Different local air-pollution responses to the COVID-19 lockdown measures: three metropolises in Latin America

Abstract Usually, urban air pollution policies are mainly based on reducing traffic. The COVID-19 lockdown gave a great opportunity to understand the relevance of traffic on urban air pollution, because year 2020 had three periods with marked differences on traffic activity. Existing studies analyse changes on air pollution during lockdown, but not for the subsequent period when traffic increased. This study analyses short-term changes in ground-level air pollution in the Metropolitan Zone of Mexico City (MZMC), Metropolitan Area of São Paulo (MASP), and Bogotá, for three phases: before lockdown (P1), the most restrictive phase (P2), and the relaxation phase (P3). The analyses using statistical tests included: (a) comparing the average 24-h mean pollutant concentration of each phase in 2020 with the same periods from 2016 to 2019; and (b) comparing the average 24-h mean pollutant concentrations among the phases. Results show that air pollution in the three metropolises behaved differently with large but site-specific reductions in primary pollutants concentrations based on mobility-restrictions’ stringency and compliance, particular environmental characteristics, and other factors influencing emission concentrations of each metropolis. Then, in order to improve air quality, it is necessary to identify for each city, the specific factors that contribute to change emissions as much as or more than traffic, for developing holistic and effective air pollution abatement policies Air quality management strategies require understanding the effectiveness and potential side impacts of restrictive measures on traffic, considering different situations. This is a key problem for urban sustainability in Latin America.