How Air Pollution Kills

The biology of death caused by particulate matter.

This is a transcript of the video.

Brian Palmer, writer, NRDC: A coal-induced smog killed 4,000 Londoners in just four days in 1952. Researchers spent the next six decades figuring out what makes air pollution so deadly.

I'm going to explain what they found, using this and this. Now, we're going to focus on just one kind of air pollution: particulate matter, which is just tiny bits of airborne stuff, like the leftovers from burning coal and gasoline.

How tiny is it? Well, if this a cross-section of a human hair, particulate matter is between this big and that big. The smaller the particle, the more hazardous to your health. To see why, let's take a field trip—up my nose.

The nose is a chaotic place. Air is blowing in all directions, there are little hairs, and mucous is everywhere.

The larger particles tend to get caught up and blown out. The smaller particles are more likely to make it past the nose, down the windpipe, and into your lungs.

Now these little guys are immune cells. They patrol the lungs looking for intruders, like this bacteria. When they find one, they gobble it up, digest it, and get it out of the body. But the immune cell can't digest particulate matter. So it calls in reinforcements; other immune cells flood the lungs.

Now this is bad because immune cells are programmed killers. A whole bunch of them hanging around inflames the delicate tissue of the lungs. This inflammation can cause or worsen asthma, emphysema, and other respiratory diseases.

But the air pollution story doesn't end in the lungs.

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The smallest particles are so tiny that the lungs' immune cells don't even bother with them. These particles settle onto the alveoli, which are tiny air sacs that pass oxygen—and this particle—into your blood.

Now the particle floats along in your bloodstream until it encounters an obstacle, like the plaque that builds up on the walls of our arteries.

Now, your blood is supposed to be sterile and pristine, so the immune cells in here will attack even the tiniest particles, and you get inflammation. The arteries already narrowed by plaque become nearly impassible, blood flow slows to a trickle, and you have a heart attack.

But that's just one way air pollution can kill you. There are many kinds of air pollutants, and many more ways they can kill through both short-term and long-term exposure.

Outdoor air pollution kills four million people every year. That's why public health authorities are fighting for tougher air pollution rules. It's also why loosening emissions limits on power plants, cars, and other sources is a very bad idea.

Because air pollution kills.

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