All masks are not created equal at limiting the spread of COVID-19, a new study has found, with some being rated as worse than wearing no mask at all.
The researchers at Duke University who performed the study, which was published in Science Advances, do not hold their report to be the final word on the effectiveness of the masks they examined, but rather the start of a conversation that can help Americans to make wise choices.
The study noted that the use of protective masks has been required during the coronavirus pandemic.
“It is assumed that wearing such masks reduces the likelihood for an infected person to spread the disease, but many of these mask designs have not been tested in practice,” the study said.
Researchers tested 14 masks, including an N95 mask that was professionally fitted to the wearer. Those are the top-grade masks used by health care workers and first responders.
The Duke team had a speaker talk without wearing a mask, then again with a mask. Each mask was tested 10 times.
The test was conducted by having the speaker talk into a box. A laser was set up to highlight the droplets that emerged when the speaker talked.
A cellphone camera then recorded the results.
The N95 masks worked the best, with surgical masks a close second.
Neck fleeces or gaiter masks, sometimes used by runners, finished last.
“We noticed that speaking through some masks (particularly the neck fleece) seemed to disperse the largest droplets into a multitude of smaller droplets … which explains the apparent increase in droplet count relative to no mask in that case. Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a mask might be counterproductive,” the study said.
“We were extremely surprised to find that the number of particles measured with the fleece actually exceeded the number of particles measured without wearing any mask,” Martin Fischer, one of the authors of the study, said, according to CNN. “We want to emphasize that we really encourage people to wear masks, but we want them to wear masks that actually work.”
Also on the less-than-effective list: folded bandanas and knitted masks.
“The idea that something’s better than nothing may not be true,” Dr. Eric Westman, an associate professor at Duke University’s medical school, told The Raleigh News & Observer.
Westman said the study also showed the extent to which droplets spray through normal speech.
“If you didn’t know that speaking can spread particles that can spread virus, you need to know that,” he said. “That was confirmed over and over and over in the hundreds of trials that we did.”
Although the researchers said people should not be playing with lasers at home, health care centers or community groups can set up mask testing centers to help educate the public.
“This is a very powerful visual tool to raise awareness that a very simple masks, like these homemade cotton masks, do really well to stop the majority of these respiratory droplets,” Fischer said. “Companies and manufacturers can set this up and test their mask designs before producing them, which would also be very useful.”
The study was very clear that its results are not a final verdict.
“[W]e want to note that the mask tests performed here (one speaker for all masks and four speakers for selected masks) should serve only as a demonstration,” it said. “Inter-subject variations are to be expected, for example due to difference in physiology, mask fit, head position, speech pattern, and such.”
Post a Comment