Intrauterine and early postnatal exposure to air pollution associated with childhood allergic rhinitis

Background Despite mounting evidence linking allergic rhinitis (AR) to air pollution, it remains unclear which major air pollutant(s) and critical window(s) of exposure play important roles in children's AR. Objective To examine the effects of intrauterine and early postnatal exposure to outdoor air pollution on children with doctor-diagnosed allergic rhinitis (DDAR). Methods A retrospective cohort study involving 8689 kindergarten children was conducted in Changsha, China, from 2019 to 2020. A questionnaire survey was conducted to collect information on the health status of children and their family members, as well as their living habits and home environment. Personal exposure to daily outdoor air pollutants (PM2.5, PM2.5-10, PM10, SO2, NO2, and CO) was estimated during 40 gestational weeks, three trimesters, the entire pregnancy, and the first year after birth. Multiple logistic regression models were used to assess the associations between air pollution and children's DDAR. Results Children's DDAR was associated with intrauterine CO exposure, with adjusted ORs (95% CI) of 1.18 (1.03-1.34) for each IQR increase in CO exposure. The second and third trimesters were critical windows for PM2.5 and CO exposure in relation to DDAR. Furthermore, early postnatal exposure to PM2.5-10 and PM10 in first year of life was associated with DDAR development, with adjusted ORs (95% CI) of 1.11 (1.01-1.22) and 1.27 (1.09, 1.47). The entire pregnancy and the first year of life were critical windows for CO and PM10 exposure. Some children were predisposed to DDAR risk due to exposure to traffic-related air pollution (TRAP). Conclusion Our findings support the hypothesis of "fetal origin of allergic rhinitis" by demonstrating that intrauterine and early postnatal exposure to air pollution plays an important role in children's DDAR.