Fact check: Cloth masks ineffective against wildfire smoke, still slow spread of COVID-19
The claim: Face masks cannot protect against inhaling wildfire smoke particulates, so they are also ineffective against COVID-19
West Coast states are experiencing some of the worst wildfires on record amid the most infectious pandemic in a century. An epidemic of misinformation hurts efforts to combat the natural disasters.
An post on Facebook juxtaposes a statement about the average size of coronavirus and wildfire smoke particulates with a screen-grabbed CDC tweet that cloth face masks "do not catch small particles found in wildfire smoke that can harm your health."
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There are red lines drawn between the numbers and the CDC statement to connect the two. The implication appears to be that face masks do not protect against either coronavirus or wildfire particulates, as viral particles are on average smaller – at "0.12-0.3 microns" – than smoke – "at 0.7-0.4 microns." USA TODAY was unable to reach the poster of the image for comment.
The claim misinterprets why cloth masks are ineffective against wildfire smoke, as well as why they are useful in slowing the spread of the coronavirus.
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Masks, respirators and wildfire smoke
The Centers for Disease Control and Prevention emphasized that cloth masks are not effective at protecting people from inhaling wildfire smoke. The agency urges people to refrain from being outside and risking exposure to heavy particulates.
“Cloth masks that are used to slow the spread of COVID-19 by blocking respiratory droplets offer little protection against wildfire smoke,” an agency blog entry reads. “They do not catch small, harmful particles in smoke that can harm your health.”
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The CDC notes that higher-quality “N95 respirators do provide protection from wildfire smoke” but that “they might be in short supply as front-line health care workers use them during the pandemic.”
The Environmental Protection Agency says “people who must be outside for extended periods of time” during fires “may benefit from using a tight-fitting N95 or P100 respirator to reduce their exposure.”
Properly worn respirators are a strong enough filter to stop smoke particles from entering a person’s lungs, where ash, smog and other compounds can inflict serious harm.
For many people living near wildfires, the smoke is inescapable. Air quality in many regions on the West Coast has reached toxic levels.
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“My advice to the public is that people should be sheltering in place as much as possible,” said JohnBalmes, a professor of medicine at the University of California-San Francisco. “Stay home with windows closed, ventilation turned to recirculate, and if possible, have a clean air room with a HEPA air purifying appliance."
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Cloth masks, coronavirus and wildfires
Cloth masks and other nonmedical-grade face coverings aren't the best way to stop a person from inhaling infectious particles and droplets. Rather, face coverings are widely mandated because they make it more difficult for infected people to spread the virus.
“Masks are recommended as a simple barrier to help prevent respiratory droplets from traveling into the air and onto other people when the person wearing the mask coughs, sneezes, talks, or raises their voice. This is called source control,” the CDC says in its guidelines.
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SARS-CoV-2, the novel coronavirus that causes COVID-19, is mostly spread through droplets and other particulates, which people share by coughing, sneezing, singing, talking or yelling.
Though cloth masks are only marginally effective at stopping viral particles from being inhaled, they are more effective at stopping people from putting more particles into their environment.
When large majorities wear face masks, the aggregate effect can seriously slow the spread of a respiratory disease such as COVID-19.
“COVID-19 can be spread by people who do not have symptoms and do not know that they are infected. That’s why it’s important for everyone to wear masks in public settings and practice social distancing,” the CDC emphasizes.
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Scientists are still debating how effective cloth masks are at protecting an individual.
Though slowing contagion is the true value of simple face coverings, researchers say cloth masks provide some protection against coronavirus; they're just uncertain how much.
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A complicated public messaging campaign
Face masks have been the subject of confusion and scrutiny during the coronavirus pandemic. In the USA, this has partly come from mixed messaging from government agencies such as the CDC, as well as the Trump administration.
Public guidelines urging the wearing of face masks have evolved over the course of the pandemic. Health officials, aware of how most widely available masks don’t provide the personal protection that medical-grade respirators offer, were hesitant to encourage widespread mask-wearing.
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The CDC reversed messaging when it became apparent that Americans could make and wear enough cloth masks to slow the virus's spread.
West Coast officials are concerned that many won’t distinguish between symptoms from exposure to wildfire smoke and COVID-19.
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The CDC and state public health departments issued guidelines for how to distinguish between the symptoms, measures to protect against smoke and coronavirus and advice that people should support each other in this time of crisis.
“Some people most vulnerable to wildfire smoke, like those over 65 or with preexisting conditions, are also those most at risk for serious impacts from COVID-19. Check on your neighbors and make sure they know how to keep the air clean in their homes,” a Medium post from the Washington Department of Health reads.
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Our ruling: Missing context
Cloth masks are not granular enough to protect against smoke and airborne particles from the wildfires gripping the Western USA, according to CDC guidelines. The CDC and other agencies still endorse masks for slowing the spread of COVID-19 because of their usefulness if widely adopted. N95 respirators and similar-quality personal protective equipment protect against both wildfire smoke and coronavirus particles but are reserved for health care workers and first responders. We rate this claim as MISSING CONTEXT, based on our research.
Our fact check sources:
- CDC, Wildfire Smoke and COVID-19
- EPA, Wildfire Smoke Factsheet: Protect Your Lungs from Wildfire Smoke or Ash
- USDA, Wildfire Smoke and COVID-19 FAQ
- USA TODAY, Sept. 14, 2020, Wildfires burned millions of acres across the West. See what that looks like
- UCSF, Aug. 21, 2020, What to Know About Wildfire Smoke and COVID-19
- CDC, Aug. 7, 2020, Considerations for Wearing Masks
- USA TODAY, July 18, 2020, WHO agrees with more than 200 medical experts that COVID-19 may spread via the air
- Emerging Infectious Diseases, July 22, 2020, Effectiveness of Cloth Masks for Protection Against Severe Acute Respiratory Syndrome Coronavirus 2
- USA TODAY, July 5, 2020, The White House has sent conflicting messages on wearing masks and the new coronavirus cases
- The Verge, April 3, 2020, Masks may be good, but the messaging around them has been very bad
- USA TODAY, April 3, 2020, Coronavirus live updates: Cloth masks in public now recommended; US death toll passes 7,100; nation lost 701K jobs in March
- CDC, June 5, 2020, Wildfire Smoke and COVID-19: Frequently Asked Questions and Resources for Air Resource Advisors and Other Environmental Health Professionals
- Washington State Dept. of Health on Medium, Sept. 10, 2020, Wildfire smoke & COVID-19 are a bad mix
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Our fact check work is supported in part by a grant from Facebook.