Can UV Light Actually Kill Coronavirus?

Earlier this month, it was revealed that New York City would start testing out ultraviolet lamps in an attempt to rid public transportation, such as subway cars and buses, of coronavirus. The pilot program will cost the Big Apple $1 million — and if it works, it could be a game changer.

"The UV light that will be used in the current overnight subway and bus disinfection program is very efficient in killing the virus that is responsible for COVID-19," David Brenner, PhD, director at the Center for Radiological Research at Columbia University, said in a press release for the MTA.

Around the same time I heard about the program, I also started seeing ads for devices that claimed to use UV light to disinfect phones and even face masks. To me, it sounded almost too simple. Why am I stocking up on hand sanitizer and disinfectant wipes when a quick shot of light could kill the SARS-CoV-2 virus?

Turns out, the rays being beamed onto the New York City subways are a little more souped up than the light that's hitting the pavement — or the light being used by phone-cleaning devices. The UV lamps they're using, from Puro Lighting, emit UV-C rays. The brand claims that this type can kill coronaviruses — plus SARS, influenza, and Ebola.

No research has looked specifically at how UV-C light fares against COVID-19. But studies have shown that when SARS — another coronavirus — was exposed to UVC for 15 minutes, the virus was "completely inactivated." The rays seem to penetrate the cells of pathogens, damaging the DNA or RNA that contain their genetic code, Jim Malley, PhD, an environmental engineer at the University of New Hampshire, told the Los Angeles Times.

With the right dose, "ultraviolet germicidal radiation" may be a way to disinfect the filters of N95 masks, too, according to the Centers for Disease Control and Prevention. That's a big deal, since PPE shortages mean some healthcare providers are reusing these masks, and they can't easily be disinfected.

UV-C rays are usually filtered out by the ozone layer before they reach our skin. That's a good thing; UV-C is the most damaging type of UV radiation, according to the World Health Organization. This means that just standing outside is probably not enough to kill errant strains of the virus.

What's more, because this light is so powerful, it's probably not what's being used in those phone-cleaning devices. "They're usually useless because many of the products that are meant for consumers have to be super safe," says Edward A. Nardell, MD, a professor of global health and social medicine at Harvard Medical School tells Refinery29. "If they're super safe, they usually put out very little UV light," Dr. Nardell says.

Some UV light devices do claim to use UV-C rays. But Mia Lieberman, PhD, a clinical veterinarian at Harvard Medical School who's studied one such product, told CNN that the light may not be intense enough to work against COVID-19. "I don't think consumers should rely on a UV device that's commercially available to eradicate coronavirus on their phone," she said. "I don't think we have the data to know how much it helps."

To sum up: UV light is showing some promise as a potential way to disinfect surfaces that may be contaminated with COVID-19. But as of now, it's not for personal use. If you're concerned about coronavirus, you'd be better off cleaning your hands with soap and water, and your phone with a disinfectant wipe.