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 it requires the right type of UV in the right dosage, a complex operation that is best administered by qualified professionals. In other words, many home UV devices that claim to kill SARS-CoV-2 are probably not a safe bet.
UV radiation can be classified into three types based on wavelength: UVA, UVB and UVC. Almost all the UV radiation that reaches the Earth is UVA, because most of the UVB rays and all UVC light is absorbed by the ozone layer, according to the Centers for disease control and prevention. And it is UVC, which has the shortest wavelength and maximum energy, which can act as a disinfectant.
reported: What is ultraviolet light?
“UVC has been used for years, it̵
UVC-254 works because this wavelength causes lesions in DNA and RNA. Enough exposure to UVC-254 damages the DNA and RNA so that they cannot replicate, effectively killing or inactivating a microorganism or virus.
“The data supporting this technology, the ease of use and the contactless nature” of UVC make it a valuable tool in the midst of the pandemic, said Kohli. But responsible and careful use is essential. UVC’s DNA damaging capabilities make it extremely dangerous for human skin and eyes, said Kohli. He warned that UVC disinfection technologies should be primarily left to medical facilities and evaluated for safety and efficacy by teams with experience in photomedicine and photobiology.
When it comes to home UVC lamps, their ability to damage the skin and eyes isn’t the only danger, said Dr. Jacob Scott, medical researcher at the Cleveland Clinic Department of Translational Hematology and Cancer Research. These devices also have low quality control, which means there is no guarantee that you are actually eliminating the pathogen, he said.
“UVC kills the virus, period, but the problem is that you have to get a sufficient dose,” Scott told Live Science. “In particular, for N95 masks, which are porous, it takes a rather large dose” of UVC-254 nm to eliminate SARS-CoV-2. This type of precision is not possible with home devices.
In hospitals, the geometry of the room, the shade, the times and the type of material or object to be disinfected are all taken into account when experts determine the right dosage of UVC needed to kill pathogens. But that kind of “quality assurance is really tough in the world, in nature,” said Scott. Home devices don’t offer that kind of precision, so using them could offer a false guarantee that SARS-CoV-2 was eliminated when it wasn’t, he noted. “Having something you think is clean, but it’s not, it’s 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. The Kohli group advises hospitals and suppliers that re-propose existing UVC equipment for decontamination of the N95 respirator. Scott’s group developed a car which can be used by smaller medical facilities and by a software program that helps users evaluate the geometry of the disinfection room so that staff can provide the most effective dose of UVC.
There are ongoing conversations in the field about installing UVC units in ceilings to decontaminate circulating air, said Kohli. And others are studying another UVC wavelength called UVC-222 or Far-UVC, which may not harm human cells, he added. But this will require further research, said Kohli. However, it is clear that “used accurately and responsibly, UVC has enormous potential”.
Originally published in Live Science.