[♪ INTRO]
London is famously foggy.
Sometimes that can mean a wistful stroll or another excuse for a cuppa tea, but when fog
mixes with the smoke and chemicals produced by industry, it becomes something new: smog.
And for a couple of centuries, London's smog could kill.
Really bad smogs could kill a thousand people in a few days, but no one did much about it
until 1952, when a five-day smog in London killed an estimated twelve thousand people.
It was called The Great Smog of London, and it helped wake up the country and the world
to the dangers of unrestricted pollution.
Fog is just a cloud that forms down here on the ground, which by itself isn't that bad;
you might not be able to see well when you're driving,
or you might not be able to land your plane, but it's nice.
But clouds can act like sponges, forming around and trapping whatever's already in the air.
This wasn't a problem until the 1200s, when a lot of London
switched from wood to coal for heating their homes.
Burning coal creates soot and smoke, which can irritate your lungs,
and also creates poisons like sulfur dioxide and carbon monoxide.
Sulfur dioxide, which is a sulfur atom bonded to two oxygen atoms, reacts with water to
form sulfuric acid, which can harm your internal organs, as you might imagine.
And carbon monoxide, which is one carbon and one oxygen, binds with the hemoglobin in your
blood to stop oxygen from getting around your body.
So when London started burning coal, all the smoke and chemicals mixed with the natural
fog, and it became thicker and darker as years passed.
It wasn't a health crisis at first,
but people did complain that the smoke smelled terrible.
And this was back in the 1200s, when everything smelled terrible already.
But it was easier to keep burning coal than to switch back to wood, so for centuries,
they just accepted the occasional thick, dark, smelly cloud hanging over the city.
As you do.
Things really got dangerous when the Industrial Revolution happened in the 1700s.
Because now, coal wasn't just heating homes.
It powered huge factories throughout the city, and all that extra smoke and soot made the
air in London's fogs much darker.
It became so common that a physician named Harold Antoine Des Voeux
invented the term "smog" to describe it.
Really smoggy days completely blacked out the center of the city, so that you couldn't
see more than a few meters ahead of you, even in the middle of the day.
The soot also irritated people's lungs, causing illnesses like bronchitis
to become more common.
Some people even suffocated from breathing so much smoke or the poisons in the air.
Individual smogs in 1873 and 1892 each killed over a thousand humans and livestock.
And we don't even know how many people died early from collecting soot in their lungs
over the course of their lives.
But coal kept London flourishing, so nobody did anything to stop it.
Then came The Great Smog.
On December 5, 1952, a thick fog rolled in and mixed with London's dirty air,
just like it did most winters.
But this time, high-pressure weather systems surrounded London
and kept the cloud from moving on.
So an especially dense, black smog stopped on London for five miserable days.
The smog was so thick that flights were grounded, most public transportation was canceled,
trains collided, and theaters and movies stopped,
because people couldn't see what they were watching.
This is difficult to imagine, this was 1952, not that long ago.
An estimated four thousand people died in those five awful days before the smog dissipated.
A lot of them suffocated because their lungs were inflamed from breathing in so much soot.
And with sulfur dioxide from the burning coal reacting with water vapor in the smog,
Londoners also spent those five days breathing air full of sulfuric acid.
That and the smoke contributed to respiratory and other health problems,
which killed around another eight thousand people in the following months.
Ultimately, roughly one in a thousand Londoners died because of The Great Smog.
Some people argued afterward that the spike in deaths was due to a flu epidemic, but scientists
have investigated that in all sorts of ways, and it's really unlikely that the flu could
have been anywhere near as devastating as the smog itself.
Four years later, Parliament finally passed a Clean Air Act that dictated
what kinds of fuels could be burned within the city.
It and other laws have helped rein in the smog problem in London.
But even today, London's air pollution lowers the life expectancy of a lot of people,
and is indirectly linked to tens of thousands of early deaths
every year throughout the United Kingdom.
Despite the Great Smog's devastation, it took a while
for other industrial powerhouses to take the hint.
New York City had a series of smogs in the 1960s that affected more than 16 million people,
and black, soot-filled rain coated Boston around the same time.
But eventually, lawmakers around the world stepped in.
Starting in the 1970s, laws got serious about limiting air pollution, forcing car companies
to make more efficient engines, and factories to produce fewer emissions.
Because it turns out, turning air into poison, is not a great idea.
Thank you for watching this episode of SciShow, you're great.
And a special thanks to all of our patrons on Patreon for making it happen!
If you'd like to help us make more episodes like this, so that everybody can have them,
regardless of whether they can pay, you can go to patreon.com/scishow,
and if you just want to support us by watching, please do that at youtube.com/scishow.
[♪ OUTRO]
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