title: Postnatal exposure to methyl mercury and neuropsychological development in 7-year-old urban inner-city children exposed to lead in the United States.
abstract: BACKGROUND
  The most common route for general population exposure to methyl mercury (MeHg) is fish consumption. Recommendations to pregnant women about consuming fish contaminated with MeHg are also applied to children, but there are few studies available about the effects of low-level postnatal MeHg exposure in them.
  
  
  OBJECTIVE
  To investigate the association between postnatal methyl mercury exposure and neuropsychological development in a study of children also exposed to lead, both measured at 7 years.
  
  
  METHODS
  We measured MeHg concentrations in blood samples from the Treatment of Lead-Exposed Children (TLC) trial in which 780 children with elevated concentrations of lead in blood were followed with neuropsychological tests from ages 12-33 months through 7 years. Here we examine blood MeHg concentration and neuropsychological test scores, both measured at age 7 years. We used a maximum likelihood method to estimate geometric mean MeHg concentration and generalized linear regression models to analyze MeHg and neuropsychological test scores.
  
  
  RESULTS
  Geometric mean MeHg concentration was 0.56 (95% confidence interval: 0.52, 0.59) μ g/L. A 1  μ g/L increase in MeHg was associated with a 2.1 (95% confidence interval: 0.4, 3.8) point increase in Full-Scale IQ and 0.2 (95% confidence interval: 0.02, 0.4) point increase in Learning Slopeindex T-score on a test of verbal memory.
  
  
  CONCLUSIONS
  Our results suggest that the relatively low MeHg exposure in US school-aged children from this population has no detectable adverse effect on neuropsychological development. The positive associations observed between MeHg and neurodevelopment may indirectly reflect consumption of beneficial polyunsaturated fatty acids from seafood.
authors: a Epidemiology Branch , National Institute of Environmental Health Sciences , Research Triangle Park , North Carolina , USA.
authors: Yan
authors: Y
authors: Wang
authors: Aimin
authors: A
authors: Chen
authors: Kim N
authors: KN
authors: Dietrich
authors: Jerilynn
authors: J
authors: Radcliffe
authors: Kathleen L
authors: KL
authors: Caldwell
authors: Walter J
authors: WJ
authors: Rogan
mesh_terms: D000328:Adult; D002648:Child; D002675:Child, Preschool; D004781:Environmental Exposure / Q000009:adverse effects*; D005247:Feeding Behavior; D005260:Female; D006197:Hair / Q000737:chemistry; D006801:Humans; D007854:Lead / Q000009:adverse effects*; D016013:Likelihood Functions; D016014:Linear Models; D008297:Male; D008767:Methylmercury Compounds / Q000009:adverse effects* / Q000032:analysis / Q000097:blood; D009483:Neuropsychological Tests; D011247:Pregnancy; D017747:Seafood; D014481:United States; D014505:Urban Population / Q000706:statistics & numerical data*
chemical_list: D008767:Methylmercury Compounds; D007854:Lead
keywords: Cognition; IQ; Lead; Methyl mercury; Neuropsychological tests; Postnatal exposure
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