Making masks fit better can reduce coronavirus exposure by 96 percent

Scientists using computational models have reported that, in general, widespread use of facemasks, when combined with lockdowns, may help prevent future waves of infection.

Face masks have been a matter of intense debate during the COVID-19 pandemic. Early on, several government officials and health authorities were discouraging healthy people from wearing masks—noting that there was little evidence for the practice’s ability to prevent spread among the general public and citing concerns that protective face coverings, which were desperately needed by healthcare workers, were in short supply. Gradually, however, governments began to either require or recommend that their citizens wear face masks in public.

In June, the World Health Organization (WHO) recommended widespread mask-use as a way to prevent coronavirus transmission. One model estimates that if at least 95 percent of people wear masks in public between June and October, approximately 33,000 deaths could be avoided in the US. 

There are three broad categories of face coverings: tight-fitting masks known as N95 respirators that are designed to filter out both aerosols (often defined as particles that are smaller than 5 micrometers in diameter) and larger airborne droplets, loose-fitting surgical masks that are fluid resistant and capable of filtering out the bigger particles, and cloth masks, which vary widely based on how they’re made.

A growing body of research supports the use of all three types of masks, though the quality of evidence varies. One of the most comprehensive examinations to date, published in The Lancetin early June, systemically assessed 172 observational studies—mostly conducted in healthcare settings—looking at the effect of physical distancing, face masks, and eye protection on the transmission of SARS-CoV-2 and two related coronaviruses. The results revealed that N95 respirators provided 96 percent protection from infection and surgical masks (or comparable reusable masks made with 12 to 16 layers of cotton or gauze) were 67 percent protective. 

widespread use of facemasks, when combined with lockdowns, may help prevent future waves of infection.

While research on cloth masks is much more limited, one group of researchers demonstrated that, in the lab, multilayer masks made of hybrid materials (cotton and silk, for example) could filter up to 90 percent of particles between 300 nanometers and 6 micrometers in size. However, it’s important to note this is only the case when there are no gaps around the edges of the mask, which are often present when people wear cloth or surgical masks. Indeed, the researchers’ findings suggest that gaps around any mask can reduce filtration by 60 percent or more. Still, scientists using computational models have reported that, in general, widespread use of facemasks, when combined with lockdowns, may help prevent future waves of infection.

“We’re recommending that N95s still be primarily saved for the healthcare situation,” says Kirsten Koehler, a professor of environmental health and engineering at Johns Hopkins University. “For individuals in the public, wearing a fabric mask is probably still the way to go.”

Credit: ScienceNews & TheScientist

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

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(link is external).

“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.

Dr. Adriaan Bax sits in front of lab equipment.NIDDK

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.