Impact of the COVID-19 Pandemic Lockdown on Air Pollution in 20 Major Cities around the World

Abstract

In order to fight against the spread of COVID-19, the most hard-hit countries in the spring of 2020 implemented different lockdown strategies. To assess the impact of the COVID-19 pandemic lockdown on air quality worldwide, Air Quality Index (AQI) data was used to estimate the change in air quality in 20 major cities on six continents. Our results show significant declines of AQI in NO2, SO2, CO, PM2.5 and PM10 in most cities, mainly due to the reduction of transportation, industry and commercial activities during lockdown. This work shows the reduction of primary pollutants, especially NO2, is mainly due to lockdown policies. However, preexisting local environmental policy regulations also contributed to declining NO2, SO2 and PM2.5 emissions, especially in Asian countries. In addition, higher rainfall during the lockdown period could cause decline of PM2.5, especially in Johannesburg. By contrast, the changes of AQI in ground-level O3 were not significant in most of cities, as meteorological variability and ratio of VOC/NOx are key factors in ground-level O3 formation.

The global impacts of COVID-19 lockdowns on urban air pollution

“…Brazil: (Dantas et al, 2020;Krecl et al, 2020;Nakada and Urban, 2020;Siciliano et al, 2020a) Other: (Mendez-Espinosa et al, 2020;Pacheco et al, 2020;Zalakeviciute et al, 2020;Zambrano-Monserrate and Ruano, 2020) Europe Multiple countries: (Baldasano, 2020;Collivignarelli et al, 2020;Filippini et al, 2020;Gautam, 2020a;Giani et al, 2020;Gualtieri et al, 2020;Higham et al, 2020;Ljubenkov et al, 2020;Sicard et al, 2020;Tobías et al, 2020;Martorell-Marugán et al, 2021) Oceania Australia: (Fu et al, 2020) New Zealand: (Patel et al, 2020) Africa Morocco: (Ass et al, 2020;Otmani et al, 2020) This includes the "discussed but not corrected" and "not discussed or corrected" categories in Figure 2. (Zheng et al, 2020), and Tianjin (Dai et al, 2020), China.…”

“…The median transportation contribution for Annex I countries was 44% (36%-56%), 14% (8%-19%), and 25% (17%-44%) for the NO x , primary PM 2.5 , and CO emissions, respectively, whereas for Annex II countries, it was 29% (5%-49%), 9% (2%-42%), and 35% (1%-75%). Although the contribution of transportation emissions varied for the above pollutants, it is evident that East Asia China (Agarwal et al, 2020), (Bao and Zhang, 2020), a (Bauwens et al, 2020), (Chen et al, 2020c), (Diamond and Wood, 2020), (Forster et al, 2020), (Gautam, 2020a), (Griffith et al, 2020) (Zhang et al, 2021), (Liu et al, 2020b), (Liu et al, 2020c), (Wang et al, 2021), a (Su et al, 2020), (Miyazaki et al, 2020), (Huang and Sun, 2020), (Wang and Zhang, 2020), (Xu et al, 2020b), a (Park et al, 2020) Japan (Ghahremanloo et al, 2020), (Ma and Kang, 2020), a (Fu et al, 2020) South Korea (Fu et al, 2020), (Han et al, 2020), a (Ju et al, 2020), a (Bauwens et al, 2020), (Ma and Kang, 2020), a (Ghahremanloo et al, 2020) Taiwan (Forster et al, 2020) (continued)…”

“…Although the onset of lockdown measures is welldefined on national or state levels, the transition to the South Asia India (Agarwal et al, 2020), (Bera et al, 2020), a (Dhaka et al, 2020), (Forster et al, 2020), (Gautam, 2020a), (Jain and Sharma, 2020), a (Kumari and Toshniwal, 2020), a , a (Metya et al, 2020), (Navinya et al, 2020), (Resmi et al, 2020), a (Selvam et al, 2020), a (Sharma et al, 2020b), a (Siddiqui et al, 2020), (Venter et al, 2020), (Fu et al, 2020), (Gautam et al, 2020), a (Biswal et al, 2020), , a (Kant et al, 2020), (Zhang et al, 2020d) (Fu et al, 2020), (Chen et al, 2020b), (Zhang et al, 2020d), (Hudda et al, 2020), a (Xiang et al, 2020), (Liu et al, 2021b), (Naeger and Murphy, 2020) Canada (Adams, 2020), a (Forster et al, 2020), (Venter et al, 2020) Mexico (Venter et al, 2020), (Fu et al, 2020) South America (Forster et al, 2020), (Gautam, 2020a), (Menut et al, 2020) (Singh and Chauhan, 2020), (Venter et al, 2020), (Fu et al, 2020), (Gautam et al, 2020), a (Mahato and Ghosh, 2020), a (Kant et al, 2020), (Zhang et al, 2020d), (Sharma et al, 2020a…”

“…As such, the index includes both measures that impact emissions and measures with no obvious consequence for emissions. East Asia China (Bao and Zhang, 2020;Chen et al, 2020c;Chen et al, 2020d;Fu et al, 2020;Shakoor et al, 2020;Silver et al, 2020;Wan et al, 2020;Wang et al, 2020a;Wang et al, 2020b;Wang et al, 2020f;Xu et al, 2020a;Xu et al, 2020c;Zhang et al, 2020a;Zhao et al, 2020b;Zheng et al, 2020;Yuan et al, 2021), (Wang and Zhang, 2020), (Xu et al, 2020b) Japan (Fu et al, 2020) South Korea (Fu et al, 2020;Han et al, 2020;Ju et al, 2020) South Asia India (Bedi et al, 2020;Bera et al, 2020;Fu et al, 2020;Gautam et al, 2020;Harshita and Vivek, 2020;Jain and Sharma, 2020;Kant et al, 2020;Kumari and Toshniwal, 2020;Navinya et al, East Asia China (Chen et al, 2020a;Chen et al, 2020c;Chen et al, 2020d;Fan et al, 2020;Fu et al, 2020;Ghahremanloo et al, 2020;Lian et al, 2020;Liu et al, 2020b;Liu et al, 2020c;Su et al, 202...…”

COVID-19 outbreak, lockdown, and air quality: fresh insights from New York City

“…Similarly, Perera et al (2021) focused on the single particulate matter (PM 2.5 ) during the COVID-19 shutdown. Likewise, Fu et al (2020) analyze the effect of lockdown on air quality in 20 major cities, including New York City. Based on the argument mentioned above, we can argue that using a single or few pollutants may not present a holistic view of air quality changes during the lockdown.…”