Synergistic disinfection of aerosolized bacteria and bacteriophage by far-UVC (222-nm) and negative air ions

Nitrate Protects Microorganisms and Promotes Formation of Toxic Nitrogenous Byproducts during Water Disinfection by Far-UVC Radiation

“…18,29−31 This suggests that Far-UVC may pose higher inactivation efficiency than UVC at 254 nm. This hypothesis is supported by recent publications about inactivation of various pathogens by Far-UVC in aerosol, 15,16,19,20,32 water, 3,13,29,33−42 and on surfaces. 43,44 inactivating bacteriophage Phi6 and human coronavirus 229E in buffered deionized water.…”

“…The UV absorption of DNA/RNA of microorganisms has been reported to be comparable (∼1 fold) at 222–254 nm, but that of proteins is much higher (∼20 fold) at 222 nm. ,− This suggests that Far-UVC may pose higher inactivation efficiency than UVC at 254 nm. This hypothesis is supported by recent publications about inactivation of various pathogens by Far-UVC in aerosol, ,,,, water, ,,,− and on surfaces. , For example, Ma et al reported that 222 nm is 12-fold and 1.4-fold, respectively, more effective than 254 nm in inactivating bacteriophage Phi6 and human coronavirus 229E in buffered deionized water . Another study also reported that the inactivation rate constant of SARS-CoV-2 in buffered deionized water is 1.8-fold higher at 222 nm than 254 nm on the same UV fluence basis .…”

“…Far-UVC radiation in the range of 200–230 nm has emerged as a promising UV disinfection tool during the COVID-19 pandemic. It can be provided via several UV radiation sources (e.g., excimer lamps and UV light-emitting diodes), among which the krypton-chloride excimer (KrCl*) lamp with an emission peak at 222 nm is the most mature and commercially available one. − The KrCl* excimer lamp has no mercury and a reasonably high wall plug efficiency (0.5–7.0%) compared to Far-UVC-LEDs (<0.5%). , It generates a negligible amount of ozone during use, , and the radiation at 222 nm is safer than 254 nm to human tissues (e.g., skin and eyes) in air/surface disinfection applications since 222 nm photons barely penetrate through the dead cell layer of skin (stratum corneum). ,− The penetration of Far-UVC in deionized water is not a problem since water molecules (H 2 O) barely absorb UV radiation at 222 nm . The UV absorption of DNA/RNA of microorganisms has been reported to be comparable (∼1 fold) at 222–254 nm, but that of proteins is much higher (∼20 fold) at 222 nm. ,− This suggests that Far-UVC may pose higher inactivation efficiency than UVC at 254 nm.…”

Negligible increase in indoor endotoxin activity by 222 nm far-UVC illumination on bioaerosols

“…, 2 mJ cm −2 ) of 222 nm can afford effective inactivation of airborne microorganisms for indoor applications. 21,44,45 By using a well-controlled chamber system, our results suggest a negligible endotoxin release under this UV dose. We encourage further investigations on the variation in endotoxin level due to 222 nm in different natural indoor environments.…”

Rapid Inactivation of Fungal Spores in Drinking Water by Far-UVC Photolysis of Free Chlorine

“…Recently, Far-UVC radiation in the wavelength range of 200–230 nm has been recognized as a very effective method for water disinfection. − It can be provided by krypton-chloride excimer (KrCl*) lamp, which is characterized by a primary emission peak centered at approximately 222 nm (UV 222 ). ,,− Such a lamp has several advantages, e.g., contains no mercury, has improving wall-plug efficiency (10–15%), and requires short stabilization time (15 s). ,, UV 222 is safer for human skin and eye tissues than conventional UV 254 because it does not substantially penetrate the stratum corneum or the corneal epithelium. ,− UV 222 , while highly absorbed by the surrounding matrix, has higher efficiency than UV 254 in the inactivation of viruses in aerosol, water, and on surfaces because it can simultaneously damage nucleic acids and proteins of the microorganisms. ,− ,,,− However, the effectiveness of UV 222 on the inactivation of fungal spores remains unclear. Unlike UV 254 , UV 222 has been demonstrated to inhibit the photoreactivation of E.…”