AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Resuspension of Spores from Urban Surfaces
JEROME GILBERRY, Jonathan Thornburg, Laurie Brixey, Alfred Eisner, Russell Wiener, Marshall Gray, RTI International
Abstract Number: 231 Working Group: Homeland Security
Abstract The SPORE program is developing a quantitative assessment of the risk of public health exposure from the resuspension of B. anthracis spores in an outdoor, urban environment. One aim is to determine the suitability of the biological simulant Btk as a surrogate for BaA in terms of resuspension from surfaces, represented in this research by coupons made of a variety of outdoor materials. The end goal is to statistically compare the two sets of data and develop a model to predict resuspension.
Coupons of outdoor surfaces were loaded with spores using custom-built deposition chambers. The dosed coupons were inserted into a small resuspension wind tunnel where a slotted nozzle generated the force required to resuspend the spores. Aerosolized spores were collected on filters that were extracted, plated, and cultured for enumeration. The experimental variables were spore type, spore preparation, jet velocity, surface type, and roughness level of each surface type. Detailed characterization of the test surfaces enabled development of a non-dimensional resuspension model.
The fraction of spores resuspended in this study agrees with previous data. Resuspension fractions varied from 1E-07 to 1E-01, depending on the spore preparation, jet velocity, and test surface characteristics. Measured Btk and BaA resuspension fractions for each spore preparation were statistically similar (p-value > 0.4). This finding allowed the Btk and BaA data to be combined for the development of the non-dimensional model. The surface energy of adhesion, the air jet velocity, and the coupon features that determined the total surface area and surface roughness were statistically significant model parameters. The modeled and experimental resuspension fractions were statistically similar, with an overall R^2 greater than 0.75.
The experimental methods and modeling approach developed in this effort can be extended to additional outdoor and indoor surfaces to further our understanding of the potential public health risks from anthrax resuspension.