Far ultraviolet not ready for deployment, say experts

A row of blue UV-C mercury lamp
Scientists from the International Ultraviolet Association (IUVA) say there is ‘not yet sufficient evidence to support the widespread application’ of far UV-C where direct human exposure is anticipated.

DESPITE the promise that far UV-C is less harmful to humans than standard UV-C, it’s not ready for general use without further research, say experts.

Scientists from the International Ultraviolet Association (IUVA) say there is ‘not yet sufficient evidence to support widespread application’ where direct human exposure is anticipated. 

The IUVA recommends that far UV-C not be implemented as an unshielded disinfection technology until sufficient evidence for safety is presented, and suitable ways to applying it in buildings are established.

Far UV-C radiation occupies the wavelength range of between 200 and 225 nanometers, while conventional UV-C is between 240 and 280 nanometres.

The lighting industry is rapidly stepping up production of disinfecting mercury lamps, which are designed to operate at the wavelength of 254 nanometres.

It sees a booming market in upper-air disinfection, disinfection chambers and other virus-killing products which can help make buildings more Covid-secure.

Interest in far UV-C has soared because it’s seen to be ‘skin safe’.

The higher energy radiation at these shorter wavelengths is absorbed by the protective outer skin cells, or in the case of eyes, the outer tear layer, and therefore does not reach susceptible tissue to cause damage. 

By contrast, bacteria and viruses do not have such shielding and are directly exposed.

Lamp technologies covering both spectral ranges have existed for many decades, though far UV-C has not been widely applied. 

To date, no clinical or long-term studies of human exposure have been conducted and the effect on injured skin or eyes is unknown. 

The IUVA says such work is essential in determining the safety of the technology before the lighting industry attempts any wide-spread application 

‘While initial findings are positive, further investigations are required on any secondary impacts of the technology when used in the presence of humans’, it said in a statement.

‘Though the capability of far UV-C radiation as a disinfectant is well demonstrated, validation of its performance in field applications is generally lacking.

For conventional [disinfection using UV-C], protocols have been agreed by academia, industry, and regulators for the validation of systems prior to use.

‘This allows for the safe and effective application of [disinfection using UV-C],. However, no such accord exists for far UV-C application and bespoke protocols must be defined to assess manufacturers’ claims.’