A new 222nm-Illuminator for the suppression of airborne viral epidemic spread

The Covid-19 epidemic has been the most consequential global health crisis since the era of the influenza pandemic of 1918 [1]. Due to its high spreading rate, the virus disseminated across the world in a very short time span, forcing the World Health Organization to declare Covid-19 a global pandemic after just 3 months from the first reported case in China. At the beginning of the pandemic, when no vaccines were available, people entrust their safety to very few devices such as personal protective equipment (face masks, shields, and gloves), lock-down, and social distancing. The lack of alternative and not conventional techniques to suppress the spread of airborne epidemics among humans has pushed the research to develop new antiviral devices. The SAVE-US project (Suppression of Airborne Viral Epidemic Spread by UV-Light Barriers) aims at developing and demonstrating an innovative antimicrobial device based on 222nm-radiation. As known from the literature, the UVC radiation (200-280 nm) is the most effective wavelength for the inactivation of viruses and bacteria, corresponding to the DNA and RNA absorption peaks, but may also be mutagenic. For this reason, UVC-light sterilization is commonly performed in the absence of living organisms. Radiation in the far-UVC, especially at 222 nm, has been recently investigated because it shows a good antimicrobial efficacy, tested already on both bacteria [2] and virus [3] models including coronavirus, with very limited risks to human health. The low risk is associated to the small penetration depth of 222 nm light (a few μm): the energy is absorbed by the superficial stratum corneum of the skin that contains dead cells, with negligible irradiation of the underlying live tissue [4]. We will present the first version of a new prototype of 222 nm-illuminator and some preliminary results on its characterization; the presented device will be used in successive in vitro and in vivo experiments with SARS-CoV-2 virus. The device embeds a far-UVC lamp emitting at 222 nm, optical filters, and the controlling electronics. We show results on the spatial homogeneity of the emission intensity and the dependence on the lamp-virus distance. We also report on the ozone production due to absorption of far-UVC light from molecular oxygen naturally present in the air in order to evaluate its safety for human being and to properly evaluate its photo-killing efficacy.