Prenatal PM 2 .5 Exposure and Airway Mechanics in Taiwanese Schoolchildren: Identifying Critical Windows of Susceptibility

ABSTRACT Background and Objective Exposure to ambient particulate matter ≤2.5 μm (PM 2.5 ) is associated with lung function impairment, particularly in children. However, the impact of prenatal PM 2.5 exposure on childhood airway mechanics remains unclear. We aimed to assess associations between prenatal PM 2.5 exposure and airway mechanics in school‐age children. Methods Data from 1324 singleton children (745 boys, 56.3%; mean age, 6.5 years) participating in a population‐based cohort in Taiwan were analysed. Prenatal ambient PM 2.5 exposure near residence was estimated using hybrid kriging‐land use regression models with an XGBoost algorithm. Airway mechanics were measured by impulse oscillometry. Results Each 10 μg/m 3 increase in prenatal PM 2.5 exposure across the entire pregnancy was associated with higher total airway resistance (R 5 : β, 0.67; 95% CI, 0.30–1.03), proximal airway resistance (R 20 : β, 0.37; 95% CI, 0.12–0.62), peripheral airway resistance (R 5 ‐R 20 : β, 0.30; 95% CI, 0.05–0.55), and airway impedance (Z 5 ) (β, 0.58; 95% CI, 0.21–0.94). Distributed lag nonlinear models identified sensitive windows during late pregnancy: 30–34 gestational weeks for R 5 , 30–34 gestational weeks for Z 5 , and at 26–33 gestational weeks for AX, respectively. Stratified analyses indicated stronger associations in girls, children exposed to prenatal environmental tobacco smoke, and those not breastfed. Conclusion Higher prenatal PM 2.5 exposure, particularly during late pregnancy, may be associated with adverse changes in airway mechanics in school‐age children, especially girls, children exposed to prenatal environmental tobacco smoke, and those not breastfed, highlighting the importance of minimizing PM 2.5 exposure during late pregnancy to protect long‐term respiratory health. image