Neighborhood air pollution slows brain growth in early adolescence

The Adolescent Brain Cognitive Development study followed 11,868 children across 21 U.S. sites, starting when they were 9 to 10.9 years old and testing them again two years later. Researchers used brain scans, cognitive tests and measures of brain network organization to create a single index of neurocognitive maturation. A sample of 3,645 children had usable data at both time points, allowing the team to compare changes over time.

High exposure was defined using U.S. Environmental Protection Agency thresholds: more than 9 µg/m³ of fine particulate matter (PM2.5) or a peak ozone level above 70 parts per billion. Children exposed to high PM2.5 or ozone were matched to controls on household income, parental education, race and ethnicity, sex and age, and analyses were adjusted for puberty, mental‑health symptoms and neighborhood disadvantage.

Children in the low‑pollution control groups showed a clear increase on the maturation index, reflecting gains in cognitive task performance, greater cortical thinning and more adult‑like brain‑network organization. Those in the high‑PM2.5 or high‑ozone groups did not show these gains, indicating attenuated neurocognitive maturation over the two years. The differences were modest but remained after accounting for exposure to the other pollutant.

The authors note that healthy cognitive development underlies resilience and academic success, and they call for stronger efforts to reduce PM2.5 and ozone in residential and school neighborhoods. They also caution that the study is observational and that pollution exposure was measured only at the start of the study, so the findings may not capture all relevant exposure or individual movements.