Date of review by ARPANSA
2 December 2024
Article publication date
29 September 2024
Summary
This study examined the effect of short wavelength ultraviolet (UV) radiation on the acute skin response in mice. Hairless mice were irradiated with UVC light of wavelengths between 200-270 nanometres (nm) at varying intensity. The mice were then visually inspected for various skin damage markers like reddening and fissures at 24, 48 and 72 hours after exposure. The UV radiation dose required to produce a perceptible skin response increased greatly as the wavelength became shorter, ranging from 80.8 J/m2 at 270 nm to 269000 J/m2 at 215 nm. Doses for wavelengths shorter than 215 nm increased further but were excluded from later discussion due to high measurement uncertainty.
The highest dose where no adverse skin effect was observed was estimated as the safe dose for that wavelength and compared to limits published by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the American Conference of Governmental Industrial Hygienists (ACGIH). The comparison shows that substantially more UVC radiation (at wavelengths below 240 nm) was needed to cause skin damage in mice than the limit values described by the ICNIRP and the ACGIH. The authors further suggest that the values derived from the mouse tests will under-estimate the threshold in humans due to the thicker outer layers in human skin.
Published in
Photochemistry and Photobiology
Link to study
Extending the acute skin response spectrum to include the far-UVC
ARPANSA's commentary
Historically, interest in UV radiation with respect to health has been mostly restrained to wavelengths that are a component of solar radiation at the Earth’s surface (280-400 nm). An increase in interest for germicidal applications of far UVC light represents a need to re-evaluate the potential health effects of this type of light so that germicidal devices can be used safely. This study presents new evidence for the level at which UVC radiation can cause acute skin effects and thus how antimicrobial technology could be more effectively operated at higher power while maintaining safety.
It should be noted that this study only investigated the acute skin effects of UVC exposure. Other well-documented effects of UV radiation like direct DNA damage (Mizutani, R. & Yokoyama, H., 2014; You, Y. et al., 2001) and the production of ozone (Claus, H. 2021) which can lead to chronic health outcomes must also be evaluated for a complete assessment of safety. The exposure limits set by the ICNIRP are designed to protect against long-term and delayed effects of UV radiation in addition to acute skin effects. Therefore, the comparison between the ICNIRP limits and the results of this study, which only considers acute skin effects, is somewhat mismatched. Further, when assessing the overall safety of far UVC light, consideration must also be given to the harmful effects to the eyes in addition to the skin.
Although exposure to UVC radiation from germicidal devices poses some hazards, exposure to intense UVA and UVB radiation from the sun remains the largest contributor to personal UV radiation exposure and risk for Australians. ARPANSA recommends following the five sun protection principles whenever the UV index is over three.
