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Blood lead concentrations < 10 microg/dL and child intelligence at 6 years of age

Todd A Jusko1, Charles R Henderson, Bruce P Lanphear

  • 1Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, WA, USA.

Environmental Health Perspectives
|February 22, 2008
PubMed

Insights

Even low blood lead levels in children can negatively impact cognitive development. This study shows that blood lead concentrations below 10 micrograms per deciliter are associated with lower IQ scores in children at age six.

Area of Science:

  • Environmental Health
  • Pediatric Health
  • Neuroscience

Background:

  • Limited data exists on the cognitive effects of blood lead concentrations below 10 µg/dL in children.
  • The Centers for Disease Control and Prevention (CDC) defines elevated blood lead levels as 10 µg/dL or higher.

Purpose of the Study:

  • To investigate the association between blood lead concentrations throughout early childhood and children's IQ at age six.
  • To determine if blood lead levels below 10 µg/dL impact cognitive function.

Main Methods:

  • Longitudinal study following 194 children from 6 months to 6 years of age.
  • Blood lead levels measured at multiple time points: 6, 12, 18, 24 months, and 3, 4, 5, 6 years.
  • Intelligence assessed at age six using the Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R).
  • Statistical analysis using general linear and semiparametric models, adjusting for confounders like maternal IQ and HOME scale scores.

Main Results:

  • A lifetime average blood lead concentration (mean 7.2 µg/dL) was inversely associated with Full-Scale IQ (p=0.006) and Performance IQ (p=0.002).
  • Children with average blood lead levels between 5 and 9.9 µg/dL scored 4.9 points lower in Full-Scale IQ compared to those below 5 µg/dL.
  • Peak blood lead levels showed a significant inverse association with Full-Scale IQ down to 2.1 µg/dL.

Conclusions:

  • Blood lead concentrations well below the CDC's elevated level of 10 µg/dL are associated with impaired intellectual functioning in children at age six.
  • These findings highlight the neurotoxic effects of lead even at lower exposure levels.
  • The study provides evidence supporting stricter public health guidelines for lead exposure in children.
Abstract

Keywords:
GAMHOMEIQLOESSRochesterWPPSI-Rcohortelectrothermal atomic absorption spectrometry

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