Abstract

Background and objectives: Epidemiologic studies have attributed adverse health effects to air pollution; however, controversy remains regarding the relationship between ambient oxidants [ozone (O₃) and nitrogen dioxide (NO₂)] and mortality, especially in Asia. We conducted a four-city time-series study to investigate acute effects of O₃ 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 O₃ and NO₂, with PM₁₀ (particulate matter ≤ 10 μm 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

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