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."
La llum UV és emesa naturalment pel sol i la majoria de les formes són perjudicials per als éssers vius -- així com per als microorganismes, com ara els virus. Aquesta llum pot ser absorbida pel genoma d'un organisme, lligar-hi nusos i evitar que es reprodueixi. Aquestes longituds d'ona nocives del sol, però, són filtrades per la capa d'ozó abans que arribin a la superfície de la Terra.
Alguns productes habituals, com ara les làmpades de tubs fluorescents, utilitzen llum UV-per enginyeria humana, però un recobriment de fòsfor blanc a l'interior protegeix les persones dels raigs UV.
"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.
Els hospitals ja utilitzen la tecnologia de llum UV per desinfectar superfícies als espais quan no hi ha gent, utilitzant robots que poden il·luminar llum UV a les sales d'operacions i de pacients entre els usos.
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.
Les noves troballes són úniques, va dir, perquè arriben al punt dolç entre la llum UV que és relativament segura per als humans i perjudicial per als virus, especialment el que causa COVID-19.
"This can be a game changer for the public use of UV light in indoor spaces," said Linden.
Mort per exposició
Per a l'estudi, Linden i el seu equip van comparar diferents longituds d'ona UV-{-usant mètodes estandarditzats desenvolupats a la indústria de la llum UV.
"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.
El paper de la desinfecció UV avui
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 imagina sistemes que podrien encendre i apagar en espais interiors per netejar rutinàriament l'aire i les superfícies, o crear una barrera permanent i invisible entre professors i estudiants, clients i treballadors de serveis, i persones en espais on no és possible el distanciament social, per desinfectar l'aire.
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.
Altres autors d'aquesta publicació inclouen: Ben Ma de CU Boulder; Patricia Gundy i Charles Gerba de la Universitat d'Arizona; i Mark Sobsey de la Universitat de Carolina del Nord, Chapel Hill.
