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 luz ultravioleta es emitida naturalmente por el sol, y la mayoría de sus formas son dañinas para los seres vivos -- así como para los microorganismos, como los virus. Esta luz puede ser absorbida por el genoma de un organismo, atarle nudos e impedir que se reproduzca. Sin embargo, estas longitudes de onda dañinas del sol son filtradas por la capa de ozono antes de que alcancen la superficie de la Tierra.
Algunos productos comunes, como las lámparas de tubos fluorescentes, usan luz ultravioleta -diseñada por humanos, pero una capa de fósforo blanco en el interior protege a las personas de los rayos ultravioleta.
"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.
Los hospitales ya utilizan tecnología de luz ultravioleta para desinfectar superficies en espacios cuando no hay personas en ellos, utilizando robots que pueden hacer brillar luz ultravioleta en quirófanos y salas de pacientes entre 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.
Los nuevos hallazgos son únicos, dijo, porque alcanzan el punto óptimo entre la luz ultravioleta que es relativamente segura para los humanos y dañina para los virus, especialmente el que causa el COVID-19.
"This can be a game changer for the public use of UV light in indoor spaces," said Linden.
Muerte por exposición
Para el estudio, Linden y su equipo compararon diferentes longitudes de onda UV una al lado de la otra-a-usando métodos estandarizados desarrollados en la industria de la luz 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 papel de la desinfección UV en la actualidad
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 sistemas que podrían encenderse y apagarse en espacios interiores para limpiar rutinariamente el aire y las superficies, o crear una barrera invisible continua entre maestros y estudiantes, clientes y trabajadores de servicios, y personas en espacios donde no es posible el distanciamiento social, para desinfectar el 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.
Otros autores de esta publicación incluyen: Ben Ma de CU Boulder; Patricia Gundy y Charles Gerba de la Universidad de Arizona; y Mark Sobsey de la Universidad de Carolina del Norte, Chapel Hill.
