Ultraviolet light has been used to stop pathogens in their tracks for decades. But does it work against SARS-CoV-2, the virus behind the pandemic?
The short answer is yes. But you need the right kind of UV in the right dose, a complex operation that is best managed by trained professionals. In other words, many home ultraviolet light devices that claim to kill SARS-CoV-2 are probably not a safe bet.
UV radiation can be classified into three types according to wavelength: UVA, UVB and UVC. Almost all the UV radiation that reaches Earth is UVA, because the ozone layer absorbs most of the UVB light and all the UVC light, according to the Centers for Disease Control and Prevention. And it is UVC, which has the shortest wavelength and highest energy, which can act as a disinfectant.
Related: What is ultraviolet light?
“UVC has been used for years, it is not new,” Indermeet Kohli, a physicist studying photomedicine in dermatology at Henry Ford Hospital in Detroit, told Live Science. UVC at a specific wavelength, 254 nanometers, has been used successfully to inactivate H1N1 flu and others coronavirussuch as severe acute respiratory virus (SARS-CoV) and Middle East respiratory syndrome (MERS-CoV), he said. A study published June 26 in the prepress database medRxiv of Kohli’s colleagues awaiting peer review now confirms that UVC also eliminates SARS-CoV-2.
UVC-254 works because this wavelength causes DNA and RNA damage. Sufficient exposure to UVC-254 damages the DNA and RNA so that they cannot replicate, effectively killing or inactivating a microorganism or virus.
“The data behind this technology, the ease of use and the contactless nature” of UVC make it a valuable tool in the midst of the pandemic, Kohli said. But responsible and accurate use is critical. UVC’s DNA-damaging capabilities make it extremely dangerous to human skin and eyes, Kohli said. She cautioned that UVC disinfection technologies should be left primarily in medical facilities and that teams with expertise in photomedicine and photobiology evaluate their safety and efficacy.
When it comes to household UVC lamps, their ability to damage the skin and eyes is not the only danger, said Dr. Jacob Scott, a research physician in the Department of Translational Hematology and Oncology Research at the Cleveland Clinic. These devices also have poor quality control, which means there is no guarantee that it is actually eliminating the pathogen, he said.
“UVC kills the virus, period, but the problem is that you have to get enough of it,” Scott told Live Science. “Particularly for N95 masks, which are porous, a fairly large dose” of UVC-254nm is needed to remove SARS-CoV-2. This type of precision is not possible with home devices.
In hospitals, the geometry of the room, the shading, the time and the type of material or object that is disinfected are taken into account when experts determine the correct dose of UVC necessary to kill pathogens. But that kind of “quality assurance is really difficult in the world, in nature,” Scott said. Devices in the home don’t offer that kind of precision, so using them could offer a false guarantee that SARS-CoV-2 has been phased out when it hasn’t been, he noted. “Having something you think is clean, but not, is worse than something you know to be dirty” because it affects your behavior towards that object, he said.
Both Kohli and Scott and their teams are working to make UVC disinfection of personal protective equipment (PPE) such as face masks and N95 respirators more efficient. Kohli’s group advises hospitals and providers to reuse existing UVC equipment for decontamination of the N95 respirator. Scott’s group developed a machine This can be used by smaller medical facilities and a software program that helps users take into account the geometry of the disinfection room so that staff can administer the most effective dose of UVC.
There are ongoing talks about installing UVC units on roofs to decontaminate circulating air, Kohli said. Still others are investigating another UVC wavelength called UVC-222 or Far-UVC, which may not harm human cells, he added. But that will require more research, Kohli said. Still, it is clear that “used with precision and responsibility, UVC has enormous potential.”
Originally published in Live Science.
