Air Pollution Mix and Emergency Room Visits for Respiratory and Cardiac Diseases in Taipei

To clarify the contribution of ambient air pollutants to acute health effects, we examined the association between daily air pollution lev- els and emergency room (ER) visits for respiratory and cardiac diseases in Taipei City, Taiwan from January 1997 to December 1998. Average daily concentrations of particulate matter less than 2.5 µm in aerodynamic diam- eter (PM2.5), PM10, carbon monoxide, sulfur dioxide, nitrogen dioxide and ozone were obtained from ambient air quality monitoring stations. The daily counts of ER visits stratified by diagnosis and age were modeled by both single-pollutant and multi-pollutant Poisson regression models with adjust- ment of confounding factors to evaluate the effects of individual pollutants. A mixture model was constructed by adding ratios of the pollutants to the multi-pollutant model to examine the air pollution mixture on ER visits. The single-pollutant models showed that an interquartile range change of PM2.5 (16 µg/m 3 ) was associated with increased ER visits for respiratory disease in all age groups, with relative risks 1.04 to 1.06 and increased ER visits for cardiac disease in adult and elderly age groups, with a relative risk of 1.05. Gaseous pollutants, mainly NO2 and CO, were also associated with increased visits by children for respiratory disease and visits by adults and elderly individuals for cardiac disease. Examination of joint effect of mixes of PM2.5 and gaseous pollutants showed that an interquartile range increase was associated with increases in ER visits by children for respiratory disease and by adults for cardiac disease, with a relative risk of 1.09.