On Aug.19, 2020, the U.S. Food and Drug Administration (FDA) issued a statement, “UV Lights and Lamps: Ultraviolet-C Radiation, Disinfection and Coronavirus”, intended primarily to address consumer questions about the use of UV-C technology, given the current interest in UV-C lamps and devices for home use. This bulletin aims to share the available evidence and to address questions regarding the effectiveness of UV-C germicidal light against coronavirus and its safety in use.
It is important for both home consumers and commercial users to conduct due diligence into any manufacturers’ technical data, scientific evidence and safety data prior to selecting and using any ultraviolet device.
Efficacy: Can UV-C lamps inactivate the SARS-CoV-2 coronavirus?254nm UV-C evidence
The evidence regarding UV-C efficacy for SARS-CoV-2 virus is still evolving, similar to overall understanding of many facets regarding the novel coronavirus and various strains. However, available evidence suggests that germicidal UV-C radiation is effective for the inactivation of SARS-CoV-2 and other microbial pathogens.
SARS-CoV and SARS CoV-2 are structurally-similar viruses; both are non-segmented, enveloped, single-stranded RNA (ssRNA) viruses and it is likely that the UV dose-response behaviors of SARS-CoV and SARS-CoV-2 will be similar. Effectiveness of UVC on SARS-CoV, MERS-CoV as well as surrogate viruses such as Human Coronavirus strain HCoV-229E, HCoV-OC43, and MS2 has been reported in the literature.
During the period of this pandemic, several early reports of responses of SARS-CoV-2 and related viruses to UV radiation have been reported in the scientific literature and in press releases.
· Bianco et al. reported even a “very small dose” of 254nm UV-C was enough to achieve full inactivation of the SARS-CoV-2 virus.
· Krawszyki et al. have also reported that SARS-CoV-2 is highly susceptible to irradiation with ultraviolet light.
Most of these studies for UVC-effectiveness were based on UV radiation at or near the wavelength (254 nm) that characterizes the output of low-pressure (LP) mercury lamps, which are the most commonly used sources of germicidal UV radiation.
· Inagaki et al. indicated that even using a deep UVC LED source emitting 280nm wavelength was effective in the inactivation of SARS-CoV-2.
In addition, 254nm UV-C disinfecting devices have been proven effective against harder-to-kill pathogens than SARS-Cov-2, such as C.difficile and MRSA found in healthcare settings, as multiple clinical studies published in peer-reviewed journals indicate.
Leading industry organizations, such as the International Ultraviolet Association (IUVA) and American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), have assembled leading experts from around the world to develop guidance on the effective use of UV technology to help reduce the transmission of COVID-19 virus and to advise on proper selection and operation of equipment for UV disinfection of air and surfaces.
Safety: Is it safe to use a UV-C lamp for disinfection purposes?
The FDA cites several potential health and safety risks to people and objects in using UV-C, including the presence of mercury, ozone emission and materials compatibility. This section addresses the proven safety of UV-C lamps.
Is UV-C exposure safe for humans?
Direct exposure to UV-C light should be avoided as it can damage the skin and the eyes. Suitable personal protective equipment (PPE) should be worn at all times, when there is a risk of UV exposure to the skin or eyes. Hence, general machine-human safety needs to be addressed in the operations manual, end-user training, and appropriate safety regulatory compliance with all disinfection devices.
Does mercury pose a safety hazard?
Many UV-C low pressure mercury lamps contain less mercury than is found in commonly used fluorescent office lamps. For an abundance of caution, it is recommended to use products, where the lamps have been encapsulated with a protective polymer encapsulation to contain the glass and small amount of mercury in case of breakage.
Does UV-C germicidal cause surface discoloration or damage?
With regards to materials compatibility, it is important to review manufacturer testing closely on a case-by-case basis. While UV-C light is not known to cause any structural or material damage to most materials, it can have slight aesthetic impact such as slight discoloration or surface etching over prolonged exposure. Minimizing exposure by running the device for the shortest manufacturer recommended cycle times can help minimize impact.
