Layered controls can significantly curb exposure to COVID-19
Mechanistic modeling study shows the combination of physical distancing, increased ventilation, and face coverings is highly effective

Date:
April 13, 2022
Source:
DOE/Brookhaven National Laboratory
Summary:
Using a new computational model that simulates the life cycle of
pathogen-laden particles, researchers found that a combination
of distancing of six feet, universal mask-wearing, and increased
room ventilation could reduce the risk of infection by more than
98 percent in more than 95 percent of scenarios studied.



FULL STORY ==========================================================================
As the COVID-19 pandemic unfolded, a team at the U.S. Department
of Energy's (DOE) Brookhaven National Laboratory set out to better
understand how well face masks, ventilation, and physical distancing can
cut down transmission of airborne pathogens like SARS-CoV-2, the virus
that causes COVID-19.


========================================================================== Using a new computational model that simulates the life cycle of
pathogen-laden particles, the researchers found that a combination
of distancing of six feet, universal mask-wearing, and increased room ventilation could reduce the risk of infection by more than 98 percent
in more than 95 percent of scenarios studied.

"Wide adoption of layered controls dramatically reduces exposure to
existing airborne viruses, such as SARS-CoV-2, and will be critical to
control outbreaks of novel airborne viruses in the future," said Laura
Fierce, an atmospheric scientist formerly with Brookhaven Lab, now at
DOE's Pacific Northwest National Laboratory. "These nonpharmaceutical interventions can be applied in combination with vaccinations." The study
is published in the journal Indoor Air. It focuses on how face masks
and ventilation work alone and in combination with distancing to reduce
the likelihood of someone inhaling virus-laden aerosol particles in
particular scenarios -- namely, where an infectious person is speaking continuously in an indoor space for three-hours -- while also accounting
for uncertainty in factors governing airborne transmission.

Fierce collaborated with Alison Robey and Catherine Hamilton --
who were participants in the DOE's Science Undergraduate Laboratory
Internships (SULI) program at Brookhaven -- to develop the model of
respiratory aerosols and droplets used in the study. The model simulates
how virus-laden particles move through the jet of air expelled by an
infectious person and within the larger indoor space. It considers how
expelled particles change in size as water evaporates, how pathogens
within those particles become inactive, and how particles are removed
through ventilation, deposition on surfaces, and gravitational settling.

The researchers' simulations showed that exposure to airborne pathogens
is significantly lowered by individual controls, such as face masks. But layering controls -- that is, using them in combination -- can be even
more effective.

According to the study, the combination of universal mask-wearing and distancing of even just three feet reduced a susceptible person's risk of infection by 99 percent. On the other hand, without the use of face masks, distancing of at least six feet was needed to avoid increased exposure
to respiratory pathogens near an infectious person. The team also showed
that increasing ventilation rates by completely replacing the air in a
room with fresh or filtered air four times per hour reduces the risk of transmission by more than 70 percent, so long as the infectious person
and susceptible person are distanced by at least six feet. On the other
hand, ventilation does little to reduce the risk of infection when the infectious person is close by.

"Our detailed modeling of respiratory particles shows how different
controls on airborne transmission work in combination, which is important
for prioritizing mitigation strategies for different indoor spaces,"
Fierce said.

This research was supported by the DOE Office of Science through
the National Virtual Biotechnology Laboratory, a consortium of DOE
national laboratories focused on response to COVID-19, with funding
provided by the Coronavirus CARES Act. This project was supported in
part by the U.S. Department of Energy through the Office of Science,
Office of Workforce Development for Teachers and Scientists (WDTS) under
the Science Undergraduate Laboratory Internships Program (SULI). The quadrature-based model was originally developed with support from the
DOE Atmospheric System Research program.


========================================================================== Story Source: Materials provided by
DOE/Brookhaven_National_Laboratory. Original written by Kelly
Zegers. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Laura Fierce, Alison J. Robey, Cathrine Hamilton. High efficacy of
layered controls for reducing exposure to airborne pathogens. Indoor
Air, 2022; 32 (2) DOI: 10.1111/ina.12989 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220413141610.htm

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