CHANGES OF SPATIAL DISPARITIES IN SATELLITE-DERIVED PM_2.5 EXPOSURES OVER 2010–2019 IN CHINA

Abstract. Air pollution, especially fine particulate matter (PM_2.5), has attracted extensive attention due to its adverse impacts on public health. Although PM_2.5 pollution was significantly reduced in China over time, while little is known how the spatial disparity of PM_2.5 exposure has evolved, especially from both absolute and relative perspectives. Here, we estimate the long-term PM_2.5 exposures in China based on satellite observations and convolutional neural network, and characterize the spatial disparity of PM_2.5 exposure using Theil index and rank-rank relationship. The result shows that both PM_2.5 exposure and absolute spatial disparity were substantially reduced between 2010 and 2019. The nation-wide concentrations (Theil index) declined from 48.0µg/m³ (0.13) to 35.5µg/m³ (0.054). The inter-provincial disparities dominate the overall disparity in 2010, while the intra-provincial disparity contributed the most in 2019. However, while absolute disparities have diminished, relative disparities persist. PM_2.5 exposures in the least 20th percentile polluted cities have increased over time, while exposures in other regions declined. On average, the more (less) polluted cities in 2010 were still the more (less) polluted cities in 2019 (except for the very most 2 percentile polluted cities), indicating that the population in more polluted cities still experiences more air pollution than others. Spatial pattern of relative disparity changes was also observed. Overall, understanding not only absolute spatial disparity but also relative disparity is required to help formulate targeted policies for an equitable environment, leaving nobody behind.