N95 respirators provide the best protection against wildfire smoke, other types of pollution, and perform better than synthetic, surgical, and cotton masks.
Lab experiments were conducted to determine whether respirators and face masks could filter particles of various sizes. The researchers placed the various mask materials on a pipe that "breathes in" air, and then placed particles inside a box.
In laboratory experiments, N95s proved so effective that researchers estimated their widespread usage could decrease hospital visits due to wildfire smoke by between 22% and 39%. These findings provide evidence-based recommendations that can be used to protect wildfire season victims.
GeoHealth, AGU’s journal that studies the intersection between human and planet health for a sustainable future, published the new study.
Wildfires are becoming more common and more intense due to climate change in the Western U.S. and this is causing serious health problems. PM 2.5 (small particles less than 2.5 microns) is what wildfire smoke contains. These tiny particles can enter the lungs and cause multiple health problems including asthma, respiratory infections, and chronic obstructive lung disease (COPD).
Many people have made face coverings second nature during the coronavirus epidemic. This has led to some wondering if respirators and masks could be used to protect against pollution and smoke. Respirators, by definition, are protective equipment that close around the nose and mouth to filter out air. To prevent disease spread, surgical-style masks for the face capture any droplets or particles that are produced by the wearer.
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People were asking if we should keep them on during the summer, when fire season begins. Jack Kodros is an atmospheric scientist at Colorado State University. He was the lead author of the new study. "There wasn't much guidance on the type of masks that would be useful for wildfire smoke," he said.
Kodros and his colleagues measured the effectiveness of N95 respirators, synthetic, cotton, and surgical masks in filtering out particles as small as 0.3 microns. They then calculated the amount of pollution exposure each face cover would reduce by taking into account their ability to filter particles and the likelihood that masks could leak onto the skin.
The best protection against wildfire smoke is N95s, which reduces the exposure of a person by 16 factors. The effectiveness of synthetic and cotton masks in filtering out wildfire smoke particles is poor. They only reduce exposure by a factor 2.2 and 1.4. Although surgical masks can filter over 90% of particles, previous research shows that they allow about half the air to escape around the mask. This makes them less effective than the synthetic and cotton options.
N95s are also effective against larger dust particles and urban pollution. These particles, which can be as small as wildfire smoke, contain particles from vehicle exhaust.
Wildfire Smoke: Reducing hospitalizations
The researchers then estimated the health benefits of wearing masks across a population in the second half of their study. The model took into consideration the likelihood of wearing masks, as well as how often they would wear them. The model was applied to the 2012 Washington State Fire Season to determine if mask wearing had any effect on the number of respiratory-related hospitalizations.
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According to the model, N95s could have prevented around 30% of hospital visits due to wildfire smoke. The visits would have been reduced by 17% and 13% respectively with synthetic and surgical masks, while those using cotton masks would have decreased only 6%.
Kodros stresses that the mask recommendations for air pollution are only applicable to coronavirus. He stated that COVID-19 requires you to wear a mask to protect your face and reduce the amount of emitted droplets. Fabric masks were proven to be beneficial for public health in the current crisis. The Centers for Disease Control and Prevention recommends masks that are snugly fitted over the nose and mouth.
Stephanie Holm is a pediatrician and environmental epidemiologist who is also co-director of Western States Pediatric Environmental Health Specialty Unit, University of California, San Francisco. She says there is currently a lot of interest, but also confusion, about how different mask materials filter out particles. She said that this study "fills a nice gap in terms if thinking about how to translate that kind of data into real levels protection, and real differences between health effects that could be seen in a population."
Holm wasn't involved in the study but she advises families about how to protect themselves against wildfire smoke. She is eager to include this information into her recommendations.
