Droughts worsen air quality and health by shifting power generation.

Fine particulate matter (PM) is a leading environmental cause of mortality. Droughts can worsen air quality in regions that rely on hydropower by shifting energy production to combustion power plants. This study quantifies drought-induced excess PM in Latin America and the Caribbean, where over 443 million people live within 50 km of a combustion power plant. Leveraging a monthly plant-level panel spanning 20 years, we link hydrological droughts, measured as negative runoff anomalies in hydropower watersheds, to changes in PM concentrations near combustion power plants. Our analysis reveals that these droughts lead to an average increase of 0.83 μg m in PM levels. Counterfactual simulations for the region reveal that this excess PM results in up to 10,000 premature deaths annually. Combining our estimates with climate, demographic, and combustion power plant phase-out projections, we demonstrate that this health burden will persist over the next four decades without targeted interventions.