This presentation is the third of three to summarize results obtained jointly by ENSCO Inc. and Battelle Memorial Institute to determine a method for modeling the rate of inactivation of B. anthracis spores under arbitrary environmental conditions using observed weather data. For part III, we describe a sample case study of a simulated release where inactivation of the spores during transport is predicted using the described method.

The intentional aerosol release of B. anthracis spores upwind of a major city during a terrorist attack is a common hypothetical scenario within the domestic preparedness community. Some emergency response models can simulate the downwind transport of an aerosol, but if the release occurs during daylight hours, the models are not equipped to simulate inactivation by exposure to sunlight. A new technique for modeling the inactivation of this pathogenic microorganism using observed weather data has been incorporated into the ENSCO SLAM particulate transport model. A case study will be presented for a hypothetical early-morning low-altitude line release of B. anthracis spores outside a metropolitan area. Simulated transport of the released spores as a particulate aerosol is examined for three cases: 1) deposition of the particles is considered and no inactivation of the pathogen occurs, 2) inactivation of the spores is taken into account using a sinusoidal function of the solar zenith angle to determine a decay rate, and 3) the method described in an accompanying presentation (part II) is used to more accurately estimate a decay rate.

The simulated downwind patterns are compared and contrasted to demonstrate the errors that are possible when the effects of environmental conditions on the inactivation of the spores are not taken into account.