Air Pollution Doesn’t Kill Like You Think It Does

The latest data on the health toll of air pollution from the World Health Organization finds it doesn’t kill people like you probably think it does.


How does air pollution kill?

The World Health Organization tallied up tallied up all the deaths all the deaths due to outdoor air pollution based on different causes. This graph shows the three major categories of deaths from air pollution. What would you think goes into those boxes?

Outdoor Air Pollution Kills WHO


My first thought would be lung cancer. Survey says?

Outdoor PM2.5 deaths not from lung cancer

Just 14%! Not nearly as large as I imagined.

Well, OK, lung cancer is just one type of lung problem. How about emphysema, bronchitis, and other lung diseases?


Hmm, we’re still only at 28% of deaths due to air pollution. So what’s hiding in that big blue piece of the pie?


Air pollution kills through heart disease not lung cancer

Heart attacks, strokes, and other diseases in our blood vessels. Really? It makes so much sense to look at our lungs because that’s where the air goes. But it turns out that we’re looking in the wrong direction. We should’ve been looking here:

Does air pollution really affect our heart and blood vessels? Here are three points of evidence.


1. More people have heart attacks on days with bad air pollution

A study in Boston found that on days with higher particulate air pollution (blue line), more people had heart attacks (red line).


Air pollution kills through heart disease

Now, we’re not talking about a wild epidemic of heart attacks. The base odds of heart attacks on any given day are low, probably one in millions. So a 50% increase is important, but it moves the odds from 1 in a million to 1.5 in a million.


2. Wearing a mask in polluted Beijing reduces blood pressure

But hey, heart attacks are for unhealthy old people, right? I’m just 32 years old. Well, two studies randomly assigned healthy adults in Beijing to wear a mask outside or not. No one had a heart attack, of course, but people without a mask had higher blood pressure and lower heart rate variability.


PM2.5 air pollution kills by raising blood pressure

3. Breathing purified air improves blood inflammation and constriction of veins

OK, OK. But maybe you’re a healthy young person, just 20 years old. Maybe your lungs are even “used to” the pollution. My friends in China joke that Chinese people have the strongest lungs in the world.

Researchers in Shanghai randomly assigned healthy college students to use a real purifier or a fake purifier for 48 hours in their dorm rooms. Here’s what the PM2.5 levels were like in their dorm with a fake purifier (blue) and a real purifier (yellow).


They tracked all sorts of effects on biomarkers. When they looked at effects on blood inflammation, the effects were pretty big!


Same for blood coagulation:


air pollution kills by attacking arteries

And constriction of veins:


air pollution kills harms blood pressure

But when they looked at effects on lung function, the effects were tiny and not statistically significant:


air pollution kills cardiovascular disease

That blew my mind. All this time we were looking in the wrong place!

If someone in Beijing or Delhi fell over and died of a heart attack, would most people think, “Ah, air pollution…”? Before I saw this research, I wouldn’t have.

Bottom Line:

Outdoor air pollution kills primarily by attacking our heart and blood vessels, not our lungs.

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