Study
demonstrates a simple way to test facial covering materials for effectiveness
Duke
University Medical Center
To watch this video on YouTube: https://www.youtube.com/watch?v=LeEBn4ttZZY&feature=youtu.be
Duke physician Eric Westman was one of the first champions of masking as a means to curtail the spread of coronavirus, working with a local non-profit to provide free masks to at-risk and under-served populations in the greater Durham community.
But
he needed to know whether the virus-blocking claims mask suppliers made were
true, to assure he wasn't providing ineffective masks that spread viruses along
with false security. So he turned to colleagues in the Duke Department of
Physics: Could someone test various masks for him?
Martin
Fischer, Ph.D., a chemist and physicist, stepped up. As director of the Advanced
Light Imaging and Spectroscopy facility, he normally focuses on exploring new
optical contrast mechanisms for molecular imaging, but for this task, he
MacGyvered a relatively inexpensive apparatus from common lab materials that
can easily be purchased online. The setup consisted of a box, a laser, a lens,
and a cell phone camera.
In a proof-of-concept study appearing online Aug. 7 in the journal Science Advances, Fischer, Westman and colleagues report that the simple, low-cost technique provided visual proof that face masks are effective in reducing droplet emissions during normal wear.
"We
confirmed that when people speak, small droplets get expelled, so disease can
be spread by talking, without coughing or sneezing," Fischer said.
"We could also see that some face coverings performed much better than
others in blocking expelled particles."
Notably,
the researchers report, the best face coverings were N95 masks without valves
-- the hospital-grade coverings that are used by front-line health care workers.
Surgical or polypropylene masks also performed well.
But
hand-made cotton face coverings provided good coverage, eliminating a
substantial amount of the spray from normal speech.
On
the other hand, bandanas and neck fleeces such as balaclavas didn't block the
droplets much at all.
"This
was just a demonstration -- more work is required to investigate variations in
masks, speakers, and how people wear them -- but it demonstrates that this sort
of test could easily be conducted by businesses and others that are providing
masks to their employees or patrons," Fischer said.
"Wearing
a mask is a simple and easy way to reduce the spread of COVID-19," Westman
said. "About half of infections are from people who don't show symptoms,
and often don't know they're infected. They can unknowingly spread the virus
when the cough, sneeze and just talk.
"If
everyone wore a mask, we could stop up to 99% of these droplets before they
reach someone else," Westman said. "In the absence of a vaccine or
antiviral medicine, it's the one proven way to protect others as well as
yourself."
Westman
and Fischer said it's important that businesses supplying masks to the public
and employees have good information about the products they're providing to
assure the best protection possible.
"We
wanted to develop a simple, low-cost method that we could share with others in
the community to encourage the testing of materials, masks prototypes and
fittings," Fischer said. "The parts for the test apparatus are
accessible and easy to assemble, and we've shown that they can provide helpful
information about the effectiveness of masking."
Westman
said he put the information immediately to use: "We were trying to make a
decision on what type of face covering to purchase in volume, and little
information was available on these new materials that were being used."
The
masks that he was about to purchase for the "Cover Durham"
initiative?
"They
were no good," Westman said. "The notion that 'anything is better
than nothing' didn't hold true."