Neighborhood air pollution linked to slower brain development in early adolescence

A new study published in Developmental Cognitive Neuroscience reveals a link between high levels of air pollution during early adolescence and slower brain development. Researchers from the Adolescent Brain Cognitive Development (ABCD) Study analyzed data from 3,645 children enrolled in the nationwide long-term project, focusing on those exposed to elevated levels of fine particulate matter (PM2.5) or ozone in their neighborhoods.

Compared to peers living in low-pollution areas, children in high-pollution environments showed smaller gains in cognitive task performance, reduced brain network organization maturation, and less cortical thinning—the typical developmental process during this period.

Fine particulate matter, or PM2.5, is of particular concern as its tiny particles can travel through the bloodstream and potentially reach the brain via the nasal cavity. Ozone, a gas present in smog, may harm nerve cells through chronic oxidative stress and brain inflammation may also play a role in pollutant-induced developmental effects.

While previous neuroimaging studies have found associations between exposure to PM2.5, ozone, and nitrogen oxides and differences in cortical thickness, brain volume, surface area, and functional connectivity in children and adolescents, the direction and significance of these associations have been inconsistent.

The study authors, led by Omid Kardan of the University of Michigan, aimed to isolate the effects of high PM2.5 and ozone exposure on neurocognitive maturation during pre- and early adolescence. Using data from the ABCD Study, they examined resting-state functional magnetic resonance imaging (fMRI) scans, structural brain scans, and cognitive tasks measuring various cognitive abilities, including attention, working memory, inhibitory control, processing speed, memory, vocabulary, and reading.

They estimated each child’s exposure based on modeled air pollution levels in the 1 km² area around their primary residence at the study's start.

High exposure to either pollutant—defined as an annual average above 9 µg/m³ for PM2.5 and a peak ozone level above 70 parts per billion—was associated with slower neurocognitive maturation. The researchers compared these groups with matched control groups based on household income, parental education, race and ethnicity, sex, and age.

After accounting for factors such as puberty, mental health symptoms, and neighborhood disadvantage, the findings showed that children in high-pollution areas exhibited less cognitive task performance improvement, reduced cortical thinning, and less maturation of brain network organization over the two-year period.

Study authors emphasized the importance of reducing air pollution levels in residential and school areas to support healthy cognitive development, as healthy brain development is crucial for resilience, academic achievement, and overall well-being.