Impacts of intrauterine and postnatal exposure to air pollution on preschool children's asthma: A key role in cumulative exposure

Background: Despite mounting evidence linking asthma to air pollution, it remains unclear which specific pollutant(s) exposure during critical time window(s) plays a pivotal role in the development of asthma.Objective: The objective of this study is to investigate the effects of intrauterine and postnatal air pollution exposure on children's asthma.Methods: From 2019 to 2020, a retrospective cohort study was conducted in Changsha, China. The inverse distance weighted (IDW) method was used to estimate each child's personal exposure to outdoor air pollutants at their home address. Associations between personal air pollution exposure and asthma were comprehensively examined.Results: The occurrence of children's asthma was found to be linked to exposure to PM2.5 and NO2 during both the intrauterine and current periods, with significant ORs (95% CI) of 1.44 (1.08-1.93) and 1.29 (1.00-1.68) for IQR increase in intrauterine exposure particularly during the 2nd trimester, and 1.26 (1.01-1.57) and 1.26 (1.04-1.51) for exposure in previous year. Post-natal PM10 exposure was linked to asthma, with an OR (95% CI) of 1.28 (1.01-1.62). Higher risks of asthma were associated with intrauterine exposure to PM2.5 and postnatal exposure to PM10. The critical time windows for PM2.5, PM2.5-10, and PM10 exposure were identified as the entire pregnancy, the second trimester, and the entire postnatal period, respectively. Cumulative exposure to PM2.5 and NO2 during gestational weeks had a notable impact on asthma. Additionally, exposure to traffic-related air pollution (TRAP) at all timing stages, as well as PM2.5-10 and SO2 at night, increased the risk of asthma. Certain subgroups were more vulnerable to asthma risk due to air pollution.Conclusion: Children's asthma was predominantly influenced by exposure to particulate matters and TRAP during both the intrauterine and postnatal periods.