Estimating Exposure to Methylmercury from Consumption of Contaminated Seafood. J. T. Heimbach, T. O. Berner, and J. Burgar, Environ International Corp.
Methylmercury (MeHg), one organic form of Hg, can accumulate up the food chain in aquatic systems and lead to high concentrations of MeHg in predatory fish, which, when consumed by humans, can result in an increased risk of adverse effects in highly exposed or sensitive populations. A National Academy of Sciences committee concluded that the most appropriate endpoint for derivation of an RfD is neurodevelopmental effects and that the population at highest risk is children of women who consume large amounts of seafood during pregnancy. The recent challenge to FDA to determine whether a consumer advisory was warranted advising women of childbearing age to limit consumption of certain species of fish contaminated with MeHg provides a case study of methods for estimating exposure to contaminants in infrequently consumed foods. The usual means of estimating dietary exposure to a contaminant is to multiply the concentration of the contaminate in food or foods by the amount of the food or foods consumed. Difficulty arises because, with rare exceptions, concern is focused on long term rather than acute exposure to the contaminant, while estimates of food consumption most often are based on surveys encompassing only 1 to 3 days. Estimates of usual intake of infrequently consumed foods are particularly problematic. This paper describes the application of probabilistic models to estimate MeHg exposures and to establish convergent validity among estimates derived using several individually flawed datasets of frequency of consumption of seafood.
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