A case-crossover analysis of traffic-related air pollution and emergency department presentations for asthma in Perth, Western Australia

Objective: To determine whether changes in 24-hour average background ozone (O-3), nitrogen dioxide (NO2), carbon monoxide (CO) and particulates < 10 mu m (PM10) increase the risk of hospital emergency department (ED) presentations for asthma among children. Design, setting and subjects: A time-stratified case-crossover method was used to analyse data of 603 children and ycung adults aged 0-19 years who were resident in a south-west metropolitan area of Perth, Western Australia, and who had presented with asthma at any public ED within Perth between 1 January 2002 and 31 December 2006. Effect sizes were assessed in relaticn to age group, sex and season of exposure. City-wide background air pollution was estimated from air monitoring network data. Main outcome measures: ED presentation with asthma. Results: Patients 0-4 years with 1-day lagged exposure to NO2 and CO showed the most significant risk of ED presentation for asthma. An interquartile range (IQR) increase in NO2 resulted in an odds ratio (OR) of 1.70 (95% Cl, 1.08-2.69). An IQR increase in CO resulted in an OR of 1.40 (95% Cl, 1.06-1.84). Conclusions: The effect sizes observed in this study were higher than those of past studies, and indicated that children aged 0-4 years were the most vulnerable to the effects of air pollution. The period of exposure most clinically relevant is the day before ED presentation. MJA 2010; 193: 511-514