Mutagenic potential of environmental samples before and after remediation of a solvent-contaminated site

Soil, sediment, and paint sludge samples were collected during a 4-year period from an abandoned solvent recovery site prior to and after site remediation. Samples were sequentially extracted with methylene chloride and methanol and redissolved in dimethyl sulfoxide for biological analysis. The mutagenic potential of the extracts was evaluated using the Salmonella/microsome assay with and without metabolic activation. Noncontaminated background soil samples collected off-site induced specific mutagenic activities that ranged from below detection to 28 net revertants per milligram of residue. Although several sludge samples induced specific activities that were relatively low, the maximum mutagenic response induced by a sludge sample was 1,258 net revertants per milligram of residue. Compared to background soil, elevated levels of mutagenic activity were also detected in the extracts of several samples collected from a drainage area downgradient from the waste storage pad and in the extract of sediment samples from a downgradient storm-water retention pond. The weighted activity of the noncontaminated background soil samples ranged from below detection to 15 revertants per gram of soil. The combined weighted activity of the sludge sample extracts ranged from below detection to 43,567 revertants per gram. The combined weighted activity of the extracts of samples collected after site remediation ranged from below detection to 1,273 revertants per gram. A visual inspection of the site following remediation suggested that all obvious signs of chemical contamination had been removed. However, the results from biological analysis indicate that soil collected following site remediation induced a weighted activity more than 30 times the maximum weighted activity observed in the noncontaminated background soil. These data suggest that additional site remediation is required if the genotoxic potential of soil is to be reduced to levels approximating those of noncontaminated background soil.