Air Pollution and Daily Mortality in Residential Areas of Beijing, China

Abstract

The relationship between air pollution and daily mortality in 1989 was examined in two residential areas in Beijing, China. Very high concentrations of sulfur dioxide (SO₂) (mean = 102 μg/m³, maximum = 630 μg/m³) and total suspended particulates (TSPs) (mean = 375 μg/m³, maximum = 1 003 μg/m³) were observed in these areas. Daily counts of deaths were regressed, using Poisson regression on the logarithm of (SO₂) and/or TSPs controlling for effects of temperature, humidity, and day of week. A highly significant association was found between ln(SO₂) and daily mortality. The risk of total mortality was estimated to increase by 11% (95% confidence interval [95% CI] = 5%–16%) with each doubling in SO₂ concentration. Separately, the association of ln(TSP) with total daily mortality was positive but not significant (4% increase in mortality with each doubling in TSP; 95% CI = −2%–11%). When mortality was analyzed separately by cause, the association with a doubling in SO₂ was significant for chronic obstructive pulmonary disease (29%), pulmonary heart disease (19%), and cardiovascular disease (11%), and marginally significant for the other nonmalignant causes (8%), but not statistically significant for cancer (2%). A similar association was noted for a doubling in TSP (4%, 38%, and 8% for total, chronic obstructive pulmonary disease, and pulmonary heart disease mortality, respectively), but the result was only statistically significant for chronic obstructive pulmonary disease. In the season-specific analysis, both SO₂ and TSP were found to be significant predictors of total daily mortality in summer. In winter, SO₂ was again significantly associated with increased mortality, but no positive association was found between TSP and mortality. In the cause-specific analysis, the strongest effects of SO₂ and TSP on mortality were consistently seen for respiratory diseases in both seasons. This study shows increased mortality associated with air pollution at SO₂ pollution levels below the current WHO recommendations.