UV light sterilization

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HIGASHIHIROSHIMA, Japan — Ultraviolet light continues to be an effective weapon against the coronavirus pandemic. The problem is standard UV light can damage human cells, making it hard to clean rooms with people in them. Luckily, a study from Japan is adding further evidence that less potent forms of UV rays can do the job. Researchers say their experiments prove Far-UVC light will destroy COVID-19 without harming anyone exposed to it.

A team at Hiroshima University finds Ultraviolet C light with a wavelength of 222 nanometers offers a safer but still effective way to kill SARS-CoV-2, the virus causing COVID-19. A nanometer equals a billionth of a meter.

Hiroshima University researchers show Ultraviolet C light effectively kills SARS-CoV-2, without harming human cells. (Credit: Hiroshima University Department of Public Relations)

Regular UV light is widely used to eliminate germs on surfaces, but has a wavelength of 254 nanometers. Study authors say this kind of intense UV exposure can actually penetrate the human body.

“It is well known that 254-nm UVC is harmful to the skin and eyes. Previous reports demonstrated that 222-nm UVC light, belonging to far-UVC (207-222 nm), has the same highly effective germicidal properties as 254-nm UVC; however, it is less harmful to the skin and eyes,” researchers write in the American Journal of Infection Control.

The study adds that 254-nm light can break through the outer layer of dead cells on the skin and eyes, irradiating human tissue. Far-UVC light cannot penetrate human skin or eyes.

How well can Far-UVC light stop COVID-19?

The Japanese team uses Ushio’s Care222 krypton-chloride excimer lamp against viral cultures of SARS-CoV-2 in an in vitro experiment. After just 30 seconds of exposure, researchers find 222-nm light kills 99.7 percent of the virus. The team says this offers hospitals safer ways to sterilize work areas while keeping staff and patients out of danger.

In June, a Columbia University study also showed evidence Far-UVC light works against several strains of coronavirus and other pathogens. That report reveals UV lamps set between 207 and 222 nanometers can kill 90 percent of airborne virus particles in just eight minutes.

Both studies see the possibility for governments to start hanging “overhead far-UVC lamps” in public spaces. This technology may help lower the spread of seasonal illnesses like the flu, as Hiroshima University adds Far-UVC can also destroy the H1N1 influenza virus.

The Japanese study cautions that while there is now proof Far-UVC light can destroy COVID-19, they still need to test these rays against real-world surfaces outside of the lab.

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About Chris Melore

Chris Melore has been a writer, researcher, editor, and producer in the New York-area since 2006. He won a local Emmy award for his work in sports television in 2011.

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