Effects of fine particulate matter and its constituents on emergency room visits for asthma in southern Taiwan during 2008-2010: a population-based study

This population-based study evaluated the short-term association between fine particulate matter (PM2.5) concentrations and its constituents and hospital emergency room visits (ERVs) for asthma in southern Taiwan during the period 2008-2010. Data on hospital ERVs for asthma and ambient PM2.5 levels and its constituents were obtained from the National Health Insurance Research database and the Environmental Protection Administration, respectively. The quasi-Poisson generalized additive model was used to explore the associations between PM2.5 and hospital ERVs for asthma. During the study period, the average daily number of ERVs for asthma and mean 24-h average level of PM2.5 was 20.0 and 39.4 mu g m(-3), respectively. The estimated effects of PM2.5 on asthma ERVs fluctuated with increasing tendencies after adjusting for O-3 and attenuating tendencies after adjusting for NO2, SO2, and CO. Children were more susceptible than other age groups to the effects of PM2.5 exposure on asthma ERVs, with the relative risks (RRs) for every 10 mu g m(-3) increase in PM2.5 being 1.016 [95% confidence interval (CI) = 1.002-1.030] and 1.018 (95% CI = 1.002-1.034), respectively, at a lag 0 day (i.e., no lag days) and lag 0-1 days. The effect of PM2.5 concentrations on asthma ERVs was similar in male and female. Furthermore, asthma ERVs was significantly associated with concentrations of nitrate (NO3 (-)), with the RR for each 1 mu g m(-3) increase in NO3 (-) concentrations being 1.004 (95% CI = 1.001-1.007) at lag 0 day. In conclusion, both PM2.5 concentrations and its chemical constituents are associated with ERVs for asthma; moreover, children were more susceptible to the effects of PM2.5 in southern Taiwan. PM2.5 constituent, nitrate, is more closely related to ERVs for asthma.