Researchers create mask filtration effectiveness hierarchy
Expired and sterilized used N95 masks are still very good at protecting wearers, study shows

Date:
August 11, 2020
Source:
University of North Carolina Health Care
Summary:
Infection prevention experts set out to gather evidence on the
fitted filtration efficiency of dozens of different types of masks
and mask modifications, including masks sterilized for reuse,
expired masks, novel masks sourced from domestic and overseas
sources, and homemade masks.



FULL STORY ==========================================================================
This spring, due to limited national supplies of N95 face masks,
hospitals across the country asked the public and private companies to
donate personal protective equipment (PPE), including many different
types of masks, to be sure healthcare workers were protected while caring
for patients.


==========================================================================
With so many options, infection prevention experts at the UNC Medical
Center set out to gather evidence on the fitted filtration efficiency
of dozens of different types of masks and mask modifications, including
masks sterilized for reuse, expired masks, novel masks sourced from
domestic and overseas sources, and homemade masks.

Their data, published today in JAMA Internal Medicine, show that reused, sterilized N95 masks and very out-of-date N95 masks retain their
effectiveness at protecting healthcare workers from COVID-19 infection.

To assess mask fitted filtration effectiveness, Emily Sickbert-Bennett,
PhD, director of Infection Prevention at UNC Medical Center and colleagues turned to someone she knew she could trust: her dad, William Bennett, PhD, professor of medicine, who leads the Mucociliary Clearance and Aerosol
Research Laboratory at the UNC Center for Environmental Medicine, Asthma,
and Lung Biology (CEMALB).

"I told him we had two types of masks -- used, sterilized and expired
N95 masks -- and we needed to know whether they would offer safe and
effective protection, in case we needed our healthcare co-workers to use
them." Sickbert- Bennett said. "And he said it would be possible for his
lab to test them and give us data upon which to base our decision-making." Thanks to a cooperative agreement with the EPA Human Studies Facility
on the UNC-Chapel Hill campus, in which Bennett's labs reside, Bennett, assistant professor Phillip Clapp, PhD, and research associate Kirby
Zeman, PhD, teamed with EPA research scientist, James Samet, PhD, to
measure the fraction of submicron particles that penetrate into the
breathing space of subjects wearing a mask while performing a series of
tasks that simulate conditions such as speech and movement during a work
shift. Such tests provided infection prevention leaders quantitative data
they used to rank the best respiratory protection options for healthcare personnel during the COVID-19 outbreak.

The researchers found that certain N95 masks -- as rated by the National Institute of Occupational Safety and Health (NIOSH) Administration --
provide greater than 95 percent effectiveness at keeping the wearer
from inhaling very small airborne particles that may carry SARS-CoV-2 --
the virus that can cause COVID-19. Furthermore, these masks retain such effectiveness many years beyond the masks' expiration dates. In addition,
these NIOSH-rated masks can be subjected to sterilization with hydrogen peroxide or ethylene oxide without compromising their efficiency. Finally, their fitted filtration procedures showed that surgical masks with ties
were approximately 70 percent effective at filtering their inhaled
particles, while surgical masks with ear loops were about 40 percent
effective. Clapp, co-first author, emphasized that, "One of the keys to protection is how snug a mask fits. An N95 mask that forms a tight seal
offers the optimal infection prevention. However, evidence from previous studies suggests that even the surgical masks with <95% efficiency are effective in preventing acquisition of epidemic coronaviruses.

"Our hierarchy of mask supplies essentially amounts to always using the
safest option on the shelf, especially for those healthcare workers caring
for COVID- 19 patients," said Sickbert-Bennett, co-first author of the
JAMA Internal Medicine paper. "We start with products of our usual make
and model, then follow with CDC-FDA-NIOSH approved products.

"To date, UNC Health has maintained adequate supplies of NIOSH-approved
PPE," Sickbert-Bennett said. "We feel confident we can maintain protection
of the UNC Health workers with the variety of face masks and respirators
tested as part of this JAMA-published study."

========================================================================== Story Source: Materials provided by
University_of_North_Carolina_Health_Care. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Emily E. Sickbert-Bennett, James M. Samet, Phillip W. Clapp,
Hao Chen,
Jon Berntsen, Kirby L. Zeman, Haiyan Tong, David J. Weber,
William D.

Bennett. Filtration Efficiency of Hospital Face Mask Alternatives
Available for Use During the COVID-19 Pandemic. JAMA Internal
Medicine, August 11, 2020; DOI: 10.1001/jamainternmed.2020.4221 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200811120128.htm

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