Substantial PM_2.5-Related Health Gains from Large-Scale Migration in China

Urbanization-driven, large-scale rural-to-urban migration in China has substantially modernized household energy use and reshaped air pollution exposure pathways. However, the magnitude, underlying drivers, and temporal evolution of the resulting health outcomes from combined indoor and outdoor air pollution remain insufficiently resolved. Here, by coupling a reconstruction of seven decades of migration (1949-2021) with nationwide household energy surveys, we quantify migration-attributable changes in integrated (indoor + outdoor) PM_2.5 exposure and mortality. Relative to a no-migration counterfactual from 1949 onward, migration reduced integrated PM_2.5 exposure by 27.6 μg·m^-3 (15.7-39.4 as the 95% confidence interval) in 2019 and cumulatively avoided 2.3 (1.9-2.6) million deaths since 1949, with reductions in indoor exposure providing the dominant contribution. Arising from rural-urban disparities in household energy use, these health gains were pronounced even during intermediate stages of societal development and are likely to occur in other transitioning economies worldwide. Our study thus challenges the conventional view that rapid urbanization in developing economies is strictly detrimental to environmental health.