title: Prenatal organochlorine and methylmercury exposure and memory and learning in school-age children in communities near the New Bedford Harbor Superfund site, Massachusetts.
abstract: BACKGROUND
  Polychlorinated biphenyls (PCBs), organochlorine pesticides, and methylmercury (MeHg) are environmentally persistent with adverse effects on neurodevelopment. However, especially among populations with commonly experienced low levels of exposure, research on neurodevelopmental effects of these toxicants has produced conflicting results.
  
  
  OBJECTIVE
  We assessed the association of low-level prenatal exposure to these contaminants with memory and learning.
  
  
  METHODS
  We studied 393 children, born between 1993 and 1998 to mothers residing near a PCB-contaminated harbor in New Bedford, Massachusetts. Cord serum PCB, DDE (dichlorodiphenyldichloroethylene), and maternal peripartum hair mercury (Hg) levels were measured to estimate prenatal exposure. Memory and learning were assessed at 8 years of age (range, 7-11 years) using the Wide Range Assessment of Memory and Learning (WRAML), age-standardized to a mean ± SD of 100 ± 15. Associations with each WRAML index-Visual Memory, Verbal Memory, and Learning-were examined with multivariable linear regression, controlling for potential confounders.
  
  
  RESULTS
  Although cord serum PCB levels were low (sum of four PCBs: mean, 0.3 ng/g serum; range, 0.01-4.4), hair Hg levels were typical of the U.S. fish-eating population (mean, 0.6 μg/g; range, 0.3-5.1). In multivariable models, each microgram per gram increase in hair Hg was associated with, on average, decrements of -2.8 on Visual Memory (95% CI: -5.0, -0.6, p = 0.01), -2.2 on Learning (95% CI: -4.6, 0.2, p = 0.08), and -1.7 on Verbal Memory (95% CI: -3.9, 0.6, p = 0.14). There were no significant adverse associations of PCBs or DDE with WRAML indices.
  
  
  CONCLUSIONS
  These results support an adverse relationship between low-level prenatal MeHg exposure and childhood memory and learning, particularly visual memory.
authors: Department of Epidemiology, Harvard School of Public Health, Boston, Massachusetts, USA.
authors: Sara T C
authors: ST
authors: Orenstein
authors: Sally W
authors: SW
authors: Thurston
authors: David C
authors: DC
authors: Bellinger
authors: Joel D
authors: JD
authors: Schwartz
authors: Chitra J
authors: CJ
authors: Amarasiriwardena
authors: Larisa M
authors: LM
authors: Altshul
authors: Susan A
authors: SA
authors: Korrick
mesh_terms: D002648:Child; D003633:Dichlorodiphenyl Dichloroethylene / Q000097:blood / Q000633:toxicity; D004781:Environmental Exposure / Q000706:statistics & numerical data*; D004785:Environmental Pollutants / Q000009:adverse effects / Q000097:blood / Q000378:metabolism* / Q000633:toxicity; D005260:Female; D006197:Hair / Q000737:chemistry; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000009:adverse effects / Q000378:metabolism* / Q000633:toxicity; D007858:Learning / Q000187:drug effects*; D008297:Male; D008404:Massachusetts / Q000453:epidemiology; D018811:Maternal Exposure / Q000009:adverse effects / Q000706:statistics & numerical data; D008568:Memory / Q000187:drug effects*; D008628:Mercury / Q000032:analysis; D008767:Methylmercury Compounds / Q000378:metabolism* / Q000633:toxicity; D015999:Multivariate Analysis; D010575:Pesticides / Q000009:adverse effects; D011078:Polychlorinated Biphenyls / Q000097:blood / Q000633:toxicity; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects
chemical_list: D004785:Environmental Pollutants; D006843:Hydrocarbons, Chlorinated; D008767:Methylmercury Compounds; D010575:Pesticides; D003633:Dichlorodiphenyl Dichloroethylene; D011078:Polychlorinated Biphenyls; D008628:Mercury