A maintenance worker wearing a protective mask and face shield uses ultraviolet light to sanitize a classroom at Nassa School in Bekasi, West Java, Indonesia. (Bloomberg Photo: Dimas Ardian, File)A study has found that using ultraviolet C light with a wavelength of 222 nanometres (1 nanometre is a billionth part of 1 metre) effectively kills SARS-CoV-2, the virus that causes Covid-19.
Ultraviolet light of wavelengths between 200 and 280 nm is known as ultraviolet C light, of UVC. Using 222 nm UVC light is safe around humans, said the researchers from Hiroshima University, who have published their study in the American Journal of Infection Control.
As in vitro experiment by the researchers showed that 99.7 per cent of the SARS-CoV-2 viral culture was killed after a 30-second exposure to 222 nm UVC irradiation. 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.
A wavelength of 222 nm UVC cannot penetrate the outer layer of the human eye and skin, so it won’t harm the cells beneath. But 254 nm UVC germicidal lamps harm exposed human tissues, and can only be used to sanitise empty rooms.
The researchers suggest further evaluation of the safety and effectiveness of 222 nm UVC irradiation in killing SARS-CoV-2 viruses in real-world surfaces.