What works, and when does UV provide a false sense of security?
Since many biology labs are working at limited capacity due to COVID-19, I wondered if any of the UV disinfection technologies used in the healthcare sector could improve safety and sustainability in biology workspaces. To consider any practical options, I found some recent studies and spoke with the Director of the University of New Hampshire Environmental Engineering Research Group, James Malley Ph.D., who is a respected expert on UV theory and practice. It turns out that there are strict scenarios for UV technology to improve safety and a couple of ways to improve sustainability.
From the height of the pandemic, Professor James Malley and his research team have provided a pro bono public service by collaborating with frontline health care providers to study UV germicidal applications to try to improve pandemic working conditions. Dr. Malley has also been featured in several news publications including USA Today and The L.A. Times. Cheers to him for sharing his insights for the Labconscious community!
Biologists have a healthy respect for UV light
Let’s start with Dr. Malley’s least favorite scenario. It’s when someone tries to wield a UV wand over materials like its a disinfection lightsaber. UV is a precision tool with strict efficacy requirements. It will not disinfect materials in this way. It’s also a great way to give yourself a headache! Happily, Labconscious readers are unlikely to attempt this. Most biologists bespeckled in safety goggles will approach excising a DNA band on a gel over a UV transilluminator with some trepidation - even under so called long wave conditions. It’s a cut quickly and cut accurately situation. Biologists are highly cognizant that UV light causes tangible damage to nucleic acids.
UV disinfection Theory in practice
Dr. Malley stressed in our conversation that environmental engineers encourage establishing multiple barriers when it comes to preventing air or waterborne disease. They don’t want to have UV alone and certainly don’t want the use of UV to make people lackadaisical about mask-wearing and social distancing. That said, technology from a reputable UV equipment maker, with a trained operator, and equipment performance maintenance, UV disinfection is a great tool!
When do UVC overhead fixtures make sense?
The CDC has emphasized that surface and close contact are the primary transmission routes for SARS-CoV-2. Examples of surfaces in biology laboratories include benches, equipment, cell culture rooms, walk in freezers, and confocal microscopy rooms. I asked Malley, should overhead UVC be implemented in these spaces?
Professor Malley explained to my surprize that overhead UVC surface disinfection caught on in a space where people are most vulnerable, hospital operating rooms. UVC, otherwise known as far UV light, is not supposed to be dangerous for room occupants, however it is a controversial area of study. UVC came into practice in operating rooms because the risk to people using an operating room from UVC equipment is balanced by the devastating risk of infection. When a surgeon repairs a joint in someone’s shoulder, the threat of hospital-acquired infection is dire. Obviously, the physical cost to the patient is terrible! There is also a financial cost to the hospital since insurance does not cover care for hospital-acquired infections.
Malley explained that surgical room conditions meet strict requirements for UVC disinfection. The space is maintained to be very clean. There can be no dust on the UVC light bulb itself or on the surfaces being treated. The overhead UVC fixtures are produced by reputable manufacturers, are well maintained, and operated by trained personnel when the room is unoccupied. This is how operating rooms meet the conditions for UV disinfection to work as intended. Even still, anywhere that light doesn’t hit isn’t disinfected. He reinforced that UVC is providing another barrier to infection, in conjunction with the chemical disinfection of materials, airflow, and PPE used in operating rooms.
Labconscious take: Overhead or lab bench UVC lights are not practical to prevent infection in typical life science lab conditions due to shadows, dust and occupancy. Intensive chemical cleaning to the level of surgical rooms would be necessary. Energy consumption for air flow could not be decreased.
Mobile robot light disinfection service
Most people would agree that disinfection would be most important after a lab facility has confirmed exposure SARS-CoV-2 - after an outbreak. Interestingly, I found that a mobile, light disinfection robot from a company called Xenex was demonstrated to inactivate SARS-CoV-2 virus on room surfaces.
The study Modeling Hospital Energy and Economic Costs for COVID-19 Infection Control Interventions funded by Johns Hopkins Hospital and the CDC shows reduced hospital-acquired secondary infections with negative airflow to select patient rooms and Xenon pulsed UV for surface contamination.
It was also nice to see that Xenex is now offering a StrikeForce disinfection service for US locations . This would be useful if a lab facility had an outbreak and wanted extra assurance that the space was decontaminated. These mobile UV robot units are expensive to the tune of many tens of thousands, so it makes sense that early adopters include large hospitals and airports. The high traffic in these spaces vastly increases the risk of an outbreak from asymptomatic carriers. Unfortunately, my request to the local Xenex representative for information on whether any certification was provided with this service went unanswered. You can learn more by watching this short video from the American Society of Mechanical Engineers of Mark Stibich, an infectious disease epidemiologist, who is the chief scientific officer and co-founder of Xenex, who discusses how UV disinfection robots are being used to destroy COVID-19 on surfaces.
