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Bad air around Covid-19

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How resuming pollution levels after the lockdown could affect a second wave of coronavirus patients.

The world feels emptier under lockdown. Traffic is down with fewer people on the streets. We burn less coal and oil. All this helps to clean up the air. Online users in various parts of the world post images of unseen blue and unpolluted skylines on social media. Better air quality is a boon. “It offers a glimpse of what the air will be like in the near future when the transition to clean energy is further along” says Lauri Myllyvirta from the Center for Research on Energy and Clean Air (CREA). But what comes after the lockdown remains uncertain.

So far, low air pollution levels helped to avoid between 7,000 to 21,000 air pollution-related deaths, experts at CREA have calculated. In normal times bad air is among the top killers, exceeding death tolls for infectious diseases and for violence.

With fear of a resurgence in air pollution after lockdown, researchers investigate the link between bad air and Covid-19 mortality. This makes sense. Organisations like the CDC in the US list asthma - also linked to bad air - as a significant Covid-19 risk factor.

For some places in the UK this could become problematic as asthma deaths surged last year to levels not seen since the early 2000s (see chart). This is partly due to air pollution, experts say. In England clinical commissioning groups (CCGs) such as NHS Windsor, Ascot and Maidenhead CCG, NHS Nottingham West CCG or NHS Bradford City CCG are among those that saw their asthma-related deaths surge over time, E&T found (see graph).

Asthma rates in England and Wales

Image credit: Ben Heubl, ONS

There are a number of preliminary non-peer-reviewed studies that draw a direct link between higher air pollution and Covid-19 mortality. Among the most credible, experts say, is a US national study by a team at Harvard University. An increase of 1μg/m3 in PM2.5 (fine particulate matter) corresponds with an 8 per cent surge in the Covid-19 death rate, it found. The study received a lot of heat for its limitations. It has proved difficult to research the topic in the midst of a global pandemic. Obtaining peer-reviewal status can take anything between months to years, time we might not have, experts argue. It is hard to avoid bias when data is inaccessible. By the end of April, the team updated its research methodology to adjust for additional confounding factors, such as the epidemic's spread, social distancing policies, and age.

If the findings hold firm for other places like the UK extra precautions might need to be considered for loosening lockdown measures. E&T considered UK locations where PM2.5 levels are usually higher (see the red circles on the map). These places largely correspond with locations where the Covid-19 death rate is also highest. Many of those are in London. Local authorities with the lowest average PM2.5 levels in 2018 (in yellow) largely encounter fewer Covid-19 deaths (as a share of all deaths).

Covid-19 rates and pm2.5 levels

Image credit: Ben Heubl, ONS

In April, scientists at Cambridge University published preliminary results of a link between living in an area of England with high levels of air pollution and the severity of Covid-19.

“Air pollution has made the pandemic materially worse, and that is an additional reason to take action on air quality, if one was needed”, adds Myllyvirta.

Government and policymakers may want to tread carefully when it comes to the time after the lockdown. “With the real possibility of a second wave of infections occurring as we come out of lockdown it would be unwise to allow emissions of pollutants to ramp up quickly, Prof Frank Kelly, at Imperial College London tells E&T. “This would lead to decreased air quality which in turn would lead to increased respiratory inflammation in some individuals which would increase their sensitivity to Covid-19”.

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