Resolving Spatially Varied PM_2.5 Toxicity in the Yangtze River Delta: Targeting Incomplete Combustion Sources

Fine particulate matter (PM_2.5) is the leading environmental risk factor for premature mortality. Although mass concentrations of PM_2.5 have declined in the past decade, the unequal toxicity in different sources remains overlooked in air-quality management. Here, we integrated source-specific toxicities of PM_2.5, derived from field measurements and cellular assays, with high-resolution emission inventories to conduct health-oriented source apportionment in the Yangtze River Delta (YRD). The average of toxicity-adjusted population-weighted PM_2.5 exposure was high in central and northern Anhui and along the Yangtze River, approximately 6.6 times that of Zhejiang and Shanghai. Residential solid fuel combustion was the dominant contributor to PM_2.5 toxicity, especially in winter (74.4%, 95% CI: [62.9%, 85.9%]). The toxicity contribution of residential combustion was negatively correlated with city-level income (r = -0.83; p < 0.0001). Targeting residential emissions effectively reduced relative toxicity-adjusted risks in low-income regions, and the costs for reducing a unit of toxicity-adjusted PM_2.5 were 2.7% of those for industrial emission control. Ship emission abatement might yield optimal cost-health benefits in coastal areas based on relative ranking under assumed marginal costs. Our findings, based on in vitro cellular toxicity, highlighted controlling residential and ship emissions, providing insights into tailored air-quality policies and regional health equity.