China has seen a drastic decrease in pollution since the coronavirus epidemic emerged there in December, according to satellite images by NASA and the European Space Agency.
The maps released by the agencies on Sunday shows levels of nitrogen dioxide in the air over eastern China before and after a government imposed quarantine over large areas of the country in late January.
Nitrogen dioxide is a noxious gas produced by vehicles, power plants and industry. It can cause or exacerbate respiratory problems, including asthma.
The gas levels decreased drastically after the quarantine started, starting in Wuhan, where the virus first emerged, then spreading outward, NASA scientists said.
Wuhan, which has 11 million residents, was put on lockdown, with transport links in and out of the city closed off. The city’s Hubei province, home to some 40 million, was also largely isolated from the rest of the world. Factories and other workplaces in the industrial region were temporarily closed.
“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.
Air pollution levels generally drop during the Lunar New Year holiday as businesses and factories close in late January and early February, but the amount of nitrogen dioxide in the air this year was much lower than in previous years, and has remained lower since the holiday’s end.
The researchers said they saw a drop in the pollutant during the economic recession in 2008, but the decrease came more slowly.
Since the start of 2020, including before the quarantine, nitrogen dioxide levels were 10 to 30 percent lower in eastern and central China than in previous years.
The images were produced using data collected by monitoring instruments on the European Space Agency’s Sentinel-5 satellite and NASA’s Aura satellite.
The novel coronavirus has infected some 89,000 people globally and killed 3,000 in over 60 countries, with the vast majority of cases in mainland China. Israel has confirmed 12 cases and no deaths.