Air pollution in Europe is decreasing as cities crash, mirroring what has happened in other parts of the world, experts said.
Satellite imagery has already revealed dramatic reductions in polluting nitrogen dioxide concentrations in China and northern Italy, coinciding with blockages to tackle the coronavirus pandemic.
And as everyday life breaks up in the UK, with a sharp reduction in traffic causing much of the air pollution in cities, air quality has started to improve here.
But it is still unclear what the health impacts of reducing air pollution will be, which causes around 40,000 early deaths in the UK each year.
Air pollution is linked to health problems including stroke, heart disease, tumors and lung diseases, respiratory diseases and infections, as well as blocking the growth of children’s lungs.
Monitoring shows the levels of key pollutants that nitrogen dioxide, which mainly comes from vehicle exhausts, and the fine particles known as PM2.5, are low across London.
Data from the London Air Quality Network, operated by King’s College London, show a decrease in both pollutants from the average levels, particularly at the roadside.
Professor Alastair Lewis, of the National Center for Atmospheric Science, University of York, said: “Air quality has started to improve in many cities in the UK, mirroring what has been seen in other countries that have limited the travel and outdoor activity levels.
“This is mainly a consequence of lower traffic volumes and some of the most noticeable reductions have been nitrogen dioxide, which mainly comes from vehicle exhaust.
“However, fine particles (PM2.5) have also decreased significantly. In London, for example, PM2.5 is significantly lower than would be expected at this time of year at the roadside, and these reductions also extend to the suburbs. “
Without a safe level of these pollutants, any improvement in air quality offers health benefits, he said, although in the midst of a respiratory crisis the best air quality could have only a small, albeit positive, effect.
Professor William Collins, a professor of meteorology at the University of Reading, said that much of the pollution of the air breathed comes from traffic.
Traffic pollution levels have plummeted with many countries blocked, while exposure to pollutants will also be reduced by people who remain off the road.
But he said: “It is too early to say whether these improvements will compensate for Covid-19’s mortality or other health problems from being confined indoors.”
Anna Hansell, professor of environmental epidemiology at the University of Leicester, said that air pollution would be dramatically in line with travel restrictions and the reduction of industrial emissions, as has already been seen in Wuhan, China and northern Italy , highly polluted.
But he said: “Unfortunately we cannot see reductions in air pollution translated into direct falls in mortality.”
There would be an increase in the number of deaths from Covid-19, as well as impacts on financial difficulties and stress, with poverty increasing the risk and severity of chronic diseases and mortality rates, he said.
There would also be negative health impacts on isolation for the elderly and the impact of restrictions on access to health care for other diseases.
But there should be a reduction in the transmission of various infections due to social distancing, leading to reductions in deaths from diseases such as non-Covid-19 pneumonia, which currently causes 25,000-30,000 deaths a year in England, he said.
The professor. Hansell also said that research was needed to see if pollution levels had contributed to the coronavirus in Wuhan and northern Italy, directly affecting infection rates or affecting gravity causing more heart and lung disease, which put people at greatest risk of serious Covid-19 disease.
While a reduction in traffic and industrial activity was already reducing some air pollutants, Dr Eiko Nemitz, of the UK’s Center for Ecology and Hydrology, said that pollution from sources such as household wood burners could increase and agricultural emissions would continue.
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The drop in pollutants such as nitrogen dioxide shows what could happen in the future when transportation moves to an electric fleet, according to Professor Hugh Coe, director of the Manchester Environmental Research Institute of the University of Manchester.
But he said: “Electric vehicles will not reduce particulate emissions from non-exhaust sources such as brake and tire wear, which will need better public transport infrastructure to reduce dependence on the use of private vehicles.” .
The research comes shortly after a study has uncovered evidence that the Earth’s ozone layer is recovering.
Ozone levels have declined rapidly in recent years, leading to an agreement known as the Montreal Protocol in force in 1987 to end the use of ozone depleting substances (ODS) worldwide.
Now, researchers from the University of Colorado Boulder have revealed that attempts to reduce harm appear to have been successful.
Antara Banerjee, who led the study, explained: “This study adds further evidence demonstrating the profound effectiveness of the Montreal protocol.
“Not only has the treaty stimulated the healing of the ozone layer, it is also driving recent changes in air circulation patterns in the southern hemisphere.”