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Evidence indicates that coronavirus can linger for some time in the air, especially indoors in tight quarters. That is unsettling since it raises the idea that you could come in contact with the virus even if you are never near the person who breathed it out. Will Stone reports on the hope that ultraviolet light can help to prevent airborne transmission.
WILL STONE, BYLINE: When you walk into Marlaina's Mediterranean Kitchen, there are few visible clues of the killing zone. It's installed high above the tables to shield the diners below from dangerous pathogens, like the coronavirus. But you can't miss the new sign. The owner, Musa Firat, put it right outside the door to his Seattle-area restaurant.
MUSA FIRAT: It says coronavirus disinfected here. That means in the dining room (laughter).
STONE: It's not the tables or chairs, it's disinfecting the air using ultraviolet light. Looking up, you can make out the subtle blue glow of the UV lamps through the gritted ceiling panels.
FIRAT: And I thought it was great idea, you know, part of public health. And I want my, you know, customers to be safe.
STONE: It's called germicidal ultraviolet light - germicidal because this specific range of UV is very effective at inactivating viruses that float on tiny airborne particles. Firat got the idea from a customer, Dr. Bruce Davidson. Back in the '90s, Davidson ran the tuberculosis program in Philadelphia. He used UV to control an outbreak of drug-resistant TB. To show how it works in the restaurant, Davidson stands next to a booth and lights a cigar.
BRUCE DAVIDSON: People exhale. They cough. They sneeze. They speak loudly. These particles, like cigarette smoke, they go in the air.
STONE: Quickly, the smoke spirals up through the ceiling panels to where the UV lights are. He says, now imagine that instead of the smoke, a customer infected with the coronavirus exhales a plume of tiny particles called aerosols, which carry bits of the coronavirus.
DAVIDSON: The fans pull exhaled air particles up through those holes. And above there is the killing zone.
STONE: UV worked against measles in this way during the '40s. It's still used for tuberculosis in other parts of the world. And research shows it can also stop another coronavirus, SARS.
DAVIDSON: The dose we have up there killed coronavirus in a lab in just 16 seconds, 90%.
STONE: This does not stop all the ways of getting infected. There can be contaminated surfaces. And if you're up close to someone, you can still inhale infectious droplets. Davidson says what UV air disinfection can do is clear the room of lingering infectious particles that have built up.
DAVIDSON: Statistically, if somebody gets in here and has undetected, unknown coronavirus but this system is working, the risk to other people is going to be very low.
STONE: Scientists are still divided over how much aerosols are responsible for spreading the coronavirus throughout a room even among people who are not in close contact. Aerosols are known to be a risk during some medical procedures. But Shelly Miller, who studies aerosols at the University of Colorado, Boulder, says there's strong evidence it can also happen elsewhere.
SHELLY MILLER: Crowded, indoor spaces with inadequate ventilation. Nobody's wearing a mask. Or half the people are not wearing a mask. And you're talking loud. And you're there for a long time.
STONE: Miller and some other experts want public health authorities to place more emphasis on this risk. The World Health Organization says it can't be ruled out but maintains aerosols are not how most people get infected. But there is growing interest in UV light. Mostly it's being used to sanitize masks or subway cars, not so much to disinfect indoor air. Dr. Edward Nardell at Harvard Medical School has spent decades studying UV as a disinfectant.
EDWARD NARDELL: It's well-proven, extremely safe technology that is underused and often misunderstood.
STONE: There is a catch, though. You can't just put it anywhere. Direct UV light can damage the eyes and burn the skin. That's why UV lamps should be mounted high up, angled away from humans. Already, people are rushing to buy UV fixtures. But Nardell says there are lots of shoddy products on the market. And not many people know how to install UV correctly.
NARDELL: I worry about the fact that everything is pretty much unregulated, that people are free to do whatever they want without expert advice.
STONE: But if done properly, Nardell says it can be used in all kinds of places - big-box stores, restaurants, schools and nursing facilities. For his restaurant near Seattle, Musa Firat says he's glad he made the investment. The UV fixtures cost about $600.
FIRAT: The response is great, absolutely great.
STONE: And that can only be good for business. For NPR News, I'm Will Stone in Seattle.
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