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 NO2 – 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.

The drop in NO2 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 NO2 in eastern and central China were significant – 10-30% – lower than what is normally observed for this time period, Nasa said.

"The reductions in air pollution in China caused by this economic disruption likely saved twenty times more lives in China than have currently been lost due to infection with the virus in that country,"