Probabilistic risk analysis for methylmercury associated with Washington State fisheries

Mark D. Sweeney

Data from published literature and publicly-available agency databases for tissue and blood mercury concentrations were analyzed to determine the risk of consuming fish from Washington State waters, both marine and freshwater. The risk analysis used a probabilistic approach to appropriately assess the variability of tissue concentrations in fish stocks and the diversity of individual pharmacokinetic responses to methylmercury exposure. This analysis evaluated the potential risk of methylmercury exposure to humans through fish consumption, and provided a decadal risk profile of consumers, by relying on fish tissue residue concentration data from the United States Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA). Blood mercury data were taken from the peer-reviewed literature and compared to agency regulatory thresholds to assess exposure risk to sensitive populations using tissue data from a human population. Exposure assessment results from the study were combined with the EPA oral reference dose (0.1 µg/kg/day) to compute a risk quotient as a basis to evaluate methylmercury risk. Probabilistic modeling results for methylmercury residues reported in national databases of fish tissue yielded risk quotients that ranged from 5.7 to 18.3. Risk quotients ranging from 2.4 to 4.5 were estimated from databases managed by Washington State agencies. Probabilistic risk modeling of blood mercury concentration vi data from Washington State data sources produced risk quotients ranging from 3.6 to 5.9. Decadal analysis of the risk quotients showed increasing risk from 1980 to 2000 for EPA datasets, but risk trends based on analysis of FDA and Washington State data were inconclusive. Sensitivity analysis showed that fish tissue concentration was the most significant contributor (60.6%) to variability in the model results, and food portion size contributed to the remaining 39.4% of modeling variability. Mercury concentration was the only contributor to variability in risk based on probabilistic modeling of blood mercury levels. The probabilistic results from this study indicate that consumption of fish from Washington State resources carries no greater risk than from global sources.

Probabilistic risk analysis for methylmercury associated with Washington State fisheries

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