Can far-UVC light reduce the spread of COVID-19 indoors?

Experts think it could be a powerful tool for crowded public spaces.

A decade or so ago, David Brenner, a professor of radiation biophysics at Columbia University Irving Medical Center in New York began thinking about the problem of drug-resistant bacteria. He’d lost a close friend to the scourge—that friend had gone to the hospital for routine surgery and died of a superbug he’d acquired while there.

Superbugs are a real concern and focus for the pharma industry, but Brenner, as a physicist, wondered if there might be something he could do: He thought about ultraviolet light. In so doing, he started down a path that has put him on COVID-19’s front lines.

For more than a century, we’ve known that UV light kills microbes, and germicidal UV light, at a wavelength of 254 nanometers (nm), has been used increasingly in recent decades to sterilize operating rooms, homeless shelters, and other spaces. But germicidal UV light can be harmful to humans—particularly the eyes and skin—and so its use is limited to spaces where humans will not be directly exposed. Brenner began to think about whether there was a type of UV light that could kill microbes but still be safe for the humans exposed to it.

In principle, there was: UV light at a wavelength of 222 nm (what many call “far-UVC”) cannot penetrate the eyes and skin. “We know exactly how far light can travel in any given material,” explains Brenner. “It’s pure physics.”

Brenner has spent the years since trying to drive forward the science to turn the insight into application. (He’s also given two TED Talks on the topic.) Though he was initially focused on drug-resistant bacteria, he and colleagues began thinking a few years ago about far-UVC and its potential to safely decontaminate air and prevent transmission of airborne viruses like influenza. His studies showed it worked: The light could efficiently kill aerosolized influenza virus in the air, in a setting similar to a public space.

Cue 2020, and COVID-19, a disease caused by a highly infectious respiratory virus thought to spread, to some extent, through airborne transmission. When Brenner learned of the outbreak of a novel coronavirus earlier this year, he and his team quickly organized a study to test whether the 222 nm light would efficiently kill aerosolized human coronaviruses—unable to get SARS-CoV-2 at the time, they used types that commonly circulate and can cause the common cold—the same way it did with influenza. It did, indicating that when continuously applied at the current regulatory exposure limit, far-UVC would inactivate roughly 90% of airborne virus in eight minutes and 99.9% in roughly 16 minutes. They’re currently running the same study with aerosolized SARS-CoV-2.

“It’s another weapon in our armory. A good one,” says Brenner, who emphasizes far-UVC is a powerful tool that should supplement existing safeguards like masks and social distancing, not replace them. Far-UVC is unlikely to prevent close range transmission via droplets that occur between close contacts, but it could do a lot to reduce airborne transmission of the aerosolized droplets that have been found to linger in indoor spaces for hours.

“We need all the weapons we can get,” adds Brenner.

At a time when the U.S. is struggling to navigate school and business reopenings amid a still-raging pandemic, you might expect far-UVC light would be in use everywhere in an effort to help reduce transmission. It’s not, for a few reasons, and some experts worry the high-potential tool is not getting the attention or investment it merits at this moment.

“We’re up to our ears in the promise of the technology,” says Ed Nardell, a professor in the departments of medicine and of global health and social medicine at Harvard Medical School and a professor in the departments of immunology and infectious diseases and of environmental health at the Harvard School of Public Health. “It’s absolutely not getting the level of attention it deserves.”

For the past several months, Nardell, as well as Brenner and other UV experts, have met over Zoom every Friday as a sort of ad hoc committee on 222 nm light and moving it forward as a tool that can be deployed to help reduce COVID’s spread. “It’s definitely underutilized, definitely understudied, definitely underfunded,” says Nardell who notes that at a two-day meeting of the National Academies of Sciences, Engineering, and Medicine on airborne transmission of COVID-19 last week, 222 nm light was only raised as something of an afterthought in the closing comments of a single talk.

