São Paulo's atmospheric pollution reduction and its social isolation effect, Brazil

Since January 2020, studies report reductions in air pollution among several countries due to social isolation measures, which have been adopted in order to contain the coronavirus outbreak progress (COVID-19). This study aims to evaluate the change in the atmospheric pollution levels by NO and NO₂ in São Paulo City for the social isolation period. The NO and NO₂ hourly concentrations were obtained through air quality monitoring stations from CETESB, from January 14, 2020 to April 12, 2020. Mann-Kendall and the Pettitt tests were performed in the air pollutant time series. We observed an overall negative trend in all stations, indicating a decreasing temporal pattern in concentrations. Regarding NO, the highest absolute decrease rates were observed in the Congonhas (- 6.39 μg m^-3 month^-1) and Marginal Tietê (- 6.19 μg m^-3 month^-1) stations; regarding NO₂, the highest rates were observed in the Marginal Tietê (- 4.45 μg m^-3 month^-1) and Cerqueira César (- 4.34 μg m^-3 month^-1) stations. In addition, we identified a turning point in the NO and NO₂ series trends that occurred close to the start date of the social isolation period (March 20, 2020). Moreover, from statistical analysis, it was found that NO₂ is a suitable surrogate for monitoring economic activities during social isolation periods. Thus, we concluded that social isolation measures implemented on March 20, 2020 caused significant changes in the air pollutant concentrations in the city of São Paulo (as high as - 200% in NO₂ levels).