title: Impact of low blood lead concentrations on IQ and school performance in Chinese children.
abstract: OBJECTIVE
  Examine the relationships between blood lead concentrations and children's intelligence quotient (IQ) and school performance.
  
  
  METHODS
  Participants were 1341 children (738 boys and 603 girls) from Jintan, China. Blood lead concentrations were measured when children were 3-5 years old. IQ was assessed using the Chinese version and norms of the Wechsler Preschool and Primary Scale of Intelligence - Revised when children were 6 years old. School performance was assessed by standardized city tests on 3 major subjects (Chinese, Math, and English [as a foreign language]) when children were age 8-10 years.
  
  
  RESULTS
  Mean blood lead concentration was 6.43 µg/dL (SD = 2.64). For blood lead concentrations, 7.8% of children (n = 105) had ≥10.0 µg/dL, 13.8% (n = 185) had 8.0 to <10.0 µg/dL, and 78.4% (n = 1051) had <8.0 µg/dL. Compared to children with blood lead concentrations <8 µg/dL, those with blood lead concentrations ≥8 µg/dL scored 2-3 points lower in IQ and 5-6 points lower in school tests. There were no significant differences in IQ or school tests between children with blood lead concentrations groups 8-10 and ≥10 µg/dL. After adjustment for child and family characteristics and IQ, blood lead concentrations ≥10 µg/dL vs <8 µg/dL at ages 3-5 years was associated with reduced scores on school tests at age 8-10 years (Chinese, β = -3.54, 95%CI = -6.46, -0.63; Math, β = -4.63, 95%CI = -7.86, -1.40; English, β = -4.66, 95%CI = -8.09, -1.23). IQ partially mediated the relationship between elevated blood lead concentrations and later school performance.
  
  
  CONCLUSIONS
  Findings support that blood lead concentrations in early childhood, even <10 µg/dL, have a long-term negative impact on cognitive development. The association between blood lead concentrations 8-10 µg/dL and cognitive development needs further study in Chinese children and children from other developing countries.
authors.affiliation: University of Pennsylvania, School of Nursing and School of Medicine, Philadelphia, Pennsylvania, USA. jhliu@nursing.upenn.edu
authors.forename: Jianghong
authors.initials: J
authors.lastname: Liu
authors.forename: Linda
authors.initials: L
authors.lastname: Li
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Wang
authors.forename: Chonghuai
authors.initials: C
authors.lastname: Yan
authors.forename: Xianchen
authors.initials: X
authors.lastname: Liu
mesh_terms: D000124:Achievement; D000704:Analysis of Variance; D044466:Asian People / Q000706:statistics & numerical data; D002648:Child; D002675:Child, Preschool; D002681:China; D005260:Female; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D007854:Lead / Q000097:blood*; D008137:Longitudinal Studies; D008297:Male
chemical_list: D007854:Lead