Acute mortality effects of carbon monoxide in the Pearl River Delta of China.
Several studies reported acute mortality and morbidity effects of exposure to carbon monoxide (CO); which, however, has been least studied in Chinese population at regional scale. We conducted a time-series analysis assessing mortality effects of CO in four cities located in the Pearl River Delta (PRD) of China, a labor and resource intensive city cluster, using daily mortality and air pollution data (2006-2008). Generalized linear model with Poisson regression incorporating natural spline functions was used to analyze the effects of exposure to ambient CO on total (nonaccidental), cardiovascular and respiratory mortality. Effect estimates were determined first for individual cities, and then focused for the mega-city Guangzhou. We found exposure to CO was significantly associated with increased mortality in the mega-city of Guangzhou and medium-sized industrial city of Foshan. In specific, per 0.5ppm increase in the average lag 1-2 (previous two days) exposure to CO was associated with 3.04% [95% confidence interval (CI), 2.18-3.90%], 3.62% (95% CI, 2.20-5.06%) and 3.72% (95% CI, 1.71-5.76%) increases in excessive risks (ERs) of total, cardiovascular and respiratory mortality, in Guangzhou. Further, we observed significant heterogeneity in mortality effects of exposure to CO among the four PRD cities of different development levels: stronger mortality effects were found in larger, more developed and industrialized cities. Exposure to ambient CO is associated with significant increases in total, cardiovascular and respiratory mortality in Chinese population. CO is an established biologic toxicant, whereas the effects and possible mechanisms of exposure to ambient level of CO and co-pollutants warrant further investigation.