Long‐term Effects of 222‐nm ultraviolet radiation C Sterilizing Lamps on Mice Susceptible to Ultraviolet Radiation

Abstract

Germicidal lamps that emit primarily 254 nm ultraviolet radiation (UV) are routinely utilized for surface sterilization but cannot be used for human skin because they cause genotoxicity. As an alternative, 222‐nm UVC has been reported to exert sterilizing ability comparable to that of 254‐nm UVC without producing cyclobutane pyrimidine dimers (CPDs), the major DNA lesions caused by UV. However, there has been no clear evidence for safety in chronic exposure to skin, particularly with respect to carcinogenesis. We therefore investigated the long‐term effects of 222‐nm UVC on skin using a highly photocarcinogenic phenotype mice that lack xeroderma pigmentosum complementation group A ( Xpa ‐) gene, which is involved in repairing of CPDs. CPDs formation was recognized only uppermost layer of epidermis even with high dose of 222‐nm UVC exposure. No tumors were observed in Xpa ‐knockout mice and wild‐type mice by repetitive irradiation with 222‐nm UVC, using a protocol which had shown to produce tumor in Xpa ‐knockout mice irradiated with broad‐band UVB. Furthermore, erythema and ear swelling were not observed in both genotype mice following 222‐nm UVC exposure. Our data suggest that 222‐nm UVC lamps can be safely used for sterilizing human skin as far as the perspective of skin cancer development.

Far-UVC light efficiently and safely inactivates airborne human coronaviruses

“…An exposure dose as low as 1.2 to 1.7 mJ/cm 2 of 222-nm light inactivates 99.9% of the airborne human coronavirus tested from both subgroups beta and alpha, respectively. Together with previous safety studies [12][13][14][15][16][17][18] and our earlier studies with aerosolized influenza A (H1N1) 23 , these results indicate that far-UVC light is a potentially powerful and practical approach for reduction of airborne viral transmission, without the human health hazards associated with conventional germicidal UVC lamps. Benchtop Aerosol Irradiation Chamber.…”

“…The sensitivity of the coronaviruses to far-UVC light, together with extensive safety data even at much higher far-UVC exposures [12][13][14][15][16][17][18] , suggests that it will be feasible and safe to have the lamps providing continuous far-UVC exposure in public places to significantly reduce the probability of of 2 would halve these disinfection times, while still maintaining safety [12][13][14][15][16][17][18] .…”

“…Thus far-UVC light has about the same highly effective germicidal properties of UV light, but without the associated human health risks [12][13][14][15] . Several groups have thus proposed that far-UVC light (207 or 222 nm), which can be generated using inexpensive excimer lamps, is a potential safe and efficient anti-microbial technology [12][13][14][15][16][17][18] which can be deployed in occupied public locations.…”

Effectiveness of 222-nm ultraviolet light on disinfecting SARS-CoV-2 surface contamination

“…In contrast, recent studies have shown that 222-nm UVC is less harmful than 254-nm UVC because far-UVC light has a very limited penetration depth in the skin or eyes and it is also an efficient anti-microbial technology. [9][10][11][12][13] Therefore, a 222-nm UVC disinfection system could be used in occupied public spaces including a hospital room, which is occupied by patients and frequented by health care workers and possibly, visitors. However, further study about the safety and efficacy of 222-nm UVC irradiation in occupied space is needed.…”

“…Previous reports demonstrated that 222-nm UVC light, belonging to far-UVC (207-222 nm), has the same highly effective germicidal properties as 254-nm UVC; however, it is less harmful to the skin and eyes than 254-nm UVC because far-UVC light has a very limited penetration depth in the skin or eye. [9][10][11][12][13] In addition, previous studies have reported that low dose of 222-nm UVC inactivated aerosolized H1N1 influenza virus and human coronaviruses alpha HCoV-229E and beta HCoV-OC43. 14,15 Although there are a few reports about the effectiveness of UV disinfection on SARS-CoV-2, 16,17 the effect of 222-nm UVC on SARS-CoV-2 is poorly understood.…”