Nonuniform impacts of COVID-19 lockdown on air quality over the United States

Abstract

Most of the state governments in United States (U.S.) issued lockdown or business restrictions amid the COVID-19 pandemic in March 2020, which created a unique opportunity to evaluate the air quality response to reduced economic activities. Data acquired from 28 long-term air quality stations across the U.S. revealed widespread but nonuniform reductions of nitrogen dioxide (NO 2 ) and carbon monoxide (CO) during the first phase of lockdown (March 15–April 25, 2020) relative to a pre-lockdown reference period and historical baselines established in 2017–2019. The reductions, up to 49% for NO 2 and 37% for CO, are statistically significant at two thirds of the sites and tend to increase with local population density. Significant reductions of particulate matter (PM 2.5 and PM 10 ) only occurred in the Northeast and California/Nevada metropolises where NO 2 declined the most, while the changes in ozone (O 3 ) were mixed and relatively minor. These findings are consistent with lower transportation and utility demands that dominate NO 2 and CO emissions, especially in major urban areas, due to the lockdown. This study provides an insight into potential public health benefits with more aggressive air quality management, which should be factored into strategies to reopen the U.S. and global economy.

Quantifying road traffic impact on air quality in urban areas: A Covid19-induced lockdown analysis in Italy

“…(2020) for the megacity of Delhi. Remarkable PM 10 reductions were also registered in Los Angeles (−57%) by Chen et al. (2020) , and in Beijing (−79%) by Shakoor et al.…”

“…(2020) in India, particularly over central and eastern regions. Comparable O 3 increases were registered by Chen et al. (2020) in NewYork (8%) and Las Vegas (17%), as well as by Connerton et al.…”

“…(2020) observed even stronger NO 2 decreases (∼65%). Following a study across 28 US locations, Chen et al. (2020) reported average NO 2 decreases ranging from 5% (Cheyenne) to 49% (Las Vegas), including Atlanta (−15%), Los Angeles (−34%), Boston (−36%), and New York (−41%).…”

“… Tobías et al., 2020 ; Mahato et al., 2020 ; Huang et al., 2020 ; Wang and Su, 2020 ; Rodríguez-Urrego and Rodríguez-Urrego, 2020 ; Agarwal et al., 2020 ) or against a mirrored period occurring during the previous year(s) (e.g. Chauhan and Singh, 2020 ; Chen et al., 2020 ; Sicard et al., 2020 ; Kerimray et al., 2020 ; Sharma et al., 2020 ; Shrestha et al., 2020 ; Singh and Chauhan, 2020 ; Shakoor et al., 2020 ; Connerton et al., 2020 ). The first approach is probably arguable, as the influence due to the changing meteorological conditions (e.g.…”

Does reduction of emissions imply improved air quality?

“…One side effect of the virus containment measures was the reduction of anthropogenic emissions resulting in smaller concentrations of pollutants as observed from space. In particular, reports on the strong reduction of tropospheric NO2 vertical column densities (TVCDs) appeared for China (e.g., Fan et al, 2020a;Liu et al, 2020;Pei et al, 2020;Zhang et al, 2020a), Italy and other countries in Europe (e.g., Bauwens et al, 2020;Tobí as et al, 85 2020;Mesas-Carrascosa et al, 2020;Sicard et al, 2020;Filippini et al, 2020;Menut et al, 2020) and later over other continents (e.g., Bauwens et al, 2020;Chen et al, 2020;Dantas et al, 2020;Kanniah et al, 2020;Patel et al, 2020;Sharma et al, 2020;Mahato et al, 2020). Reductions in NO2 TVCDs on the order of 50% were reported in the scientific literature (Fan et al, 2020a;Liu et al, 2020;Sicard et al, 2020).…”