Prenatal Exposure to Nitrogen Dioxide, Fine Particulates, and Ozone in Relation to Child Behavior: The Environmental...

Growing evidence links prenatal air pollution with early behavioral outcomes, yet U.S. studies remain sparse. We analyzed data from 8370 mother-child dyads from 28 Environmental influences on Child Health Outcomes (ECHO) Cohort sites. Prenatal nitrogen dioxide (NO₂), fine particulate (PM_2.5), and ozone (O₃) levels were estimated using residential addresses. Caregiver-reported Child Behavior Checklist for ages 1.5-5 (CBCL/1.5-5) assessed internalizing and externalizing problems. Covariate-adjusted linear mixed-effects models estimated associations between pollutants and CBCL/1.5-5 T-scores. Child sex, socioeconomic neighborhood conditions, and prenatal depressive symptoms were evaluated as potential modifiers. Each interquartile range increase in pregnancy-average PM_2.5 was associated with higher externalizing (β_{externalizing} = 0.52, 95% confidence intervals: 0.15-0.90) and internalizing (β_{internalizing} = 0.45, 0.07-0.83) T-scores. Trimester-specific associations were observed: first-trimester PM_2.5 was associated with externalizing (β_{externalizing} = 0.39, 0.08-0.70) and second-trimester PM_2.5 with internalizing (β_{internalizing} = 0.32, 0.01-0.64) T-scores. Third-trimester NO₂ was linked to higher behavioral T-scores (β_{externalizing} = 0.52, 0.03-1.01; β_{internalizing} = 0.51, 0.00-1.01). Associations for O₃ were nonsignificant. Children from the lowest-opportunity neighborhoods exhibited stronger positive associations for NO₂. Males and children whose mothers reported lower prenatal depressive symptoms showed stronger inverse associations for O₃. Overall, prenatal PM_2.5 and NO₂ exposures may be associated with modest increases in early behavioral problems, potentially affecting many children given widespread exposure.