title: Neurotoxicity from prenatal and postnatal exposure to methylmercury.
abstract: The extent to which postnatal methylmercury exposure contributes to neurobehavioral delays is uncertain. Confounding may occur because the child's dietary exposure likely correlates with the mother's. This conundrum was examined in the Faroese birth cohort 1 born in 1986-1987. Exposure parameters included mercury concentrations in maternal hair at parturition, cord blood, and child blood and hair at the age-7 clinical examination (N=923). In regression analyses, the child's current blood-mercury at age 7 (N=694) showed only weak associations with the neuropsychological test variables, but visuospatial memory revealed a significant negative association. Mutual adjustment caused decreases of the apparent effect of the prenatal exposure. However, such adjustment may lead to underestimations due to the presence of correlated, error-prone exposure variables. In structural equation models, all methylmercury exposure parameters were instead entered into a latent exposure variable that reflected the total methylmercury load. This latent exposure showed significant associations with neurodevelopmental deficits, with prenatal exposure providing the main information. However, postnatal methylmercury exposure appeared to contribute to neurotoxic effects, in particular in regard to visuospatial processing and memory. Thus, addition in the regression analysis of exposure information obtained at a different point in time was not informative and should be avoided. Further studies with better information on exposure profiles are needed to characterize the effects of postnatal methylmercury exposure.
authors.affiliation: Institute of Public Health, University of Southern Denmark, Odense, Denmark; Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. Electronic address: pgrand@sdu.dk.
authors.forename: Philippe
authors.initials: P
authors.lastname: Grandjean
authors.affiliation: Faroese Hospital System, Tórshavn, Faroe Islands.
authors.forename: Pal
authors.initials: P
authors.lastname: Weihe
authors.affiliation: Faroese Hospital System, Tórshavn, Faroe Islands.
authors.forename: Frodi
authors.initials: F
authors.lastname: Debes
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Choi
authors.affiliation: Department of Biostatistics, University of Copenhagen, Copenhagen N, Denmark.
authors.forename: Esben
authors.initials: E
authors.lastname: Budtz-Jørgensen
mesh_terms: D002648:Child; D003072:Cognition Disorders / Q000209:etiology; D015331:Cohort Studies; D002658:Developmental Disabilities / Q000139:chemically induced* / Q000209:etiology; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D006801:Humans; D008297:Male; D008628:Mercury / Q000032:analysis; D020262:Mercury Poisoning, Nervous System / Q000150:complications* / Q000209:etiology*; D008767:Methylmercury Compounds / Q000633:toxicity*; D009460:Neurologic Examination; D009483:Neuropsychological Tests; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000503:physiopathology*; D011596:Psychomotor Disorders / Q000209:etiology
chemical_list: D008767:Methylmercury Compounds; D008628:Mercury; C004925:methylmercuric chloride
keywords: Methylmercury compounds; Neuropsychological tests; Postnatal development; Prenatal exposure delayed effects; Preschool child