Further evidence that far‐UVC for disinfection is unlikely to cause erythema or pre‐mutagenic DNA lesions in skin

Abstract

It is well understood that ultraviolet-C (UVC) radiation is effective for the destruction of microorganisms and drug-resistant bacteria and is being investigated for its effectiveness at destroying the virus responsible for the current COVID-19 global pandemic. 1-4 Far-UVC (200-220 nm) has been proposed as an effective disinfection radiation that is safe to humans. 5 In 2014, Woods et al undertook a first-in-person study to assess the effect on skin of a 222 nm UVC emitting device (Sterilray disinfectant wand, Healthy

Predicting airborne coronavirus inactivation by far-UVC in populated rooms using a high-fidelity coupled radiation-CFD model

“…Fortuitously, recent advances in UV lamp technology, in particular excimer lamps [6][7][8] and light-emitting diodes [9][10][11] , now permit narrow bandwidth, short wavelength UVC (207-222 nm) to be generated. As these far-UVC wavelengths cannot penetrate either the human stratum corneum or ocular tear layer 12 , they are not carcinogenic or cataractogenic [13][14][15][16][17] and can therefore be safely used in people-facing applications 18 .…”

Exposure of Human Skin Models to KrCl Excimer Lamps: The Impact of Optical Filtering†

“…These more penetrating photons can potentially damage the DNA of cells deeper within human tissues. In fact, when phototype I and II skin of healthy volunteers was exposed to a KrCl source that had a~3% component from wavelengths above 250 nm, erythema and DNA photodamage ensued (18,19). Using Monte Carlo simulations of ultraviolet radiation transport in skin, it was estimated that the contribution to DNA photodamage in the epidermis from wavelengths shorter than 230 nm was negligible (19,20).…”

“…In fact, when phototype I and II skin of healthy volunteers was exposed to a KrCl source that had a~3% component from wavelengths above 250 nm, erythema and DNA photodamage ensued (18,19). Using Monte Carlo simulations of ultraviolet radiation transport in skin, it was estimated that the contribution to DNA photodamage in the epidermis from wavelengths shorter than 230 nm was negligible (19,20). With germicidal far-UVC sources proposed to be used in occupied locations, such findings emphasize the importance of characterization of their emission spectra in order to ensure that the recommended safety exposure limits are not exceeded (21,22).…”

UV‐C light: A powerful technique for inactivating microorganisms and the related side effects to the skin

“…In 2014, Woods et al found that the 222‐nm UV‐C‐emitting device was able to induce CPD formation on basal layer (of 2 out of 4 volunteers) and hypothesized that a small amount (3%) of contained wavelength UVC above 250 nm may contribute to the observed effect 44 . There is a new evidence demonstrating that far‐UVC radiation at 222 nm penetrates mostly on the upper epidermis but not into the basal layer 45 . It should be noted that filter out the wavelength UVC above 250 nm (particularly in 270‐310 nm) might be important.…”