Air pollution and emergency department visits for asthma in Windsor, Canada.

OBJECTIVES The city of Windsor is recognized to have poor air quality in comparison with other Canadian cities. However, relatively few studies have evaluated associations between day-to-day fluctuations in air pollution levels and respiratory health in Windsor. In this study, we examined associations between short-term changes in ambient air pollution and emergency department (ED) visits for asthma in Windsor. METHODS A time-stratified case-crossover design was applied to 3,728 ED visits for asthma that occurred in Windsor area hospitals between 2002 and 2009. Daily air pollution levels for the region were estimated using Environment Canada's network of fixed-site monitors. ED visits were identified through the National Ambulatory Care Reporting System (NACRS). Odds ratios and their corresponding 95% confidence intervals were estimated using conditional logistic regression, and were adjusted for the confounding influence of daily number of influenza ED visits and weather variables using natural spline functions. RESULTS Statistically significant associations were observed between ambient air pollution levels and ED visits for asthma in Windsor. Effects were particularly pronounced among children 2 to 14 years of age between April and September. Namely, increases in the interquartile range with 1-day lagged exposure to SO2, NO2 and CO levels were associated with increased risks of an asthma visit of 19%, 25% and 36%, respectively. CONCLUSION Exposure in Windsor to ambient air pollution increases the risk of ED visits for asthma, particularly among children.