Could a specific wavelength of ultraviolet light safely disinfect occupied public spaces?
In short: Conventional germicidal UVC light is effective at killing microbes, but it poses significant health risks to humans. However, a specialized wavelength known as far-UVC might offer a way to continuously disinfect indoor environments, such as trains and hospitals, without damaging the living cells of the people inside them.
Standard UVC light, typically at a 254 nm wavelength, is a powerful disinfectant used to clean unoccupied areas like empty hospital rooms. However, because it can damage human tissue, it cannot be used safely while people are present. Researchers at Columbia University's Vagelos College of Physicians and Surgeons have been investigating a safer alternative: far-UVC light with a 222 nm wavelength.
The mechanism behind this safety lies in the light's inability to penetrate certain biological barriers. Far-UVC light cannot pass through the tear layer of the eye or the outer layer of dead cells on human skin. This means that while the light can reach and destroy airborne pathogens, it does not reach the living cells of the human body.
In a study published in Scientific Reports, researchers tested the efficacy of this 222 nm light against seasonal coronaviruses. By using a misting device to aerosolize the viruses and flowing them past a far-UVC lamp, they found the light was incredibly efficient. Even with very low exposure, the light killed more than 99.9% of the airborne coronaviruses.
This discovery has significant implications for public health. David Brenner, a radiation biophysicist at Columbia, suggests that continuous disinfection at current regulatory limits could drastically reduce airborne virus levels in crowded indoor spaces like nursing homes or public transport. Based on the study's data, researchers estimate that continuous exposure could kill 90% of airborne viruses in about 8 minutes, or 99.9% in approximately 25 minutes.
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Sources
- Summary by Intellect · source: David Brenner: Can light stop the coronavirus?
- Also: Far-UVC Light Safely Kills Airborne Coronaviruses
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