Coronavirus Lockdowns and the Impact on Global Nitrogen Dioxide

by | Jun 16, 2020 | 2020, COVID-19, Environmental Health, Lung Cancer, Pollution, Respiratory Health

Written by Joyce Smith, BS. Levels of nitrogen dioxide (NO2), a major pollutant, were significantly reduced in response to lockdowns following the COVID-19 pandemic, while simultaneously a secondary pollutant called ground level ozone was significantly increased in China.

COVID-19 - Lung HealthNO2, among the highest air polluters in industrialized areas, functions as a catalyst for ozone formation and as a precursor of secondary inorganic aerosols that affect our climate and our physical health 1. Fossil fuel combustion contributes 65% of global total NO2 emissions with forest fires, lightning and soils making up the remaining 35%. Even our human activities contribute substantially to increased NO@ levels, with the exception of Sundays or days of rest when levels drop substantially in most countries 2 and during public holidays such as the Chinese New Year 3. Using satellites and in situ measurements, many countries with regulated NO2 levels have been able to quantify the impact of short-term emission regulations during events such as the Olympic Games 4 and the Shanghai World Expo 5.

The global COVID-19 pandemic, with its subsequent social distancing and isolation, has disrupted social and economic activities, and even poses the risk of a global recession 6. Bauwens and colleagues 7 investigated the impact of social isolation and economic suppression on NO2 levels in the eight major epicenters of the COVID-19 outbreak: China, South Korea, Italy, Spain, France, Germany, Iran, and the U.S. Using two high resolution satellite sensors, the Tropospheric Monitoring Instrument (TROPOMI), on board the  Copernicus Sentinel-5 Precursor satellite launched in October 2017 8, and the Ozone Monitoring Instrument (OMI) 9 launched in 2004, enabled them to collect accurate global data on NO2 levels. Data showed that nitrogen dioxide pollution in some cities in northern China (Wuhan and Xi’an) and other cities in Western Europe and the  U.S. that were most impacted by lockdown measures, decreased by as much as 60 % as compared to the same time last year. In addition to nitrogen dioxide, particulate matter pollution (particles smaller than 2.5 microns) has decreased by 35 percent in northern China. (Particulate matter is composed of solid particles and liquid droplets that are small enough to penetrate deep into the lungs and cause damage).This unprecedented significant 60% drop in emissions is comparable only to the short-term reductions in China’s emissions due to strict regulations during events like the 2008 Beijing Olympics 4. However, in many cities, nitrogen dioxide pollution decreased by an average of 40 % (Chinese cities) and by 20 to 38 % over cities in Western Europe and the United States that were less impacted by the  lockdown, as compared to the same time in 2019. NO2 pollution did not decrease over Iran, one of the earliest and hardest hit countries, possibly because complete lockdowns weren’t in place until late March and before that, stay-at-home orders were largely ignored. A dip in emissions did occur during the Iranian New Year holiday after March 20, which is probably due to the fact that it is an annual Iranian celebration.

According to a new study by Shi and  Brasseur 10, data collected from 800 local Chinese monitoring stations revealed that the large drop in levels of NO2 (a primary pollutant) led to a simultaneous increase in secondary pollutants. While mean levels of PM2.5 (30%) and NO2 (40-60%) decreased substantially in the city of Wuhan China, the ozone concentrations increased by a factor of 2.0± 0.2 over the lockdown period following the coronavirus outbreak. Ozone is a secondary pollutant formed when sunlight and high temperatures catalyze chemical reactions in the lower atmosphere. In highly polluted areas, particularly in winter, surface ozone can be destroyed by nitrogen oxides, so ozone levels can increase when nitrogen dioxide pollution goes down. Therefore, although air quality has largely improved in many regions of China, surface ozone remains a problem 10.

Source: Bauwens, M., S. Compernolle, T. Stavrakou, J‐F. Müller, J. van Gent, H. Eskes, P. F. Levelt et al. “Impact of coronavirus outbreak on NO2 pollution assessed using TROPOMI and OMI observations.” Geophysical Research Letters (2020): e2020GL087978.

©2020 American Geophysical Union. All rights reserved.

Posted June 15, 2020.

Joyce Smith, BS, is a degreed laboratory technologist. She received her bachelor of arts with a major in Chemistry and a minor in Biology from  the University of Saskatchewan and her internship through the University of Saskatchewan College of Medicine and the Royal University Hospital in Saskatoon, Saskatchewan. She currently resides in Bloomingdale, IL.

References:

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