Outdoor Air Pollution Is Related to Amygdala Subregion Volume and Apportionment in Early Adolescence

Outdoor air pollution exposure is associated with structural and functional brain differences and an increased risk for psychopathology. Although the neural mechanisms remain unclear, air pollutants may impact mental health by altering brain regions implicated in psychopathology, such as the amygdala. Here, we examined the association between ambient air pollution exposure and amygdala subregion volumes in 9- to 10-year-olds.

Cross-sectional data from 4473 (55.4% male) Adolescent Brain Cognitive Development (ABCD) Study participants were leveraged. Air pollution exposure was estimated based on each participant's primary residential address. Using the CIT168 atlas, we quantified total amygdala and 9 subregion volumes from T1- and T2-weighted images. We investigated associations between criteria pollutants (i.e., fine particulate matter [PM_2.5], nitrogen dioxide, and ground-level ozone), 15 PM_2.5 components, and amygdala subregion volumes and relative volume fractions using both single-pollutant linear mixed-effects regression and partial least squares correlation (PLSC) co-exposure modeling approaches.

No significant associations were detected using single-pollutant models. Rather, in examining mixtures of exposures with PLSC, 1 latent dimension (52% variance explained) captured a positive association between calcium and several basolateral subregions. Latent dimensions were also identified for amygdala relative volume fractions (ranging from 30% to 82% variance explained), with PM_2.5 and component co-exposure being associated with increases in lateral, but decreases in medial and central, relative volume fractions.

PM_2.5 and its components are associated with distinct amygdala differences, potentially playing a role in risk for adolescent mental health problems.