Nasa satellite images show a dramatic decline in pollution levels over China, which the US space agency believes is “partly related” to an economic slowdown due to the coronavirus.

Nasa scientists said the reduction in nitrogen dioxide levels, the noxious gas emitted from motor vehicles, power plants and industrial facilities, was first evident near Wuhan city, the source of the outbreak, but then spread across the country.

Images from Nasa and the European Space Agency (ESA) pollution monitoring satellites were used to compare the first two months of 2019 with the same period this year.

The maps show NO 2 – nitrogen dioxide – values across China from 1-20 January, before the quarantine, and 10-25 February, during the quarantine. The decline comes as China’s manufacturers stop work in an effort to contain coronavirus.

“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 centre.

Facebook Twitter Pinterest Nasa maps showing NO2 values over Wuhan during January and February. Photograph: Nasa Handout/EPA

Liu said there was a drop in NO 2 over several countries during the economic recession that began in 2008, but the decrease was gradual. Scientists had also observed a significant reduction around Beijing during the 2008 Olympics, but pollution levels rose again after the Games ended.

The drop in NO 2 levels in 2020 also coincided with lunar new year celebrations in China and across much of Asia, when businesses and factories generally close. Usually levels increase at the end of this festive period.

While the lunar new year may have played a role in the recent drop-off, researchers believe this decrease is more than a holiday effect or weather-related variation. Levels of NO 2 in eastern and central China were significantly – 10-30% – lower than what is normally observed for this time period, Nasa said.

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