Far ultraviolet-C radiation from a filtered KrCl lamp does not result in migration of Langerhans cells in human skin

ABSTRACT

There is global interest in both the beneficial and detrimental health effects of ultraviolet-C (UVC) radiation in the wavelength range 200-230 nm (known as Far-UVC). Technology using Far-UVC is proposed as a highly effective control measure for reducing the transmission of COVID-19. Far-UVC, and other wavelengths of UVC, are well-known to efficiently inactivate pathogens in air and on surfaces. Although studies have shown irradiation of skin with 254 nm UV results in DNA damage in the epidermal basal layer, irradiation with Far-UVC (222 nm) shows minimal DNA damage and only in the granular layer, which is comprised of non-proliferating keratinocytes. Therefore, accumulation of these DNA photoproducts would not be expected to be associated with cancer risk. It has also been shown that even high doses of Far-UVC exposure to human skin do not induce erythema. However, the effects of Far-UVC on the immune system are, to the best of our knowledge, unknown. It is well-reported that both ultraviolet B (UVB 280-315 nm) and ultraviolet-A (UVA 315-400 nm) have effects on cutaneous Langerhans cells (LC), inducing migration from the epidermis to the draining lymph nodes, thereby suppressing skin immune function. Here we present data generated in a range of skin types (Fitzpatrick II-V) demonstrating little or no impact of Far-UVC on the cutaneous immune system, as assessed by Langerhans cell migration, at doses of up to 3,000 mJ/cm2 (US daily limit is 450 mJ/cm2). These results support the safety of filtered Far-UVC use, which could have a transformative effect on public health, allowing effective virus inactivation and reduction of transmission independent of human behavior. Conflict of interest disclosure the authors state no conflict of interest. However, MJC and RPH are directors of Ten Bio Ltd, a company focused on developing human skin explant models.