BIOASSAY-BASED RISK ASSESSMENT OF COMPLEX-MIXTURES

In order to compare a standard chemical-based risk assessment with in vitro genotoxicity assays, two complex environmental mixtures from a w ood-preserving site were analyzed in the Salmonella/microsome and E. c oli prophage induction assays. Using GC/MS, sample 003 was found to co ntain relatively low levels of polycyclic aromatic hydrocarbons (PAHs) and elevated levels of polychlorinated dibenzo-p-dioxins (PCDDs), whi le sample 005 had higher levels of PAHs and relatively low levels of P CDDs. The complex mixtures were sequentially extracted with methylene chloride and methanol for analysis in Salmonella, or extracted with a 1:1 hexane:acetone mixture for analysis in the E. coli prophage induct ion assay. At a dose of 1.0mg/plate in Salmonella strain TA98 with met abolic activation, the methanol extract of sample 003 induced 197 net revertants, while sample 005 induced 436 net revertants. In the propha ge induction assay, with activation, the hexane:acetone extract of sam ple 003 induced a genotoxic response that was slightly lower than that observed with sample 005. The estimated incremental carcinogenic risk for ingestion of PAHs was 1.5E - 3 for sample 003, while for sample 0 05 the estimated risk was 1.5E - 2. Thus, the sample which induced the maximum response in both bioassays also had the highest estimated can cer risk. However, the frequency of PAH-DNA adducts in both skin and l iver tissues was appreciably higher with sample 003 than with sample 0 05. A combined testing protocol, using both biological and chemical an alysis, therefore provides more accurate information from which to ass ess risk than the use of either method alone.