Abstract
Prenatal methylmercury exposure is associated with neuropsychological deficits in Faroese children at age 7 years. Lower confidence bounds of benchmark doses (BMDLs) have now been calculated. With the cord-blood mercury concentration as the dose parameter, a logarithmic dose-response model tended to show a better fit than a linear dose model for the attention, language and verbal memory tests. The lowest BMDLs averaged ≈5 μg/l cord blood, which corresponds to a maternal hair concentration of ≈1 μg/g. However, most BMDLs for hair mercury concentrations were higher. Thus, the results of the benchmark calculations depend on the assumed dose-response model.
Highlights
Methylmercury is a common contaminant of seafood and freshwater fish (EPA, 1997)
Values of benchmark dose (BMD) and BMDL may be calculated using a statistical dose-response model based on power functions (Crump, 1995) for the dependence of a child’s expected test score on the mercury dose (d): μ(d) = β ⋅ dK The power parameter K is restricted to values equal to or above 1, allowing the doseresponse curve to be nonlinear
The BMDLs obtained with the two models are clearly different
Summary
Methylmercury is a common contaminant of seafood and freshwater fish (EPA, 1997). While adverse effects have been unequivocally demonstrated in poisoning incidents, the implications of lower-level exposures in fish-eating populations have been controversial (Davidson et al, 1998; Mahaffey, 1998). With the cord-blood mercury concentration as the dose parameter, a logarithmic dose-response model tended to show a better fit than a linear dose model for the attention, language and verbal memory tests.
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