Satellite images from Nasa show pollution over China has cleared due to the coronavirus epidemic closing factories and keeping people inside their homes.
The Chinese government has operated strict curfews and isolation policies to curtail the spread of the deadly virus that has killed more than 2,850 people globally.
This has partly led to a decrease in nitrogen dioxide levels over the past eight weeks, according to Nasa and the European Space Agency (ESA).
Fei Liu, Air Quality Researcher at Nasa’s Goddard Space Flight Center, said: “This is the first time I have seen such a dramatic drop-off over such a wide area for a specific event.”
Nasa and the ESA used pollution monitoring satellites to analyse the changes and then released two maps to show the differences.
The first map shows how Beijing and Shanghai was covered with large clouds of gas for most of January.
In the second map from February, this drastically changed after the air cleared when coronavirus epicentre Wuhan and other areas were put in lockdown.
The levels of nitrogen dioxide, which is emitted by cars and factories, initially started to drop in Wuhan when roads and businesses were shut.
The drop in nitrogen dioxide was also helped by new environmental regulations and the Lunar New Year holiday when people were off work.
Meanwhile, a further three patients in England have tested positive for coronavirus, bringing the total number of confirmed cases in the UK to 23.
Two of the patients had recently travelled back from Italy while the other had returned from Asia, Chief Medical Officer Professor Chris Whitty said.
The three cases – one in Gloucestershire, one in Hertfordshire and another in Berkshire – are being investigated and any individuals who had contact with the patients are now being traced.
More than 10,000 people in the UK had been tested for the virus, also known as Covid-19 – with 23 confirmed as positive.
The number of people sickened by the virus climbed to more than 85,000 globally on Saturday.