Abstract
Ambient air pollution poses a significant risk for a group of common and often debilitating respiratory diseases, but its direct impact on cause-specific respiratory diseases using emergency room visit (ERV) as an indicator remains to be fully explored. In this study, we conducted a time-series study of ambient PM2.5, NO2, SO2 and their association with ERV for asthma, COPD and pneumonia in a four-year time span. Relative risks for ERV as per log increase in the level of ambient pollutants with time lags of up to 10 days were calculated, using a generalized additive model of Poisson regression. Daily 24-h average concentrations of PM2.5 and pollutant gases were obtained from a local Gutting air quality monitoring station. Results showed that the ERVs for pneumonia and asthma were associated with the level of PM2.5. The effects of PM2.5 on the risk of ERV for asthma were found to be significant at lag days 1 and 2 with increasing risk of 4.34% [RR: 1.091; CI: 1.020-1.166 (95%)] and 3.58% [RR: 1.074; CI: 1.007-1.146 (95%)], respectively. The ERV for pneumonia was associated with the level of PM2.5 at lag days 5, 6 and 7, with increasing risk of 1.92% [RR: 1.039; CI: 1.009-1.070 (95%)], 2.03% [RR: 1.041; CI: 1.009-1.075 (95%)], and 1.82% [RR: 1.037; CI: 1.001-1.075 (95%)], respectively. Further, PM2.5, but not NO2 and SO2, posed a significant risk of ERV for asthma during spring at lag days 0, 1 and 2 (17.12%, RR: 1.408, CI: 1.075-1.238; 15.30%, RR: 1.358 CI: 1.158-1.166; 11.94%, RR: 1.165, CI: 1.004-1.121), which was particularly evident for those who were younger than 75 years of age. In contrast, only PM2.5 was a significant risk of ERV for COPD, which was primarily for those who were younger than 75 years of age during summer season at lag days 3, 4 and 5. (26.66%, RR: 1.704, CI: 1.104-2.632; 26.99%; RR: 1.716, CI: 1.151-2.557; 24.09%; RR: 1.619, CI: 1.111-2.360). Collectively, these results suggested significant seasonal variation and differential time lag effects of PM2.5 on ERV for asthma, COPD and pneumonia.