In a significant breakthrough, researchers have discovered that using Ultraviolet C (UVC) light with a wavelength of 222 nanometres (touted as safer to use around humans) effectively kills the COVID-19 virus.

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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. According to the study, published in the American Journal of Infection Control, in-vitro experiment by Hiroshima University researchers showed that 99.7 percent of the SARS-CoV-2 viral culture was killed after a 30-second exposure to 222 nm UVC irradiation. "This study shows the efficacy of 222-nm UVC irradiation against SARS-CoV-2 contamination in an in vitro experiment," said study author Hiroki Kitagawa from Hiroshima University.

Tests were conducted using a UVC lamp. A solution containing the virus was spread onto a plate. The researchers allowed it to dry before placing the UVC lamp 24 cm above the surface of the plates. According to the researchers, 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. A nanometer is equivalent to one billionth of a metre.

This makes it a safer but an equally potent alternative to the more damaging 254 nm UVC germicidal lamps increasingly used in disinfecting healthcare facilities. Since 254 nm UVC harms exposed human tissues, it can only be used to sanitize empty rooms. But 222 nm UVC can be a promising disinfection system for occupied public spaces including hospitals where nosocomial infections are a possibility, according to the study. The researchers, however, suggest 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.