Researchers propose that humidity from masks may lessen severity of COVID-19

NIDDK’s Dr. Joseph Courtney breathes into sealed box while wearing a mask

Masks help protect the people wearing them from getting or spreading SARS-CoV-2, the virus that causes COVID-19, but now researchers from the National Institutes of Health have added evidence for yet another potential benefit for wearers: The humidity created inside the mask may help combat respiratory diseases such as COVID-19.

The study, led by researchers in the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), found that face masks substantially increase the humidity in the air that the mask-wearer breathes in. This higher level of humidity in inhaled air, the researchers suggest, could help explain why wearing masks has been linked to lower disease severity in people infected with SARS-CoV-2, because hydration of the respiratory tract is known to benefit the immune system. The study published in the Biophysical Journal.

“We found that face masks strongly increase the humidity in inhaled air and propose that the resulting hydration of the respiratory tract could be responsible for the documented finding that links lower COVID-19 disease severity to wearing a mask,” said the study’s lead author, Adriaan Bax, Ph.D., NIH Distinguished Investigator. “High levels of humidity have been shown to mitigate severity of the flu, and it may be applicable to severity of COVID-19 through a similar mechanism.”

High levels of humidity can limit the spread of a virus to the lungs by promoting mucociliary clearance (MCC), a defense mechanism that removes mucus ? and potentially harmful particles within the mucus ? from the lungs. High levels of humidity can also bolster the immune system by producing special proteins, called interferons, that fight against viruses ? a process known as the interferon response. Low levels of humidity have been shown to impair both MCC and the interferon response, which may be one reason why people are likelier to get respiratory infections in cold weather.

The study tested four common types of masks: an N95 mask, a three-ply disposable surgical mask, a two-ply cotton-polyester mask, and a heavy cotton mask. The researchers measured the level of humidity by having a volunteer breathe into a sealed steel box. When the person wore no mask, the water vapor of the exhaled breath filled the box, leading to a rapid increase in humidity inside the box.

When the person wore a mask, the buildup of humidity inside the box greatly decreased, due to most of the water vapor remaining in the mask, becoming condensed, and being re-inhaled. To ensure no leakage, the masks were tightly fitted against the volunteer’s face using high-density foam rubber. Measurements were taken at three different air temperatures, ranging from about 46 to 98 degrees Fahrenheit.

The results showed that all four masks increased the level of humidity of inhaled air, but to varying degrees. At lower temperatures, the humidifying effects of all masks greatly increased. At all temperatures, the thick cotton mask led to the most increased level of humidity.

“The increased level of humidity is something most mask-wearers probably felt without being able to recognize, and without realizing that this humidity might actually be good for them,” Bax said.

The researchers did not look at which masks are most effective against inhalation or transmission of the virus and defer to the CDC for guidance on choosing a mask. Earlier studies from Bax and his colleagues showed that any cloth mask can help block the thousands of saliva droplets that people release through simple speech ? droplets that, if released, can remain in the air for many minutes. While the current study did not examine respiratory droplets, it does offer more evidence as to why masks are essential to battling COVID-19.

“Even as more people nationwide begin to get vaccinated, we must remain vigilant about doing our part to prevent the spread of the coronavirus that causes COVID-19,” said NIDDK Director Dr. Griffin P. Rodgers. “This research supports the importance of mask-wearing as a simple, yet effective, way to protect the people around us and to protect ourselves from respiratory infection, especially during these winter months when susceptibility to these viruses increases.”

Disposable surgical masks best for being heard clearly when speaking, study finds

Masks are an important tool for fighting COVID-19 but wearing one can make it difficult for others to hear us speak. Using a unique laboratory setup, Illinois researcher Ryan Corey tested how different types of masks affect the acoustics of speech.

Press Release:

CHAMPAIGN, Ill. — Researcher Ryan Corey recently heard from a friend who teaches at a school where some of the students have hearing loss. The friend wanted to know if he had any ideas to help her communicate with these students while wearing a mask to slow the spread of COVID-19. Corey, who also has hearing loss, did not know what to tell her. So, he headed to the Illinois Augmented Listening Laboratory to look for solutions.

Corey, an electrical and computer engineering postdoctoral researcher under professor Andrew Singer at the University of Illinois Urbana-Champaign, leads a team that studies audio signal processing, especially for listening devices like hearing aids. The results of the team’s new study evaluating the acoustic effects of face masks on speech are published in The Journal of the Acoustical Society of America.

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Researchers rank various mask protection, modifications against COVID-19

Medical procedure mask and modifications designed to enhance mask fit or comfort for the wearer. A mask w/ear loops (A) modified by tying the ear loops and tucking in the side pleats (B), attaching ear loops to a 3D-printed “ear guard” (C), fastening ear loops with a 23mm claw-type hair clip placed behind the wearer’s head (D), placing ring of three, ganged, rubber bands over the mask and around the wearer’s ears (E), and sliding a 10-inch segment of nylon hosiery over the fitted mask (F).

Press Release:

CHAPEL HILL, NC – It’s been shown that when two people wearing masks interact, the chance of COVID-19 transmission is drastically reduced. This is why public health officials have pleaded for all people to wear masks: they not only protect the wearer from expelling particles that might carry SARS-CoV-2, the virus that causes coronavirus 2019 (COVID-19), but masks also protect the wearer from inhaling particles that carry the virus. Some people, though, still refuse to wear a mask. So UNC School of Medicine scientists, in collaboration with the Environmental Protection Agency, researched the protectiveness of various kinds of consumer-grade and modified masks, assuming the mask wearer was exposed to the virus, like when we interact with an unmasked infected person.

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