AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Comparison of DNATrax and Bacillus anthracis Surrogate Resuspension from Subway Surfaces
JOHN ARCHER, Adam Hook, Jerome Gilberry, Denise Aslett, Ahmed Abdel-Hady, M. Worth Calfee, Robert Yaga, Donald Bansleben, US EPA
Abstract Number: 851 Working Group: Bioaerosols
Abstract Selection of appropriate biological warfare agent surrogates is crucial to understand fate and transport mechanisms of agents in uncontrolled field environments. An inert, sugar-based surrogate for a biological agent developed at Lawrence Livermore National Laboratory, known as DNATrax®, has previously been used as a surrogate for Bacillus anthracis (Ba) spores in controlled aerosol releases. These tests were designed to both measure and verify models of contaminant fate and transport following the release. Since the particle size of a DNATrax particle is similar to a single Ba spore and other established non-pathogenic biological spore simulants, its behavior in aerosol transport and deposition is also expected to be similar to Ba. However, once the aerosol is deposited onto surfaces, it is unknown as to whether DNATrax is a suitable surrogate to study resuspension from surfaces. To investigate this research gap through a Department of Homeland Security (DHS)-funded study, Environmental Protection Agency (EPA) researchers are evaluating resuspension characteristics of DNATrax and an established biological surrogate of Ba (Bacillus thuringiensis var. kurstaki [Btk]) from representative porous and non-porous surfaces. Btk was selected because it has been demonstrated to be a suitable surrogate in previous EPA resuspension studies. Following particle seeding of surface coupons (stainless steel and concrete) via a dry deposition eductor system, particles are resuspended via forced air in a controlled resuspension wind tunnel (RWT) designed solely for resuspension comparison studies. Once particles are resuspended, they are transported through the tunnel into a settling chamber for full volume particle sampling and real-time particle sizing. Multiple measurements of particle counts, particle size distribution, DNA copies, colony forming units, and particle characterization are made to compare the resuspension (resuspension fraction) of the two particles under varied environmental conditions (30%/80% relative humidity and wind speeds of 5 and 25 meters per second). Results to date have shown that the designed eductor system produces comparable particle size distributions for two surrogates. Results of the resuspension comparison tests will be presented and will guide the selection of biological surrogate agents for future field studies.
This work was supported and funded by an Interagency Agreement (EPA No. RW-070-95935001-0) with the Department of Homeland Security (DHS) Science and Technology Directorate (S&T) 70RSAT18KPM000176.