Air pollution exposure during pregnancy and lung function in childhood: The LUIS study.

Background: The adverse effects of high air pollution levels on childhood lung function are well-known. Limited evidence exists on the effects of moderate exposure levels during early life on childhood lung function. We investigated the association of exposure to moderate air pollution during pregnancy, infancy, and preschool time with lung function at school age in a Swiss population-based study.

Methods: Fine-scale spatiotemporal model estimates of particulate matter with a diameter <2.5 µm (PM_2.5) and nitrogen dioxide (NO₂) were linked with residential address histories. We compared air pollution exposures within different time windows (whole pregnancy, first, second, and third trimester of pregnancy, first year of life, preschool age) with forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC) measured cross-sectionally using linear regression models adjusted for potential confounders.

Results: We included 2182 children, ages 6-17 years. Prenatal air pollution exposure was associated with reduced lung function at school age. In children aged 12 years, per 10 µg·m^-3 increase in PM_2.5 during pregnancy, FEV₁ was 55 mL lower (95% CI -84 to -25 mL) and FVC 62 mL lower (95% CI -96 to -28 mL). Associations were age-dependent since they were stronger in younger and weaker in older children. PM_2.5 exposure after birth was not associated with reduced lung function. There was no association between NO₂ exposure and lung function.

Conclusion: In utero lung development is most sensitive to air pollution exposure, since even modest PM_2.5 exposure during the prenatal time was associated with reduced lung function, most prominent in younger children.