Extreme Exposure to Filtered Far-UVC: A Case Study

Abstract

Far-UVC devices are being commercially sold as "safe for humans" for the inactivation of SARS-CoV-2, without supporting human safety data. We felt there was a need for rapid proof-of-concept human self-exposure, to inform future controlled research and promote informed discussion. A Fitzpatrick Skin Type II individual exposed their inner forearms to large radiant exposures from a filtered Krypton-Chloride (KrCl) far-UVC system (SafeZoneUVC, Ushio Inc., Tokyo, Japan) with peak emission at 222 nm. No visible skin changes were observed at 1,500 mJcm-2, whereas skin yellowing that appeared immediately and resolved within 24 hours occurred with a 6,000 mJcm-2 exposure. No erythema was observed at any time point with exposures up to 18,000 mJcm-2. These results combined with Monte Carlo Radiative Transfer computer modelling suggest that filtering longer ultraviolet wavelengths is critical for the human skin safety of far-UVC devices. This work also contributes to growing arguments for the exploration of exposure limit expansion, which would subsequently enable faster inactivation of viruses.

Rights

Copyright © 2021 The Authors. Photochemistry and Photobiology published by Wiley Periodicals LLC on behalf of American Society for Photobiology. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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DOI

https://doi.org/10.1111/php.13385

Repository URI

http://hdl.handle.net/10023/21468