Virus inactivation and skin safety studies using far‐ UVC LEDs

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 cm 2 /mJ, which corresponds to a D 90 of 0.58 mJ/cm 2 . 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 cm 2 /mJ and k 1_233‐glass = 7.2 ± 3.0 cm 2 /mJ which were not significantly different. For safety evaluation, human skin biopsies exposed to 100 mJ/cm 2 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/cm 2 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.