Environmental and public health effects of vehicle emissions in a large metropolis: Case study of a truck driver strike in Sao Paulo, Brazil

In 2018, a truck-driver strike in Sao Paulo, Brazil, provided conditions for conducting a real-world experiment on the relationship between vehicle emissions, air quality, and public health. During the strike, no truck traffic, a 40–70% bus-traffic reduction, and a reduction in auto traffic was observed. The objective of this study is to evaluate the effects of vehicle-traffic reduction on the air quality and public health in Sao Paulo by taking advantage of the truck-driver strike. The corresponding analysis was based on the comparison of the air quality (NOx (nitrogen oxides), PM10 (particle matter of diameter less than 10 μm), and O3 (ozone) concentrations) during the strike and that registered on days having similar meteorological conditions. A relative-risk function was used to associate the decrease in the PM10 concentration during the strike with avoided mortality. The results demonstrated that, on workdays, the reduction in vehicle traffic during the strike was responsible for a 29.4%–40.9% improvement in NOx air quality and 19.2%–21.4% in PM10 concentration. The reduction in the PM10 concentration resulted in the prevention of between six and eight deaths during the strike, which implies between 321 and 442 avoided deaths in a year. In terms of the O3 concentration, no difference was identified between strike days and the comparative ones. An analysis of different sites of the city revealed that the greatest air-quality improvement was observed near an arterial road and near a bus terminal. Air-quality improvement was also detected in a park that was distant from the main roads. The results of the study provide evidence for supporting cleaner transportation investments and traffic restriction policies.