“…Research groups in major cities such as Sao Paulo, Brazil; Wuhan, China; and Barcelona, Spain reported decreases in traffic-related air pollutant concentrations from January to May 2020 (Abdullah et al, 2020;Cadotte, 2020;Kambalagere, 2020;Li et al, 2020;Tobías et al, 2020;Zambrano-Monserrate et al, 2020;Zheng et al, 2020), which they suggest is a result of reduced vehicle emissions. Several studies have also shown similar reductions in pollutant concentrations by comparing 2020 concentrations to those measured in previous years (Chen et al, 2020;Dantas et al, 2020;Dutheil et al, 2020;Freitas et al, 2020;Isaifan, 2020;Muhammad et al, 2020;Nakada and Urban, 2020;Sharma et al, 2020;Xu et al, 2020). Similar work has been completed in the US, but to a much lesser extent (Berman and Ebisu, 2020;EarthSky Team, 2020;Muhammad et al, 2020;Porterfield, 2020;Stein, 2020;Volcovici, 2020).…”