Exposure to multiple ambient air pollutants changes white matter microstructure during early adolescence with...

Air pollution is ubiquitous, yet questions remain regarding its impact on the developing brain. Large changes occur in white matter microstructure across adolescence, with notable differences by sex.

We investigate sex-stratified effects of annual exposure to fine particulate matter (PM_2.5), nitrogen dioxide (NO₂), and ozone (O₃) at ages 9-10 years on longitudinal patterns of white matter microstructure over a 2-year period. Diffusion-weighted imaging was collected on 3T MRI scanners for 8182 participants (1-2 scans per subject; 45% with two scans) from the Adolescent Brain Cognitive Development (ABCD) Study®. Restriction spectrum imaging was performed to quantify intracellular isotropic (RNI) and directional (RND) diffusion. Ensemble-based air pollution concentrations were assigned to each child's primary residential address. Multi-pollutant, sex-stratified linear mixed-effect models assessed associations between pollutants and RNI/RND with age over time, adjusting for sociodemographic factors.

Here we show higher PM_2.5 exposure is associated with higher RND at age 9 in both sexes, with no significant effects of PM_2.5 on RNI/RND change over time. Higher NO₂ exposure is associated with higher RNI at age 9 in both sexes, as well as attenuating RNI over time in females. Higher O₃ exposure is associated with differences in RND and RNI at age 9, as well as changes in RND and RNI over time in both sexes.

Criteria air pollutants influence patterns of white matter maturation between 9-13 years old, with some sex-specific differences in the magnitude and anatomical locations of affected tracts. This occurs at concentrations that are below current U.S. standards, suggesting exposure to low-level pollution during adolescence may have long-term consequences.