Virus inactivation and skin safety studies using far‐ <scp>UVC LEDs</scp>

Reducing airborne disease transmission is a public health goal. Far-UVC light, defined as 200-235 nm, is a promising technology to inactivate viruses within occupied spaces. This work examines state of the art far-UVC emitting LEDs, with a center emission wavelength of 233 nm, for virus inactivation efficacy and for DNA damage to skin models. The LEDs were used to expose an aerosolized surrogate of SARS-CoV2, the human coronavirus OC43, and survival results estimated a susceptibility constant of k_233-aerosol = 4.0 ± 0.2 cm²/mJ, which corresponds to a D₉₀ of 0.58 mJ/cm². HCoV-OC43 was also exposed after drying on a plastic or glass surface, and inactivation results estimated susceptibility values of k_{1_233-plastic} = 6.7 ± 3.8 cm²/mJ and k_{1_233-glass} = 7.2 ± 3.0 cm²/mJ which were not significantly different. For safety evaluation, human skin biopsies exposed to 100 mJ/cm² from the 233 nm LEDs indicated only 8% of the epidermal cells were positive for DNA damage, whereas the same dose from a 254 nm lamp showed damage in 45% of epidermal cells. A radiant exposure of 100 mJ/cm² from the 233 nm LEDs did not produce DNA double strand breaks within the skin biopsies. These tests for the safety and efficacy of a 233 nm far-UVC LED system provide support for the continued development of far-UVC LED sources.