Prenatal Exposure to Ambient Air Pollution and Early Childhood Neurodevelopment: A Longitudinal Birth Cohort Study in an Urban Region of the Southeastern U.S.

Abstract

Background: Animal studies indicate that air pollution may be neurotoxic, but evidence in humans is limited. We analyzed associations between prenatal air pollution and childhood neurodevelopment in a large birth cohort in Shelby County, TN.Methods: We included mother-child dyads who completed a preschool visit in the Conditions Affecting Neurocognitive Development and Early Childhood (CANDLE) study. Primary outcomes were internalizing and externalizing behavior scores (Child Behavior Checklist) and full-scale IQ score as a measure of general cognition. Prenatal exposures to nitrogen dioxide (NO2) and particulate matter less than 10 microns (PM10) at maternal residences were estimated using a national annual average universal kriging model (land-use regression with spatial smoothing). We also measured distance to nearest major roadway as a proxy for traffic-related pollution. In regression models, we adjusted for confounding by individual and neighborhood socioeconomic status, maternal IQ, and other determinants of child neurodevelopment; and tested for effect modification by child sex, maternal race, and prenatal nutrition.Results: The study population (N=1009) was predominantly low-income and 69% African American; mean child age at assessment was 4.4 years. Mean NO2 and PM10 exposures were 12.9 ppb and 20.9 μg/m3, respectively. In fully adjusted models, a 5 ppb increase in prenatal NO2 was associated with 13% higher externalizing behavior score (95% CI: 0.5, 28%) and 2.8 times higher odds (95% CI: 1.0, 7.9) of an externalizing score above the clinical threshold. Full-scale IQ scores averaged 2.5 points (95% CI: 0.1, 4.8) lower per 5 ug/m3 increase in PM10. We found no statistically significant evidence of associations with road proximity or interaction by demographics or nutrition.Conclusions: Our findings support the hypothesis that air pollution impairs neurodevelopment. We observed the most consistent associations between NO2 and externalizing behaviors.