Face Shields Not a Good Mask Substitute
The mask with the valve worked as expected – sending unfiltered droplets into the surrounding air.
“Over time, these droplets can disperse over a wide area in the lateral and longitudinal directions, but with decreasing droplet concentration,” FAU researcher Manhar Dhanak said in a university statement. .
The standard mask, on the other hand, did a much better job of containing the droplets – allowing less to be expelled and limiting their spread. (The tests involved “surgical” masks which are marketed to the public and not recommended for medical use.)
The study, published on September 1 in the journal Fluid physics, has only tested the ability of face coverings to prevent the transmission of SARS-CoV-2, the virus that causes COVID-19.
In the real world, that would depend on many factors, said Dr Gregory Poland, an infectious disease specialist at the Mayo Clinic in Rochester, Minn.
Droplets that escape a face mask would have to contain an infectious virus – and expose another person to a sufficiently large “load” of those particles – to transmit the disease, he explained.
That said, the downsides of the face shield are obvious – including for the wearer, according to Poland. “The air is drawn in and under,” he says. “You increase the chances of breathing what is in the surrounding air.”
Like Kullar, Poland favors the mask-shield combination. But as a stand-alone solution, he said, the face shield is “the less successful option.”
Of course, cloth masks only work if worn correctly.
“Don’t wear it under your nose,” Poland stressed. Leaving your nose exposed in public places “is the riskiest thing you can do,” he said.
And while wearing a mask is important, Kullar said that’s not enough on its own: Maintaining physical distance from others remains essential – including outdoors.
“I don’t think we put enough emphasis on this message,” Kullar said. “The risk is lower on the outside than on the inside, but the risk is still there.”
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SOURCES: Ravina Kullar, PharmD, MPH, adjunct faculty, David Geffen School of Medicine, University of California, Los Angeles, and spokesperson, Infectious Diseases Society of America, Arlington, Va .; Gregory Poland, MD, professor, medicine and director, Vaccine Research Group, Mayo Clinic, Rochester, Minn .;Fluid physics, September 1, 2020, online
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