Clean air paradox: exacerbating urban-rural inequality in PM2.5 exposure.

Urban-rural disparity in fine particulate matter (PM2.5) exposure undermines health equity, yet the trends in long-term exposure remain unclear. Here, we systematically quantify income-stratified PM2.5 exposure across urban and rural populations in China from 2005 to 2019, integrating field-measured source-specific toxicity profiles with modeled PM2.5 exposure. Paradoxically, the urban-rural PM2.5 exposure disparity broadened by 55.6%, despite drastic reductions in PM2.5 mass during China's Clean Air Actions (2013-2019). Rural residents experienced 3.2-fold higher PM2.5 exposure than urban residents across the Chinese mainland in 2019. After accounting for source-specific toxicity, this ratio increased to 15.0-fold, primarily due to residential burning (>85.2%). Scenario analysis indicates that a 20% reduction in residential emissions could achieve 88.9% inequality mitigation in developed regions, compared to a more limited effect from a 60% cut in low-income areas. More focus on low-income rural households during the clean energy transition is recommended to advance health-equitable air policies and achieve broader social welfare.