SNP ministers have been warned by a government document that poor air pollution levels “could potentially amplify” the heath impacts of Covid-19 if the infection is “still in circulation at significant levels”.

The alarm, raised in a Scottish Government report, points to a number of studies that have “identified an association between air pollution and both exacerbated symptoms and mortality levels attributed to Covid-19".

Air pollution is thought to be responsible for approximately 1,700 attributable premature deaths in Scotland each year.

The British Lung Foundation has called for low emission zone (LEZ) plans to be expanded beyond large cities while action has been demanded to ensure pollution levels are cut back permanently as people return to offices and given confidence to use public transport.

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The Scottish Government research stresses that during the initial lockdown last year, air pollution levels decreased as commuter traffic was cut – with a monitoring station in Glasgow showing a 72% peak decrease.

But the report warns that “pollution levels gradually increased again once lockdown measures began to be relaxed and in many locations gradually returned to pre-lockdown levels”.

It adds: “The significant decrease in pollution levels during lockdown was still not as much as expected, despite large reductions in traffic. This is because much of urban ambient NO2 is from heavy diesel vehicle emissions, and small numbers of trucks and buses contribute disproportionately to pollution levels.”

The document stresses that if the spread of infection remains at high levels as restrictions are eased next week and then again on August 9, the return to pre-pandemic levels of air pollution could add to the strain on the NHS.

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Scottish Government research will inform “how to support employers to encourage sustained home working as businesses recover from the pandemic”, the report adds.

But fears have been raised about giving people the confidence to use public transport again, particularly if high infection rates remain, despite the progress of the vaccination programme.

Earlier this year, ScotRail’s managing director, Alex Hynes, told a Holyrood committee that it was unlikely passenger numbers would return to normal, even when the pandemic has been resolved.

He said: “Nobody knows how passenger demand will recover, rebound, emerge post-pandemic.

“Roughly one third of our traffic is commuters. Will we go back to pre-pandemic levels of commuting? I don’t think so.”

Joseph Carter, head of Asthma UK and British Lung Foundation Scotland, has called for low emissions zones to be expanded beyond Edinburgh, Glasgow, Dundee and Aberdeen.

He said: “We welcome the publishing of the clean air strategy for Scotland and are glad it considers the decimating effect that Covid-19 has had on the nation’s lung health.

“The evidence cited within the report confirms what we’ve long suspected about the risk that long-term exposure to pollution has on people’s respiratory health.

“Lockdowns temporarily reduced the levels of air pollution we were exposed to due to the huge reduction in traffic on our roads and many people reported an improvement in their lung condition as a result.

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“As we begin to return to normality, it is vital that the Scottish Government take action against air pollution and expand the proposed low emission zones (LEZs) further than just out four main cities to protect our lung health no matter where we live in Scotland."

Scottish Labour’s net zero, energy and transport spokesperson, Monica Lennon said: “Air pollution is damaging to the environment and poses a serious threat to public health.

“It’s reckless to allow the health of the people of Scotland to be damaged by unacceptable levels of pollution, when preventative measures are staring us in the face.

“The risks posed by climate crisis and Covid-19 should be a wake-up call to the Scottish Government to take radical and urgent action to invest in active travel, reduce car dependency and make public transport free.”

The Scottish Conservatives have called for a clear strategy to be drawn up to tackle air pollution.

The party’s net zero spokesperson, Liam Kerr, said: “As restrictions continue to ease, SNP ministers cannot simply accept we go back to a trend of rising air pollution levels.

“We all recognise that tackling the climate emergency is one of the biggest challenges we are facing as we look to achieve a net-zero society.

“Rising air pollution levels are proven to have devastating health impacts as well, including links with Covid cases.

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“It is imperative SNP ministers act on this report and set out a clear plan to encourage people to safely use public transport once again, something that will help to drive down air pollution levels.

“All too often when it comes to tackling rising pollution levels, the SNP are full of warm words but little meaningful action and that attitude must change.”

A Scottish Government spokesperson said: “We’re continuing work to help introduce Scotland’s low emission zones. This will protect public health by improving air quality in our four biggest cities.

“Funding for active travel is now at record levels – with over £500 million being invested over the next five years to support walking, wheeling and cycling infrastructure, access to bikes and behaviour change schemes.

“We are also investing £500 million for bus priority infrastructure to tackle the negative impacts of congestion on bus services. This aims to make bus trips faster and more attractive to passengers.”