Computer Modeling Indicates Dramatically Less DNA Damage from Far‐UVC Krypton Chloride Lamps (222 nm) than from Sunlight Exposure

This study aims to investigate, with computer modeling, the DNA damage (assessed by cyclobutane pyrimidine dimer (CPD) formation) from far‐ultraviolet C (far‐UVC) in comparison with sunlight exposure in both a temperate (Harwell, England) and Mediterranean (Thessaloniki, Greece) climate. The research utilizes the published results from Barnard et al. [Barnard, I.R.M (2020) Photodermatol. Photoimmunol. Photomed. 36, 476–477] to determine the relative CPD yield of unfiltered and filtered far‐UVC and sunlight exposure. Under current American Conference of Governmental Industrial Hygienists (ACGIH) exposure limits, 10 min of sunlight at an ultraviolet (UV) Index of 4—typical throughout the day in a temperate climate from Spring to Autumn—produces equivalent numbers of CPD as 700 h of unfiltered far‐UVC or more than 30 000 h of filtered far‐UVC at the basal layer. At the top of the epidermis, these values are reduced to 30 and 300 h, respectively. In terms of DNA damage induction, as assessed by CPD formation, the risk from sunlight exposure greatly exceeds the risk from far‐UVC. However, the photochemistry that will occur in the stratum corneum from absorption of the vast majority of the high‐energy far‐UVC photons is unknown, as are the consequences. There is concerted scientific effort to research ultraviolet‐C (UVC) at wavelengths below 230 nm (often called “far‐UVC”) because of the germicidal properties, specifically its ability to quickly inactivate SARS‐CoV‐2. An apparent lack of acute adverse health effects has led to claims of “far‐UVC” being “safe for humans.” Nothing is truly “safe” but it can be helpful to put risk in the context of everyday experiences. In this study, we find through computation that two UVC sources produce dramatically less cyclobutane pyrimidine dimers (CPD—a type of DNA damage) in the skin than just ten minutes of daylight exposure.