Air Pollution, Allergic Co-morbidity, and Emergency Department Visit for Pediatric Asthma in Taiwan

Background: Alterations in allergic susceptibility are a central feature of several chronic respiratory diseases. This study was conducted to determine whether variation in individual allergic susceptibility alters the air pollution effects on attacks of pediatric asthma. Methods: Daily records of personal asthma emergency department visits among children in school-age and ambient air pollutant concentration were obtained from 2000 to 2008 in Taipei basin, Taiwan. Subjects who had ever had a clinical visit in the departments of otolaryngology and pediatrics or a visit to the emergency department due to allergic rhinitis before their first asthma-related emergency department visit were defined as having allergic rhinitis co-morbidities. A time-stratified approach for the case-crossover technique and a conditional logistic regression were used to examine whether allergic co-morbidity modified air pollution-induced asthma attacks. Results: Particulate matter with an aerodynamic diameter of 2.5 mu m or less (PM2.5) was found to be associated with asthma-related emergency department visits on the day of exposure among children with allergic rhinitis co-morbidity (2(nd) quartile OR = 1.19; 3(rd) quartile OR = 1.37; 4(th) quartile OR = 1.38). High ozone levels were associated with emergency room visits for asthma on a 1-day lag assumption among children with allergic rhinitis co-morbidity (4(th) quartile OR = 1.38). Conclusion: The negative effects of air pollution were observed for subjects who had an allergic co-morbidity. The variation in allergic co-morbidity was associated with differences in susceptibility to the adverse effects of air pollutants on respiratory disease.