The impact of particulate matter on daily mortality in Bangkok, Thailand

Several studies conducted in U.S. cities report an association between acut e exposures to particulate matter (PM), usually measured as PM10 and mortal ity. Evidence of high concentrations of PM10 in Eastern Europe and in large metropolitan areas outside of the United States, such as Mexico City and B angkok, underscores the need to determine whether these same associations o ccur outside of the United States. In addition, conducting studies of morta lity and air pollution in regions that have distinctly different seasonal p atterns than those of the United States provides an effective opportunity t o assess the potentially confounding aspects of seasonality Over the last f ew years, daily measures of ambient PM10 have been collected in Bangkok, a tropical city of over 6 million people, In this metropolitan area, PM10 con sists largely of fine particles generated from diesel- and gasoline-powered automobiles, and from two-stroke motorcycle engines. Our analysis involved the examination of the relationship between PM10 and daily mortality for 1 992 through 1995. In addition to counts of daily natural mortality (total m ortality net of accidents, homicides, and suicides), the data were compiled to assess both cardiovascular and respiratory mortality, and natural morta lity by age group. A multivariate Poisson regression model was used to expl ain daily mortality while controlling for several covariates including temp erature, humidity, day of the week, season, and time. The analysis indicate d a statistically significant association between PM10 and all of the alter native measures of mortality. The results suggest a 10-mu g/m(3) change in daily PM10 is associated with a 1-2% increase in natural mortality, a 1-2% increase in cardiovascular mortality, and a 3-6% increase in respiratory mo rtality. These relative risks are generally consistent with or greater than those reported in most studies undertaken in the United States.