“It’s a discipline issue,” he adds. “If you ask engineers in developed countries about how to get rid of an air contaminant, the first thought is ventilation, and the second thought is filtration. They haven’t learned about germicidal UV; it’s not even in their toolbox in this country.” Nardell notes germicidal UV light has been used in other countries to control tuberculosis and measles outbreaks; he ran a study that established safe dosing levels.

Beyond awareness, there are other issues slowing the adoption of far-UVC. While Nardell and his colleagues are quite confident that human exposure to it is safe—a couple, including an expert on UV’s effects on the eyes, have been exposing themselves to 222 nm light—he concedes “the safety studies aren’t there yet.” Challengingly, there was a study conducted several years ago in Dundee, Scotland, by one of the world’s top photobiology groups, in which two of four volunteers exposed to 222 nm suffered skin damage, though investigators concluded in two papers that the effect was the result of contamination by higher-wavelength light (the lamp was not well filtered). The Dundee lab is planning to repeat the study with many more subjects and a well-filtered lamp as soon as they secure funding for it, says Nardell.

Brenner, who notes the importance of establishing safety data, says his lab and others in the U.S. and other countries have conducted lots of studies demonstrating safety in a variety of systems—primarily studying human skin and eyes and skin in mice. His lab is nearing completion of a 60-week study in which they’ve exposed 100 hairless mice to 222 nm light—at doses much higher than the regulatory limit—for eight hours a day, five days a week. The mice are regularly being tested for overall health and eye and skin issues but have shown none thus far.

For its part, the FDA offers this primer on UV light and COVID-19 and says: “Currently there is limited published data about the wavelength, dose, and duration of UVC radiation required to inactivate the SARS-CoV-2 virus.”

While the researchers are focused on shoring up safety data, there are no regulations beyond limits on UV exposure levels that prevent businesses or other organizations from implementing far-UVC lighting.

There is indeed more demand for the lighting than there is capacity to make it at the moment. A small but growing number of companies—including Sterilray, a New Hampshire company that started working on 222 nm lamps in the early 2000s, and Ushio, a Japanese company that has been studying far-UVC since coming across Brenner’s work in 2013 and which introduced its 222 nm excimer lamp in the U.S. in 2018—make the lighting, but not at a huge scale. They’ve all been ramping up production since the start of the pandemic.

Ushio has experienced a drastic increase in demand coming from “hospitals, airplanes, schools, restaurants, offices, everywhere people are exposed to the ‘3Cs’ (crowded, closed, confined),” says Shinji Kameda, COO of the company’s U.S. unit. Ushio, which has partnered with America’s largest lighting company, Acuity Brands, plans to begin mass production in late fall.

Healthe, a Florida-based lighting company that recently got the backing of investor Matt Higgins, a Shark Tank guest judge and the CEO of RSE Ventures, has introduced a line of 222 nm products, from overhead lighting to a sanitizing entry gate, that are destined for Equinox gyms (as well as nursing homes, prisons, colleges, and other spaces) and already in place at New York’s Magnolia Bakery, the Space Needle, and facilities for the Miami Dolphins.

Nardell, along with his committee, is trying to organize a Round Robin in which the group would independently test the various far-UVC technologies on the market to ensure they are properly filtered and produce only 222 nm UV and not other, longer harmful wavelengths. He’s also concerned about the promises being made for some products; he is skeptical of portal-like offerings such as Healthe’s, explaining that far-UVC is most effective at continuously decontaminating air around people in occupied rooms (and to some extent, directly exposed clean surfaces). Far-UVC is not good at instantaneously disinfecting the body, and it can’t disinfect areas that are shadowed or that aren’t in far-UVC’s direct line. Healthe concedes its entry gate may not be as critical as its 222 nm products focused on air decontamination, but says it a valuable part of its layered approach to disinfection.

“That gives UV a bad name,” Nardell says. “We want to use it where it is effective and not pretend to use it where it’s ineffective.” Like Brenner, he hopes far-UVC becomes a disease-fighting tool that outlasts the pandemic.

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