Don’t throw out your neck gaiters just yet.
A new study has spurred numerous headlines declaring that neck gaiters may be worse than wearing no mask at all for controlling the spread of COVID-19. But the actual study, published August 7 in Science Advances, isn’t that conclusive, nor was it designed to be.
“The headline that neck gaiters can be worse is totally inaccurate,” says Monica Gandhi, an infectious diseases specialist at the University of California, San Francisco. Publicity like this is worrisome because “it can turn people off of mask wearing, which we know can protect both the individual wearing the mask and those around them,” she says.
Here are four reasons why you shouldn’t use this study to decide which mask to wear:
1. The study tested how to test masks, not which masks are best.
Masks have emerged as a crucial, science-backed tool for slowing the spread of COVID-19 (SN: 6/26/20). Since most people don’t have a personal stockpile of surgical masks, many have gotten creative, fashioning masks from T-shirts, bandanas or neck gaiters. But there hasn’t been much published research weighing whether some of these makeshift masks work better than others (SN: 4/9/20).
Martin Fischer, a chemist at Duke University, and his colleagues set out to develop a cheap and easy way that many labs could test the relative effectiveness of masks. In their setup, a masked person in a dark room speaks into a wide laser beam. Droplets spewed from the person’s speech show up neon green in the laser beam, moving like tiny meteor showers. Video captured on a cell phone is used to calculate the number of droplets.
The researchers tested their setup by having one person speak the phrase, “Stay healthy, people,” into the laser beam while wearing one of 14 different mask types, including surgical masks, bandanas and knitted masks. (Some masks were tested on four people.) The team measured differences in the number of droplets over 10 trials.
The researchers calculated the fraction of droplet transmission from masks, setting a 100 percent baseline based on someone talking with no mask. A fitted N95 mask transmitted below 0.1 percent of particles, while the neck gaiter transmitted 110 percent. The authors argue this extra 10 percent might come from the fabric of the neck gaiter shearing large droplets into many smaller ones, which could, in principle, leave infectious particles airborne for longer (SN: 7/7/20).
Various news outlets seized on that extra 10 percent as evidence that neck gaiters don’t work and may even be worse than nothing. Such conclusions, which were sometimes supported in news stories by the authors themselves, are too strong for a study its authors describe as a “proof-of-concept.”
“We tried to be as careful with our language as possible in interviews,” says Warren S. Warren, a Duke chemist and coauthor of the study. While he says their observations suggest some thin gaiters might be problematic, “the press coverage has careened out of control” for a study testing a measuring technique and that looked at just one mask of each type.
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2. Testing one wearer is not enough.
In general, a sample size of one is an anecdote, not data. To actually evaluate whether a mask is effective, researchers would need to test the mask on a variety of wearers. “At an absolute minimum you’d need to test six to 10 different subjects, and six to 10 samples of the same kind of mask,” says Charles Haas, an environmental engineer at Drexel University in Philadelphia.
Masks may sit differently on different faces, which could affect how well they filter particles. And people vary in the number of droplets they produce when talking. In fact, when the authors tested more than one person, they found some talkers produced five times more droplets than others. And that’s after testing just four people.
Neck gaiters come in a wide variety of materials and thicknesses, too, and can be folded when worn, which would influence their effectiveness. “The study didn’t provide much detail on what the gaiters were made from, or how they were constructed,” which could affect how they work, Haas says.
In the study, the authors themselves note that the experiment “should serve only as a demonstration. Inter-subject variations are to be expected, for example due to differences in physiology, mask fit, head position, speech pattern and such.”
Says Haas: “It’s an interesting technique that could be useful. But the results of this study have been misinterpreted beyond what the authors intended.”
3. Testing just for talking probably isn’t enough.
Talking is just one way to produce droplets, and it may not be relevant to all situations. For instance, neck gaiters are especially popular among runners. How well these masks block droplets from heavy breathing, rather than talking, might be a more informative measure of their utility. Future research could also test how different masks fare while coughing, sneezing or singing.
“There are so many different sources of variability that influence how well a mask works,” Haas says. “Without addressing those, making conclusions that differences are due to the type of mask is really a stretch.”
4. Droplet number doesn’t necessarily equate to risk of transmission.
The whole point of testing the effectiveness of different masks is to understand how each limits transmission of viral particles, and thus risk of spreading infection. “The best way to do that would be to take the coronavirus and expose individuals to it wearing different types of masks,” says Gandhi, the infectious diseases specialist. “Because we cannot do that for obvious ethical reasons, everything else is an approximation.”
Measuring droplets is a reasonable proxy, she says, but doesn’t necessarily reflect how much a mask cuts risk of disease transmission, both from the wearer to others, as well as from others to the wearer. The environment factors in too, since indoor transmission has been shown to be more common than outdoor transmission (SN: 4/17/20).
“I’m not convinced that this study accurately simulates how people are actually around each other,” she says. Even if, after testing enough people, certain masks weren’t as good as others, they still might be good enough to slow the spread of the virus.
While we still have much to learn about masks and transmission, Gandhi says the preponderance of evidence, both for COVID-19 and earlier viruses, suggests “that cloth face masks, and that includes properly worn neck gaiters, filter out the majority of viral particles and provide some protection for an individual.”