Comparative study of inactivation efficacy of far-UVC (222 nm) and germicidal UVC (254 nm) radiation against virus-laden aerosols of artificial human saliva.

Virus-laden aerosols play a substantial role in the spread of numerous infectious diseases, particularly in enclosed indoor settings. Ultraviolet-C (UVC) disinfection is known to be a highly efficient method for disinfecting pathogenic airborne viruses. Recent recommendations suggest using far-UVC radiation (222 nm) emitted by KrCl* (krypton-chloride) excimer lamps to disinfect high-risk public spaces due to lower exposure risks than low-pressure (LP) mercury lamps (254 nm). This study experimentally explored the comparative effectiveness of far-UVC (222 nm) and germicidal UVC (254 nm) in inactivating virus-laden aerosols of different protective vector media in an air disinfection chamber. The UVC inactivation performances of individual filtered KrCl* excimer lamp and LP mercury lamp were determined for inactivating the bacteriophages, MS2 (icosahedral and non-enveloped ssRNA virus) and Phi6 (spherical and enveloped dsRNA virus) aerosolized from artificial human saliva or sodium chloride and magnesium sulfate (SM) buffer as a vector media. Disinfection efficacy of filtered KrCl* excimer lamp (222 nm) and LP mercury lamp (254 nm) were evaluated for highly concentrated viral aerosols, which replicate those exhaled from infected individuals and remain suspended in air or deposited on surfaces as fomites. Our results show that using individual filtered KrCl* excimer lamp (222 nm) and LP mercury lamp (254 nm) could greatly accelerate the inactivation of the viral bioaerosols formed from artificial human saliva and SM buffer. In the case of 222 nm exposure, Phi6 exhibited significantly more susceptibility in artificial human saliva than in SM buffer whereas MS2 showed comparable vulnerability in both artificial human saliva and SM buffer. However, in the case of 254 nm exposure, both Phi6 and MS2 demonstrated significantly greater susceptibility in artificial human saliva than in SM buffer. This study offers valuable insights and improves our understanding of the influence of different vector media on UVC disinfection of exhaled virus-laden aerosols in indoor environments. These findings can guide the deployment of UVC devices which could greatly contribute to mitigating the transmission of exhaled bioaerosols in public settings.