Links between air pollution and cancer risk

Bhatti and his colleagues are currently analyzing data from the Women’s Health Initiative — a large, long-term research study that involved more than 161,000 postmenopausal women in the U.S. — to see if the link to increased cancer risk holds true in that specific population as well.

To understand the specifics of this increased risk of cancer — and the possible biology behind it — you have to first understand what air pollution is and how researchers classify it. There are several types of air pollutants that can harm human health and the environment, according to the Environmental Protection Agency, but the type that appears to most influence cancer risk is known as particulate matter.

As the name implies, these are literally tiny particles thrown into the air as a result of less-than-clean burning — and, unlike some modern, fuel-efficient cars, wildfires burn really dirty. Tiny bits of wood and ash get into the air, and into our lungs.

One kind of particulate Bhatti and his colleagues track in epidemiology studies is called PM 2.5, referring to the smallest bits, which measure less than 2.5 microns across. (That’s about one-thirtieth the width of an average human hair.)

“They’re really tiny particles,” Bhatti said. “The reason we are particularly concerned with those is because those penetrate to the deeper parts of the lung and can actually get into your circulation.”

A recent analysis of data from several studies found that an overall, long-term increase in the concentration of these particles of 10 micrograms per cubic meter of air (slightly less than a doubling of the average yearly level considered “clean” air by California state standards) is linked to a 9 percent increase in lung cancer cases.

That boost is significant, but it’s a drop in the pond of lung cancer cases compared to cigarette smoking. Regular smoking increases the risk of lung cancer by 1,000 to more than 2,000 percent, according to the American Lung Association.

“On an individual basis, smoking is a much more brutal exposure,” Bhatti said. “Air pollution doesn’t even come close. However, given how widespread the exposure to air pollution can be, it has the opportunity to negatively impact the health of many more people.”

The two likely work in similar ways to trigger cancer. Like smoking, particulate matter in the air leads to inflammation in the lung, which is known to spur cancer formation.

How air pollution might trigger cancers in other parts of the body is a bit more of a mystery, however. Certain chemicals toxic to human DNA often stick to the small particles, and it’s possible those chemicals are triggering mutations deep in our cells that spur the formation of cancer, Bhatti said. But the particles themselves might also inflict damage.

What if summer wildfires get worse?

While they can worsen asthma and other lung conditions as well as heart disease, isolated incidents of wildfire smoke like the one that recently…

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