Effect of Air Pollution on the Cognitive Function of Adolescents (ATENC!Ó): An Experimental Study in High Schools in Barcelona, Spain

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Background: The recent evidence of the short-term impact of air pollution on youth cognitive functions is based primarily on observational studies. We conducted an experimental study to assess whether air pollution in high schools can affect the adolescents' attention processes.Methods: A total of 2124 adolescents (14-15 years old) were recruited in 33 high schools in Barcelona province (Spain). In each school, adolescents were randomly split into two equal-sized groups. For each school, each group was assigned to a different classroom. One classroom had an internal air purifier (recirculation and filtration) and the other had the same device but without the filter (only recirculation). Students were masked to intervention allocation and were asked to complete several computerized activities for two hours, including an attention test (Flanker task) to perform at baseline and after the intervention. We measured the response speed consistency, expressed as hit reaction time standard error (HRT-SE), as our primary outcome. Analyses were conducted using conditional linear regressions with classroom as strata, adjusted for variables that may differ from one class to another such as temperature, humidity and carbon dioxide concentration.Results: Average levels of PM2.5 and black carbon for the two hours of experiment were 89% and 87% lower in the classrooms with purified air than in the control classrooms. We found a non-significant 1.84% (95% confidence interval -2.27%, 6.12%) difference in the median of HRT-SE between classrooms with purified or normal air. Sensitivity analyses and results with secondary outcomes resulted in similar findings.Conclusions: Cleaning the air of a classroom to reduce exposure to air pollutants for a duration of two hours did not have an impact on the attention of high-school students. Experimental studies with longer duration of the intervention could shed more light on the potential association between air pollution and adolescents’ cognitive function.