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 CU 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.

Full Article at https://phys.org/news/2021-10-specific-uv-wavelength-low-cost-safe.html

Full Research Publication : Ben Ma et al, 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