Abstract
Early brain development is highly sensitive to environmental influences. While prenatal exposure to airborne particulate matter (PM(2.5)) has been broadly associated with harmful effects, PM(2.5) also contains trace elements such as iron, copper and zinc, which are essential for brain growth. This study examined both the overall impact of prenatal PM(2.5) exposure and the specific role of these trace elements on neonatal myelinated white matter-a key marker of brain maturation. This population-based study included 93 neonates recruited from three major hospitals in Barcelona (2018-2021). PM(2.5) exposure was estimated for the embryonic and late fetal periods using land-use regression models incorporating time-weighted maternal mobility data. MRI was performed at 29 days postnatally. Global myelinated white matter was manually segmented, and automated cortical myelination measures were obtained in 85 cases. Associations were examined using linear regression models with and without adjustment for potential confounders. Higher prenatal PM(2.5) exposure was associated with lower myelinated white matter content. Trace elements showed a similar pattern, but their associations became nonsignificant after adjusting for overall PM(2.5) exposure. The findings suggest that prenatal air pollution exposure may delay early myelination. Moreover, no specific associations were identified for iron, copper, or zinc. However, given the dynamic nature of white matter maturation, such delays may not necessarily be detrimental. This study underscores the impact of environmental factors on neonatal brain development and the importance of stringent air quality policies, while emphasizing the need for longitudinal research to assess long-term cognitive and behavioral outcomes.