Background: Recent findings suggest that exposure to outdoor air pollutants may increase the risk of allergic rhinitis. The results of these studies are inconsistent, but warrant further attention. The objective of the study was to assess the effect of relation between exposure to urban air pollution and the prevalence allergic rhinitis among school children.
Methods: We conducted a nationwide cross-sectional study of 32,143 Taiwanese school children. We obtained routine air-pollution monitoring data for sulphur dioxide (SO2), nitrogen oxides (NOx), ozone (O3), carbon monoxide (CO), and particles with an aerodynamic diameter of 10 microm or less (PM10). A parent-administered questionnaire provided information on individual characteristics and indoor environments (response rate 92%). Municipal-level exposure was calculated using the mean of the 2000 monthly averages. The effect estimates were presented as odds ratios (ORs) per 10 ppb change for SO2, NOx, and O3, 100 ppb change for CO, and 10 microg/m3 change for PM10.
Results: In two-stage hierarchical model adjusting for confounding, the prevalence of allergic rhinitis was significantly associated with SO2 (adjusted odds ratio (OR) = 1.43, 95% confidence interval (CI): 1.25, 1.64), CO (aOR = 1.05, 95% CI: 1.04, 1.07), and NOx (aOR = 1.11, 95% CI: 1.08, 1.15). Contrary to our hypothesis, the prevalence of allergic rhinitis was weakly or not related to O3 (aOR = 1.05, 95% CI: 0.98, 1.12) and PM10 (aOR = 1.00, 95% CI: 0.99, 1.02).
Conclusion: Persistent exposure to NOx, CO, and SO2 may increase the prevalence of allergic rhinitis in children.