In an effort to curb the spread of the novel coronavirus, which has affected more than 80,000 and killed more than 3,000 people in China, the country has shuttered factories and quarantined many of its citizens. However, as the country's factories slowly return online from the aftermath, there has been one unexpected side effect to the decline in economic activity.

Pollution has vanished.

Satellite imagery from NASA and the European Space Agency have spotted an enormous decline in airborne pollutants, specifically nitrogen dioxide (NO2), in large areas of China, according to a statement from NASA's Earth Observatory.

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“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’s Goddard Space Flight Center, said in the statement.

The images show a drastic decline in nitrogen dioxide levels from January 1-20 (before the quarantine in Wuhan, China) to February 10-25, during the quarantine. NASA scientists added that the reduction in NO2 pollution "was first apparent near Wuhan, but eventually spread across the country."

Nitrogen dioxide is a harmful gas that is emitted by factories and "primarily gets in the air from the burning of fuel," according to the Environmental Protection Agency. It is considered harmful to the environment as well as humans, resulting in respiratory problems.

This type of decline in nitrogen dioxide pollution has occurred twice in recent memory: during the Great Recession (spread over several countries) and the 2008 Beijing Olympics. It was localized around China's capital and returned soon after, NASA added.

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Although not all of the drop in pollutants can be attributed to the disease — NASA added some of it could be due to the Lunar New Year holiday — the government agency explained that "there is evidence that the change is at least partly related to the economic slowdown following the outbreak of coronavirus."

In prior years, the decline in pollutants would pick back up after the Lunar New Year holiday ended. But not this year.

“This year, the reduction rate is more significant than in past years and it has lasted longer. I am not surprised because many cities nationwide have taken measures to minimize spread of the virus," Liu said.

The coronavirus (COVID-19) has affected more than 89,000 people worldwide and resulted in more than 3,000 deaths, according to data compiled by Fox News.

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