Blood mercury levels in avid seafood consumers indicate need for targeted education

Methylmercury is a neurotoxicant that can produce damaging health effects on the developing child as well as in adults. The EPA established a reference dose (RfD) for methylmercury in 1999 to define a level of human daily exposure to be without appreciable risk including for sensitive populations such as the developing child; the RfD of 0.1 µg mercury/kg body weight/day corresponds to a blood level of 5.8 µg/L. Since 1999 several studies have identified neurodevelopmental effects from exposures at levels below the current RfD, suggesting the RfD may not afford adequate protection. Seafood consumption is the primary non-occupational exposure source to methylmercury. We examined seafood consumption patterns and blood mercury levels in a cohort of 285 avid adult seafood consumers from Long Island, NY. We measured their blood mercury levels and estimated their seafood intake using a food frequency questionnaire. The mean Hg concentration for female avid seafood consumers (geometric mean = 4.52 µg/L) was 5-fold higher than that of women in the general U.S. population, estimated by the 2009-2010 US National health and Nutrition Examination Survey (NHANES). We found that 26% of avid seafood consuming females of child bearing age (18-49 years old) had blood mercury levels above the RfD (geometric mean = 3.47 µg/L) as compared to about 5% of women aged 16-49 in the general U.S. population as estimated by NHANES. As seen in other studies, blood mercury levels increased with increasing age; 60% of participants ≥60 years old had blood mercury levels greater than the EPA RfD (geometric mean=6.36 µg/L). These findings identify an at-risk population of avid seafood consumers that could benefit from information on how to enjoy seafood while making low-mercury seafood choices. Our results will inform recommendations for how to advise avid seafood consumers.