Masks help protect people who wear them from catching or spreading SARS-CoV-2, the virus that causes COVID-19, but researchers at the National Institutes of Health have now added evidence of another potential benefit for users: moisture created inside the mask can help fight respiratory diseases like COVID-19.
The study, led by researchers at the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), found that the masks substantially increase the humidity of the air that the mask user inspires. This higher level of humidity in the inhaled air, the researchers suggest may help explain why the use of masks has been associated with less severe disease in people infected with SARS-CoV-2, because the hydration of the respiratory tract is known for benefiting the immune system. The study published in Biophysical Journal.
“We found that the masks strongly increase the humidity of the inhaled air and we propose that the hydration resulting from the respiratory tract may be responsible for the documented discovery that it associates the reduction of the severity of COVID-19 disease with the use of a mask,” said the main author of the report. study, Adriaan Bax, Ph.D., NIH Distinguished Investigator. “It has been shown that high humidity levels attenuate the severity of the flu and can be applied to the severity of COVID-19 through a similar mechanism.”
High levels of humidity can limit the spread of a virus to the lungs, promoting mucociliary clearance (MCC), a defense mechanism that removes mucus. and potentially harmful particles inside the mucus? of the lungs. High levels of humidity can also strengthen the immune system, producing special proteins, called interferons, that fight viruses. a process known as the interferon response. Low humidity levels have been shown to impair both MCC and interferon response, which may be one of the reasons why people are more likely to get respiratory infections in cold climates.
The study tested four common types of masks: an N95 mask, a disposable three-layer surgical mask, a two-layer cotton-polyester mask and a heavy cotton mask. The researchers measured the humidity level by having a volunteer breathe in a sealed steel box. When the person was not wearing a mask, water vapor from the exhaled air filled the box, leading to a rapid increase in humidity inside the box.
When the person wore a mask, the accumulation of moisture inside the box decreased significantly, due to most of the water vapor that remains in the mask, condensing and being inhaled again. To ensure that there was no leakage, the masks were well adjusted to the volunteer’s face using high density rubber foam. The measurements were made at three different air temperatures, ranging from about 46 to 98 degrees Fahrenheit.
The results showed that all four masks increased the humidity level of the inspired air, but to varying degrees. At lower temperatures, the moisturizing effects of all masks have greatly increased. At all temperatures, the thick cotton mask led to the highest humidity level.
“Raising the humidity level is something that most mask users have probably felt without being able to recognize it and without realizing that this moisture can actually be good for them,” said Bax.
The researchers did not see which masks are most effective against inhaling or transmitting the virus and referred the CDC for guidance on choosing a mask. Previous studies by Bax and his colleagues have shown that any cloth mask can help block the thousands of drops of saliva that people release through simple speech. droplets that, if released, can remain in the air for several minutes. Although the current study did not examine respiratory droplets, it does offer more evidence as to why masks are essential to combat COVID-19.
“Even with more people across the country starting 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 wearing a mask as a simple but effective way of protecting people around us and protecting us from respiratory infections, especially during the winter months, when susceptibility to these viruses increases.”
The research was supported by the NIDDK Intramural Research Program and the NIH Intramural Antiviral Target Program.