222-nm far UVC exposure results in DNA damage and transcriptional changes to mammalian cells

Abstract

Ultraviolet (UV) germicidal tools have recently gained attention as a disinfection strategy against the COVID-19 pandemic but the safety profile arising from their exposure have been controversial and impeded larger scale implementation. We compare the emerging 222-nm far UVC and 277-nm UVC LED disinfection modules with the traditional UVC mercury lamp emitting at 254 nm to understand their effects on human retinal cell line ARPE-19 and HEK-A keratinocytes. Cells illuminated with 222-nm far UVC survived while those treated with 254-nm and 277-nm wavelengths underwent apoptosis via JNK/ATF2 pathway. However, cells exposed to 222-nm far UVC presented the highest degree of DNA damage as evidenced by yH2AX staining. Globally, these cells presented transcriptional changes in cell cycle and senescence pathways. Thus, the introduction of 222-nm far UVC lamps for disinfection purposes should be carefully considered and designed with the inherent dangers involved.

Actinic Radiation, Viruses, Bacteria, the Open Air Factor (OAF) and Indoor Sterilization with UV-C Radiation

“…From an indoor point of view, the use of 222 nm and 254 nm radiation will not only be a potential hazard to people via the direct effect of the radiation, but also by their photochemical effects [5] on indoor airborne compounds. While there are papers saying that 222 nm radiation is safe in regard to eye and skin damage [16][17][18], there is also work showing DNA damage in cells [19]. The 222 nm wavelength just overlaps the Schumann-Runge absorption system of O 2 , which initiates the production of odd oxygen, while the 254 nm wavelength is centred in the oxygen atom and excited oxygen molecule producing Hartley band of the ozone, the mechanism for producing oxygen atoms and ozone naturally in the stratosphere and the polluted troposphere.…”

Model Evaluation of Secondary Chemistry due to Disinfection of Indoor Air with Germicidal Ultraviolet Lamps

“…4 As 254 nm UV can cause skin and eye irritation, 5 GUV254 is usually applied near the ceiling (Figure 1a) or inside ventilation ducts. Recently, 222 nm UV has been shown to not only have strong capability of inactivating airborne viruses, 6 but also is claimed to be safe to humans 7 (although this is controversial), 8 potentially allowing whole-room GUV applications (“GUV222”) (Fig. 1b).…”

“…4 As 254 nm UV can cause skin and eye irritation on overexposure, 5 GUV254 is usually applied near the ceiling, either inside an enclosed ceiling-mounted box, or irradiating the open air in the upper room (Figure 1a) or inside ventilation ducts. Recently, 222 nm UV has been shown to not only have strong capability of inactivating airborne viruses, 6 but also is reported by some 7 to be safer to humans (despite reports of the contrary), 8 potentially allowing whole-room GUV applications (GUV222) (Fig. 1b).…”