Biological Impact of Shorter Wavelength Ultraviolet Radiation‐C^†

Abstract

Life on earth has constantly coped with the impact of solar radiation, especially solar ultraviolet radiation (solar UV). Various biological mechanisms protect us from solar UV. New devices emitting shorter wavelengths UV-C, i.e. <254 nm emitted by conventional UV germicidal lamps, have emerged. These shorter wavelength UV-C emitting devices are useful for various purposes, including microorganism inactivation. However, as solar UV-C does not reach the earth surface, biological impacts of UV-C has been studied using 254 nm germicidal lamps, and those using shorter wavelength UV-C is rarely known. To balance the utility and risk of UV-C, the biological effect of these new UV-C emitting devices must be investigated. In addition, our knowledge of biological impacts of the wavelength-dependent entire UV (100-400 nm) must be enhanced. In this review, we briefly summarize the biological impacts of shorter wavelength UV-C. Mechanisms of UV-C-induced cellular damage and factors affecting the microorganism inactivation efficiency of UV-C have been discussed. In addition, we theoretically estimate the probable photocarcinogenic action spectrum of shorter wavelength UV-C. We propose that increasing the knowledge on UV-C will facilitate the adoption of shorter wavelength UV-C emitting new devices in an optimal and appropriate manner.

New insights into the effects of UV light on individual Nosema bombycis spores, as determined using single‐cell optical approaches

“…UV light primarily induces DNA/RNA damage in organisms and should also act on the nucleic acids of microsporidia; 41 previous studies have mainly focused on the inactivating effect of UV radiation on microsporidia. 13,14,[29][30][31] However, the germination of Nb spores is not related to nucleic acids, but is an intricate process involving stimulated signal transduction and the extrusion of polar filaments.…”

Assessing the safety of new germicidal far‐UVC technologies

“…Wavelengths below approximately 235 nm are strongly absorbed by proteins (Figure 3) and lipids in the stratum corneum, which significantly reduces their penetration into the skin (Figure 4). 10,14,[54][55][56][57][58] There are slight differences in the optical properties between the stratum corneum, epidermis and dermis. 59 Absorption and scattering is less pronounced in the stratum corneum compared to the other layers.…”

“…Previous studies of transmittance in the stratum corneum and epidermis have mostly been limited to wavelengths above 240 nm. 14 Therefore, it will be essential to measure the spectral transmittance of far-UVC to understand how different wavelengths interact with these layers. As its thickness can vary at different body sites and with interventions like the application of exfoliating agents or shaving, experiments should generally monitor the integrity and thickness of the stratum corneum.…”

“…The increased safety of far-UVC is attributed to its limited penetration into living tissues. 10,14,15 These findings spurred academic and commercial interest in far-UVC for "wholeroom" disinfection, particularly during the COVID-19 pandemic. Crucially, the whole-room approach allows for direct exposure within the lower room, providing rapid disinfection of airborne pathogens within the occupant's breathing zones.…”

“…determined that 222 nm achieved approximately twice the rate of inactivation as 254 nm for a select number of respiratory viruses. The increased safety of far‐UVC is attributed to its limited penetration into living tissues 10,14,15 . These findings spurred academic and commercial interest in far‐UVC for “whole‐room” disinfection, particularly during the COVID‐19 pandemic.…”