Non-negligible disparities in source-specific ambient PM2.5 across economic groups over space and time in China.

Inequality in exposure to air pollution is widespread within countries. Previous studies in the United States have explored the source contributions to exposure disparities, revealing the primary emissions that disproportionately affect minorities. However, the magnitude of exposure disparities stratified by source contributions remains unclear among economic groups in China over space and time. It's essential to examine whether mitigating air pollution from specific sources can yield improved exposure equality among populations. Here, we estimate the source contributions to ambient fine particle matter (PM2.5) from five major sectors by integrating GEOS-Chem model with the Shapley additive explanation method. The exposure disparities in source-specific PM2.5 are evaluated across economic groups in China from 2001 to 2019. We find that source-specific PM2.5 substantially impacts associated exposure among economic groups. While overall absolute exposure disparities have been alleviated in mainland China, concerns regarding the higher exposure for populations in poorer regions may still arise in densely populated areas such as central eastern China (CEC). Notably in 2019, populations in the wealthiest group of CEC are exposed to 3.11 μg/m3 [95% confidence interval (CI), 2.35 μg/m3-3.88 μg/m3] lower ambient PM2.5 from the sum of five anthropogenic emission sectors compared with the poorest group. The unfavorable differences are mainly contributed by PM2.5 from the residential and agricultural sectors for 1.74 μg/m3 (95% CI, 1.35 μg/m3-2.15 μg/m3) and 1.80 μg/m3 (95% CI, 1.37 μg/m3-2.29 μg/m3), respectively. Though the air pollution control after 2013 has reduced exposure disparities for particular sources, the inequality could be intensified in the long term due to larger emission reductions in wealthy areas, especially for the residential and industry sectors.