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Evaluation of Liquid-, Foam-, and Gel-Based Decontaminants Report
Citation:
Calfee, W., Vipin Rastogi, S. Hurst, E. Jakabhazy, L. Mickelsen, R. Rupert, AND S. Serre. Evaluation of Liquid-, Foam-, and Gel-Based Decontaminants Report. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-18/229, 2018.
Impact/Purpose:
The objective of this effort was to compare three delivery methods (i.e., liquids, foam and gel) of liquid disinfectants on concrete and steel in vertical orientation. Two decontaminants, Spor-Klenz® and pAB (representing two distinct chemistries) were selected for this study, yet only one (pAB) was ultimately evaluated. Environmental conditions were varied to include: 50 ºF/70% RH and 90 ºF/25% RH, with fan ON or OFF to simulate wind velocity. Runoff was collected to assess mechanical dislodgment vs. sporicidal efficacy, and panels were wipe-sampled following the 30 minute contact time to estimate the amount of viable spores remaining. Unfortunately, the gel application was discontinued midway through the work because of issues related to its application after re-formulation. A modified gel was requested from the manufacturer to lack 10% aqueous component in order for 10% decontaminant volume to be reconstituted during testing without changing the formulation viscosity. This was unable to be procured from the vendor, forcing discontinuation. Overall, the results of this study show that vertically-oriented surfaces are difficult to decontaminate with just one application of a sporicidal chemical, regardless of decontaminant formulation (liquid or foam). Direct observation tests showed that foam application maintained surface wetness longer than liquid. However, no significant difference in efficacy in terms of log reduction with the use of foam was observed relative to liquid application. This research seeks to enhance responder capabilities by providing science from which decontamination decisions can be made.
Description:
This report focus for fixed site surface decontamination and cleanup, two distinct options among liquid disinfectants include pH-adjusted bleach (pAB) and Spor-Klenz® (S-K; per-acetic/peroxide formulations). Efficacy of these two sterilants in lab-scale studies has been well-documented. In a recent study completed by a multi-agency group led by EPA, pAB was found to be effective; however, some collateral damage was evident (EPA/600/S-15/001). In different studies throughout recent years, disinfectants have been applied as liquids, foams, or gels. While no information is currently available on comparative effectiveness of foam or gel over liquids, it is often hypothesized that foam- or gel-based decontaminants will be more effective because of prolonged wetted contact times. Scientific data supporting this hypothesis is lacking. This study aimed to evaluate liquid-, foam-, and gel-based decontaminants for Bacillus anthracis, to determine if gel and foam additives can increase the effectiveness over liquid when applied to common material types.liquid. However, no significant difference in efficacy in terms of log reduction with the use of foam was observed relative to liquid application.