Ambient air pollution and daily mortality in Anshan, China: a time-stratified case-crossover analysis.
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Few case-crossover studies were conducted in China to investigate the acute health effects of air pollution. We conducted a time-stratified case-crossover analysis to examine the association between air pollution and daily mortality in Anshan, a heavily-polluted industrial city in northeastern China. Daily mortality, air pollution, and weather data in 2004-2006 in Anshan were collected. Time-stratified case-crossover approach was used to estimate the effect of air pollutants (PM(10), SO(2), NO(2) and CO) on total and cardiopulmonary mortality. Controls were selected as matched days of the week in the same month. Potential effect modifiers, such as gender and age, were also examined. We found significant associations between air pollution and daily mortality from cardiovascular diseases in Anshan. A 10g/m(3) elevation of 2-day moving average (lag 01) concentration in PM(10), SO(2), NO(2) and CO corresponded to 0.67% (95% CI: 0.29%, 1.04%), 0.38% (95% CI: -0.06%, 0.83%), 2.11% (95% CI: 0.22%, 4.00%) and 0.04% (95% CI: 0.01%, 0.07%) increase of cardiovascular mortality. The associations for total and respiratory mortality were generally positive but statistically insignificant. The air pollution health effects were significantly modified by age, but not by gender. Conclusively, our study showed that short-term exposure to air pollution was associated with increased cardiovascular mortality in Anshan. These findings may have implications for local environmental and social policies.