By ECRI
The COVID-19 pandemic has thrust many medical technologies into the spotlight. Ultraviolet (UV) disinfection systems – devices that use light from the UV spectrum to disinfect surfaces – are one of those technologies. “We’re getting questions every day about ways hospitals can use these systems to help stop the spread of the SARS-CoV-2 virus,” explains Mairead Smith, senior project engineer in ECRI’s device evaluation group.
ECRI’s evaluations of two different configurations – moveable towers used for room disinfection and countertop models designed to disinfect tablets, phones and other small devices – show that the technology can effectively reduce bioburden on surfaces. With respect to SARS-CoV-2 in particular, experts expect its response will be similar to other coronaviruses, like SARS-CoV-1 and MERS-CoV, which have been shown to be inactivated by UV light. “But,” Smith stresses, “proper use is key.”
Note: This article was developed in early April 2020. With the rapid pace of change associated with the COVID-19 pandemic, the challenges facing hospitals and the evidence supporting various methods may evolve substantially by the time of publication.
Disinfecting with UV Light
At the right wavelengths and with an appropriate exposure time, UV energy can disrupt the DNA or RNA of microorganisms that are exposed to the light, preventing them from replicating. Studies indicate that sufficient exposure to UV light can inactivate a wide range of microbes, including methicillin-resistant Staphylococcus aureus (MRSA) and Clostridioides difficile (C. diff). Most UV disinfection devices use UVC light – that is, light within the 200-280 nm range, although some systems use UVB or far-UV wavelengths.
Within a health care facility, the technology may be applied in various ways:
- Room disinfection devices typically consist of a movable tower that houses mercury or xenon lamps that emit UV light. The devices may be placed in patient rooms, procedure rooms or other locations following cleaning to help fight environmental contamination. Depending on the system, the tower (or towers) may remain in one location during the disinfection cycle, or the cycle may be paused, and the device repositioned midway through the treatment period.
- Countertop models are smaller, enclosed devices that are typically used to disinfect mobile devices such as phones or tablets – items that may be susceptible to damage by chemical disinfection methods. Users first clean the surface of the item to remove debris; then they place it in the UV device and initiate the disinfection cycle.
- Additional designs include wall- or ceiling-mounted systems, systems designed for use in air-handling units and other configurations.
When used properly and as a supplement to normal cleaning and disinfection processes, UV disinfection can be effective at reducing the environmental bioburden in a facility. However, UV disinfection technology may be less effective, or on occasion dangerous, if not used properly.
During the COVID-19 pandemic, it has been suggested that UV disinfection units could be used to disinfect N95 respirators to help address personal protective equipment (PPE) shortages. At the time of this writing, ECRI considers that approach acceptable in limited reuse situations, but cautions that UV disinfection could (1) be ineffective at successfully deactivating pathogens located deep within the layers of filter material or (2) damage the respirator in a way that reduces its effectiveness, such as by degrading the elasticity of the strap that secures the mask to the wearer. Research in this area is evolving rapidly, however, and recommendations may change by the date of publication.
9 Things to Know about UV Disinfection
The safe and effective use of UV disinfection devices requires a clear understanding of what the technology can and can’t do. ECRI stresses the following points in its studies:
- UV disinfection is a supplement; cleaning is still required. Solid particles and residues act to shield microbes from UV irradiation. Surfaces must be cleaned before UV disinfection is used.
- UV does not offer sterilization. The dose provided is sufficient only for disinfection of non-critical items, not sterilization. Countertop UV disinfecting devices, for example, cannot be used to sterilize materials such as surgical supplies or devices.
- Line of sight is key. Surfaces that are not in a direct line of sight from the source may not be exposed to sufficient UV light and will not be reliably disinfected, unless steps are taken to increase exposure. Commonly shadowed surfaces include the undersides of tables, the backs of devices and door handles, and low areas such as under beds or chairs.
- System settings and device positioning make a difference. The germicidal effectiveness of a system is related to the exposure of UV light incident on a surface. That depends on factors such as the output of the UV device, the distance from the light source, the wavelength emitted and the exposure time.
- UV may not reliably disinfect fabrics, the inside of tubing or other materials. UV disinfection has not been proven to be effective on fabrics, like privacy curtains. Additionally, UV doesn’t penetrate through most materials, including clear or translucent plastics. Thus, the lumens of clear plastic tubing won’t receive an effective dose. The same can be true of the nooks and crannies on devices. Just because a device or object has been exposed to UV, that doesn’t mean it’s been effectively disinfected.
- UV light can harm patients and staff. Safety precautions are needed to limit human exposure to UV light, which can damage an individual’s eyes or skin. To reduce the risk, many UV room disinfection devices require the use of door or motion sensors that terminate the disinfection cycle if triggered, and manufacturers may recommend the use of signs outside the treatment room.
- UV light can damage certain equipment. UV light breaks down certain materials over time. The degree of damage depends on the cumulative dose of UV and the type of material. Damage occurs more quickly for certain plastics and organic materials and if treatment cycles deliver higher UV doses or are performed more frequently.
- UV disinfection systems are not regulated as medical devices. UV disinfection systems are not classified as medical devices and thus are not regulated by FDA. Further, there are no standardized test methods for comparing systems. Thus, facilities should regard manufacturer claims with a healthy dose of skepticism; be sure to read the fine print and look for citations that provide study details.
- Other practices should take precedence. UV disinfection is not a requirement – thus there’s no need to purchase a system if you don’t already have one – and it is not a standalone solution that can address your disinfection needs. Proper cleaning of surfaces and equipment is required regardless of whether or not UV is used; and proper hand hygiene and PPE use still must be observed. If UV technology is to be used, be sure to use it in accordance with manufacturer recommendations and best practices.
This article is adapted from ECRI’s evaluations of UV room disinfection systems and countertop UV disinfection devices. Additional guidance is also available through ECRI’s COVID-19 Resource Center, a free public resource to help hospitals protect healthcare workers and patients during the COVID-19 pandemic. Access that site at www.ecri.org/coronavirus-covid-19-outbreak-preparedness-center. To learn more about ECRI’s device evaluation program, visit https://www.ecri.org/solutions/device-evaluations, or contact ECRI at (610) 825-6000, ext. 5891, or by e-mail at clientservices@ecri.org.