New kind of ultraviolet light renders indoor air as safe as outdoor air

New kind of ultraviolet light renders indoor air as safe as outdoor air

A novel type of ultraviolet light that is safe for people reduced the number of indoor airborne bacteria by more than 98 percent in less than five minutes, according to a joint study conducted by scientists at Columbia University Vagelos College of Physicians and Surgeons and in the United Kingdom. Even as more germs were sprayed into the room, the level remained relatively low as long as the lights were turned on.

According to the findings, far-UVC light from ceiling-mounted lamps could be a highly effective passive solution for minimising person-to-person transmission of airborne-mediated diseases like COVID and influenza inside, as well as lowering the danger of the next pandemic.

“Far-UVC rapidly reduces the amount of active microbes in the indoor air to almost zero, making indoor air essentially as safe as outdoor air,” says David Brenner, PhD, co-author of the study and director of the Center for Radiological Research at Columbia University Vagelos College of Physicians and Surgeons. “Using this technology in places where people congregate indoors could help to avert the next dangerous epidemic.”

The findings was published on March 23 in the Nature journal Scientific Reports.

“Far-UVC light is simple to install, inexpensive, does not require people to modify their behaviour, and most importantly, it is a safe means to prevent the transmission of any virus, including the COVID virus and its variants, influenza, and any potential future pandemic viruses,” Brenner explains.

What exactly is far-UVC light?

Disinfecting indoor air with far-UVC light is a novel way for safely and efficiently destroying airborne viruses in occupied settings, including COVID and influenza viruses.

For decades, scientists have known that a form of ultraviolet light known as UVC light rapidly destroys microorganisms such as bacteria and viruses. However, because it is potentially harmful to the skin and eyes, traditional germicidal UVC light cannot be utilised directly to eliminate airborne viruses in populated interior settings.

Around a decade ago, Columbia University researchers claimed that a distinct sort of UVC light, known as far-UVC light, would be just as effective at eliminating bacteria and viruses while avoiding the safety problems associated with traditional germicidal UVC.

Far-UVC light is harmless for humans since it has a lower wavelength than ordinary germicidal UVC and so cannot penetrate living human skin or eye cells. It is, however, as effective at killing bacteria and viruses that are considerably smaller than human cells.

Many studies conducted across the world over the last decade have proven that far-UVC is both effective at destroying airborne germs and viruses and safe to use around people. However, until today, these investigations have only been carried out in small experimental chambers, rather than full-sized rooms simulating real-world situations.

According to a new study, far-UVC is extremely effective in a real-world situation.

Researchers from the Universities of St. Andrews, Dundee, Leeds, and Columbia University examined the efficacy of far-UVC light in a big room-sized chamber with the same ventilation rate as a normal home or workplace (about three air changes per hour).

Throughout the experiment, an aerosol mist of S. aureus germs was continually discharged into the room by a sprayer. (The researchers chose this microbe because it is significantly less susceptible to far-UVC radiation than coronaviruses, presenting them with an appropriately conservative model.) When the microorganism concentration in the room had stabilised, the researchers switched on commercially available overhead far-UVC lights.

The far-UVC lamps inactivated more than 98 percent of the airborne microorganisms in just five minutes at an intensity based on the existing regulation limit on far-UVC light exposure set by the American Conference of Governmental Industrial Hygienists. Even though microorganisms were still sprayed into the room, the low amount of viable germs was maintained throughout time.

The effectiveness of various methods for lowering indoor virus levels is often quantified in terms of equivalent air changes per hour. Far-UVC lamps produced the equivalent of 184 equivalent air exchanges per hour in this investigation. This outperforms any other method of disinfecting inhabited indoor environments, where the most that can be achieved effectively is five to twenty equivalent air changes each hour.

“Our trials produced spectacular results, far exceeding what is possible with ventilation alone,” says Kenneth Wood, PhD, lecturer in the School of Physics and Astronomy at the University of St. Andrews and senior author of the study. “In terms of preventing airborne disease transmission, far-UVC lights could make indoor places as safe as being outside on the golf course on a breezy day at St. Andrews.”

Far-UVC light is resistant to variations

“Previous research has demonstrated that far-UVC light can kill the COVID virus, other human coronaviruses, influenza, and drug-resistant microorganisms,” explains Brenner. “What makes far-UVC technology particularly appealing as a practical method of preventing indoor disease transmission is that it will be equally effective at inactivating all future COVID variants, as well as new infectious viruses that have yet to emerge, while retaining efficacy against ‘old fashioned’ viruses like influenza and measles.”

Finally, because ultraviolet light kills germs in the same way that vaccinations and medicine treatments do, viruses and bacteria cannot build resistance to it.

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