Specific UV light wavelength could offer low-cost, safe way to curb
COVID-19 spread

Date:
October 4, 2021
Source:
University of Colorado at Boulder
Summary:
A specific wavelength of ultraviolet (UV) light is not only
extremely effective at killing the virus which causes COVID-19,
but is also safer for use in public spaces, finds new research.



FULL STORY ==========================================================================
A specific wavelength of ultraviolet (UV) light is not only extremely
effective at killing the virus which causes COVID-19, but is also safer
for use in public spaces, finds new University of Colorado Boulder
research.


==========================================================================
The study, published this month in Applied and Environmental Microbiology,
is the first to comprehensively analyze the effects of different
wavelengths of UV light on SARS-CoV-2 and other respiratory viruses,
including the only wavelength safer for living beings to be exposed to
without protection.

The findings, which the authors refer to as a "game changer" for UV light
use, could lead to new affordable, safe and highly effective systems
for reducing viral spread in crowded public spaces like airports and
concert venues.

"Of almost every pathogen we have ever studied, this virus is one of
the easiest, by far, to kill with UV light," said senior author Karl
Linden, professor of environmental engineering. "It takes a very low
dose. This indicates that UV technology could be a really good solution
for protecting public spaces." UV light is naturally emitted by the sun,
and most forms are harmful to living beings -- as well as microorganisms,
like viruses. This light can get absorbed by the genome of an organism,
tie knots in it and prevent it from reproducing.

These harmful wavelengths from the sun, however, are filtered out by
the ozone layer before they reach the surface of the Earth.

Some common products, like fluorescent tube lamps, use human-engineered
UV light, but a white phosphorous coating on the inside protects people
from the UV rays.



========================================================================== "When we take that coating off, we can emit those wavelengths, and
they can be harmful for our skin and our eyes -- but they can also kill pathogens," said Linden.

Hospitals already use UV light technology to disinfect surfaces in spaces
when there are no people in them, utilizing robots which can shine UV
light in operating and patient rooms between uses.

And many gadgets on the market today clean everything from cell phones
to water bottles with UV light. But safety protocols are still being
developed by the FDA and EPA. Linden cautions against using any personal
or "germicidal" devices in which a person is exposed to UV light.

The new findings are unique, he said, because they hit the sweet spot
between UV light that is relatively safe for humans and harmful for
viruses, especially the one that causes COVID-19.

"This can be a game changer for the public use of UV light in indoor
spaces," said Linden.



========================================================================== Death by exposure For the study, Linden and his team compared different
UV wavelengths side-by- side using standardized methods developed across
the UV light industry.

"We thought, let's come together and make a definitive statement on
what UV exposure is required to kill off SARS-CoV-2," said Linden. "We
wanted to make sure that if UV light is being used to control disease,
you're delivering the right dose that's protective of human health
and human skin, but also going to be killing off these pathogens."
The opportunity to do this kind of work is rare, as there are extremely rigorous safety standards required to work with SARS-CoV-2. So Linden and
Ben Ma, postdoctoral researcher in Linden's research group, collaborated
with virologist Charles Gerba at the University of Arizona, at a lab
cleared to work with the virus and its variants.

The researchers found that while the virus was quite susceptible to
UV light in general, a specific wavelength of Far ultraviolet-C,
at 222 nanometers, was particularly effective. Created by what's
known as a krypton chloride excimer lamp, fueled by molecules
moving between different states of energy, this wavelength is very
high energy. Therefore, it's able to inflict greater viral protein
and nucleic acid damage to the virus compared to other UV-C devices,
as well as be blocked by the very top layers of human skin and eyes --
meaning that it has limited to no detrimental health effects at doses
that are capable of killing off viruses.

"Not only is it safe, it's also the most effective," said Linden.

The role of UV disinfection today UV light in various forms has been
used widely since the early 20th century to disinfect water, air and
surfaces. As early as the 1940s, it was used to reduce the transmission
of tuberculosis in hospitals and classrooms, by shining the light at
the ceiling to disinfect air as it circulated throughout the room.

Today, it's used not only in hospitals, but in some public bathrooms
and airplanes when there are no people in those spaces.

In a recent White Paper published by the International UV Association,
"Far UV- C Radiation: Current State-of Knowledge," which accompanies
the new study, Linden and co-authors argue that this safer wavelength
of Far UV-C light could serve as a key mitigation measure against the
current and future pandemics, in addition to improved ventilation,
mask wearing and vaccination.

Linden imagines systems that could either cycle on and off in indoor
spaces to routinely clean the air and surfaces, or create an ongoing,
invisible barrier between teachers and students, customers and service
workers, and people in spaces where social distancing is not possible,
to disinfect the air.

UV light disinfection can even rival the positive effects of improved
indoor ventilation by providing the equivalent protection of increased
air changes per hour within a room. It's also much cheaper to install
UV lights than to upgrade an entire HVAC system.

"There is an opportunity here to save money and energy while protecting
public health in the same way. It's really exciting," said Linden.

Additional authors on this publication include: Ben Ma of CU Boulder;
Patricia Gundy and Charles Gerba of the University of Arizona; and Mark
Sobsey of the University of North Carolina, Chapel Hill.

========================================================================== Story Source: Materials provided by
University_of_Colorado_at_Boulder. Original written by Kelsey
Simpkins. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ben Ma, Patricia M. Gundy, Charles P. Gerba, Mark D. Sobsey, Karl G.

Linden. UV Inactivation of SARS-CoV-2 across the UVC spectrum: KrCl*
excimer, mercury-vapor, and LED sources. Applied and Environmental
Microbiology, 2021; DOI: 10.1128/AEM.01532-21 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211004115142.htm

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