By P.J. Heller
The benefits of using ultraviolet light in healthcare applications – killing microbes and bacteria and sterilizing surgical instruments and operating rooms -- has long been known. But the risks posed to people associated with using so-called germicidal UVC light, particularly skin cancer and cataracts, have prevented its widespread use in public spaces.
Now, however, researchers have reported that low doses of far ultraviolet light (far-UVC) can not only kill airborne viruses – including the influenza virus that this season has already claimed more than 80 children’s lives nationwide – but do so without harming human tissue.
The study, by the Center for Radiological Research at Columbia University Irving Medical Center (CUIMC), could have a far ranging impact in battling airborne viruses, including influenza, measles, tuberculosis, chickenpox, smallpox and possibly even anthrax.
“I think it does [have huge potential],” said David J. Brenner, the study leader and director of the Center for Radiological Research at CUIMC. “If it only took a bite out of influenza it would be just terrific.”
Installing far-UVC lights in places such as airports, airplanes, schools and medical facilities, could slow seasonal flu epidemics or even a flu pandemic that could spread rapidly from country to country.
“Our results indicate that far-UVC light is a powerful and inexpensive approach for prevention and reduction of airborne viral infections without the human health hazards inherent with conventional germicidal UVC lamps,” Brenner said. “If these results are confirmed in other scenarios, it follows that the use of overhead very low level far-UVC light in public locations may represent a safe and efficient methodology for limiting the transmission and spread of airborne-mediated microbial diseases.
“Public locations such as hospitals, doctors’ offices, schools, airports and airplanes might be considered here. This approach may help limit seasonal influenza epidemics, transmission of tuberculosis, as well as major pandemics,” he said.
Some published reports hailed the study, which has been conducted over the last five years, as a “breakthrough.”
Others, including Brenner, himself, were not willing to go that far since the use of UVC at certain wavelengths has long been proven effective for germicidal irradiation. Germicidal UVC peaks around 254 nm, Brenner noted. The far-UVC lamps used in the study had a single wavelength of 222 nm.
“I think we were expecting those results. I don't think we were too surprised,” said Brenner, the Higgins Professor of Radiation Biophysics and professor of Environmental Health Sciences. “What we saw in bacteria-killing experiments with far-UVC light was roughly the same efficiency of killing bacteria with germicidal UVC.”
The major difference, he noted, was that tests on human skin models and on mice, using side-by-side tests of far-UVC and germicidal UVC, showed no harmful effects with the far-UVC light with the single 222 nm wavelength.
“Due to its strong absorbance in biological materials, far-UVC light does not have sufficient range to penetrate through even the outer layer on the surface of human skin, nor the outer tear layer on the outer surface of the eye, neither of which contain living cells; however, because bacteria and viruses are typically of micron or smaller dimensions, far-UVC light can still efficiently traverse and inactivate them,” the study said.
The study used the H1N1 virus carried by aerosols in a bench-top aerosol UV irradiation chamber. The generated aerosol droplets were similar in size to those generated by human coughing and breathing, according to the study results published in Scientific Reports.
UVC light is divided into three wavelengths, UVA, UVB and UVC. UVA has the longest wavelength, from 400 nanometers to 320 nm and accounts for approximately 95 per cent of the UV radiation reaching the Earth's surface. UVB ranges from 320 nm to 290 nm; most solar UVB is filtered by the atmosphere. UVC has the shortest wavelength, from 290 nm to 100 nm and is absorbed by the atmosphere and doesn’t reach the Earth’s surface.
“With 222 nanometer light we have never seen any biological damage whereas with the conventional germicidal lamps we always see biological damage,” Brenner reported.
Dr. Trish Perl, chief of the Division of Infectious Diseases and a professor at the University of Texas Southwestern Medical Center, called Brenner’s study “very exciting and very interesting.”
Perl, who was not involved in the study, said the results could be a paradigm shift.
“I think it could be unbelievably important,” she said, noting that trying to prevent the flu virus has been limited to basically three strategies: vaccine, hand washing and wearing masks. Because people often skip some of those steps, “we need something that’s better,” she said.
“What’s also exciting about this is that this really could be used against other viruses,” Perl said. “Everyone is thinking about influenza right now, but there are other viruses out there that are equally problematic . . .”
