RESUMO
Objective Using case-crossover design to explore the association between ambient air pollution and the hospital emergency room visits for respiratory diseases (International Classification of Diseases, tenth vision ICD-10: J00-J99) in Beijing, China. Methods Data regarding the daily hospital emergency room visits' of the respiratory diseases (ICD-10: J00-J99)were obtained in 2004.01.01-2005.12.31, from the Peking University Third Hospital and data on relevant air pollution and meteorological factors from the local municipal environmental monitoring center and meteorology bureau of Beijing, respectively. Time-stratified case-crossover technique was used to evaluate their relationships. Results from the bi-directional control sampling approach were compared with unidirectional approach. Results Using a unidirectional control sampling approach,the results obtained from a conditional logistic regression model (multi-pollutant model) after adjusting for meteorological variables, showed that the ORs of the hospital emergency room visits for the respiratory diseases associated with each 10 μg/m3 increment of PM10, SO2, NO2 were 1.010(95%CI: 1.005-1.014), 1.010(95%CI: 1.001-1.018) ,0.996(95%CI:0.983-1.009) respectively.In the bi-directional control sampling approach, the ORs were 1.002(95%CI:0.998-1.005)、 1.011 (95%CI:1.003-1.018)、 1.012(95%CI: 1.001-1.022). Conclusion Results from this study provided evidence that higher levels of ambient air pollutants increased the risk of hospital emergency room visits for respiratory diseases.