This paper examines the causal effects of air pollution on migration by exploiting a natural experiment in which desulfurization technologies were rapidly implemented in coal-burning power plants in the Czech Republic without per se affecting economic activity. The results based on a difference-in-differences estimator imply that improvements in air quality reduced emigration from previously heavily polluted municipalities by 24%. We find that the effect of air pollution on emigration tended to be larger in municipalities with weaker social capital and fewer man-made amenities.