An event-by-event probabilistic methodology for assessing the health risksof persistent chemicals in fish: A case study at the Palos Verdes Shelf

A human health risk assessment of recreational anglers who consume fish fro m the Pales Verdes Shelf was conducted. The uptake of DDT. DDE, and DDD (co llectively total DDT or tDDT) and polychlorinated biphenyls (PCBs) due to f ish ingestion was characterized using Monte Carlo techniques. This analysis relied upon 176 probability density functions developed from over 300,000 individual pieces of information to represent 17 different exposure factors that influence the human uptake of persistent organic chemicals in fish. T he carcinogenic and noncarcinogenic risks were estimated using a microexpos ure event modeling approach that estimates exposure on an event-by-event ba sis. This evaluation relied upon several large studies that provided site-s pecific data on angler behavior and concentrations of chemicals in 13 fish species. Our results indicate that the median theoretical increased lifetim e cancer risk associated with estimated exposure to tDDT and PCBs was 5 x 1 0(-8) for anglers who fish on commercial passenger fishing vessels (CPFVs) and who catch and eat fish from the Palos Verdes Shelf. The mean risk for t hese anglers was 2 x 10(-7), and the 95th percentile risk was 8 x 10(-7). A t the 95th percentile, the hazard quotients for anglers were less than 1, i ndicating that noncancer effects are unlikely. These results are in contras t with prior risk assessments of this site that suggested that consumption of white croaker alone posed a cancer risk of 2 x 10(-3) and a hazard quoti ent of 32. Our results were validated by their agreement with several indep endent local studies regarding fishing and consumption practices. This asse ssment indicates that the levels of tDDT and PCB in fish at the Palos Verde s Shelf do not pose a significant risk to human health among recreational a nglers. Based on the size of the local angler population, no cases of cance r would be expected to result from eating Pales Verdes Shelf fish. The meth odology used here should be applicable to characterizing the risks to those who ingest fish from the waterways of most industrialized nations.