Dispersion modelling for biological threat

Accidental release scenario related to chemical can be simulated through different software application available in market. CHARM® is one of the software applications which handle movement of airborne particles in complex terrain. The aim of this paper is to explain how dispersion for Biological threat can be achieved by using same software package. Inhalation Anthrax Toxin is being considered to model the scenario. Bacillus anthracis, the causative agent of inhalation anthrax, is one of the most extensively researched biological threat agents¹. The lethaldose at which 50% of an untreated exposed population would die (LD50) from inhalation anthrax is believed to be between 2,000 and 55,000 spores, with a nominal value of 8,000-10,000 spores¹. Since the anthrax will be modeled assolid particles which do not evaporate unlike chemicals therefore it will be handled accordingly. The way to model dispersion of Anthrax there are several consideration which may be deliberated like creation of a particle size distribution i.e. monodisperse and to set the surface tension very large to so that particle may be assumed to not be deformed at high speeds of falling. All the particles are assumed to be initially all of one size - about 1.0 um diameter. As time passes, the particles may coagulate to larger sizes. Since there is no evaporation, the particles should never be smaller than the original size. In CHARM (Complex Hazardous Air Release Model) user-Specified conditions of release may be considered and the particles may not the chemical selected. With these and other similar settings, CHARM should let the particles disperse, coagulate, and settle toward the ground. Coagulation and settling may be fairly minimal for particles of 1.0 um diameter.