To evaluate the safety of repeated eye and skin exposure to a 222-nm germicide lamp, xeroderma pigmentosum group A model mice were used in this study.
Compared to wild-type mice, these model mice have an increased sensitivity to ultraviolet radiation and an over 10,000 fold increased risk of developing skin cancer.
In the group that was exposed to UVB (280-315 nm), the wavelength range equivalent to skin cancer caused by sunlight, all mice developed skin cancer and displayed adverse effects such as cataracts and cornea damage.
Conversely, mice in the 222-nm germicide lamp group did not develop skin cancer at all. The effect on their eyes was investigated in cooperation with Shimane University’s Department of Ophthalmology (Professor TANITO Masaki et al.). There were no abnormalities visible, even when examined under a microscope (Figure 1).
It was understood that 222-nm produced no adverse effects due to the level of skin penetration. The 254-nm UVC currently used in germicide lamps penetrates down to the basal cell layer, the bottommost layer of the skin, and damages the DNA of cells. On the other hand, it was shown that 222-nm UVC doesn’t damage the DNA of skin cells because it only travels as far as the stratum corneum, the outermost layer of the skin.
These research results indicate that even though 222-nm UVC is a powerful sterilizer, it can also be used directly on human skin. Beginning with hand sanitization in medical institutions, it is expected that this technology will have a wide range of antiviral and antibacterial applications in places that people enter, such as schools, welfare facilities, food factories, toilets and kitchens.