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 methlimercury exposure. Becasue of the increased risks associated with exposures during prenatal and early postnatal development, biomarker results must be interpreted with regard to the age-dependent susceptibillity. The authors compared regression coefficients for five sets of exposure biomarkers in 917 children from the Faroe Islands examined at birth, 1 year, and 7 years. Outcome varibales were the results of neuropsychologic exemination carried out in 1993–1994 at age 7 years. After adjustment for covariates, the cord-blood concentration showed the clearest associations with deficits in language, atention, and memory. Fine-moteor function deficits were particularly associated with the maternal hair mercury at parturition. Mercury concentrations in the child‘s blood and hair at age 7 years were significant predicors only of performance on memory for visuopatial information. These flndings emphaisze the usefulness of the cord-blood mercury concentration as a main risk indicator. They also support the notion that the greatest susceptibility to methlymercury neurotoxicity occurs during late gestation, while early postnatal vulnerability is less, and they suggest that the time-dependent susceptibility may vary for different brain functions. Am J Epidemiol 1999; 149; 301–5.