Modeling Urban Atmospheric Anthrax Spores Dispersion: Assessment of Health Impacts and Policy Implications

Abstract

PurposeTo model atmospheric dispersion of weapon grade anthrax spores over an urban region using a mass transit system (subway) as a delivery system. IntroductionThe accessibility and carrying capacity of mass transit system (s) makes it an attractive target for terrorists. There are multiple, historical accounts of terrorists attacks involving transit systems. Metropolitan underground transportation rail systems (subways) are of special interest because of a potential harm to a large number of commuters and damage to the transportation infrastructure. MethodsWe assumed that multiple release points of anthrax spores within the National Capital Region (NCR‐Washington, District of Columbia) METRO rail system will result in the escape of the spores into the atmosphere. Potential factors affecting atmospheric dispersion of spores and the regional infrastructure were the subject of literature searches, modeling exercises and expert reviews. A Geographic Information System (GIS) and the Operational Multiscale Environment Model with Grid Adaptivity (OMEGA) were used to model the affected area. ResultsThe GIS together with the OMEGA software programs characterized the extent of the ground footprint and provided the number of the NCR residential, businesses and health care infrastructure under the plume at 120 minutes after the release. It was concluded that the maximum environmental and health impacts would occur if the spores were released in the early morning during the summer months (low humidity and ultra‐violet radiation). This assumption was based on the analysis of the weather patterns and prevailing winds in the NCR. ConclusionsThe atmospheric dispersion model superimposed over the regional GIS suggests that the extent of the affected infrastructure will be negligible. However it has the potential to disrupt the functioning of the mass transit system, affect serviced residential areas, commercial and/or federal facilities. While the number of affected medical and other facilities will be minimal, a significant number of commuters and resident will be exposed to the spores and overload the existing health care infrastructure. Policy implicationsAdopting a set of realistic threats assessment tools using GIS and atmospheric modeling, and addressing risk reduction strategies such as deploying real time biological agents monitoring sensors, can significantly improve the security of metropolitan communities served by interconnected mass transport systems. Field testing to validate our modeling assumptions and results will help with the training of disaster response teams, health care providers, transportation system operators and improve passengers' safety. Limitations This study has not been validated by actual field test data and as such is hypothetical and subject to a significant bias. Assumption of a release of a large amount (several kilograms) of anthrax spores undetected might be unrealistic based on existing physical surveillance and security practices. Patterns of spores' dispersion into fixed struct...

Atmospheric dispersion modelling of bioaerosols that are pathogenic to humans and livestock – A review to inform risk assessment studies

“…They estimated that the number of infected persons would range from 15,000 (0.01 kg anthrax) to 49,000 (1 kg). Nicogossian et al (2011) used the Operational Multiscale Environment Model with Grid Adaptivity (OMEGA) model to simulate a hypothetical release of one million spores in the subway of Washington D.C. (USA), with subsequent dispersion in the outdoor environment. They concluded that a significant number of commuters and resident would have been exposed and being overload the existing health care infrastructure.…”

“…Three pragmatic approaches were identified from the studies discussed in Section 4, namely the use of: -Arbitrary emission data, thus leading to relative concentration maps (Fossum et al, 2012;Gloster et al, 1984;Lighthart and Frisch, 1976;Sorber et al, 1976;Van Leuken et al, 2015;Wallensten et al, 2010). -Realistic assumptions, such as a release of 10 15 B. anthracis spores (Craft et al, 2005;Isukapalli et al, 2008;Nicogossian et al, 2011;Stuart and Wilkening, 2005), or the use of morbidity, severity and duration of the disease as a proxy for emission (Gloster, 1983)although the reliability may be arguable. -Varying emission rates through sensitivity analyses (e.g., Buckeridge et al, 2006) In all other studies measurements (Section 5.1.1) or emission models (Section 5.1.2) were applied to determine emission rates.…”

Systematic Review and Evaluation of Mathematical Attack Models of Human Inhalational Anthrax for Supporting Public Health Decision Making and Response

“…A total of 13 mathematical modelling studies of human inhalational anthrax attacks 9-21 were identified, and Table 1 shows the type of identified studies. All the selected studies were categorized into two main types: studies that took dispersion of anthrax spores into consideration and used dispersion modelling as part of their model (six papers); 10,[12][13][14] and studies that did not consider dispersion of anthrax spores (seven papers). 9,11,15,16,18,20 Three models simulated the outbreak scenario in Sverdlovsk in 1979 or used the Sverdlovsk outbreak data, 15,16,18 and four models simulated the US anthrax attack in 2001 or used the data for modelling.…”

Perspective on Improving Environmental Monitoring of Biothreats

“…The release of a BTA as an aerosol has the potential to kill thousands of individuals (Riedel, 2004 ; Nicogossian et al, 2011 ). The initial phase of an undetected attack would be silent and unremarkable.…”

“…During the past 12 years of the program's operation, numerous technical and operational challenges of city-wide, outdoor bioaerosol monitoring have become apparent. For example, detection of a BTA can be problematic due to dilution effects as a plume of aerosolized material travels and mixes with surrounding air (Craft et al, 2005 ; Stuart and Wilkening, 2005 ; Buckeridge et al, 2006 ; Nicogossian et al, 2011 ). The ability of a given particle collector to collect an aerosolized agent can also vary widely because city-wide airflow patterns are highly variable.…”