A lesson from the Faroese birth cohort study

Abstract

Because methylmercury accumulates in aquatic and marine food chains, recent research has focused on adverse effects of dietary exposures in humans and on the concentration levels that may affect the progeny of the exposed population. Following the outbreaks of methylmercury poisoning in Japan and Iraq, large-scale follow-up studies were carried out in the Faroe Islands, Seychelles and New Zealand, to clarify the effects of prenatal methylmercury exposure on child neurodevelopment. This review outlines the experience obtained in the Faroese birth cohort study. Mercury exposures among the children in the study were assessed through analyses of cord blood samples at birth and hair samples taken at ages 7 and 14. Significant dose-effect relationships between prenatal methylmercury exposures and both neurobehavioral and neurophysiological endpoints were observed; also, several potential sources of bias or confounders have been considered. Their main effect seems to be an underestimation of the true neurotoxic effect of developmental methylmercury. This evidence suggests that underestimation may also affect the findings of other studies in this field.