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Evaluation of Acute Reactions on Mouse Skin Irradiated with 222 and 235 nm UV-C.

ABSTRACT: Biological response and DNA damage following irradiation with shorter wavelengths in the UV-C range were evaluated to investigate the safety at three wavelengths because of the recent emergence of germicidal equipment emitting short-wavelength UV-C for various purposes, including medical uses. To estimate an acceptable safety dose for human skin in the UV-C range, especially short UV-C, we studied the biological effects of 207, 222 and 235 nm UV-C using albino hairless mice and evaluated the inflammatory reactions in the skin. To explore an appropriate indicator to evaluate the biological response, we employed determination of the minimal perceptible response dose (MPRD), by which any subtle cutaneous response; erythema, edema and scale could be observed by visual inspection. Erythema was rarely observed, but edema and scale formation were evident for short UV-C wavelengths. The MPRD at 207, 222 and 235 nm was determined to be > 15, 15 and 2.0 kJ m^-2 , respectively. These values could be thresholds and indicators for possible safety assessments. Our data suggest that the current human exposure limits for short UV-C wavelengths below 254 nm are overly restrictive and should be reconsidered for future disinfection lamps with short UV-C wavelengths.

SUBMITTER: Yamano N

PROVIDER: S-EPMC8359381 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundIn dentistry, instruments, appliances, and body fluids such as saliva or blood are possible sources of infection. Although conventional antiseptic procedures effectively prevent infection, spittoons cannot be sanitized between each treated patient and are usually washed only with running water. However, there is currently no fast and efficient disinfection method that can be implemented between treatments. An optically filtered krypton chloride excimer lamp using ultraviolet light (Far UV-C) in the 200-230 nm wavelength range (innocuous to humans) has been recently used as a virus- and bacteria-inactivating technology. This study aimed to identify the bioburden of a dental spittoon and examine the susceptibility of two oral Streptococcus and two Enterococci to 222-nm Far UV-C by irradiating the spittoon with 222 nm Far UV-C for 5 min before evaluating the disinfection effect.MethodsBacterial analysis and real-time polymerase-chain reaction testing was used to confirm the spittoon's biological contamination. Bacterial susceptibility to a 222-nm Far UV-C was determined with a graded dose irradiation test. After each treatment, the spittoon was irradiated with 222-nm Far UV-C for 5 min, and the disinfecting effect was evaluated. Microbial analysis of the spittoon's surface was performed using the Silva database.ResultsWe found that > 97% of the microbes consisted of six bacterial phyla, whereas no viruses were found. Pseudomonas aeruginosa was frequently detected. The 1-log reduction value of two oral-derived Streptococci and two Enterococci species at 222-nm Far UV-C was 4.5-7.3 mJ/cm2. Exposure of the spittoon to 222-nm Far UV-C at 3.6-13.5 mJ/cm2 significantly decreased bacterial counts (p < 0.001).ConclusionsIrradiation with 222-nm Far UV-C at 3.6-13.5 mJ/cm2 significantly eliminates bacteria in spittoons, even when they are only rinsed with water. Hence, 222-nm Far UV-C irradiation may inhibit the risk of bacterial transmission from droplets in sink surfaces.

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Evaluation of Acute Reactions on Mouse Skin Irradiated with 222 and 235 nm UV-C.

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