Anti-microbial effect of filtered 222nm excimer lamps in a hospital waiting area

Background Hospital aquired infections is a considerable challenge for voulnerable patients. Ultraviolet light based on the excitation of mercury emit light at 254nm and has well established anti-microbial effects but the use hereof in populated areas is hindered by the carcinogenic properties of 254nm light. This is in contrast to the recently developed excimer lamps based on Krypton Chloride. These lamps emit light with a peak intensity at a wavelength of 222nm and have recently been demonstrated to have broad bactericidal and viricidal effects includ-ing efficient inactivation of SARS-CoV2. It is, however, unclear how efficiently 222nm lamps perform in a real-life setting such as a hospital waiting area. In this study we aimed to as-sess the antimicrobial efficacy of filtered 222nm excimer lamps in a real-world setting at an out-patient pulmonological clinic. Methods Filtered KrCl 222nm excimer lamps (UV222 lamps) were installed in a densely populated waiting room at the out-patient waiting area at department of Respiratory Diseases and Allergy at Aarhus University Hospital, Aarhus, Denmark. Furniture sufaces were sampled and analyzed for bacterial load in a single arm interventional longitudinal study with and without exposure to filtered 222nm UVC-light. Furthermore, bacterial species were identi-fied using MALDI-ToF mass-spectrometry. Findings The exposure to filtered 222nm UVC-light significantly reduced the number of colony-forming-units, and patches with high desity of bacteria. Pathogenic bacteria such as Staphy-lococcus Aureus and Staphylococcus Epidermidis were detected only in the non-exposed areas suggesting that these species are highly sensitive to inactivation by 222nm UVC-light. Conclusion Filtered 222nm UVC-light is highly anti-microbial in a real-world clinical setting reducing bacterial load and eradicating clinically concerning bacteria species. Filtered 222nm UVC-light has the potential to become an important part of current and future anti-microbial measures in the clinic.