Temporal relationship between air pollution and hospital admissions for asthmatic children in Hong Kong.

Background Many epidemiological studies have shown positive association between respiratory health and current levels of outdoor air pollution in Europe and America. Objective The aim of this study was to investigate the association between air pollution and the number of childhood admissions for asthma in Hong Kong. Methods Daily counts of childhood admission for asthma to a large teaching Hospital were obtained from the computerized database for the period 1993–1994. A Poisson regression allowing for seasonal patterns and meteorological conditions was used to assess the associations between the number of Hospital admissions and the three pollutants: nitrogen dioxide, sulphur dioxide and inhalable particles (measured as PM10, particles < 10 µm in aerodynamic diameter). Results A total of 1217 children under 15 years of age were admitted for asthma during the study period. The calculated annual hospitalization rates were 283 and 178 per 100 000 for boys and girls, respectively. The mean PM10, NO2 and SO2 levels were 44.1 µg/m3, 43.3 µg/m3, and 12.2 µg/m3, respectively. Daily admission for asthma increased significantly with increasing ambient level of nitrogen dioxide (relative risk (RR) = 1.08 per 10 µg/m3 increase), sulphur dioxide (RR = 1.06) and inhalable particles (RR = 1.03). No association was found between hospital admission and humidity, temperature or atmospheric pressure. Conclusion This is the first daily time series study of childhood admissions for asthma and air pollution in Hong Kong. The results support that current levels of air pollution contribute to the respiratory morbidity in asthmatic children in Hong Kong.