Images of alarming sulphur dioxide forecasts in Wuhan are not a sign of mass cremations, experts have said.

Maps from the weather service Windy.com were widely shared online last week, purporting to show high SO2 levels at ground zero of the coronavirus outbreak.

It prompted speculation that the gas was being emitted in vast quantities because of a surge in cremations.

But Windy.com says its maps are a forecast rather than a current snapshot, meaning they could not be reflecting events in recent days.

China's environment ministry has also rejected the claims, insisting that SO2 levels in Wuhan are normal.

This map was widely shared last week, purporting to show high SO2 levels in Wuhan - but the website Windy.com says it is a forecast, not a snapshot which could reflect current events

Windy.com gets its SO2 data from a NASA model called GEOS-5, but does not display archive data, the website says. The images which circulated on social media are not satellite pictures.

NASA meteorologist Dr Arlindo M da Silva told Full Fact the forecasts are based on past data and do not 'assimilate real satellite data'.

'These emissions do not account for the day-to-day variations in SO2 emissions and as such cannot account for sudden changes in human activity,' he explained.

'In [the model], day-to-day variations in SO2 are due to variations in the meteorological conditions, in particular winds.'

The images which circulated on social media had suggested that SO2 levels in Wuhan could reach a staggering 1,350 micrograms per cubic metre (µg/m3).

For comparison, the World Health Organisation (WHO) says a dosage of 500 µg/m3 should not be exceeded for more than 10 minutes.

However, Chinese authorities say that the figures 'could not be trusted'.

The country's National Environmental Monitoring Centre said the forecast was a 'serious distortion', according to the state-run Global Times.

Sulphur dioxide readings in Wuhan were never higher than 11.5 µg/m3 in the week up to February 9, the centre said.

The Czech-based website's data for Beijing and other cities also 'deviated greatly from the facts', they said.

Wuhan has been in lockdown for weeks with 11million people in quarantine, meaning that claims about the city are difficult to verify.

China has decreed that the bodies of coronavirus victims should be cremated in low-key funerals to prevent large public gatherings.

The country's National Health Commission said earlier this month that bodies should be 'cremated close by and immediately'.

Health workers in protective suits stand by the body of a man wearing a face mask who died in Wuhan. China has decreed that virus victims be quickly cremated

Sulphur dioxide is released in cremations and when medical waste is incinerated, but also when fossil fuels are burned.

The World Health Organisation says that high or prolonged exposure to sulphur dioxide can cause 'serious risks to health'.

The gas can play a role in health problems such as asthma, lung inflammation and reduced lung function, experts say.

'SO2 can affect the respiratory system and the functions of the lungs, and causes irritation of the eyes,' the WHO says.

'Inflammation of the respiratory tract causes coughing, mucus secretion, aggravation of asthma and chronic bronchitis and makes people more prone to infections of the respiratory tract.

'Hospital admissions for cardiac disease and mortality increase on days with higher SO2 levels.

'When SO2 combines with water, it forms sulphuric acid; this is the main component of acid rain which is a cause of deforestation.'

The total coronavirus death toll jumped to 1,770 today after 105 more people died, China's National Health Commission said.

More than 70,500 have now been infected nationwide by the virus, which first emerged in December in Hubei province before spreading across the country.

Outside China, the biggest cluster of infections is from the Diamond Princess cruise ship in Japan, where an additional 99 cases were revealed on Monday.

That brought the total to 454 diagnosed despite passengers being confined to their cabins during a 14-day quarantine.