Prenatal Exposure to Nitrogen Dioxide, Fine Particulates, and Ozone in Relation to Child Behavior: The Environmental Influences on Child Health Outcomes Cohort

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 (NO 2 ), fine particulate (PM 2.5 ), and ozone (O 3 ) 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 NO 2 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 O 3 were nonsignificant. Children from the lowest-opportunity neighborhoods exhibited stronger positive associations for NO 2 . Males and children whose mothers reported lower prenatal depressive symptoms showed stronger inverse associations for O 3 . Overall, prenatal PM 2.5 and NO 2 exposures may be associated with modest increases in early behavioral problems, potentially affecting many children given widespread exposure.