Effect of Prenatal Lead Exposure on Intellectual Ability of 84-Month-Old Japanese Children

Abstract

BACKGROUND: Postnatal lead exposure has been shown to be associated with poor intellectual ability in children, although the effects of prenatal exposure are less well studied. OBJECTIVE: The purpose of this study was to determine the relationship of low cord-blood lead concentrations with intellectual ability in Japanese children. METHODS: We have been conducting a prospective cohort study, the Tohoku Study of Child Development, to examine the effects of perinatal exposure to chemical substances on neurobehavioral development in Japanese children. A total of 599 singleton births were recruited during 2001-2003, and 364 had complete data for all included covariates for this analysis. The Wechsler Intelligence Scale for Children-Third Edition (WISC-III) was used to assess the intellectual ability in children 84 months old. We assessed lead as well as other chemical substances such as polychlorinated biphenyls (PCB), total mercury (THg), and selenium in cord blood and used these variables as confounders. RESULTS: The median values of chemicals were 1.0 (5th and 95th percentiles, 0.5 - 1.8) µg/dL for lead, 47.6 (17.1 - 115.9) ng/g-lipid for total PCB, 10.1 (4.2 - 22.2) ng/g for total mercury (THg), and 191.6 (128.8 - 268.5) ng/mL for selenium in whole cord blood. A negative association between the lead concentration and the performance IQ (PIQ) of the WISC-III was observed (ß=-0.103, p=0.043) even after adjusting for total PCB, THg, selenium in cord blood and confounders such as child gender, birth order, and family annual income. CONCLUSION: The findings are consistent with other reports about the adverse impact of prenatal lead exposure on the intellectual ability of children, although these associations appeared at relatively low exposure levels.