Ultraviolet light disinfection, or ultraviolet germicidal irradiation (UVGI), is a fast-growing and invaluable option for preventing the spread of hospital acquired infections. Since the pandemic of Coronavirus Disease 2019 (COVID-19) caused by the novel coronavirus SARS-CoV-2, more consumers are interested in purchasing ultraviolet light products to disinfect surfaces in the home, office, transit, and other commercial spaces. This demand led to more UV manufacturing companies quickly forming to take advantage of the “opportunity.” While we encourage the utilization of this quick, reliable, chemical-free disinfection method, there is a combination of misconceptions and a lack of technical know-how that can lead to purchasing ineffective devices. Today, with so many UV light options on the market, how do you know what to choose? Here are some factors to consider when purchasing an ultraviolet light disinfection device.
PAY ATTENTION TO WAVELENGTH
THE THREE Ds: DOSE, DISTANCE, AND DIRECTION
The degree of inactivation by ultraviolet light is directly related to the UV-C dose applied. The UV-C dose is the product of intensity and exposure time. Light needs to contact surfaces at the correct intensity for the correct length of time to get the right dosage necessary to achieve the log reduction needed for inactivation of your target organism. When analyzing a UV-C device, compare the intensity of each unit at a certain distance. This will remove the subjective claims such as effective, fast, etc. with specific and quantifiable claims like “Device X” has an intensity of 180 microwatts per cm2 at an 8-foot distance. Many of the UV-C lamps sold for non-commercial or home use have a very low intensity, so it will require a longer exposure on a given surface area to provide effective inactivation of a bacteria or virus.
UV-C can only inactivate organisms if they are directly exposed to the light. Therefore, the disinfection of surfaces may not be effective if the UV-C light is blocked or shaded, creating shadowed or hidden areas. Similarly, consider the size of the space or the equipment you are disinfecting because as distance from the lamp increases, effectiveness against microorganisms decreases. You may need to choose a light that is tall or angled to best reach areas of concern. Additionally, you may also consider the use of multiple lights at different angles and heights to maximize exposure. If only utilizing one light, it may be necessary to relocate it to multiple locations in order to maximize UV-C exposure of surfaces within the space.
HANDHELD UV-C WANDS
Some ultraviolet light companies sell handheld wands for swiping over surfaces to kill organisms. Such products are easy to find on sites like Amazon and eBay, and their product descriptions are definitely alluring. However, problems with the wands outweigh any potential disinfection benefits. Regardless of the product, UV-C should not be exposed to skin or eyes as it will inflict a severe “sunburn”. If wands are to be effective, they would need to put out enough UV-C intensity to be very hazardous to the operator. If the wand has a low enough output to be safe for operator presence, it would be too low to effectively kill organisms. Regardless of output, the operator needs to have very precise timing hovering over surfaces in order for a wand to be effective at all. For that reason, ClorDiSys does not sell or recommend the use of UV-C handheld wands.
THE IMPORTANCE OF QUARTZ GLASS
Most glass and plastics have limited to no permeability, blocking the UV-C from disinfecting the surfaces and items on the other side. Quartz glass is the best material for bulbs and any shelving within an ultraviolet light device as it will transmit UV light from 180 nm to 400 nm right through it. This characteristic allows UV-C to shine optimally and disinfect surfaces sitting on quartz glass shelving, rather than prevent those surfaces from being treated. Some devices utilize metal grills which still provide kill, but not to where the items are sitting on the actual grill wires.
PURCHASE FROM AN EPA REGISTERED FACILITY
Ultraviolet lights that are sold or distributed with claims that the product can be used for preventing, destroying, repelling or mitigating any pest (plant, animal, virus, bacteria or other microorganism) are federally regulated by the Environmental Protection Agency (EPA) under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Generally, without such claims, a UV-C light would not be subject to FIFRA. While UV-C devices do not need to be registered by the EPA and, in turn, are not subject to a premarket review by the EPA, if a manufacturer is making claims of preventing or disinfecting viruses, bacteria or other microorganisms, they could be unfounded. In 2015, the Federal Trade Commission went after two companies marketing UV-C disinfectant devices because of false claims about eliminating foot fungus, methicillin-resistant Staphylococcus aureus, E. coli and Salmonella. The most trusted UV-C products will be manufactured in a US EPA registered facility.
CONTINUOUS vs. PULSED UV-C
Some companies claim that pulsed xenon is a more effective way to kill harmful pathogens. Claiming similarities to a punch of a fist on a wall, more punches will weaken it better than one punch. However, light is not a fist. Light is a form of energy, and continual energy is more effective than rapidly turning it on and off. The US Veterans Administration commissioned an infection prevention research team led by Curtis Donskey, M.D., to conduct an independent study of continuous ultraviolet disinfection versus xenon pulse UV-C disinfection. The results showed surprisingly low pathogen kill rates for the pulsed xenon device, about .5 log for both C.diff and VRE, even as close as 4 feet. The continuous UV-C device demonstrated a much higher CFU reduction for the pathogens C. difficile, MRSA and VRE. The study states, “PX-UV was less effective than continuous UV-C in reducing pathogen recovery on glass slides with a 10-minute exposure time in similar hospital rooms” and “the UV-C device achieved significantly greater log10 CFU reductions than the PX-UV device”.
United States Environmental Protection Agency. (2020, October). EPA Regulations About UV Lights that Claim to Kill or Be Effective Against Viruses and Bacteria. https://www.epa.gov/sites/production/files/2020-10/documents/uvlight-complianceadvisory.pdf
United States Food and Drug Administration. (2020, August). UV Lights and Lamps: Ultraviolet-C Radiation, Disinfection, and Coronavirus. https://www.fda.gov/medical-devices/coronavirus-covid-19-and-medicaldevices/uv-lights-and-lamps-ultraviolet-c-radiation-disinfection-and-coronavirus
Erdmann, J. (2020, August). UV Light Wands Are Supposed to Kill Viruses. But Do They Really Work? https://www.discovermagazine.com/health/uv-light-wands-are-supposed-to-kill-viruses-but-dothey-really-work
Infection Prevention Technologies, LLC. (2015, March). VA Funded Study Validates Continuous UV-C Technology For Pathogen Reduction. https://www.prnewswire.com/news-releases/va-funded-studyvalidates-continuous-uv-c-technology-for-pathogen-reduction-300057832.html