ASSESSMENT OF POTENTIAL CANCER RISK FROM CONSUMPTION OF PCBS BIOACCUMULATED IN FISH AND SHELLFISH

We evaluated the potential cancer risk to adults from ingesting polych lorinated biphenyls (PCBs) in fish and shellfish using an equilibrium partitioning model of PCB bioaccumulation in the aquatic animal. Estim ated potential cancer risk to humans increased exponentially with incr easing hydrophobicity of the PCB. However, the addition of food-chain sources of PCBs was necessary to cause potential cancer risk to exceed 10(-6). Environmental degradation of the PCB reduced cancer risk by r educing the exposure concentration; 3.3 degradation half-lives were re quired to reduce cancer risk estimates by one order of magnitude. PCB biotransformation to nongenotoxic metabolites (no increase in the canc er slope factor) by the aquatic animal reduced cancer risk by reducing the steady-state concentration of PCBs in the edible tissue. Even rel atively slow biotransformation (e.g., metabolic half-life of 100 days) reduced cancer risk estimates under the default model conditions. non equilibrium conditions, such as limited exposure time, reduced potenti al cancer risk by reducing contaminant concentrations in the aquatic a nimal. Risk assessment using toxic equivalency factors predicted subst antially greater potential risk for specific congeners than for PCB mi xtures. Our evaluation demonstrates that deviation from conventional a ssumptions used in risk assessment (e.g., negligible biotransformation and degradation; steady-state equilibrium) can significantly affect c ancer risk estimates.