Smoggier skies, lower scores? A Brazilian study examines the effects of air pollution on students’ cognitive performance

The Journal of the Association of Environmental and Resource Economists has published a new study that examines the relationship between outdoor pollution and cognitive performance of Brazilian students.
Juliana Carneiro and Matthew A. Cole (authors of "The Effects Of Air Pollution On Students' Cognitive Performance: Evidence From Brazilian University Entrance Exams") use Brazilian data on concentrations (O3) and particulate (PM10), as well as data sets of student scores, to study the effects of air pollution on students' academic performance in national exams. This data panel focuses on Rio de Janeiro (the most industrialized state in Brazil) and So Paulo (the rest of Brazil). It uses data from weather stations and air pollution to create a unique data panel for 2015-17.

To address any endogeneity concerns, the authors created individual-level panel data across three years. They also note that they take advantage of "plausibly exogenous spatial, temporal variation in PM10 between municipalities in the state of Rio de Janeiro or So Paulo" and use an instrumental variable approach based upon wind direction.

Students' scores are affected by an increase in PM10 of 10 micrograms per square meter (mg/m3) on the day of the exam. This is a decrease of 6.1 points (8% SD). They note that even though we included a flexible measure of treatment, which uses a dummy variable in order to account for days when PM10 exceeded WHO's acceptable threshold, the findings still show negative effects of air pollution on cognitive performance during exams. Placebo and sensitivity tests, falsifications and falsifications testing all confirmed the main findings, which showed a connection between exam performance and air pollution.

The authors found evidence that air pollution has a greater impact on exam performance than previously reported. This is consistent with previous studies. Our results also indicate that students who are poorer than those who are wealthier may be more vulnerable to air pollution," they write. They add that their findings offer plausible evidence that poor air quality may affect cognitive performance, but not equally.