Study is first to show proof that safer UV light kills COVID-19 virus
Hiroshima University researchers found that using Ultraviolet C light with a 222-nm wavelength, which doesn't harm living cells in the human eye and skin, effectively kills the SARS-CoV-2 virus. [Photo credit: Hiroshima University]
A study conducted by Hiroshima University researchers in Japan found that using Ultraviolet C light with a wavelength of 222 nanometers (nm), which is safer to use around humans, effectively kills SARS-CoV-2. It is the first research in the world to prove its efficacy against the virus that causes COVID-19.
Other studies involving 222-nm UVC, also known as Far-UVC, have so far only looked at its potency in eradicating seasonal coronaviruses that are structurally similar to the SARS-CoV-2, but not on the COVID-19-causing virus itself. A nanometer is equivalent to one-billionth of a meter.
An in-vitro experiment by HU researchers showed that 99.7% of the SARS-CoV-2 viral culture was killed after a 30-second exposure to 222-nm UVC irradiation at 0.1 mW/cm2. The study is published in the American Journal of Infection Control.
Tests were conducted using Ushio's Care222 krypton-chloride excimer lamp, which is commercially available. A 100-microliter solution containing the virus (ca. 5 × 106 TCID50/mL) was spread onto a 9-cm sterile polystyrene plate. The researchers allowed it to dry in a biosafety cabinet at room temperature before placing the Far-UVC lamp 24 cm above the surface of the plates.
A wavelength of 222-nm UVC cannot penetrate the outer, non-living layer of the human eye and skin, so it won't cause harm to the living cells beneath. This makes it a safer, but equally potent, alternative to the more damaging 254-nm UVC germicidal lamps increasingly used in disinfecting healthcare facilities.
Since 254-nm UVC can harm exposed human tissues, it can only be used to sanitize empty rooms. The 222-nm UVC lights, however, may prove to be a promising disinfection system for occupied public spaces including hospitals, where nosocomial (originating in the hospital) infections are a possibility.
The researchers are stressing further evaluation of the safety and effectiveness of 222-nm UVC irradiation in killing SARS-CoV-2 viruses in real-world surfaces, as their study only investigated its in-vitro efficacy.
This Far-UVC research was one of four COVID-19 studies conducted by Hiroshima University scientists that received funding from the Japan Agency for Medical Research and Development.
Designfax Editor's Note: These study results need more investigation -- especially because they could affect important health issues. We do not encourage buying 222-nm UVC bulbs at this time based solely on these findings. Overall, this looks like a promising development.
Source: Hiroshima University
Published November 2020
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