Researchers have 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.
No inflammatory response induced by 222‐nm UVC irradiation
Chronic 222‐nm UVC irradiation did not induce skin tumors
No effect of chronic 222‐nm UVC on the mouse eye
222‐nm UVC did not produce dipyrimidine photoproducts and inflammatory responses in mouse skin
In conclusion, they suggested the safety of 222‐nm UVC lamps for the sterilization of human skin, with no evidence of skin carcinogenesis on long‐term exposure, even for highly skin photocarcinogenesis phenotype mice, in addition to no inflammatory reactions and no harmful effects on mouse eyes.