenol.; While chemical concentrations declined with treatment, soil gentoxicity was relatively unchanged. At Day 0 and Day 360 mean weighted activities for soil samples were 293 ± 115 and 325 ± 54 revertants/g soil, respectively. Groundwater samples exhibited a decrease in toxicity corresponding with a decline in chemical concentration with treatment. Samples from the oil-water separator were positive in the E. coli assay with fold increases ranging from 14 to 21; samples from the bioreactor produced negative results with fold increases of less than three. In the post-labeling assay no significant difference was exhibited between Day 0 and Day 360 samples even though chemical concentrations were approximately one-third that of Day 0. Relative adduct levels at Day 0 and Day 360 for skin ranged from 127 ± 21 to 92 ± 33 and for lung from 20 ± 4 to 15 ± 2, respectively.; The results of this research indicated: (1) the contaminant levels in soil appeared to be reduced after treatment although the genotoxicity associated with the sample extracts was unchanged; (2) contaminant levels in groundwater were reduced to within target levels and genotoxicity as measured in the E. coli assay was eliminated; and (3) based on chemical concentrations, the estimated cancer risk associated with soil after 360 days of treatment was 5.7 × 10−5. The reduced risk based on chemical analysis was not reflected in either the Salmonella or 32P-postlabeling assay. Overall, these data indicate chemical analysis may not accurately predict the genotoxic potential of complex mixtures The results of the genotoxicity bioassays suggest unidentified mixture components or unknown chemical interactions may be influencing the genotoxicity.