Exposure risk assessment and synergistic control pathway construction for O3–PM2.5 compound pollution in China

Abstract

The increasingly pronounced compound pollution issue of fine particulate matter (PM_2.5) and surface ozone (O₃) concentrations in China has exacerbated the risk of human morbidity and death. In this study, the spatial and temporal characteristics, health risks and synergistic control pathways of PM_2.5–O₃ compound pollution in 365 cities in China from 2015 to 2020 were investigated based on spatial statistical analysis, integrated risk index model and spatial correlation analysis. The results show that: The strict air pollution control measures lead to a sustained decrease in PM_2.5 leading polluted cities and a sustained increase in clean cities during the study period. However, there is a trend of increasing (2015–2017) and then decreasing (2018–2020) in cities with compound PM_2.5 and O₃ pollution because of changes in volatile organic compounds (VOCs) and NOx caused by human activities. According to the exposure analysis method, the population exposed to PM_2.5 dominated polluted cities declined by 471 million from 2015 to 2020; in contrast, the population living in clean cities increased by 460 million. With the intensification of PM_2.5–O₃ compound pollution in China, the exposure to PM_2.5–O₃ compound pollution urban population increases sharply from 349 million in 2015 to 622.5 million in 2018, an increase of more than 40 %; as air quality improves after 2017, the population exposed to PM_2.5–O₃ compound pollution gradually decreases, falling to the equivalent level in 2015 by 2020. Meanwhile, the population health risks attributed to PM_2.5 pollution were reduced, whereas the population health risks attributed to PM_2.5–O₃ compound pollution were aggravated. From a spatial perspective, PM_2.5–O₃ compound pollution and health risk exacerbation regions were concentrated in northern and eastern China. In addition, we found that PM_2.5 and O₃ concentrations have significant synergistic trends, which are consistent with the spatial distribution of VOCs and NOx. Therefore, the establishment of a scientific early warning system for PM_2.5–O₃ compound pollution and the continuous and vigorous promotion of comprehensive emission reduction of NOx and VOCs are conducive to the synergistic management of PM_2.5 and O₃ in China.