According to a Duke University study, a common masking pattern may not help limit the spread of the coronavirus.
Researchers found that while most cotton, cloth or surgical masks tested were effective in limiting the amount of airway drops a person excreted during conversation, the “mantle” or the wool on the neck actually results in many smaller drops being ejected.
“We think this is because wool, the textile, breaks those large particles into many small particles,”; said Martin Fischer, associate professor of research at Duke.
According to most experts, the new coronavirus that causes COVID-19 is spread from person to person mainly through respiratory drops that we all push out of our mouths when we talk, sneeze, cough, or breathe badly.
Maybe releasing many smaller drops through a thin mask is worse than expelling larger droplets without a barrier, Fischer said.
“[The smaller particles] Fischers tend to stay in the air longer, they can fly more easily in the air, so this can actually be counterproductive when wearing such a mask, ”says Fischer. “Not in all cases having a mask is better than nothing. There are some masks that are actually more damaging than doing well. ”
However, some say that conclusion is too early and we don’t have enough information to claim that those masks do more harm than good. Slate news director Susan Matthews points out that researchers tested a single subject with an antique mask, increasing the likelihood that the mask won’t fit or have some other problem with the mask. or test object.
Subject also repeated only the concise phrase “stay healthy, everyone,” 10 times for each mask. Subject did not speak at different volume levels, coughing, sneezing, or simulating other conditions such as heavy breathing during exercise. Gaiter masks are very popular among runners because of their lighter construction and a better fit.
A University of Wisconsin-Madison study from July found that masks were more effective than other masks at catching water droplets from a simulated coughing fit, but that study used Use homemade “snug” walkers made of tightly woven fabric with metal nose and elastic to ensure a perfect fit.
Matthews also notes that we don’t know whether a person who produces many small drops of saliva is more contagious than someone who produces fewer larger blobs and more viral-filled saliva.
The Duke team’s findings were published online last week in Science Advances, a peer-reviewed journal.
Fisher and his team at Duke tested 14 different types of masks made of cardboard, laser lights, and cell phone cameras, as you can see in the short video below.
Subject repeats the same phrase into a story, first without masks, then with different masking styles to see which works best. The laser makes the droplets coming out of a person’s mouth visible and the camera records the drops for counting.
The team found that surgical masks, as well as cotton, fabric, and polypropylene masks were effective in preventing the droplets from spreading when the subject spoke with his normal voice. The respirator that works best is a medical grade N95 respirator – without a valve – used by medical professionals.
The fleece neck (Mask No. 11 in the photo above) actually results in more drops being counted. The bandana reduces the number of drops by about half, others reduce the number of drops to 20 percent or less the amount without the mask.
One of the researchers told The Washington Post that the poorly checked jacket was made of a lightweight material, spandex polyester, which was marketed as a breathable item for outdoor sports. .
“If you can see through it when you bring it to the light and you can blow through it easily, then it might not protect anyone,” says Warren S. Warren, co-author of the article told Post.
The valves are designed to prevent water droplets from entering the mask from the outside, not to prevent the person wearing the mask from pushing droplets that others may inhale, researchers note.
However, the overall draw from the article is clear. Although some masks work better than others, most are effective in reducing the droplets that spread coronavirus.
“Masking is a simple and easy way to reduce the spread of COVID-19,” said Dr. Eric Westman, a physician at Duke who worked with Fischer on designing the experiment, in a press release. news. About half of all infections come from people who don’t show symptoms and often don’t know they have the infection. They can unknowingly spread the virus by coughing, sneezing and just talking.
“If everyone was wearing a mask, we could stop up to 99% of these water droplets before they reach someone else. In the absence of a vaccine or antiviral drug, it’s the only proven way to protect others as well as yourself. “
This study was designed as an evidence of the researchers’ technique for measuring droplet propagation. More research is needed to test different types of masks under a variety of conditions, such as speaking at different volumes or coughing and sneezing, the researchers said.
“We definitely encourage people to wear masks, but we want to make sure that when you wear it and have trouble wearing it, you will either make one or wear one that really doesn’t just help. you but also help everyone ”. Fischer said.