Methylmercury appears to have irreversible, adverse effects on the nervous system that are much more

widespread and serious in children than in adults, but better dose-response information is needed. The

proposed project will analyze 1,000 to 1,500 stored umbilical cords for mercury to determine the impact

of prenatal mercury exposure from maternal fish intake during pregnancy on the nervous system

development, which has already been assessed in the cohort subjects during 16 years of follow-up. This

information will be useful for future recommendations and guidelines on optimal seafood diets during

pregnancy.

The cords will be freeze-dried before analysis to obtain the dry-weight-based total mercury concentration

as the best available indicator of prenatal methylmercury exposure. This methodology has been

standardized and validated using large sample materials from birth cohorts in the Faroe Islands (where

cord tissue, cord blood, and other samples were available and were analysed for mercury).

Samples will be selected among the approximately 7,500 available to represent those that alfready have

GWAS data or otherwise the most complete phenotype data.

Follow-up through age 16 years will be utilized in regard to neurodevelopment and associated markers of

heart function as indicators of neurotoxicity. Possible adverse impacts of prenatal methylmercury

exposure on highly relevant neurodevelopmental functions will be examined, as will the possible

interactions caused by beneficial nutrients from maternal fish diets and the significance of relevant

heterogeneities involved in methylmercury metabolism and/or brain development processes that may be

susceptible to methylmercury toxicity.

The following three hypotheses will be examined: 1) Methylmercury-associated deficits in sensitive

domains are present at low-level prenatal methylmercury exposures and remain detectable through to

adolescence. 2) Beneficial nutrients from maternal seafood intake affect the same outcomes to

counterbalance methylmercury-associated deficits. And 3) Heterogeneities for metabolic and

neruodevelopmental genes affect the degree of methylmercury neurotoxicity.

Data analysis will be carried out jointly and will also include similar data from the largest Faroese birth

cohort (N = 1,000).