With Jacopo Bonan, Stefania Renna, and Luis Sarmiento.
We randomize the installation of air purifiers across primary school classrooms to reduce children’s exposure to air pollution. The intervention reduces indoor PM2.5 concentrations by 32% and decreases student absenteeism by 12.5%. We find larger effects among students with higher pre-treatment absenteeism. The impact is also greater when outdoor air pollution is relatively low and diminishes as outdoor pollution intensifies, consistent with non-linear marginal effects of air quality on health. Treated students report fewer respiratory symptoms and exhibit greater awareness of air quality. Each avoided absence day costs approximately €11, yielding a conservative cost-benefit ratio of one-to-nine.