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. 2013 May 29;8(5):e65230.
doi: 10.1371/journal.pone.0065230. Print 2013.

Impact of low blood lead concentrations on IQ and school performance in Chinese children

Jianghong Liu  1 , Linda Li, Yingjie Wang, Chonghuai Yan, Xianchen Liu
Affiliations

Impact of low blood lead concentrations on IQ and school performance in Chinese children

Jianghong Liu et al. PLoS One. .

Abstract

Objectives: Examine the relationships between blood lead concentrations and children's intelligence quotient (IQ) and school performance.

Participants and 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.

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Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. FIQ, VIQ, and PIQ test scores by blood lead concentration (µg/dl) with estimated 95% confidence bands.
Note: The dotted line's y-intercept is at the mean IQ test score.
See this image and copyright information in PMC

References

    1. Needleman HL, Schell A, Bellinger D, Leviton A, Allred EN (1990) The long-term effects of exposure to low doses of lead in childhood. An 11-year follow-up report. N Engl J Med 322: 83–88. - PubMed
    1. Dietrich KN, Ris MD, Succop PA, Berger OG, Bornschein RL (2001) Early exposure to lead and juvenile delinquency. Neurotoxicol Teratol 23: 511–8. - PubMed
    1. Lanphear BP, Hornung R, Khoury J, Yolton K, Baghurst P, et al. (2005) Low-level environmental lead exposure and children's intellectual function: an international pooled analysis. Environ Health Perspect 113: 894–899. - PMC - PubMed
    1. Canfield RL, Henderson CR Jr, Cory-Slechta DA, Cox C, Jusko TA, et al. (2003) Intellectual impairment in children with blood lead concentrations below 10 microg per deciliter. N Engl J Med 348: 1517–1526. - PMC - PubMed
    1. Jusko TA, Henderson CR, Lanphear BP, Cory-Slechta DA, Parsons PJ, et al. (2008) Blood lead concentrations <10 microg/dL and child intelligence at 6 years of age. Environ Health Perspect 116: 243–248. - PMC - PubMed

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