Face masks play a critical role in helping to limit the spread of the novel coronavirus, en could save tens of thousands of lives in the US as everyone wore them in public, experts have said.
Yes, some face masks are more protective than others. But that does not mean that wearing jackets around the neck – stretchy pieces of fabric that people, especially runners, bring up to cover their noses and mouths – is worse than wearing no masks, as some recent news articles have suggested.
These news articles were based on a study published August 7 in the journal Science Advances, in which researchers are testing a new method for evaluating the effectiveness of face masks. In other words, it was a study conducted to test a methodology. However, the researchers examined some mask effectiveness in a “proof-of-principle” test, to evaluate whether they could use this particular method to measure mask effectiveness. To do this, they had a handful of participants try on different types of masks.
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“The mask tests carried out here … should only serve as a demonstration,” the authors wrote in the paper. “Subject variations are to be expected, for example due to differences in physiology, mask fit, head position, speech pattern, and so on.”
In this setup, a person wears a face mask and speaks in the direction of a laser beam arranged in a box that extends to a light sheet – and the droplets that come out of their mouths and scatter light through the masks, which is detected with a mobile camera. A simple computer algorithm counts the drops in the recorded video. The researchers demonstrated their method using 15 different face masks and face masks; one participant tried all the masks and four tried a subset of the masks. In each experiment, the researchers told participants “stay five healthy, people,” and measured the number of drops they emitted.
The authors found that the number of drops escaping through the masks varied greatly. For example, they saw “no noticeable drop” emission of the N95 respirator, although it should usually be reserved for health care workers, said co-author Martin Fischer, a chemist and physicist at Duke University in North Carolina, on in news briefing today (Aug. 13). The Duke team also tested a range of cotton masks and found that they blocked about 80% of the drops from the mouth, Fischer said.
In this proof-of-principle setup, however, some masks appear to let more drops through than others. The gaiter mask produced 10% more drops than when the person did not wear a mask, according to the study. The researchers hypothesized that this may be because the gaiter mask split the large droplets from the person’s mouth into smaller droplets, which increased their count. That’s “something to do,” because small droplets can hover in the air longer and can be easily carried by air currents, Fischer said.
“Absolutely not” proof
That being said, the corridor is only testing on one person, making it likely that differences between individual speakers outweigh any differences between masks they notice. What’s more, the researchers tested a gaiter with one neck (one that was very thin and consisted of a mix of 8% spandex and 92% polyester).
The public should use this “absolutely not” as evidence that neck gear is worse than not wearing a mask at all, Fischer said. “We’re testing one mask because we’re just lying around that mask … there are a lot of other gaiters out there,” some said, adding that may be more protective. Even the way people wear them can change how protective they are, he added.
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Some experts are not convinced that this particular neck crusher made more particles in the first place.
“It’s unclear to me if they actually measured respiratory droplets,” said William Ristenpart, a professor of chemical engineering at the University of California, Davis, who was not part of the study. Instead, the Duke team may have measured dusty particles of dust coming out of the masks. “Research from my group in peer review at the moment indicates that some substances emit substantial numbers of particles that disrupt measurements for mask effectiveness,” Ristenpart told Live Science.
There are still many that we do not know about the effectiveness of face mask, and more tests are needed to pin that down, said study senior author Dr. Eric Westman, an associate professor of medicine at Duke University. Although this study proves nothing about face masks such as gaiters, people should take a “break” if they use bad face coverings, such as a “single-layer, spandex, polyester stretch fabric that you can easily inhale and blow a candle through,” told Westman to Live Science. Such types of masks are unlikely to be very protective, while a two-layer mask, for example, may be better, he noted.
Another study, published June 30 in the journal Physics of liquids used another method to evaluate the effectiveness of non-medical masks: a masked or unmasked mannequin connected to a fog machine. This team found that without mask drops could travel up to 3.7 meters (3.7 meters) from the mannequin, but with a mask that significantly reduced the distance, according to an earlier report by Live Science.
These researchers found that a knitted cotton mask that fit well and had multiple layers reduced the spread the most, but a cone style mask also worked well. A bandana with one layer (made of an elastic T-shirt material) and a folded handkerchief were not as effective. The Centers for Disease Control and Prevention (CDC) recently updated their guidance to warn against the use of masks with exhalation valves, which may protect the wearer of the mask, but not others, according to another Live Science report.
There are still more questions than answers, but one of the key takeaways from this new study highlights that, “just talking about potential can spread this [virus] to other people, I do not have to cry, I do not have to sneeze or cough, “said Westman.
Originally published on Live Science.
