What's the Best Mask to Wear for Wildfire Smoke? Probably the Same One You Used for COVID

Fact checked by Nick Blackmer

• Smoke drifted down into the U.S. from Canadian wildfires this week, causing poor air quality for many people in the Northeast and Midwest

• The smoky skies could be dangerous for people’s health, experts said. People who are more sensitive to poor air quality—including children, older adults, and those with chronic illness—may want to mask when they go outside.

• N95s, KF94s, and other masks that provide ample protection against COVID should be able to do a great job of protecting people from smoke, so long as they fit well.

Large swaths of the United States are currently experiencing poor air quality due to smoke from wildfires in Canada, and health officials are urging people to take precautions.

In New York City in particular, air quality and visibility deteriorated as the smoke moved through on Wednesday, giving the five boroughs some of the worst air quality in the world.

The air quality has continued to marginally improve since Wednesday afternoon in New York City, but levels are still considered unhealthy. The same is true in most of the Mid-Atlantic region.

When air quality is this poor, it can be quite dangerous to people’s health, explained Sara Adar, ScD, associate professor and associate chair of epidemiology at the University of Michigan School of Public Health. That’s why it may be a smart decision to put on a high quality mask—like the ones commonly donned during the COVID-19 pandemic—if someone’s spending an extended amount of time outside.

“COVID is of similar size to what the particles are in smoke, so similar rules hold—an N95 is going to be the most protective option for you,” Adar told Health.

Here’s what experts had to say about why smoky air can be so dangerous, who should consider taking precautions, and the best practices for masking when there’s poor air quality in your city.

How Does Bad Air Quality Affect Your Health?

This smoky air may be an anomaly for people living in the Midwest or on the East Coast, but it’s much more common in the West, and scientists know a good deal about its effects on human health.

Wildfire smoke contains PM2.5, or fine particulate matter, which is the real cause for concern, said Joseph Allen, DSc, MPH, associate professor at the Harvard T.H. Chan School of Public Health and coauthor of Healthy Buildings: How Indoor Spaces Can Make You Sick—or Keep You Well. 

“[PM2.5 is] basically small airborne particles that are small enough to reach the deepest parts of our lungs,” he told Health. “It’s one of the most well-studied and well-known environmental hazards.”

These tiny particles, Adar and Allen said, are so small that they get deep into the lungs when people breathe them in, which can cause a number of health problems.

“They can trigger inflammation in our lungs that can then go elsewhere,” Adar said. “They can activate the nerves in our lungs that then speak to our brain, and can sort of change the regulation of our bodies.”

This lung inflammation and brain dysregulation can culminate in cardiovascular issues after longer periods of exposure—fine particulate matter has been associated with arrhythmia, hypertension, stroke, and exacerbated heart failure in people who are more susceptible. PM2.5 has been associated with low weight and preterm births, and worsened asthma symptoms. And wildfire smoke in particular could be linked to an increased risk of lung disease.

Even in the short term, breathing in unhealthy levels of these particles can cause issues, such as coughing or breathing difficulties, skin or eye irritation, and headaches.

“There’s a whole host of health effects,” Allen said. “We see these effects at levels that are ten times lower than what we’re currently seeing on the East Coast.”

Poor air quality peaked in New York City between noon and 3 pm on Wednesday, when PM2.5 was recorded at a concentration of about 800 µg/m³. Typically 35 µg/m³ is the standard for fine particulate matter.

Related: How Safe Is It to Exercise Indoors or Outdoors When Air Quality Is Bad?

Who Should Wear a Mask, and What Kind is Best?

Staying safe when there’s issues with air quality depend largely on the circumstances—for one, moderate PM2.5 levels may be extremely bothersome for one person, but fine for another. It depends on how sensitive someone is to the pollution or the smoke.

“Young children breathe in more air per their body size than adults do, so they’re at higher risk,” Adar explained. “The elderly are at higher risk, pregnant women are at higher risk, and people who have chronic illness, say heart disease or lung disease, are going to be at higher risk.”

It also depends how much time a person is spending outside, Adar added.

“The longer you’re outside, the more pollution you’re going to be breathing in, and so, the higher risk there is to your body,” she said. “So duration outside could weigh into those decisions as well.”

But when PM2.5 levels are unhealthy or extremely unhealthy, Allen said, they can be dangerous to everyone, so people should consider masking outside if they’re concerned.

“A high quality mask can be very effective at capturing these airborne particles,” Allen said, regardless of whether those particles are from a wildfire or someone’s cough.

So what makes a good mask for COVID also makes a good mask for protecting against PM2.5, experts agreed.

“You want to think of the two Fs—filtration and fit. When it comes to filtration you want a high grade mask, whether it’s an N95 or a KF94,” Allen said. A KN95 would also be acceptable. “You want that mask snug on your face so that all the air you’re breathing is forced to go through the filter of the mask,” Allen added.

But other masks—like surgical or cloth masks—which don’t have the same filtration or fit capabilities likely won’t offer much protection.

Related: Do Masks Work? What the Cochrane Review Can and Can’t Tell Us

Staying Safe in Smoky Air Conditions

Mask wearing can be beneficial when people are breathing in unhealthy air outside, but it’s equally important that they’re staying safe indoors, too.

People can consider buying air purifiers to help get the fine particulate matter out of the air in their homes, and they should keep windows closed. It’s also important to only run air conditioners if they don’t pull in air from outdoors and have a filter.

People can try building a Corsi-Rosenthal Box, which is essentially a DIY-version of an air purifier if the real deal is inaccessible, Adar said. This involves simply duct taping furnace filters around a box fan—the contraption can clean particulate matter out of the home.

Adar and Allen agreed that this bout of smokey air won’t last for much longer in the affected areas. But in the meantime, people should stay inside and do what they can to reduce their exposure to any potentially harmful PM2.5.

“My number one recommendation is to just spend more time indoors right now, if you can, while the smoke is really strong in your location,” Adar said. “I would try avoidance first, and then if you are susceptible, I would wear a mask if you have to be outside for a long period of time.”

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Read the original article on Health.