Effective ultraviolet C light disinfection of respirators demonstrated in challenges with Geobacillus stearothermophilus spores and SARS-CoV-2 virus

Abstract

Background The global Covid-19 pandemic accompanied by spikes in the number of patients in hospitals, required substantial amounts of respiratory protective devices (respirators) thereby causing shortages. Disinfection of used respirators by applying UVC light may enable safe reuse, reducing shortages. Here, UVC light is explored for disinfection of respirators. Aim To determine whether UVC disinfection is applicable to enable repeated safe reuse of respirators. Methods The UVC chamber (BioShift™, Signify, The Netherlands) equipped with LP mercury discharge lamps emitting at 254 nm, was used to determine the sporicidal and virucidal effects. Respirators challenged with spores and viruses were exposed to various UVC energy levels. Deactivation of the biological agents was studied and UVC effects on particle filtration properties and respirator fit. Findings A 5-log reduction of G. thermophilus spore viability by a UVC dose of 1.1 J/cm 2 was observed. By simulating spores present in the middle of the respirators, a 5-log reduction was achieved at a UVC dose of 10 J/cm 2 . SARS-CoV-2 viruses were inactivated by 4 logs upon exposure to 19.5 mJ/cm 2 UVC. In case UVC must be transmitted through all layers of the respirators to reach the spores and virus, a more than 5-log reduction was achieved using a UVC dose of 10 J/cm 2 . Exposure to a six times higher UVC dose did not significantly affect the integrity of the fit nor aerosol filtering capacity of the respirator. Conclusion UVC was shown to be a mild and effective way of respirator disinfection allowing for reuse of the UVC treated respirators.

Photoactive decontamination and reuse of face masks

“…When the dose of UVC is 10 J/cm 2 , UVC can contact with viruses and microorganisms in all parts of the mask, and make their reduction of >5 log10 (The J/cm 2 is widely used in decontamination literature to show UVC flux). At doses up to 6 times higher than the standard dose, the respirator fitting integrity and filtration capacity would not be significantly affected [75] . Studies have shown that the ideal dose of some N95 FFRs is 1.5J/cm 2 [29] .…”

Irradiation of human oral mucosa by 233 nm far UV-C LEDs for the safe inactivation of nosocomial pathogens

“…Conventionally, UV-C sources at 254 nm are used for the disinfection of surfaces 13 , instruments 14 or room air 15 , 16 in shielded air cleaners that prevent human exposure. This is crucial, as UV-C radiation at 254 nm is highly cytotoxic, reduces cell viability 17 and causes a large amount of DNA damage.…”