This image of the air pollution over China might make anyone faint of heart.

Image courtesy of NASA

Particulate Matter and the Heart

­Our bodies can't run with­out oxygen. All of our cells need it, and they rely on our lungs and heart to deliver it.

Every breath we take brings oxygen into our lungs, and the lungs are the first destination for the blood pumped out by the heart. When the right atrium contracts, it squeezes blood into the lungs so it can pick up oxygen from the air there. That oxygenated blood then enters the left atrium, which sends it out to the rest of the body.

But what happens when there's carbon monoxide, particulates or sulfur oxides in our lungs right alongside the oxygen? The blood picks up that stuff, too, and it gets to the blood supply, the heart and to every inch of our bodies.

That's the problem: It's all connected. Unfortunately, the heart reacts just as badly to air pollution as our lungs do. While the main causes of heart disease are poor diet, family history, obesity, diabetes and smoking, there's increasing evidence that heart problems are significantly impacted by pollution. For instance, carbon monoxide from secondhand smoke decreases the amount of oxygen our blood can carry, which can starve the heart muscle of the oxygen it needs to work properly. Particulates in diesel exhaust can cause blood vessels to constrict, limiting blood flow.

These particulates appear to be especially damaging in terms of heart health.

Particulates are tiny bits of liquid or solid matter. When we talk about this type of air pollution harming the heart, we're usually talking about PM2.5 -- particulate matter that's less than 2.5 micrometers in diameter. That's roughly 1/10,000th of an inch, or about one-tenth the diameter of a human hair. These particles are small enough to get deep into the lungs. The American Heart Association reports a 1.4 percent increase in heart-related deaths for each 10 micrograms of particulates per cubic foot of air [source: AHA]. And 10 micrograms is not a lot. The U.S. Environmental Protection Agency (EPA) considers the low concentration of 35.5 micrograms (average over the course of 24 hours) to be acceptable for health purposes [source: GADNR].

­Some researchers have found that even those EPA-approved levels can cause damage to the heart and blood vessels, though, especially in people already suffering from heart disease. And now they might know why.

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