While flu vaccines have to be formulated each year to deal with a particular strain, far-UVC lamps would remain the same.
“Unlike flu vaccines, far-UVC is likely to be effective against all airborne microbes, even newly emerging strains,” Brenner said. “It’s going to kill all the different strains pretty much the same.”
He also agreed with Perl that far-UVC lights would also be effective against other airborne-mediated microbial diseases.
“If you have these lamps in the ceiling, they're not going to distinguish between which bugs are floating around,” he said.
Temperature, humidity and airflow were not expected to have any impact on the efficacy of far-UVC.
“As long as the far-UVC light hits the bug, I think it would be independent of all those things,” Brenner said.
He admitted that researchers had initially been focused on using far-UVC to kill bacteria rather than viruses. That focus was sparked by concern over multi-drug resistant bacteria and superbugs.
“One of the really good things about UV light is that it kills bacteria by a different mechanism than drugs,” he explained. “A big issue in the bacteria world is its multi-drug resistance. UV doesn’t suffer from that. It kills bugs irrespective of their drug resistance. We were very concerned about superbugs in the future. That’s really where we started from.”
The first target of the research was MRSA (methicillin-resistant Staphylococcus aureus), a bacteria that is resistant to many of the antibiotics used to treat ordinary staph infections.
The initial research was focused on surgical site infections, which Brenner estimated occurred in about 5 percent of all surgeries. The idea was to use the far-UVC lamps directly above the surgical area, essentially creating a clean zone above a wound to prevent bacteria from floating down in the air and infecting the wound.
Brenner noted that a conventional UVC system had been utilized like that since World War II, but the health risks to those in the operating room and their unwillingness to put on bulky protective clothing, prevented the system from catching on.
“That’s where we started from. But as we were going along, we started to think about viruses because the same logic applies to viruses,” he said.
The study attempted to simulate in a test chamber what happens when a person with influenza would sneeze. When that happens, viruses are shot out into the air, then quickly attach themselves to aerosols such as dust particles or water vapor. They then float around in the air attached to the aerosols, eventually being breathed in by someone else.
“What we tried to do was simulate that system,” Brenner explained. “We started with the influenza virus, attached them to aerosols and then flowed them across a window and exposed the window to far-UVC light. We then looked to see if the viruses were alive or dead . . . how well could the far-UVC light kill viruses in the air in real life situation attached to aerosols. The answer was very well, indeed.”
While the results are promising, both Brenner and Perl say more research needs to be done.
“This is what I would call a preliminary report,” Perl said. “Now the hard work has to continue.”
That work would include determining whether the far-UVC light was effective at various distances as well as further ensuring that it was safe to be used around people, she suggested.
In a typically envisioned situation, the lights, which are about 2 inches by 2 inches by one-quarter inch thick, would be placed or grouped in a ceiling and the intensity of the lights could be adjusted to best meet that environment, Brenner said.
“You have to consider, in a hospital room or an airport, what is the typical concentration of bugs you would expect in those rooms and you would set the intensity appropriately,” he explained.
The far-UVC lights emit a purple light when on and might in the future incorporate conventional white visible light.
The study has prompted interest from school districts and other wanting to use the lights. Brenner says such use is probably at least two years away with success hinging on three areas: showing it works, proving it’s safe and bringing down the cost of the lamps.
“I feel reasonably comfortable about the efficacy of far-UVC. I think it definitely works. It does kill microbes. If any of these applications come to pass, you need to be 350 percent certain that it’s safe . . . We’ve never done studies where we’ve specifically looked at skin cancer. We’ve always looked at DNA damage. I think we need to do some experiments [looking explicitly at skin cancer],” he said, adding that he plans to conduct about a year-long study into that safety issue.
He said there was little concern about far-UVC affecting skin microbiome, which consists of thousands of species of bacteria.
Widespread use of the lights could also be hampered by their cost, now about $1,000 each. Mass production of the lights could cut that cost by more than 90 percent, Brenner predicted.
Approvals from federal government agencies would also likely be required before the lights could be used in public.
Brenner and Perl are optimistic about the future of the lights.
“These technologies are really going to be another arm of what we need for protection against infection,” Perl said.
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