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Graduate School of Economics and Management, Tohoku University

Professor, Graduate School of Economics and Management, Tohoku University

Road traffic accidents are a leading cause of preventable death, but little is known about how environmental conditions shape the driver behavior behind them. This paper estimates the effect of short-term exposure to fine particulate matter (PM2.5) on traffic accidents in Brazil and through which behavioral channels it operates. We use daily Highway Patrol records for 2017–2019 from São Paulo, Rio de Janeiro, Espírito Santo and Minas Gerais. Each accident is classified by primary cause: aggressive driving, driver error, or substance-related and other causes. To address the endogeneity of pollution, we instrument PM2.5 with thermal inversions in a two-stage least squares framework. Pollution increases the number of accidents. The effects are driven by aggressive driving and driver error, while substance-related and other causes, used as a placebo, show no significant response. The effect is concentrated on the day of exposure, with no significant leads or lags. These results suggest that PM2.5 affects road safety through behavioral and cognitive channels, so air quality policy may bring road safety benefits as well as health gains.(JEL Classification: Q53, R41, I18, C26)