Labconscious take: UV robot disinfection services are useful for lab spaces with confirmed COVID-19 exposure. It can prevent some asymptomatic spread in high risk healthcare environments. Biomedical labs storing protein containing solutions on open shelves, or within glass front refrigerators would be incompatible due to risks for protein deactivation or chemical composition changes. Mobile UV robot requires trained operators, deep chemical cleaning and no occupancy during application.
Disinfection of lab items could be handy to mitigate supply chains risks. Can common UV lab equipment disinfect lab supplies for re-use?
Another UV surface disinfection scenario that healthcare providers explored during the pandemic was if they could use laboratory grade UV disinfection cabinets, or even covered UV transilluminators to disinfect masks. While large hospital systems were able to set up re-processing centers for their N95 masks using the FDA’s approved hydrogen peroxide vapor disinfection process, these high throughput re-processing centers are not available to many healthcare settings in the United States. As you can see in the video below featuring a radiologist last spring, medical facilities were resorting to DIY UV decontamination of disposable masks.
The UNH Environmental Engineering Research group collaborated with frontline healthcare workers in Denver and Minnesota on converting commercial-grade, benchtop UV decontamination boxes from biomolecular labs into service for N95 mask reuse. Dr. Malley explained that the universal goal is to verify that users were getting the UV light dosage right. Time is not that important with regard to dosage. The line of sight is absolutely critical. Dosage should be verified with tests. It’s a complex scenario that should be designed to be effective by an engineer.
This University of New Hampshire Environmental Engineering Research Group UV dosing study demonstrates how the positive control yellow progressively fades with chalk dust, shadow, and two target conditions.
A healthcare DIY ultraviolet disinfection and sterilization box video from spring 2020 ...
Labconscious take: UV disinfection of labs supplies is a challenge that requires a reputably designed instrument, or at a minimum, input from an environmental engineer who can design and verify protocols. Lab grade UV disinfection cabinets can reduce lab waste and mitigate shortages by disinfecting lab goggles, visors, masks for re-use before recycling.
Air disinfection is where UV really shines!
Dr. Malley explained that, “Disinfection of flowing liquid, like water or air, is where UV technology really shines. In fact, many cities rely on UV light disinfection to clean their water supplies. It’s very effective. “ It was great to hear that there is proven UVC technology that can help to prevent indoor air related outbreaks. The question now is if it will be necessary to implement this technology at a massive scale.
The CDC advice on qualified indoor airborne transmission
The U.S. CDC has updated its guidance for airborne and surface transmission of COVID-19, in an effort to clarify conflicting reports in a controversial area of research. I was concerned in March when researchers reported in the New England Journal of Medicine that viable SARS-CoV-2 can remain aerosolized for up to three hours. Then the CDC released this Scientific Brief on October 5th SARS-CoV-2 and Potential Airborne Transmission. This brief states that airborne transmission in public health is defined as infections capable of being transmitted through exposure to infectious, pathogen-containing, small droplets and particles suspended in the air over long distances and that persist in the air for long times. The CDC goes on to explain that SARS-CoV-2 infections spread mostly through close contact, but airborne transmission can occur under uncommon, special circumstances. The addition of special engineering controls was not called for in the general community at this time
The most interesting piece of research on the airborne transmission to me was this one: Identification of SARS-CoV-2 RNA in Healthcare Heating, Ventilation, and Air Conditioning Unit. As explained by author Kevin Van De Wymelenberg, from The Institute for Health in the Built environment at the University of Oregon his group has collected COVID-19 RNA from the surface, passive, settled air, and active pumped air in a hospital treating patients with COVID-19. Viral particles can make it past filters through air returns floors away. It is unclear if these viral particles were infectious or in concentrations high enough to permit transmission.
Dr. Wymelenberg’s team is building a case for building monitoring for COVID-19 to help people return to work and to modulate energy usage. If live, infectious SARS-CoV-2 virus is proven to be getting past filters, environmental monitoring becomes a highly reassuring concept to prevent asymptomatic outbreaks. Asymptomatic carriers are a problem since number one, the time from when a person develops a SARS-CoV-2 infection to when they show symptoms is many days longer than influenza, for example. Number two, SARS-CoV-2 spreads faster since it is so highly infectious. According to this ASHRAE journal technical report; HVAC and COVID-19 Filling the Knowledge Gaps, today, HVAC UVC disinfection in air duct controls are almost exclusively used in hospitals. Buildings that retrofit for these systems can increase HVAC energy efficiency by 10 to 25% through prevention of biofilms which affect heat transfer to and from the airstream. If building monitoring studies show that live infectious viral particles are not carried through air handling systems, UV air disinfection would not be necessary and air handling systems might be safely adjusted to conserve energy. If clear cases of airborne transmission arise in schools or lab facilities, hospital grade UV air disinfection is worth a look as another barrier. More research from the Wymelenberg group and others is forthcoming.
Studies are ongoing to demonstrate if energy efficient UVC HVAC retrofits are necessary to prevent indoor air transmission and increase lab facility working capacity. RT-PCR based building monitoring may be useful to reduce negative airflow requirements while maintaining health and safety.
We hope that this information on germicidal UV theory is useful to making essential biology work safer and sustainable! Best wishes!
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