Recently, the UK recorded air pollution as a cause of death for the 1st time: 9yr old Ella Kissi-Debrah lived in Lewisham, London, & officially died from acute respiratory failure, severe asthma, & air pollution.

A 🧵on air pollution & why it matters:
First: we already know that air pollution is dangerous: the WHO estimates that it kills 4 to 7 million *each year*. But recent research has been showing just how dangerous & pernicious it is-and how the effects can go far beyond respiratory conditions...
It's bad for the economy: a study used satellites to measure impact of air poll on economic activity. A 1μg/m3 increase (0.1 of mean) in PM2.5 (particular matter of diameter <2.5µm) caused 0.8% fall in real GDP via ⬇️ labour productivity & ⬆️ absenteeism.
Bad for babies: in her job market paper, @NannaFukushima finds that the reduction in air pollution between 1957 & 1973 due to the UK's Clean Air Act can account for *70% of the decline in infant mortality* over that period.
Air pollution is bad for your brain too: in chess, an increase in PM2.5 of 10µg/m3 raises the chance of an error by 1.5pp, & increases the magnitude of the errors by 9.4%--and these results are worse under time pressure.
Bad behaviour: attending a school downwind of a highway (=> greater air poll.) associated w/ 0.04 of a std dev in decreased test scores, *4.1pp increase in behavioural incidents*, & a 0.5pp increase in rate of absences compared to attending upwind schools.
Bad for discourse: Heyes, @riversNic, and Schaufele find that if the same (Canadian) politicians give a speech on a polluted day, with PM concentration exceeding 15µg/m3, there is a 2.3% reduction in the quality of the speech. (Sadly no Canadian MP gif!)
It's worse than just cognitive decline: leveraging within- & between-county quasi-random variation, a 1μg/m3 increase in decadal PM2.5 increases the probability of a dementia diagnosis by 1.68pp according to this NBER working paper  by @ketchman et al.
Bad for bumps: Vehicle traffic is a big contributor to air pollution. But air pollution affects drivers! Lutz Sager finds increase of 0.3–0.6% in # of vehicles involved in accidents per day for each additional 1μg/m3 of PM2.5 using UK data from 2009--2014.
But all PM is bad for health: this Nature Sustainability paper uses measurements of Saharan dust to show that a 10μg/m3 increase in annual mean PM2.5 causes a *24% increase* in infant mortality across Sub-Saharan Africa.
A lot of these papers talk about PM2.5 and, by this stage, you're probably wondering what it is and how big a micron (1μm) is. The EPA has the handy diagram below. The WHO recommend keeping PM2.5 below 10μg/m3. The message is: keep PM levels in check.
Okay, back to the UK: let's look at some data on PM2.5 for 2010-2019. *Caveat:* some local authorities changed names/structure over that period, and I have excluded them. Data are from DEFRA and are population-weighted annual means: 
In the UK, anthropogenic PM2.5 has *slightly* fallen since 2010 (but it's still far higher than the background level we'd have without human sources). However, most regions are below the WHO guideline.
Looking at the mean concentration by local authority for 2010-2019, we can see that the worst affected local authorities in each country are in built-up areas. London has a string of authorities with >10mg/m3

Pre-coronavirus, I worked in the UK's worst PM2.5 hotspot most days 😞
Where is the PM2.5 coming from (for the UK)? Analysis by DEFRA suggests domestic combustion (44%), commercial combustion (29%), & road transport (11%; though not all from exhaust fumes, a lot is from tyres and roads).
Progress is definitely being made (see this recent report: but even in the UK we need to reduce it more: for both health and wealth!
What's the long-term solution? Whichever way you cut it, electrification using clean energy sources is needed, and on a huge scale. Thankfully the grid is already using fewer fuels that are burned; and less burning = less PM2.5. But we're going to need a *lot* more electricity...
Renewables+fission are part of the solution, especially as solar & wind prices have absolutely plummeted. But we'll probably need *even more* than they can feasibly provide given economics, politics, and social factors.
One very ambitious & exciting additional solution is #nuclearfusion - so exciting that I'm writing a book about it! #TheStarBuilders tells the story of attempts to turn the Sun's power source into Earth's power source (with ~0 PM2.5)! Find out more here:
That's all folks, thanks for reading this thread. Did I miss any interesting recent research on air pollution and the effects of PM2.5? Reply and let me know!
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