Causal Association of Prenatal Ozone Exposure with Impaired Lung Function in Childhood

Human lung growth involves complex processes. Previous studies have suggested associations of prenatal ambient ozone (O₃) exposure with impaired lung function, but the causal relationships remain unclear. In this cross-sectional cohort study, pulmonary function tests were conducted on recruited participants. Prenatal exposure to the maximum daily 8 h average of daily O₃ (MDA8 O₃) and other environmental factors were estimated. Generalized linear model, generalized propensity score, and inverse probability weighting were used to investigate the causal relationship between MDA8 O₃ and impaired lung function. Finally, a total of 1058 children were included. Each 10 μg/m³ increase in MDA8 O₃ during the entire pregnancy, the first trimester, and the third trimester was positively associated with the risk of impaired lung function in childhood, with odd ratios and 95% confidence intervals of 1.52 (95%CI: 1.06-2.18), 1.22 (95%CI: 1.06-1.41), and 1.47 (95%CI: 1.19-1.83), respectively. The associations for participants exposed to a high ambient temperature (TM), low relative humidity (RH), and low residential greenness during the pregnancy were higher. Prenatal exposure to higher MDA8 O₃ concentrations may cause impaired lung function in childhood. The adverse influence of the presence of O₃ may be amplified by elevated ambient TM and attenuated by RH and residential greenness.