On Wednesday, March 9, 2022, R-Zero hosted a webinar entitled, “Disinfection Using Ultraviolet Radiation to Advance Environmental Safety in Healthcare.” The webinar featured Dr. Edward Nardell and Dr. David Brenner. These two UV experts provided a compelling, in-depth look at the history, safety, science, and efficacy behind UV-C disinfection in public spaces.
Dr. Edward Nardell, MD, is a Professor of Medicine at Harvard Medical School. His research interests include applications of UV to help manage tuberculosis transmission. He studies the pathogenesis of drug-resistant tuberculosis, its airborne transmission, and transmission control in institutions.
Dr. David Brenner is the Director of the Columbia University Center for Radiological Research, which is the oldest and largest radiological research laboratory in the world. He divides his research time between the effects of high doses of ionizing radiation (relating to radiation therapy) and the effects of low doses of radiation (relating to radiological, environmental, and occupational exposures).
The Spread of Infections and Upper Room UV-C
Dr. Nardell began his presentation by discussing how airborne transmission has been the most common transmission mode for the SARS-COV-2 virus. Being in a room with an infected person creates the opportunity for active virus to be spread by breathing. Some organizations have worried that the airborne nature of the virus might mean it can travel through ventilation systems and have wondered about adding expensive filtration systems to their HVAC. In response to these concerns, Dr. Nardell explained that viruses are fragile, and when they are forced through a ventilation system, they become damaged and diluted in air ducts, which negates the risk of their traveling via ventilation.
To demonstrate airborne transmission risk, Dr. Nardell showed the results of a study from a classroom. A clear pattern of transmission emerged, originating from where the teacher stood at the front of the room. The students who became ill were sitting in a fan-shaped arrangement relative to where the teacher was standing. “It’s an example of where one could imagine a cloud of bioparticles being dispersed in the room and breaking up as it moves away from the teacher in the front of the room,” said Dr. Nardell. He added, “Even if we were to go to putting MERV filters in the ventilation as has been strongly recommended for schools, it’s of little comfort to these students in the room to know the air is going to be disinfected after it leaves the room.”
Given the need for air disinfection in real time, Dr. Nardell explained the various options for air disinfection in an enclosed space. They include natural ventilation (opening windows to allow air to exchange naturally), mechanical ventilation, room air cleaners, and Germicidal UV air disinfection (GUV). In terms of effective removal of viruses from the air, natural ventilation will allow that, but it isn’t always possible to open windows due to temperatures and weather or other factors. Both mechanical ventilation and room air cleaners are inadequate for the task. Their air flow is too limited to achieve efficacy. The best option is GUV through upper room UV-C or whole room UV-C.
Dr. Nardell highlighted two schools outside of Philadelphia, Swarthmore and Germantown, which were combating outbreaks of the measles in the 1930s. In 1937, W. F. Wells and T. S. Wilder conducted a measles study and demonstrated the efficacy of upper room UV-C in combating the measles virus. “It’s very important to know that virtually all pathogens from viruses to even mold are vulnerable to germicidal UV because it damages the very core of life, RNA and DNA,” Dr. Nardell explained. He also added, “Although UV functions by causing mutations, there have been ugly rumors that perhaps UV is going to somehow lead to more viral variants. And that is simply not the case. There is no biological basis to think that UV-C would lead to viral variations. Mutations occur naturally in animals and people already.”
Guidance from the CDC suggests that air should be exchanged between six and 12 times per hour to ensure air quality. These quantities of air changes are effective in achieving a one or two log reduction in the room. Dr. Nardell added, “If there’s an infectious source continuing to generate aerosol, we need much ventilation under those circumstances.” For some systems, increased ventilation can prove an expensive challenge. However, upper room UV-C runs continuously and can meet that challenge more effectively and efficiently. UV-C uses less energy and is the most cost effective method available, which is especially important when windows can’t be opened. CO2 levels rise with reduced ventilation, as do virus and germ levels.
The Benefits of Far-UV
Dr. Brenner began his presentation by stating that Far-UV, or UV-C light at 222 nanometers (nm), is a safe and effective tool for reducing infection. Far-UV doesn’t penetrate human skin or eyes, but it is able to effectively inactivate airborne microorganisms. “The biophysical basis of safety is simply that the far UV-C light can’t reach any of the key cells,” said Dr. Brenner.
According to Dr. Brenner, the two questions scientists have about Far-UV are “Is it safe?” and “Does it work?” Over the course of his presentation, Dr. Brenner demonstrated that Far-UV is absolutely safe. He pointed to a number of research studies proving that Far-UV does not pose a risk to human skin models, human skin, mouse skin, and mouse eyes. He also noted that as of this year, the American Conference of Governmental Industrial Hygienists (ACGIH), which sets standards for levels of safe exposure, has increased the recommended thresholds for exposure to Far U-V.
Proving the Efficacy
To prove Far-UV’s efficacy, Dr. Brenner cited a study he conducted where Human Coronavirus (not COVID-19) in an aerosolized form was exposed to Far-UV light in a controlled experimental environment. In the study, he and his fellow researchers saw dramatic reductions in the active virus after Far-UV exposure. Additional studies achieved very similar results. These repeatable demonstrations of viral reduction clearly prove the effectiveness of Far-UV light. Dr. Brenner also cited another study in which this same test of efficacy occurred in a real-world setting – a medium-sized room – to test virtual reduction at different levels of exposure as set out by past and current ACGIH limits. Using the older standard of Far-UV exposure, the UV-C lamps ran for 15 minutes. The result was a 92 percent reduction in live airborne microorganisms, which was equivalent to 35 air changes an hour. Using the updated ACGIH limits, the Far-UV lamps yielded a 98 percent reduction in microorganisms, which equated to 180 air changes per hour. This quantity of air changes was equivalent to being outdoors.
The sensitivity of a virus to UV-C is due to the genomic size. According to Dr. Brenner, most human viruses have a similar genomic size. Therefore, it is safe to say that all human viruses and variants will have a similar sensitivity to UV-C light. UV-C can be applied to yearly flu epidemics, current epidemics, and future outbreaks.
According to Dr. Brenner, “Far-UVC can be used anywhere indoors where people are coming together. It’s pretty easy to retrofit.” And it’s a passive technology, so the public doesn’t have to think about it or take any action, unlike masks or vaccines. This ease of incorporation makes Far-UVC a nearly ideal method of disinfection.
To conclude the webinar, Dr. Nardell and Dr. Brenner answered questions from participants. These questions addressed topics such as concerns about possible damage from UV light to those with skin conditions or sensitivities; the consistency of the light emitted; and even cleaning and maintenance of UV devices.
Watch “Disinfection Using UV-C” Webinar
The full webinar is now available for on-demand viewing. Please click here to watch.
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