The Effect of Air Purifiers in Schools

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%. Effects are larger among students with higher pre-treatment absenteeism. The impact is 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. The treatment students report fewer respiratory symptoms and exhibit greater awareness of air quality. The cost per absence day avoided is approximately € 11, resulting in a conservative cost-benefit ratio of one-to-nine.

JEL codes: C93, I21, Q53, Q51
Keywords: Indoor air quality, air purifiers, school absences, randomized controlled trial

Jacopo Bonan

Associate Professor at the University of Brescia

Francesco Granella

Postdoctoral Researcher at RFF-CMCC

Stefania Renna

PhD Student at Politecnico di Milano

Luis Sarmiento

Junior Scientist at the European Institute on Economics and the Environment

Massimo Tavoni

Director of the European Institute on Economics and the Environment

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