Inactivation of a Bacillus anthracis Spore Surrogate on Outdoor Materials Via the Spray Application of Sodium Dichloro-s- triazinetrione and Other Chlorine-Based Decontaminant Solutions
Citation:
Wood, Joe, S. Serre, A. Mikelonis, L. Mickelsen, A. Tschursin, R. Rupert, D. Popeo, AND D. Touati. Inactivation of a Bacillus anthracis Spore Surrogate on Outdoor Materials Via the Spray Application of Sodium Dichloro-s- triazinetrione and Other Chlorine-Based Decontaminant Solutions. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-21/004, 2021.
Impact/Purpose:
In the event of a release of Bacillus anthracis spores (bacteria causing anthrax disease) into the environment, proven decontamination methods will be needed. Materials used in outside environments are typically porous and may be comprised of organic matter, making their decontamination difficult. Little information or data has been reported on the efficacy of using commercial, off-the-shelf (COTS) pool chemicals (mixed with water) for inactivation of B. anthracis spores on building and outdoor materials. In this study, we evaluated the decontamination efficacy for solutions of the COTS pool chemical sodium dichloro-s-triazinetrione dihydrate (CAS Number 51580-86-0), also known as sodium dichloroisocyanurate dihydrate, or simply “dichlor”. We also evaluated solutions of other chlorine based decontaminants for comparison. The use of a widely available granular chemical such as dichlor, that could simply be mixed with water at its point of use, would be an advantageous decontamination tool to have in the event of a wide area release of B. anthracis spores. The results of the study showed that the decontamination efficacy of dichlor is generally similar to that of diluted bleach.
Description:
The U.S. Environmental Protection Agency’s Homeland Security Strategic Research Action Plan was established to advance EPA’s capabilities to recover from a wide-area contamination incident, and the study described in this report supports that objective. This small study evaluated the effectiveness of readily available and inexpensive chlorine-based decontaminant solutions for inactivating spores of Bacillus atrophaeus var. globigii (Bg; a widely used surrogate for Bacillus anthracis) on outdoor surfaces. More specifically, the primary purpose of this study was to evaluate the decontamination efficacy of sodium dichloro-s-triazinetrione (also known as dichlor, a common pool disinfection chemical), and compare the results to more well-known decontaminants such as pH-adjusted bleach (pAB) and diluted bleach. The outdoor materials evaluated in this study included concrete, wood, asphalt, and brick. Initial scoping tests were conducted at bench-scale using 18-mm diameter coupons of the four materials, with the test chemical applied to the coupons via an automated spray apparatus. Following these scoping tests, the chlorine-based solutions were evaluated at a larger scale, whereby an electrostatic sprayer was used to apply test chemicals onto 14-inch by 14-inch coupons. In both scales of tests, decontamination efficacy was determined in terms of log10 reduction (LR) of colony forming units, based on the difference in the number of Bg spores recovered from surfaces of positive controls and test materials. For the bench-scale tests, the average decontamination efficacy for dichlor for the four materials was a LR of 5.7, which was similar to the average LR achieved for the diluted bleach (an average LR of 5.5 for the four materials). The pilot-scale tests produced somewhat similar decontamination efficacy results. On average, the decontamination efficacy was highest with the diluted bleach (an average LR of 6.0 for the four materials), followed by dichlor (an average LR of 5.4 for the four materials). Decontamination efficacy results for the two pAB solutions were the lowest of the four decontaminant solutions studied.