Factors affecting mercury and selenium levels in New Jersey flatfish: low risk to human consumers

Some fish contain high levels of mercury (Hg), which could pose a risk to fish eaters themselves or their children. In making decisions about fish consumption, people must decide whether to eat fish, how much to eat, what species to eat, and what size fish to eat, as well as suitable (or unsuitable) locations, among other factors. Yet to make sound decisions, people need to know the levels of Hg in fish as a function of species, size, and location of capture. Levels of Hg and selenium (Se) were examined in three species of flatfish (fluke or summer flounder [Paralichthys dentatus], winter flounder [Pseudopleuronectes americanus], and windowpane [Scophthalmus aquosus]) from New Jersey as a function of species, fish size, season, and location. Flatfish were postulated to have low levels of Hg because they are low on the food chain and are bottom feeders, and data were generated to provide individuals with information on a species that might be safe to eat regularly. Although there were interspecific differences in Hg levels in the 3 species, total Hg levels averaged 0.18, 0.14, and 0.06 ppm (microg/g, wet weigh) in windowpane, fluke, and winter flounder, and selenium levels averaged 0.36, 0.35, and 0.25 ppm, respectively. For windowpane, 15% had Hg levels above 0.3 ppm, but no individual fish had Hg levels over 0.5 ppm. There were no significant seasonal differences in Hg levels, although Se was significantly higher in fluke in summer compared to spring. There were few geographical differences among New Jersey locations. Correlations between Hg and Se levels were low. Data, based on 464 fish samples, indicate that Hg levels are below various advisory levels and pose little risk to typical New Jersey fish consumers. A 70-kg person eating 1 meal (8 oz or 227 g) per week would not exceed the U.S. Environmental Protection Agency reference dose of 0.1 microg/kg body weight/d of methylmercury (MeHg). However, high-end fish eaters consuming several such meals per week may exceed recommended levels.