Effects of Prenatal and Postnatal Methylmercury Exposure From Fish Consumption on Neurodevelopment

Abstract

Context.-Human neurodevelopmental consequences of exposure to methylmercury (MeHg) from eating fish remain a question of public health concern. Objective.-To study the association between MeHg exposure and the developmental outcomes of children in the Republic of Seychelles at 66 months of age. Design.-A prospective longitudinal cohort study. Participants.-A total of 711 of 779 cohort mother-child pairs initially enrolled in the Seychelles Child Development Study in 1989. Setting.-The Republic of Seychelles, an archipelago in the Indian Ocean where 85% of the population consumes ocean fish daily. Main Outcome Measures.-Prenatal and postnatal MeHg exposure and 6 age-appropriate neurodevelopmental tests: the McCarthy Scales of Children's Abilities, the Preschool Language Scale, the Woodcock-Johnson Applied Problems and Letter and Word Recognition Tests of Achievement, the Bender Gestalt test, and the Child Behavior Checklist. Results.-The mean maternal hair total mercury level was 6.8 ppm and the mean child hair total mercury level at age 66 months was 6.5 ppm. No adverse outcomes at 66 months were associated with either prenatal or postnatal MeHg exposure. Conclusion.-In the population studied, consumption of a diet high in ocean fish appears to pose no threat to developmental outcomes through 66 months of age.

Delayed brainstem auditory evoked potential latencies in 14-year-old children exposed to methylmercury

“…5 The total analytical imprecision for this analysis was estimated to be 4.3% and 5.5% at mercury concentrations of 4.7 g/g and 11.1 g/g, respectively. Accuracy was 6 ensured by participation in the Canadian Hair Mercury Quality Control Program; all our results were within one SD of the adjusted mean. The high analytical quality is comparable to previous performance.…”

“…1,7 Emphasis in risk assessment has therefore been placed on neurological functions of children with intrauterine exposure to this neurotoxicant, and previous studies have applied neuropsychological function as a key measure of adverse effects. [4][5][6] In parallel, neurophysiological tests, such as BAEP assessment, have found use in population studies as highly standardized, rapid, painless, and inexpensive procedures. 16,25 Prolonged BAEP latencies have been reported as an effect of exposure to MeHg [13][14][15] and other neurotoxicants, such as lead.…”

“…[2][3] Early adverse effects have been characterized by administering neurobehavioral tests to children exposed in utero from maternal seafood diets. [4][5][6] Thus, a National Research Council (NRC) committee 7 recently concluded that intrauterine MeHg exposure was the most critical and emphasized the findings from a prospective birth cohort study carried out in the Faroe Islands. 5 The damage to the developing nervous system is thought to be potentially irreversible.…”

Assessment of exposure to methylmercury in pregnant Japanese women by FFQ

“…In contrast to several studies (1)(2)(3) , no consistent pattern of adverse effects of prenatal MeHg exposure was found in others such as the Seychells Table 2 Frequency and amount of consumption, and estimated methylmercury (MeHg) intake, for the thirteen seafood items: 609 pregnant Japanese women enrolled in the Tohoku Study of The median, mean and SD were calculated for every subject (n 609). study (24,25) , which focused on nutrients in fish (26,27) . Another large epidemiological study has also suggested the benefits of seafood intake (11) .…”

Toxicity of mercury

“…32 Other studies have linked fish consumption and increased methylmercury levels in man, though without overt symptoms of poisoning. 35,36 (Further studies are presently underway.) Other more direct poisonings from methlymercury have arisen owing to its use as a fungicide particularly in Second and Third World countries.…”