If you live in a city like London one thing you might have been wondering throughout lockdown is: well this is rubbish in all sorts of ways but on the bright side at least pollution is going to fall. But has it? Some surprising answers from the data...

There are many different forms of air pollution in cities but often scientists focus on oxides of nitrogen eg NO2 and particulate matter (PM10 and PM2.5). PM in particular captures a broad range of pollutants both from cars, wood burning and other air quality issues.

By the way this matters because poor air quality costs lives. Indeed it can damage the lungs and leave you more vulnerable to COVID-19. So many had hoped that at least some lives might be saved thanks to lower pollution due to the lockdown.

And on one of those fronts, NO2, pollution levels are indeed down in London. You can see they’ve dropped by 55% around Marylebone Road and 36% by Euston road, two of the capital’s busiest roads. Reductions slightly less dramatic elsewhere tho.

But here’s the thing: particulate matter pollution ROSE following the lockdown. And not just a little. Up to the highest level so far this year. That's both PM10 and PM2.5. Up near roads, up elsewhere too. In spite of the lockdown, in spite of the fall in road traffic.

As the Kings College report which collected & analysed this data points out, far from offsetting #COVID19 rise in mortality, higher pollution levels might be exacerbating it - tho difficult to model (& lockdown means ppl staying inside away from pollution) https://assets.ctfassets.net/9qe8184l2nz4/2TM8WJUt2w1cHecdjkVIRQ/2e5a91667d676b3c63f1e748156b68c4/ERG_response_to_Defra.pdf

Still it's a reminder that when it comes to reducing pollution, UK cannot do it alone. Much of the extra PM pollution, says Kings, is “imported” - from other European countries, where emissions are higher. Another reminder that while we're an island we're not an island

Finally, the good news is while PM pollution levels were high in April it kills from more up to date measures as if they've now dropped. Daily measures here: http://www.londonair.org.uk/LondonAir/nowcast.aspx

Turns out a Harvard study has found that more particulate matter pollution in the air is linked with higher #COVID19 mortality. It's long-term exposure they're modelling but even so, v striking that PM2.5 was v v high in London during the peak period for mortality ( see thread)