A Novel Approach to Assessing the Joint Effects of Mercury and Fish Consumption on Neurodevelopment in the New Bedford Cohort.

Understanding health risks from methylmercury (MeHg) exposure is complicated by its link to fish consumption which may confound or modify toxicities. One solution is to include fish intake and a biomarker of MeHg exposure in the same model, but resulting estimates do not reflect the independent impact of accumulated MeHg or fish exposures. In fish-eating populations, this can be addressed by separating MeHg exposure into fish intake and average Hg content of the consumed fish. We assessed the joint association of prenatal MeHg exposure (maternal hair Hg) and fish intake (among fish-eating mothers) with neurodevelopment in 361 eight-year-olds from the New Bedford Cohort (born 1993-1998). Neurodevelopmental assessments used standardized tests of IQ, language, memory, and attention. Covariate-adjusted regression assessed the association of maternal fish consumption, stratified by tertiles of estimated average fish Hg, with neurodevelopment. Associations between maternal fish intake and child outcomes were generally beneficial for those in the lowest average fish Hg tertile, but detrimental in the highest average fish Hg tertile where, for example, each serving of fish was associated with 1.3 fewer correct responses (95% CI: -2.2, -0.4) on the Boston Naming test. Standard analyses showed no outcome associations with hair Hg or fish intake.