NASA scientists revealed satellite images that showed air quality trends in several regions of China. A decrease in nitrogen dioxide, a primary air pollutant released from fossil fuel burning, has been observed in the troposphere due to quarantine measures against coronavirus, Lunar New Year and economic recession.

Coronavirus and its impacts

As of March 10, 2020, the global coronavirus (COVID-19) related deaths have crossed 4,000 while 113,000 people have been infected with the virus. While COVID-19 has caused a recession in the global economy, as several sporting, cultural, music and scientific events have been either delayed or canceled. Tourism, hospitality, airline, energy, and the pharmaceutical sector are under a lot of stress since the outbreak.

While China along with other countries is trying to control the spread of COVID-19, fewer people are traveling which means fewer vehicles are on the road, fewer factories and industries are running. This is why emissions have reduced and in some places clear skies are observed. Air pollution causes almost 1 million premature deaths in China each year. Fine particles (PM 2.5) can enter the bloodstream through the respiratory system and are linked to respiratory issues like asthma and heart attacks.

China is the biggest contributor to greenhouse gas emissions in the world but current weeks have shown up to a 30% reduction in air pollution. The world has seen environmental activism, protests, campaigns, the rise of environmental organizations, sustainable/green businesses, carbon tax, regional and global environmental agreements being signed. But a microscopic pathogen that does not even have a cell and probably isn’t even alive may be capable of accomplishing what our political leaders thus far could not.

A significant decrease in nitrogen dioxide levels has been observed in China, according to NASA and the European Space Agency (ESA) pollution monitoring satellites. The decline in emissions is partly related to the economic slowdown in China following the coronavirus outbreak. According to NASA decrease in nitrogen dioxide pollution was first apparent near Wuhan, but eventually spread across the country as millions of people have been quarantined.

Map showing air pollution levels in China after coronavirus quarantine
Image Credit: NASA Observatory

The maps reveal NO2 values across China from January 1-20, 2020 (before the quarantine) and February 10-25 (during the quarantine). The data was collected by the Tropospheric Monitoring Instrument TROPOMI) on ESA’s Sentinel-5 satellite

“This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event,” said Fei Liu, an air quality researcher at NASA. Liu recalls seeing a gradual decrease in nitrogen dioxide over several countries during the 2008 financial crisis Scientists also observed a significant reduction around Beijing during the 2008 Olympics, as the Chinese government shut down factories and limited car travel before and after the Olympic Games. The effect was mostly localized around that city, and pollution levels rose again once the Olympics ended.

“It would be the wrong assumption to say that the COVID-19 was beneficial to health because of these air pollution reductions,” says Jill Baumgartner, associate professor at McGill University.

“The health impacts from the virus itself, the stress on the health-care system, the stress on people’s lives — those health impacts are likely to be much greater than the short-term benefits of air pollution on health,” she says. For example, people isolated at home and those who avoid crowds may also have been exposed to increased indoor air pollution due to smoking, traditional wood or coal stove heating.

Maps revealing nitrogen dioxide levels in China due to coronavirus quarantine
Image Credit: NASA Observatory

The maps above reveal nitrogen dioxide levels over three periods in 2020: January 1-20 (before Lunar New Year), January 28-February 9 (around New Year celebrations), and February 10-25 (after the event).  The drop in nitrogen dioxide coincided with the Lunar New Year celebrations in China. To celebrate the festival, businesses and factories in China remain closed from the end of January to early February. Barry Lefer a scientist at NASA said, “There is a decrease in the number of air pollutants in China around the Lunar New Year festival.” Barry noted that overall values in 2020 were lower than in 2019 due to strict environmental regulations enforced by the government over the past few years.

Global crises in the past have shown to decrease the emission of harmful gases and air pollutants but the increase in pollution and emission increased as soon as the world moved on and recovered. Therefore, it is expected that we will experience a decrease in emissions and air pollution, as the virus has started to spread all over the world. Once the coronavirus crisis is averted, traffic returns to normal, factories and industries start working again to offset economic losses, the air pollution and emission of gases will resurface in China and in other parts of the world.


Airborne Nitrogen Dioxide Plummets Over China.
NO2 amounts have dropped with the coronavirus quarantine, Chinese New Year, and a related economic slowdown.

Image of the Day | March 2, 2020 | NASA Earth Observatory, USA.

CITE THIS ARTICLE: "Dramatic effect of Coronavirus quarantine on air quality of China," in Geoscience Daily, March 10, 2020,