Methylmercury exposure biomarkers as indicators of neurotoxicity in children aged 7 years

The mercury concentration in blood or scalp hair has been widely used as a biomarker for methylmercury exposure. Because of the increased risks associ ated with exposures during prenatal and early postnatal development, biomar ker results must be interpreted with regard to the age-dependent susceptibi lity. The authors compared regression coefficients for five sets of exposur e biomarkers in 917 children from the Faroe Islands examined at birth, 1 ye ar, and 7 years. Outcome variables were the results of neuropsychologic exa mination carried out in 1993-1994 at age 7 years. After adjustment for cova riates, the cord-blood concentration showed the dearest associations with d eficits in language, attention, and memory. Fine-motor function deficits we re particularly associated with the maternal hair mercury at parturition. M ercury concentrations in the child's blood and hair at age 7 years were sig nificant predictors only of performance on memory for visuospatial informat ion. These findings emphasize the usefulness of the cord-blood mercury conc entration as a main risk indicator. They also support the notion that the g reatest susceptibility to methylmercury neurotoxicity occurs during late ge station, while early postnatal vulnerability is less, and they suggest that the time-dependent susceptibility may vary for different brain functions.