Residential ambient air pollution exposure and the development of white matter microstructure throughout adolescence

Background: Recent evidence suggests an association of air pollution exposure with brain development, but evidence on white matter microstructure in children is scarce. We investigated how air pollution exposure during pregnancy and childhood impacts longitudinal development of white matter microstructure throughout adolescence.

Methods: Our study population consisted of 4108 participants of Generation R, a large population-based birth cohort from Rotterdam, the Netherlands. Residential air pollution exposure to 14 air pollutants during pregnancy and childhood was estimated with land-use regression models. Diffusion tensor images were obtained around age 10 and 14, resulting in a total of 5422 useable scans (n = 3082 for wave 1 and n = 2340 for wave 2; n = 1314 for participants with data on both waves). We calculated whole-brain fractional anisotropy (FA) and mean diffusivity (MD) and performed single- and multi-pollutant analyses using mixed effects models adjusted for life-style and socioeconomic status variables.

Results: Higher exposure to PM_2.5 during pregnancy, and PM₁₀, PM_2.5, PM_2.5-10, and NO_X during childhood was associated with a consistently lower whole-brain FA throughout adolescence (e.g. - 0.07 × 10^-2 FA [95%CI -0.12; -0.02] per 1 standard deviation higher PM_2.5 exposure during pregnancy). Higher exposure to silicon (Si) in PM_2.5 and oxidative potential of PM_2.5 during pregnancy, and PM_2.5 during childhood was associated with an initial higher MD followed by a faster decrease in MD throughout adolescence (e.g. - 0.02 × 10^-5 mm²/s MD [95%CI -0.03; -0.00] per year of age per 1 standard deviation higher Si exposure during pregnancy). Results were comparable when performing the analysis in children with complete data on the outcome for both neuroimaging assessments.

Conclusions: Exposure to several pollutants was associated with a consistently lower whole-brain FA throughout adolescence. The association of few pollutants with whole-brain MD at baseline attenuated throughout adolescence. These findings suggest both persistent and age-limited associations of air pollution exposure with white matter microstructure.