The first few weeks of the Covid-19 lockdown cut levels of dangerous pollutants by as much as 40% in towns and cities, according to new research.

Data gathered on behalf of the Department for Environment, Food and Rural Affairs (Defra) found dramatic drops in nitrogen oxides and nitrogen dioxide between the start of lockdown and April 30.

While the positive effects of the shutdown on air quality was not felt evenly across the country, urban environments saw drops in the levels of nitrogen oxides of between 30% to 40% on average.

There is significant evidence these gasses exacerbate and may even cause asthma over time, and have been linked to heart disease, diabetes and may have an impact on birth outcomes.

Nitrogen dioxide also dropped by an average 20% to 30% in urban centres, with the greatest falls recorded at roadsides.

The gas was of particular interest to scientists during the coronavirus pandemic because it inflames the lungs and can reduce immunity to lung infections.

One of the biggest drivers in the drop in pollutants is believed to be road traffic, which fell by 70% over the period in question according to the Department for Transport.

The data was published following a call for evidence by Defra’s Air Quality Expert Group.

More than 50 organisations submitted data by the close of the call on April 30, including university research groups, commercial organisations, industry bodies and local authorities.

One of its stated aims was to try and gain insight into the impact of air quality on viral infection.
It said it would “not be surprising” if there was a link between an individual’s exposure to air pollution and the occurrence or the severity of Covid-19 infection.

But it added: “Such studies require very careful control for confounding influences, and further work is needed before there can be confidence in their findings.”

Another of the initial findings was a 55% drop in daytime carbon dioxide emissions in central London, and around 20% across the country.

As we begin to recover from Covid-19, we must keep these levels down and push them lower, to protect everyone’s lungs

While not a gas of specific concern to lung health, the report said it can act as a marker for “overall reduction in fossil fuel combustion from all sources” and associated pollutants such as nitrogen oxides and fine particulate matter.

The report’s authors warned much of the data obtained has yet to be peer reviewed or given final quality assurance.

They said they expect more comprehensive peer-reviewed research will be published towards the end of the year.

Sarah MacFadyen, head of policy and public affairs at Asthma UK and the British Lung Foundation, said: “This report is vital to show the impact of the pandemic on air quality.”

“As we begin to recover from Covid-19, we must keep these levels down and push them lower, to protect everyone’s lungs,” she said.

“The report highlights that there could be links between exposure to air pollution and how likely someone is to develop Covid-19, or to develop a more severe form of Covid-19.

“We urgently need more research to understand this link”

Ms MacFadyen called for new legal limits on fine particulate matter in line with World Health Organisation recommendations, and for these new standards to be met by 2030 at the latest.

Asthma UK and the British Lung Foundation also want to see planned Clean Air Zones that have been delayed in some cities due to the pandemic to be implemented as soon as possible.