UV phone sanitizers work, but you don't need one for covid

Almost a year into the coronavirus pandemic, the United States is a little cleaning obsessed. Disinfectant wipes were a hot-ticket item for most of 2020. Face masks, first a DIY project, are now a staple for seemingly every brand. Air purifiers saw a bump as more was learned about how the virus spreads.

And one long-used but perhaps lesser-known disinfecting technology — ultraviolet light — got a big boost as consumers sought to protect the one item they touch the most: their phone.

Personal UV sanitizing devices can run from as little as $10 for a wand-style model to more than $100 for an enclosed box that will also charge your phone, with room to spare for your wallet and keys.

If you’ve been considering buying a UV phone sanitizer, consider this: Although the experts we spoke to say that this type of device works if it produces UV-C light in the appropriate dose, they still don’t recommend buying one.

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Ultraviolet light can indeed neutralize viruses, said Arthur Reingold, head of epidemiology and biostatistics at the University of California at Berkeley’s School of Public Health. “There’s a long history of using ultraviolet light on infectious agents to reduce transmission.” It’s widely used to deactivate pathogens in hospital rooms, either through aerial or direct exposure, on surgical tools and surfaces, and to decontaminate and treat wastewater.

“It attacks the genetic material of an organism and basically ties knots in the DNA and RNA of viruses, so they can’t reproduce,” said Karl G. Linden, a professor of environmental engineering and sustainable development at the University of Colorado at Boulder.

A device has to emit the right range of wavelengths and light intensity to bust those cell bonds, said Linden, who has studied UV light disinfection for 25 years. Light in the UV-C range between 200 and 280 nanometers will be absorbed by an organism’s DNA and RNA and damage its bonds; the most commonly used wavelength in sanitation settings is 254 nanometers. Although not all UV phone sanitizers list the wavelengths they use, several we found that did give this information had light in the proper range.

A study in the January 2018 issue of the Journal of the American Association for Laboratory Animal Science evaluated six disinfection methods on tablets and smartphones used in hospitals. It found that two UV-C devices that used 254 nanometers “were an effective nonliquid method for smartphone sanitization.” (The study included a PhoneSoap smartphone sanitizer and a Flashbox-mini disinfection chamber designed for use in health-care and research settings.)

UV sanitization can happen in seconds if the device has enough power, Linden said. In a health-care setting, rooms and tools can be sanitized in seconds, because they’re operating at high strength and are powered by mercury, excimer, pulsed xenon lamps or LED lights. Many of the popular devices on the market say they sanitize in about five to 10 minutes; a longer incubation period means they could use lower-powered lights.

One important caveat: Depending on the material you put into the chamber, Linden said, repeated exposure could decay some materials over time.

If you do purchase a gadget sanitizer, Linden said, get an enclosed-box model, which can concentrate the light safely and effectively, rather than a wand model. Wands won’t be as effective, because they don’t concentrate the light on the objects and could also carry more risk, because the light is not contained. The devices are best used on hard, nonporous objects with flat surfaces. (The study in the Journal of the American Association for Laboratory Animal Science found that the most bacteria was left behind in the crevices in between the tablet’s case and screen.) Look for a device with a sensor or timer that shuts off the device when it’s done, so you’re not exposing your eyes or skin to the light, Linden said.

The real question, Reingold and other experts say, is whether these devices are necessary to prevent transmission of viruses — and they said no. “It’s not a question of whether the UV works; that’s not the issue. The question is: ‘Does it actually translate into a health benefit?’ ” said Amesh A. Adalja, an infectious-disease physician and senior scholar at the Johns Hopkins Center for Health Security.

Some studies have found that viruses, such as coronavirus and norovirus, can survive on surfaces such as keyboards and cellphones. But the Centers for Disease Control and Prevention has said that surfaces are not thought to be a common way that the virus that causes covid-19 spreads. “I think there are a lot of people who are trying to capitalize on people’s concern about germs and transmission of disease,” Adalja said. “Yes, you could do that to your phone, but I don’t know that it does much to decrease your risk of infection. I’m someone who takes care of covid patients, and I’ve never once done that to my phone, because I don’t have to.”

Reingold agreed. “I think this frankly falls into the category of security theater,” Reingold said. “I personally would not buy something to irradiate my phone with UV light at home, just like I don’t need my packages or vegetables scrubbed with Lysol.”

A common claim (often repeated by companies selling cleaning devices) is that phones are much dirtier than other household objects, such as toilets. But the presence of microbes doesn’t mean anything in terms of whether it can make you sick, said Paula Cannon, professor of molecular microbiology and immunology at the University of Southern California’s Keck School of Medicine. “It doesn’t mean you had any danger. If you took a tiny pinch of yogurt and put it on a plate, you would have hundreds of microbes, and nobody is going to say that’s more dangerous than a toilet seat,” she said. “It’s using semi-truthful scientific facts out of context to build a narrative to sell a product.”

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And trying to get rid of all the microbes that could be present on your phone isn’t a worthwhile goal, Adalja said, because it’s impossible; microbes are everywhere and on every surface or object you could touch — even on your body. Many of them aren’t harmful to humans, he said, and transmission risk from your phone is probably low. “Not all microbes are major transmission risks, but most of them can be obviated by just washing your hands.”

Cannon worries that these devices could deter consumers from practicing more easy, reliable hygiene methods, such as regular hand-washing, and could create a false sense of security. If you’re concerned about the cleanliness of your phone, she said, wiping it with a tissue or disinfectant wipe is sufficient, but she discourages worrying about disinfecting phones too much.

Washing your hands regularly with soap and water is an effective way to prevent illness transmission, she said. And to prevent coronavirus transmission specifically, she advises the same methods that have now become second nature to many of us: practicing social distancing, wearing masks and hand-washing.

Editing by Kendra Nichols. Copy editing by Rachael Bolek. Photo editing by Monique Woo. Illustration by SanQian. Design by Alla Dreyvitser.

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