222 nm far-UVC light and skin health: Assessment of DNA damage across different skin types.

Due to a limited penetration into skin and eyes combined with a broad germicidal effectiveness, far-UVC light (200-235 nm) has been proposed as an effective intervention for airborne pandemic control. Specifically, 222 nm light is not predicted to damage skin because it is primarily absorbed by the proteins in the superficial stratum corneum of the epidermis. Thus, it is hypothesized that the thickness of the stratum corneum is one of the most significant contributing factors to the risk of skin damage from exposure to far-UVC. From measurements of the stratum corneum thickness in live human skin biopsies, it was found that none of the donor demographics studied had an impact on the thickness of the stratum corneum. While multiple studies suggest that exposure to 222 nm is minimally damaging to skin, a few studies to date have investigated effects as a function of skin characteristics (e.g., individual's age and sex). In selected tissues, the induction of DNA damage following an acute exposure to 100 or 500 mJ/cm² from 222 nm light was analyzed as a function of donor demographics. The results agree with previous studies using other models of human skin and show that in human skin biopsies, 222 nm induces minor DNA damage only at high doses, especially in skin with low melanin content (phototype).