Innovative 222-nm light sources against airborne infections for public health

Background: The antimicrobial use of ultraviolet (UV) radiation, such as 254-nm lamps, has long been known, along with their mutagenic risks. This project investigates the potential of 222-nm UV light barriers for controlling airborne infections through a multidisciplinary approach. Recent studies indicate low toxicity and strong absorption at 222 nm by the superficial stratum corneum, reducing mutagenic hazards. Materials and Methods: Irradiation prototypes based on 222-nm excimer lamps were designed, built, and characterized. Their efficacy was tested through photokilling experiments on in vitro reference and clinical multi-resistant strains of bacteria and viruses. An advanced setup was also developed to simulate in vivo antimicrobial efficacy in airborne conditions, using cages with healthy and infected mice separated by a UV light barrier to assess viral containment. Preliminary Results: In vitro experiments on P. aeruginosa, S. aureus, and SARS-CoV-2 showed a significant reduction in viable pathogens (approximately 3–5 logs) at doses of tens of mJ/cm² for bacteria and a few mJ/cm² for viruses. These doses can be delivered within seconds using low-power commercial excimer lamps. The results demonstrate strong sterilization capability and support the feasibility of developing UV light barriers for controlled airflow environments (e.g., buses, aircraft, waiting rooms) while maintaining safety.