Estimated Acute Effects of Ambient Ozone and Nitrogen Dioxide on Mortality in the Pearl River Delta of Southern China

BACKGROUND AND OBJECTIVES: Epidemiologic studies have attributed, adverse health effects to air pollution; however, controversy remains regarding the relationship between ambient oxidants [ozone (O-3) and nitrogen dioxide (NO2)] and mortality, especially in Asia. We conducted a four-city time-series study to investigate acute effects of O-3 and NO2 in the Pearl River Delta (PRD) of southern China, using data from 2006 through 2008. METHODS: We used generalized linear models with Poisson regression incorporating natural spline functions to analyze acute mortality in association with O-3 and NO2, with PM10 (particulate matter <= 10 mu m in diameter) included as a major confounder. Effect estimates were determined for individual cities and for the four cities as a whole. We stratified the analysis according to high- and low- exposure periods for O-3. RESULTS: We found consistent positive associations between ambient oxidants and daily mortality across the PRD cities. Overall, 10-mu g/m(3) increases in average O-3 and NO2 concentrations over the previous 2 days were associated with 0.81% [95% confidence interval (Cl): 0.63%, 1.00%] and 1.95% (95% CI: 1.62%, 2.29%) increases in total mortality, respectively, with stronger estimated effects for cardiovascular and respiratory mortality. After adjusting for PM10, estimated effects of O-3 on total and cardiovascular mortality were stronger for exposure during high-exposure months (September through November), whereas respiratory mortality was associated with O-3 exposure during nonpeak exposure months only. CONCLUSIONS: Our findings suggest significant acute mortality effects of O-3 and NO2 in the PRD and strengthen the rationale for further limiting the ambient pollution levels in the area.Environmental SciencesPublic, Environmental & Occupational HealthToxicologySCI(E)PubMed20ARTICLE3393-39812