Association of Air Pollution with Hospital Outpatient Visits in Beijing

Abstract

Data collected at a community-based hospital in Beijing, China, were analyzed in an assessment of the association of air pollution with daily outpatient visits. Total suspended particle (TSP) measurements were available for 210 d (mean, 388 μg/m³; maximum, 1 255 μg/m³), and sulfur dioxide (SO₂) measurements were available for 2 d (mean, 119 μg/m³; maximum, 478 μg/m³). The average number of daily hospital outpatient visits was 1 386; approximately 8.5% of these visits were to the surgery department, 7.9% were to the pediatrics department, and 20.6% were to the internal medicine department. A large increase in nonsurgery outpatient visits was observed in association with increases in both SO₂, and TSP in linear regression models, after adjusting for temperature, humidity, season, and day of the week. The estimated effects (in which the most polluted days were compared with the least polluted days) on nonsurgery outpatient visits were increases of 20% (SE = 5%) and 17% (SE = 4%) in association with increases in SO₂ and TSP, respectively. In a department-specific analysis, the association was found to be 1.5- to 2.0-fold stronger for pediatrics and internal medicine visits than for other types of visits. The separate associations of SO₂ and TSP with internal medicine visits remained statistically significant when both SO₂, and TSP were considered simultaneously and when adjustment was made for surgery visits. SO₂ and TSP were found to be significant, independent predictors of internal medicine visits in both winter and summer. The association between outpatient visits and air pollution appeared to be stronger in summer than in winter, although the summer daily mean SO₂ concentration was only 17 μg/m3 (maximum, 51 μg/m³). These data, together with data obtained in previous studies, provide coherent evidence that current air-pollution levels in Beijing are associated with adverse health outcomes, and they also suggest that air pollution in Beijing needs to be controlled more effectively.