AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Evaluation of Outdoor Surface Adhesion and Reaerosolization of Anthrax: Reaerosolization from a Sod Matrix
JACKY ANN ROSATI ROWE, Laurie Brixey, Zora Drake-Richmon, Jonathan Thornburg, Alfred Eisner, US EPA
Abstract Number: 708 Working Group: Homeland Security
Abstract A large outdoor release of Bacillus anthracis could result in spores being dispersed and deposited on a wide range of outdoor surfaces. In the 2001 Bacillus anthracis letter incidents, the spores that deposited on various indoor surfaces were reaerosolized (i.e., reaerosolized) by human activity, which not only spread contamination but exposed persons in contaminated areas to inhalation hazards (Weis et al., 2002). In addition, spores adhered to shoes and clothing and were tracked to other buildings and locations by evacuees and first responders. Based on prior research, it is known that temperature, humidity, air movement, and physical disruption affect the amount of reaerosolization and tracking (Rosati et al., 2008). This research sought to determine the reaerosolization fraction from a soil/sod matrix if such an incident were to occur.
Turf type tall fescue sod (soil-grass matrix) was chosen to represent the type of grass used on the National Mall in Washington, D.C. This sod was placed in shallow trays and was sprayed with a solution containing Bacillus thuringiensis var. kurstaki (BtK) in sterile distilled water. A controlled large scale wind tunnel was used for testing. Environmental conditions included an ambient temperature of 23°C, a wind speed of 2.2 m/s, and an RH of 30% and 70%. Filter-based sampling was used to evaluate the amount of spores reaerosolized.
Reaerosolization was determined to be consistent after the initial (0 h) sample even though the grass-soil matrix became dessicated as the experiment progressed. The fraction reaerosolized at low RH (1.33 x 10-4) was an order of magnitude higher than the fraction reaerosolized during high RH tests at the same wind speed (1.95 x 10-5). This is likely because a significantly greater force was required to detach the spores under high RH conditions.