Ambient PM1-Related Health Burdens and Mortality Influencing Factors in China: Historical Trends to Future Projections.

Because of its small particle size and toxic potential, PM1 may pose substantial health risks. However, long-term historical and future PM1-attributable health burdens and their influencing factors remain poorly understood for China. Here, we estimated historical PM1 exposure across China for 2016-2024 using an Extremely Randomized Trees (ERT) model, projected future PM1 exposure for 2025-2100 under the Shared Socioeconomic Pathways (SSPs) of the Coupled Model Intercomparison Project Phase 6 (CMIP6), and quantified PM1-attributable mortality using the Environmental Benefits Mapping and Analysis Program (BenMAP). We further employed counterfactual analysis to quantify the independent impacts of PM1 concentrations, population size, and age-structure changes on mortality variations. The results show that national-average PM1 concentrations in China fell by 45.25% over 2016-2024, corresponding to an annual decline of 5.04% (1.37 μg/m3 yr-1). Across the three SSP scenarios, PM1 concentrations are projected to drop by an average of 49.67% from 2025 to 2100. PM1-attributable all-cause deaths decreased by 42.66% between 2016 and 2024. The largest mortality reduction (59.20%) was projected to occur under the SSP1-2.6 scenario for 2025-2100. PM1-related deaths exhibited substantial geographic disparities across provinces. The largest estimated effect on PM1-related deaths was projected to shift from PM1 concentrations to age-structure changes between the historical period and the future. These findings highlighted the necessity of continuously reducing PM1 exposure, pursuing cleaner development pathways, adopting province-specific interventions, and strengthening health protection for older adults.