Global, continental, and national variation in PM2.5, O3, and NO2 concentrations during the early 2020 COVID-19 lockdown

Abstract

Lockdowns implemented in response to COVID-19 have caused an unprecedented reduction in global economic and transport activity. In this study, variation in the concentration of health-threatening air pollutants (PM 2.5 , NO 2 , and O 3 ) pre- and post-lockdown was investigated at global, continental, and national scales. We analyzed ground-based data from >10,000 monitoring stations in 380 cities across the globe. Global-scale results during lockdown (March to May 2020) showed that concentrations of PM 2.5 and NO 2 decreased by 16.1% and 45.8%, respectively, compared to the baseline period (2015–2019). However, O 3 concentration increased by 5.4%. At the continental scale, concentrations of PM 2.5 and NO 2 substantially dropped in 2020 across all continents during lockdown compared to the baseline, with a maximum reduction of 20.4% for PM 2.5 in East Asia and 42.5% for NO 2 in Europe. The maximum reduction in O 3 was observed in North America (7.8%), followed by Asia (0.7%), while small increases were found in other continents. At the national scale, PM 2.5 and NO 2 concentrations decreased significantly during lockdown, but O 3 concentration showed varying patterns among countries. We found maximum reductions of 50.8% for PM 2.5 in India and 103.5% for NO 2 in Spain. The maximum reduction in O 3 (22.5%) was found in India. Improvements in air quality were temporary as pollution levels increased in cities since lockdowns were lifted. We posit that these unprecedented changes in air pollutants were mainly attributable to reductions in traffic and industrial activities. Column reductions could also be explained by meteorological variability and a decline in emissions caused by environmental policy regulations. Our results have implications for the continued implementation of strict air quality policies and emission control strategies to improve environmental and human health.

PM2.5, NO2, wildfires, and other environmental exposures are linked to higher Covid 19 incidence, severity, and death rates

“…An analysis of 10,000+ sampling sites in 380 World Cities reported that during the 2020 lockdown periods PM 2.5 and NO 2 fell by an average of 16.1 and 45.8%, while ozone levels rose by an average of 5.4% (He et al 2021 ). A study of 50 more polluted capital cities reported a mean drop in PM 2.5 of 11% (Rodríguez-Urrego and Rodríguez-Urrego 2020 ).…”

Air quality index variation before and after the onset of COVID-19 pandemic: a comprehensive study on 87 capital, industrial and polluted cities of the world

“…This reduction in the concentration of pollutants improves the air quality index (AQI) of cities and has positive effects on community health. However, despite the widespread lockdown caused by COVID-19 in some areas, the concentrations of many pollutants, including sulfur dioxide and ozone, have increased [ 36 – 40 ].…”

Reduction of Air Pollution in Poland in Spring 2020 during the Lockdown Caused by the COVID-19 Pandemic

“…However, we used data only from stations where complete 10-year time series was available, while in 2019-2020 the number of stations increased. On a national scale, other studies have reported a 19% reduction of PM 2.5 concentrations in China [48], a 21% reduction in Italy and a 20% reduction in Chile [49]. Although agreement between different studies is encouraging, it has to be noted that environmental conditions across different countries differ significantly, COVID-19-related restrictions were not imposed exactly at the same time worldwide and the time span of analysed time series differed (in this study the longest being a 10-year perspective).…”