2024 Yes Short-term effect of air pollution on attention function in adolescents (ATENC!Ó): A randomized controlled trial in high schools in Barcelona, Spain https://www.sciencedirect.com/science/article/pii/S0160412021002397 Gignac, Florence Europe Exposure Students High School (9-12) Filtration Test performance Air pollution Adolescents Attention Randomised control trial High school A randomized trial with 2,123 Spanish adolescents tested air cleaners in classrooms. Despite 87-89% pollutant reduction, no short-term improvement in attention was found, indicating further research on exposure duration and age is needed. 2021