Prenatal Air Pollution Exposure and Autism Spectrum Disorder in the ECHO Consortium.

The relationship between prenatal exposure to low-level air pollution and child autism spectrum disorder (ASD) is unclear. To examine associations of prenatal air pollution exposure with autism. We analyzed data from 8,035 mother-child pairs from 44 United States cohorts in the Environmental influences on Child Health Outcomes (ECHO) Cohort. Fine particulate matter (PM2.5), nitrogen dioxide (NO2), and 8-hour-max ozone (O3) levels were estimated at residential addresses during pregnancy. Parents rated children's autism-related traits using the Social Responsiveness Scale (SRS) (mean age 9.4 years, SD=3.6) and reported physician-diagnosed ASD. We examined associations of the three air pollutants with SRS scores (10th, 50th, and 90th quantiles) using quantile regression and with ASD diagnosis using logistic regression. Models were run within census divisions, and coefficients were pooled in a meta-analysis. Average (SD) pregnancy exposures were 9.3 µg/m3 (2.7) for PM2.5, 21.8 ppb (8.8) for NO2, and 40.3 ppb (5.5) for O3, with variations across census divisions. The median SRS T-score was 46 (IQR=41 to 52), and 444 children (5.5%) had an ASD diagnosis. Higher PM2.5 was associated with higher SRS scores at the 10th quantile (β=0.74, 95% CI: 0.09, 1.40) but not at the median or highest quantile. The association between PM2.5 and ASD diagnosis was highly heterogeneous, with associations present in the South Central, Mountain, and Pacific census divisions. Heterogeneity was also high in the association between NO2 and SRS at the median and only in the mid-Atlantic, West North Central, and South Atlantic census divisions. Higher O3 was associated with higher SRS scores at the median (β per IQR increment=0.83, 95% CI: 0.05, 1.61) and highest quantile (β=2.19, 95% CI: 0.06, 4.32) in the meta-analysis. Higher O3 also was associated with ASD. Associations with ASD outcomes were present even at low levels of air pollutants. https://doi.org/10.1289/EHP16675.