Prenatal, concurrent, and sex-specific associations between blood lead concentrations and IQ in preschool Canadian children
Article [Version of Record]
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Environment international ; vol. 121, pp. 1235-1242.Publisher(s)
ElsevierAuthor(s)
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Abstract(s)
Background: Lead exposure predicts altered neurodevelopment and lower intelligence quotient (IQ) in children,
but few studies have examined this association in children who have relatively low blood lead concentrations.
Objectives: To test the associations between blood lead concentrations and cognitive function in Canadian
preschoolers, with a possible moderation by sex.
Methods: The data were gathered from 609 mother-child pairs from the Maternal–Infant Research on
Environmental Chemicals (MIREC) Study. Lead was measured in umbilical and maternal blood, and in children's
venous blood at age 3–4 years. Cognitive function was measured with the Wechsler Preschool and Primary Scale
of Intelligence (WPPSI-III) at 3–4 years. We tested the relationship between WPPSI-III scores and blood lead
concentrations with multiple linear regression, adding child sex as a moderator.
Results: Median blood lead concentrations for the mother at 1st trimester and 3rd trimester of pregnancy, and for
cord and child blood were 0.60 μg/dL, 0.58 μg/dL, 0.79 μg/dL and 0.67 μg/dL, respectively. We found no association between cord blood lead concentrations and WPPSI-III scores in multivariable analyses. However, cord
blood lead concentrations showed a negative association with Performance IQ in boys but not in girls (B = 3.44;
SE = 1.62; 95% CI: 0.82, 5.98). No associations were found between WPPSI-III scores and prenatal maternal
blood or concurrent child blood lead concentrations.
Conclusions: Prenatal blood lead concentrations below 5 μg/dL were still associated with a decline in cognitive
function in this Canadian cohort, but only for boys.