Trends of outdoor air pollution and the impact on premature mortality in the Pearl River Delta region of southern China during 2006-2015.

Severe air pollution in the Pearl River Delta (PRD) region of southern China has increased attention of both the scientific community and policy makers. Air quality data collected at the PRD Regional Air Quality Monitoring Network during 2006-2015 were analyzed for assessing the effectiveness of pollution control measures and for estimating the trends of premature mortality attributable to ambient PM2.5 and O3. Statistically significant decreasing trends were detected for PM2.5 (-1.74 to -1.83 μg m-3 yr-1), PM10 (-2.70 to -2.78 μg m-3 yr-1), NO (-0.61 to -0.74 μg m-3 yr-1), NO2 (-1.20 to -1.22 μg m-3 yr-1), and SO2 (-3.46 to -4.01 μg m-3 yr-1), while an increasing trend was found for O3 (0.70-0.86 μg m-3 yr-1) during the study period. The findings demonstrate the effectiveness of control measures implemented in the last decade for primary pollutants and also indicate the challenges for controlling secondary pollutants. The PM2.5-related premature deaths varied little, e.g., from 40.6 thousand deaths in 2006 to 40.4 thousand deaths in 2015, due to the two contrasting factors, i.e., the decreased PM2.5 concentration and increased population. The increases in both O3 concentration and exposed population resulted in a significant rising trend for the O3-related premature deaths, which increased from 2.7 thousand deaths in 2006 to 4.5 thousand deaths in 2015, at a rate of 165 deaths yr-1. Consistent with the spatial distribution of air pollution and population density, high levels of premature deaths from PM2.5 and O3 were located in the central PRD including Guangzhou, Foshan, Dongguan, and Shenzhen. Decreasing PM2.5 concentration is the most effective way in reducing the regional mortality burden from air pollution in the near future. Besides controlling primary emissions of PM2.5, reducing VOCs emissions is also important for limiting atmospheric oxidizing capacity and associated secondary PM2.5 formation.