Chemical mixture exposures during pregnancy and cognitive abilities in school-aged children

Introduction: Gestational exposure to chemical mixtures, which is prevalent among pregnant women, may be associated with adverse childhood neurodevelopment. However, few studies have examined relations between gestational chemical mixture exposure and children's cognitive abilities.

Methods: In a cohort of 253 pregnant women and their children from Cincinnati, OH (enrolled 2003-2006), we quantified biomarker concentrations of 43 metals, phthalates, phenols, polybrominated diphenyl ethers, organophosphate and organochlorine pesticides, polychlorinated biphenyls, perfluoroalkyl substances, and environmental tobacco smoke in blood or urine. Using k-means clustering and principal component (PC) analysis, we characterized chemical mixtures among pregnant women. We assessed children's cognitive abilities using the Wechsler Preschool and Primary Scale of Intelligence-III and Wechsler Intelligence Scale for Children-IV at ages 5 and 8 years, respectively. We estimated covariate-adjusted differences in children's cognitive ability scores ]=cross clusters, and with increasing PC scores and individual biomarker concentrations.

Results: Geometric mean biomarker concentrations were generally highest, intermediate, and lowest among women in clusters 1, 2, and 3, respectively. Children born to women in clusters 1 and 2 had 5.1 (95% CI: 9.4,-0.8) and 2.0 (95% CI: 5.5, 1,4) lower performance IQ scores compared to children in cluster 3, respectively. PC scores and individual chemical biomarker concentrations were not associated with cognitive abilities.

Conclusions: In this cohort, combined prenatal exposure to phenols, certain phthalates, pesticides, and perfluoroalkyl substances was inversely associated with children's cognition, but some individual chemical biomarker concentrations were not. Additional studies should determine if the aggregate impact of these chemicals on cognition is different from their individual effects.