December 28, 2001—UltraViolet Devices, Inc. (UVDI) announced the initial results from its joint research with Pennsylvania State University into the disinfection of Bacillus anthracis spores (anthrax) with ultraviolet (UVC) technology.
Following a directive from UVDI, researchers at Pennsylvania State University have identified what they believe to be the most appropriate rate constant for killing Bacillus anthracis using ultraviolet germicidal irradiation (UVGI).
With Bacillus anthracis it is very important to differentiate between the vegetive and spore forms. Spore forms are most likely to be used for bio-terrorism and are much more robust and difficult to disable with most disinfectants, including ultraviolet light.
After analyzing the results of these three published studies, as well as prior work completed at Pennsylvania State University relating to airborne pathogens, UVDI’s previous position stating that it is necessary to provide high dosages of UV to “kill” Bacillus anthracis, was confirmed. Data for Bacillus anthracis spores from a 1986 study by G.B. Knudson were analyzed and charted. From this the microorganism’s sensitivity (“rate constant”) to ultraviolet light was calculated. It was delineated that the dose required for 90% disinfection could be as high as 74,000 microwatt seconds/cm2, or 220,000 microwatt seconds/cm2 for 99.9% disinfection. To put this in perspective, this organism, in spore form, would require about 50 times the UV dose required to disinfect Smallpox, Tuberculosis, and Legionella. It is even more robust than the Aspergillis Niger spore that is considered one of the toughest airborne pathogens.
According to David Witham, Vice President Technology at UVDI, “This leads us to conclude that control of anthrax by UV alone is not practical.” However, he went on to point out that “due to its relatively large size, about 1.2 microns in its most lethal single cell size, it can be effectively filtered … Once captured on a filter it can be readily disinfected with UV light.” Other pathogens, such as Smallpox, can be readily handled by Ultraviolet alone but may be more difficult to filter. Solutions with the proper UV dosage and filter efficiency can be tailored to most HVAC systems.
In partnership with Pennsylvania State University, UVDI has developed a proprietary software tool that supports the mathematical modeling of heating, ventilation and air conditioning (HVAC) systems utilizing a variety of UVGI and filtration strategies. This model incorporates numerous variables to predict “kill-rates” for airborne and surface pathogens and its accuracy as a modeling tool has been validated by a third party laboratory. For more information, contact UVDI.
