Health Effects of Coarse Particulate Matter: A Time-series Analysis in Hong Kong

O-31A1-2 Background/Aims: Many epidemiologic studies linked daily counts of hospital admissions to PM10 and PM2.5. Fewer studies have investigated the relationship of hospital admissions with coarse particles (PMc: particulate matter between 2.5 and 10 μm in aerodynamic diameter), to estimate the health effects of PMc on hospital admissions of cardiovascular and respiratory diseases in Hong Kong after controlling for PM2.5. Methods: Daily time series data from January 2000 to December 2005 included city-wide hospital admission counts for cardiovascular and respiratory outcomes, daily mean temperature and humidity, PM2.5, and PMc concentrations. PMc concentrations were estimated by subtracting PM2.5 from PM10 measurements. Generalized additive model with log link allowing Poisson autoregression and overdispersion was used to model the relationship between particulate matter and hospital admissions. The results were reported as the excess risk (ER%) for admissions per 10 μg/m3 increase in the concentration of PM. Results: The average concentrations of PM2.5 and PMc were 39.45 μg/m3 and 16.62 μg/m3, respectively. A 10 μg/m3 increase in the 4-day moving average (lag 03) concentration of PMc corresponded to 1.33% (95% CI: 0.57%, 2.10%) and 1.78% (95% CI: 1.14%, 2.42%) increases of emergency cardiovascular and respiratory admissions, respectively. Parameter estimates for PMc were generally higher than those for PM2.5. After controlling for PM2.5 in the 2-pollutant model, the effect of PMc on respiratory admissions was attenuated but remained statistically significant while its effect on cardiovascular admissions decreased largely and lost statistical significance. Conclusion: Elevated PMc levels were associated with increased hospital admissions of respiratory diseases in Hong Kong. The effect of PMc on cardiovascular admissions was uncertain.