Department of Homeland Security Bioterrorism Risk Assessment A Call for Change (2008) / Chapter Skim
Currently Skimming:
3 Description and Analysis of the Department of Homeland Security's Biological Threat Risk Assessment of 2006
3 Description and Analysis of the Department of Homeland Security's Biological Threat Risk Assessment of 2006
Pages 20-33
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 20... ...
The committee described in Bioterrorism Risk Assessment, a report from also found valuable an earlier foundation work, "NUREG the DHS Biological Threat Characterization Center of the 75/014" (U.S. Nuclear Regulatory Commission, 1975)
|
From page 21... ...
of 2006. In this figure, biological agents versus normalized risk, a sample display is based on fictitious data that represents only the general appearance of a key BTRA result.
|
From page 22... ...
SOURCE: Tracy Hale, Battelle Memorial Institute, "2008 DHS Bioterrorism Risk Assessment: Planned Improvements," presented to this committee on February 10, 2007, Washington, D.C. R01268, Figure 3-3 and indirect economic consequences.
|
From page 23... ...
by using a distribution of event probabilities from events in Stage 2 may depend on the outcomes chosen for which a particular probability is sampled; that is, adopting prior events in Stage 1. the convention that from a node, each branching outcome The BTRA analyzes each of the 28 agents as follows: "selects" a successor event, each such event leading to an outcome has a probability distribution over its probability 1. selection probability of the agent under study is set The of selection.
|
From page 24... ...
Event Detection 2, 3, 4 3 1,003,290,624 6,048 Response 18 Consequences tbd 10 10,032,906,240 tbd Final Outcome FIGURE 3.4 Successive stages in the Biological Threat Risk Assessment (BTRA) event tree.
|
From page 25... ...
Here, Stage 2, "Target Selection," is amplified into eight outcomes. The Biological Threat Risk Assessment represents the choice of each outcome with a probability and refers to this as a "split fraction" (i.e., conditional arc probability)
|
From page 26... ...
In event trees, Memorial Institute, Columbus, Ohio, but that subsequent all outcomes are modeled as random events determined by work will draw from a much wider pool of experience. some probability distribution; decision trees allow the possi- Some observations by the committee about the details in bility that outcomes are chosen by the defender or attacker to these steps follow.
|
From page 27... ...
subject-matter experts in the form of subjective discrete probability distributions of likely outcomes, and by some Traci Hale, Battelle Memorial Institute, "2008 DHS Bioterrorism Risk application of information on the spread of infectious agent, Assessment: Planned Improvements," presented to this committee on Februatmospheric dispersion, and so on. ary 10, 2007, Washington, D.C.
|
From page 28... ...
Thus, the implicit, homogeneous steady-state Poisson process underlying the rate used for "Frequency of Initiation The Mathematics Used by the BTRA in by Terrorist Group" will almost surely be rendered invalid by Modeling Multiple Attacks Has Errors any detected attack, whether successful or not, and whether Given a successful attack, the PRA tree's Stage 16, Po- interdicted or not. Subsequent to any such event, the BTRA tential for Multiple Attacks (see Figure 3.4)
|
From page 29... ...
. For these reasons, the committee's finding is that the Because of this, the consequence distribution can be epistemic features of the BTRA probabilistic risk assesscalculated without sampling from the outcome probability ment are unnecessary and that they increase computation distributions.
|
From page 30... ...
drives the BTRA. The analy sequence represents a particular scenario's contribution to sis has been frustrated by the sheer size of the PRA tree for the total expected consequence associated with the use of all biological threat agents, and as a practical matter, the that agent.
|
From page 31... ...
Critical knowledge gaps provide the greatest opportuni "Prioritization" with a strict ranking by specific agent ties for the reduction of uncertainty in risk analysis, while may not be the best way to present results. For instance, if critical biodefense vulnerabilities provide the greatest areas one simple, cheap action can remediate the consequences of for the reduction of risk.
|
From page 32... ...
insufficient scientific knowledge to verify or validate these models. • The consequence models will employ epistemic sam- • In addition to indoor aerosol dispersion models, DHS pling, and there will be more than 10 consequence bins is particularly interested in modeling an agent release in the discrete consequence distributions.
|
From page 33... ...
2007. Homeland Security Presidential Directive 18 scription of the DHS Bioterrorism Risk Assessment." Written com [HSPD-18]
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.