Coronavirus FAQ: I’m Using UV Light To Disinfect Stuff. Is That A Good Idea?

Enlarge this image

A handheld UV-C wand is waved over the surface of a computer keyboard.

Michele Abercrombie/NPR

hide caption

toggle caption

Michele Abercrombie/NPR

Goats and Soda
Coronavirus FAQ: Why Am I Suddenly Hearing So Much About KF94 Masks?

Another issue is that the UV-C lamps you can buy online are often smaller than the industrial lamps used to kill viruses in labs. Or they emit light from only one angle, which can become a big problem since the light rays aren’t effective at wiping out pathogens if they’re obstructed by really anything — like dust, little crevices or room angles that form shadows.

Maybe more problematic is the temptation to turn on these portable lamps throughout the day to fight germs. But the room must be cleared of absolutely everyone before you use it: Otherwise, ultraviolet light lamps could hurt your eyes — or the eyes of your co-workers or family members or roommates — if used incorrectly.

Dr. Guillermo Amescua, an ophthalmology specialist with the Bascom Palmer Eye Institute at the University of Miami, warns of a condition called photokeratitis. It is like a sunburn causing inflammatory damage to several layers of the eye itself, not just the skin around it, with symptoms such as severe eye pain or redness, blurry vision, eye twitching, light sensitivity or even temporary loss of vision.

Though photokeratitis can be caused by looking directly into the lamp as it radiates ultraviolet light (similar to bare eyes staring at the solar eclipse back in 2017), it can also happen if you’re in the same room as a UV-C device that produces light, which is why using them can get tricky.

While some manufacturers are quite clear in their recommendation that the room, big or small, must be free of living creatures (including animals) when the lamp is turned on, others use generic language like «no people or pets around,» which might imply it’s okay to distance yourself a bit and hang around in the same room — but it’s not. When the light is on, you should be out.

Amescua has been hearing about a lot of patients diagnosed with photokeratitis after staying in the room while their UV-C lamp was on before coming in with symptoms. And there’s been a lot more of them than usual. So many, in fact, that he and his colleagues authored a research article to alert people of the danger after a big uptick in cases after the start of the pandemic.

Goats and Soda
VIDEO: 3 Tips To Improve Your Physical Distancing. One Involves Pool Noodles

Many times, the harmful effects are quick to reveal themselves. «It could be four to six hours after being exposed that patients come in with eye damage, depending on the amount of energy of the lamp and the amount of time exposed,» Amescua says, noting it can happen in as quickly as 15 or 20 minutes. Luckily, he says most patients fully recover with treatments like prescription eye drops, eye rest and sometimes a special contact lens.

But the buck doesn’t stop at short-term eye damage when we’re talking humans using UV lights for sanitizing. The FDA warns of other serious and long-term risks of repeatedly exposing your eyes or skin by being in the same room with them, including deadly skin cancers or long-term eye damage like cataracts.

And to further complicate things, some UV-C lamps sold online also emit ozone, an invisible gas that can also kill microbes. Most of these lamps, which often boast of their «ozone power» in marketing lingo, also require an «air-out» period — a block of time when humans and pets shouldn’t come back in the room even after the lamp turns off — to give the ozone gas time to dissipate, as it can irritate the lungs if inhaled.

So you can draw your conclusions about UV-C lamps from the data — and warnings — now available. But whatever you conclude, keep in mind that they can’t take the place of other ways we fight the spread of coronavirus, says Dr. Peter Gulick, an infectious disease doctor and virologist at Michigan State University. He emphasizes the utmost importance of wearing masks, staying 6 feet away from people and washing your hands often.

«If you’re going to use [UV light] then use it, very carefully. But don’t think it’s going to substitute for other protective practices that we know are working,» says Gulick. «We don’t want to have situations where people say, ‘Ah, we’ve used UV light in here, so it’s safe to forget everything else.’ «

Kristen Kendrick is a board-certified family physician in Washington, D.C., and a health and media fellow at NPR and Georgetown University School of Medicine.

• coronavirus faqs