Can wildfire smoke increase one’s chances of contracting it?

It’s possible, experts tell Fortune. But it’s also complicated—and for many researchers, the jury is still out on how exactly one results in the other.

More than a dozen studies have examined the potential connection between air pollutants like wildfire smoke and pneumonia, which occurs when the lungs’ air sacs fill with pus. About half of those studies found a connection. Additional studies found evidence suggesting one, but nothing definitive, Shahir Masri tells Fortune. He’s an associate specialist in air pollution exposure assessment and epidemiology at University of California Irvine Public Health.

Recent studies have shown associations between increased exposure to air pollutants like wildfire particulates and higher death rates among COVID patients, with pneumonia being just one of the many ways the disease can kill.

“That’s kind of the way science works—you have a bunch of people hacking away at a given research question, and some studies find an association and some do not,” Masri says. “You follow the preponderance of evidence over time.”

But one thing’s for certain, he says: “You can’t call anyone crazy for thinking their pneumonia might have been caused by air pollution.”

How could wildfire smoke contribute to pneumonia?

There are a number of possible ways, experts contend.

Indirectly: Air pollution like wildfire smoke can cause or contribute to the development of health problems like heart attack, stroke, diabetes, and high blood pressure, Masri says. These conditions increase the chance of infection with respiratory illnesses like COVID and bronchitis, which can lead to pneumonia.

It’s also possible that wildfire smoke amplifies existing inflammation in the body—caused by infections or health conditions—to the same effect, he adds.

It’s additionally possible that air pollution wears down the lungs’ protective barrier, making them more susceptible to disease, Dr. Ilias Kavouras tells Fortune. He’s chairperson of the environmental, occupational, and geospatial health sciences department at the City University of New York School of Public Health.

If your lungs are compromised due to a health condition like COPD or asthma—or long-term exposure to air pollutants—and you catch a respiratory bug, “you have more chance of that developing into pneumonia,” he says.

Directly: Fine particulates from wildfire or other sources of air pollution may be able to carry pathogens deep into the lungs, where they can cause pneumonia, Masri says. 

Exposure to wildfire smoke is one of many risk factors for developing pneumonia that can stack and interact, Kavouras says. Other risk factors include:

• pre-existing disease like asthma, COPD, and diabetes
• an illness like COVID or bronchitis
• advanced age
• a lack of mobility, which increases the chance of fluid getting into the lungs

How to protect yourself from the negative effects of wildfire smoke

So, what’s a person in an area with wildfire smoke to do? Nothing, if they’re not already at greater risk for pneumonia? Not so, experts say. Health is easily taken for granted until it’s lost, which is why they recommend the following:

1. Stay indoors as much as possible.

If wildfire smoke is in the area, do your best to stay inside. Keep windows and doors closed. And if you can, run your air conditioning, which will remove large particles of pollution.

Outdoor workers may not have that luxury, Dr. Jon Samet, a pulmonologist and epidemiologist, and dean of the Colorado School of Public Health, tells Fortune, adding that employers of such workers should be mindful of the air quality locally.

2. Don’t exercise outside.

Or if you must, wear an N95 mask while doing so, Kavouras suggests. The reason: Exercising increases respiration—and thus the volume of pollution you inhale.

3. Stay cool and hydrated.

There is evidence that heat exacerbates poor air quality, Samet and Kavouras say. Keep cool as much as possible, and drink plenty of fluids. In the case of poor air quality, especially, “you don’t want to provide another stressor on your body due to dehydration,” Kavouras says.

4. Keep your eye on your area’s AQ, or air quality index.

You can view your area’s at airnow.gov. And follow recommendations of local health authorities, if applicable.

5. If the smoke in your area is severe and you’re at high risk of pneumonia, contact your doctor.

Your doctor may consider altering your medication regimen, Samet says.

Kavouras recommends those coping with wildfire smoke “exercise common sense, and be on the safe side.” While few want to hear the message anymore, perhaps the best advice for coping with wildfire particulates is to “go back to using masks,” he says. 

“They’re not a bad thing. This is what they’re meant for.”