Short-term exposure to sulfur dioxide and daily mortality in 17 Chinese cities: The China air pollution and health effects study (CAPES)

Abstract

Sulfur dioxide (SO2) is a major air pollutant and has significant impacts upon human health. Few multi-city studies in Asia have examined the acute health effects of SO2. As part of the China Air Pollution and Health Effects Study (CAPES), this study aimed at investigating the short-term association between SO2 and daily mortality in 17 Chinese cities. We applied two-stage Bayesian hierarchical models to obtain city-specific and national average estimates for SO2. In each city, we used Poisson regression models incorporating natural spline smoothing functions to adjust for long-term and seasonal trend of mortality, as well as other time-varying covariates. We examined the associations by age, gender and education status. As a result, the combined analysis showed that an increase of 10μg/m3 of two-day moving averaged SO2 was associated with 0.75% [95% posterior interval (PI), 0.47 to 1.02], 0.83% (0.95% PI, 0.47 to 1.19) and 1.25% (95% PI, 0.78 to 1.73) increase of total, cardiovascular and respiratory mortality, respectively. The effects of SO2 appeared more evident among the elderly. These associations were generally independent of particles with aerodynamic diameter <10μm (PM10) but did not persist after adjustment for nitrogen dioxide (NO2). In conclusions, this largest epidemiologic study of air pollution in China to date suggests that short-term exposure to SO2 is associated with increased mortality risk; however, these associations may be attributable to SO2 serving as a surrogate of other substances. Further studies are needed to tackle the independent health effect of SO2.