Sources of PM2.5 exposure and health benefits of clean air actions in Shanghai

Estimating PM_2.5 exposure and its health impacts in cities involves large uncertainty due to the limitations of model resolutions. Consequently, attributing the sources of PM_2.5-related health impacts at the city level remains challenging. We characterize the health impacts associated with chronic PM_2.5 exposure and anthropogenic emissions in Shanghai using a chemical transport model (GEOS-Chem) and its adjoint. By incorporating high-resolution satellited-derived PM_2.5 estimates into the calculation, we investigate the response of PM_2.5 exposure and its related health impacts in Shanghai to changes in anthropogenic emissions from each individual region, species, sector, and month. We estimate that a 10% decrease in anthropogenic emissions throughout China avoids over 752 (506-1,044) PM_2.5-related premature deaths in Shanghai, with changes in local emissions potentially saving 241 (161-334) lives. Ammonia (NH₃) emissions are identified as the marginal dominant contributor to the health impacts due to the NH₃-limited PM_2.5 formation within the city, thus controlling NH₃ emissions at both the local and regional scales are effective at reducing the population's exposure to PM_2.5. A negative response of the PM_2.5 exposure to local nitrogen oxides (NO_x) emission changes is detected in winter. Even so, controlling NO_x emissions is still justified since the negative impacts decrease as anthropogenic emissions decline and NO_x emission reductions benefit the public health on average. The anthropogenic emission changes due to Clean Air Actions helped avoid 3,132 (2,108-4,346) PM_2.5-related premature deaths in 2019 relative to 2013, most of which are associated with emission reductions in the agricultural and industrial sectors.