A type of ultraviolet light known as far-UVC could be safely used to disinfect air in public places which could help in the fight against Covid-19, according to new research.

The joint study from the University of St Andrews and Ninewells Hospital in Dundee used computer simulations to study the impact of far-UVC disinfectant lamps on human skin.

Researchers found that shorter wavelengths do not cause the kind of problems typically associated with ultraviolet light.

There are three types of ultraviolet light – UVA, UVB and UVC – all of which have the potential to damage human skin.

Our new simulations provide further support for existing laboratory research showing that the upper layers of the skin provide a natural protection against shorter-wavelength-UVC

Isla Barnard, a medical physics PhD student at St Andrews, said: “The earth’s atmosphere protects us by absorbing all the UVC from the sun and we must be very careful to protect ourselves from some existing UVC disinfectant lamps which are known to cause skin damage.

“Using our computer model, we have shown that longer UVC wavelengths can damage the skin whilst wavelengths shorter than 230 nanometers (nm) had much more limited penetration in the skin.”

UVC light from special germicidal lamps with wavelengths in the range 200nm to 280nm kills germs such as bacteria and viruses, and has been used as a means of disinfecting hospital wards and operating theatres for decades.

However, the wards must be empty of people because the germicidal lamps operate mainly at a wavelength of 254nm that can penetrate the eyes and skin, causing inflammation and pain.

Researchers found that far-UVC lamps that emit at wavelengths around 222nm may be safer because proteins in the skin efficiently absorb this light and provide a natural protective barrier.

Dr Ewan Eadie, of the photobiology unit at Ninewells Hospital, said: “Our new simulations provide further support for existing laboratory research showing that the upper layers of the skin provide a natural protection against shorter-wavelength-UVC.

“Lamps that are engineered to filter out ultraviolet wavelengths longer than 230nm are safer than existing germicidal lamps.

“We now require real-life in-person studies to support our computer simulations and the laboratory evidence.”

The computer codes at the heart of the work were originally developed by St Andrews astrophysicist Dr Kenny Wood and have been adapted to help treat patients.

Lamps that emit at the shorter 222nm wavelength are now being investigated around the world as a means to help eliminate the virus responsible for the current pandemic.

The St Andrews-Ninewells team is working with several other groups developing far-UVC lamps and their computer simulations are being used to ensure they are safe for human skin.

The research has been accepted for publication in the journal Photodermatology, Photoimmunology and Photomedicine.