COVID-19 and the Improvement of the Global Air Quality: The Bright Side of a Pandemic

Abstract

The objective of this investigation is to study the impacts of the global response to COVID-19 on air pollution and air quality changes in major cities across the globe over the past few months. Air quality data (NO2, CO, PM2.5, and O3) were downloaded from the World Air Quality Index project for the January 2019–April 2020 period. Results show a significant reduction in the levels of 2020 NO2, CO, and PM2.5 compared to their levels in 2019. These reductions were as high as 63% (Wuhan, China), 61% (Lima, Peru), and 61% (Berlin, Germany), in NO2, CO, and PM2.5 levels, respectively. In contrast, 2020 O3 levels increased substantially, as high as 86% (Milan, Italy), in an apparent response to the decrease in titration by nitrogen monoxide and its derivatives. Significant differences in the weather conditions across the globe do not seem to impact this air quality improvement trend. Will this trend in the reduction in most air pollutants to unprecedented levels continue in the next few weeks or even months? The response to this and other questions will depend on the future global economic and environmental policies.

The Effect of Lockdown Period during the COVID-19 Pandemic on Air Quality in Sydney Region, Australia

“…Using monitoring data, the effect of the lockdown could be masked by different meteorological conditions and emissions in 2017, 2018, 2019, and 2020. Our results are consistent with the results from other studies in cities around the world such as [ 10 ] in Shanghai, [ 7 ] in 10 major world cities including Sydney and Perth in Australia, [ 11 ] in Chinese cities, [ 13 ] and in Singapore. Rodríguez-Urregoa et al (2020) [ 5 ] compared the PM 2.5 time series of a typical week during the lockdown with that of 1 week before the lockdown for the 50 most polluted cities in the world.…”

“…However, an analysis based on the above assumption can give us some indication of the comparative pollutant concentration and insights of air quality during the COVID-19 lockdown in 2020. This method of comparing the “control” group and “treatment” group was used by most authors such as [ 3 , 5 , 7 , 8 , 9 , 11 , 13 , 15 ]. However, as Zangari et al (2020) [ 19 ] pointed out, recently the improvement trend in air quality before and after the lockdown could also be due to other factors.…”

“…Chauhana and Singh (2020) [ 6 ], also reported the PM 2.5 reduction in major cities around the world with the most pronounced reduction in Delhi and Mumbai in India. Similarly, Habibi et al (2020) [ 7 ], using the same method of daily data of major cities around the world from the World Air Quality Index (WAQI) project for the January 2019–April 2020 period, has reported that NO 2 , CO, and PM 2.5 levels reduced while O 3 (Ozone) increased for most of the world’s major cities between February, March, and April 2020, as compared to the levels of the corresponding period in 2019. Berman and Ebisu [ 8 ] analyzed NO 2 and PM 2.5 air quality data in 2020 as compared to 2019 and reported that the levels of these pollutants decreased across the continental US.…”

“…In this study, we focus on the effect of lockdown on air quality in the Greater Metropolitan Region (GMR) of Sydney from April to June 2020, specifically on criteria pollutants CO, NO 2 , PM 2.5 , and O 3 . This study is different from some of the previous studies [ 5 , 6 , 7 , 15 ], in that we use a number of methods. We compare the air quality during the lockdown of 2020 with the air quality in the corresponding period of 2019 but also in previous years of 2016, 2017, and 2018 and a pooled ensemble of these previous years, as well as the diurnal analysis to control for the effect of meteorological variability.…”

Changes in Air Quality Associated with Mobility Trends and Meteorological Conditions during COVID-19 Lockdown in Northern England, UK

“…Rodríguez-Urrego and Rodríguez-Urrego [13] in a global study of PM 2.5 in the most polluted cities, found an average reduction of 12% in PM 2.5 concentrations, while reporting the highest reductions in Bogota and Kuwait City. Habibi et al [14] reported reductions as high as 60% in the levels of air pollutants (NO 2 , CO, and PM 2.5 ) in Wuhan, Lima, and Berlin. In another global study of eight cities, Wang and Li [15] noted nonlinear relationships between COVID-19 lockdown and pollution, and variations in the magnitude of changes in pollutant levels due to local conditions.…”