A New Standard in Disinfection

The impact of far-UVC radiation (200–230 nm) on pathogens, cells, skin, and eyes – a collection and analysis of a hundred years of data

Martin Hessling Robin Haag Nicole Sieber Petra Vatter

UVC light, particularly at the 222 nm wavelength, is redefining decontamination practices across industries. More than 100 papers on far-UVC disinfection, published within the last 100 years, were found. Far-UVC radiation, especially the 222 nm emission of KrCl excimer lamps, exhibits strong antimicrobial properties. The average necessary log-reduction doses are 1.3 times higher than with 254 nm irradiation. A dose of 100 mJ/cm2 reduces all pathogens by several orders of magnitude without harming human cells, if optical filters block emissions above 230 nm.

Inactivation of Microorganisms

More than 100 studies on the impact of far-UVC radiation on microorganisms were found in the literature. Among them, many investigations dated from the first half of the last century and some were even performed about a hundred years ago, an impressive accomplishment con-sidering the available (lamp) technology at that time. Unfortunately, not all of these investigations could be in-cluded in the following analysis because the inactivated microorganisms were not determined, or the inactivation doses were given in dimensions such as energy per volume, which could not be converted to today’s typical dose dimension of energy per area. The more recent far-UVC investigations were mostly performed with krypton chloride (KrCl) excimer lamps with a peak emission at 222 nm. Only a few re-searchers applied a broadband UVC source in combina-tion with a monochromator or optical filters or even lasers. The data collection – about 250 single far-UVC results for 14 bacterial species, 9 bacterial spores, 5 fungi, 23 viruses and one protist – can be found in Table 1, divided into bacteria, bacterial spores, fungi, viruses, and protists and sorted by microorganism, wavelength and media (L: liquid, S: surface, A: air/aerosol), which were in most cases liquids (salt solutions). For each microorganism (species), the median value for the log-reduction dose was determined and compared to the median log-reduction dose for the wavelength of 254 nm of mercury vapor lamps by calculation of the log-reduction dose ratio.

Hessling – The impact of far-UVC radiation (200–230 nm) on pathogens, cells, skin, and eye.

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UV222® inactivation of pathogens