1
Background and Overview

The U.S. air transportation system is an attractive target for terrorists because of the potential for attacks on the system to cause immediate harm and anxiety to large numbers of people, as well as to cause massive economic disruption to the United States and the world. The system is vulnerable because of its mission to provide service to people with a minimum of intrusion on privacy and disruption of access. The detection and mitigation of attacks on air transportation are made more difficult because of the transience of passengers, the small quantity of threat agent that may be required for an effective attack, and the fact that passengers commonly carry baggage, making it relatively easy to conceal threat materials. The September 11, 2001, attacks on the Pentagon and the World Trade Center, in which commercial airliners were used as weapons, also broadened concepts of what constitutes a threat to U.S. assets in general and to the air transportation system in particular.

Based on the history of terrorist attacks, which have mostly involved hijacking and bombing of aircraft, current threat-detection measures have concentrated on detecting weapons or explosives. In the future, terrorist attacks could also involve the use of toxic chemicals, chemical and biological warfare agents, or even radiological and nuclear materials.1,2

The government agency charged with responsibility for the implementation of technology for countering such threats is the Transportation Security Administration (TSA) in the Department of Homeland Security. The TSA, and the Federal Aviation Administration before it, have invested extensively in the development and deployment of technological and procedural systems designed to protect the traveling public. In support of its mission, TSA has tasked the National Research Council (NRC) with assessing a variety of technological opportunities for protecting the U.S. transportation system, with a focus on the air transportation system.

STATEMENT OF TASK AND COMMITTEE APPROACH

The TSA has given the NRC the following statement of task for this study:

This study will explore opportunities for technology to address national needs for transportation security. While the primary role of the committee is to respond to the government’s request for assessments in particular applications, the committee may offer advice on specific matters as required. The committee will: (1) identify potential applications for technology in transportation security with a focus on likely threats; (2) evaluate technology approaches to threat detection, effect mitigation, and consequence management; and (3) assess the need for research, development, and deployment to enable implementation of new security technologies. These tasks will be done in the context of current, near-term, and long-term requirements.

The committee will perform the following specific tasks:

  1. Identify potential applications for technology in transportation security with a focus on likely threats derived from threat analyses that drive security system requirements. Review security system developments structured to meet the changing threat environment. Assess government and commercial industry plans designed to address these threats.

  2. Evaluate technology approaches to threat detection, effect mitigation, and consequence management. Delineate the benefits of the insertion of new technologies into existing security systems. Evaluate the trade-offs between effectiveness and cost, including the cost of changing the security system architectures.

1  

The President’s Homeland Security Department Proposal, available online at http://www.whitehouse.gov/deptofhomeland/bill/index.html. Accessed October 3, 2005.

2  

National Research Council, Making the Nation Safer: The Role of Science and Technology in Countering Terrorism, Washington, D.C.: The National Academies Press, 2002.



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Defending the U.S. Air Transportation System Against Chemical and Biological Threats 1 Background and Overview The U.S. air transportation system is an attractive target for terrorists because of the potential for attacks on the system to cause immediate harm and anxiety to large numbers of people, as well as to cause massive economic disruption to the United States and the world. The system is vulnerable because of its mission to provide service to people with a minimum of intrusion on privacy and disruption of access. The detection and mitigation of attacks on air transportation are made more difficult because of the transience of passengers, the small quantity of threat agent that may be required for an effective attack, and the fact that passengers commonly carry baggage, making it relatively easy to conceal threat materials. The September 11, 2001, attacks on the Pentagon and the World Trade Center, in which commercial airliners were used as weapons, also broadened concepts of what constitutes a threat to U.S. assets in general and to the air transportation system in particular. Based on the history of terrorist attacks, which have mostly involved hijacking and bombing of aircraft, current threat-detection measures have concentrated on detecting weapons or explosives. In the future, terrorist attacks could also involve the use of toxic chemicals, chemical and biological warfare agents, or even radiological and nuclear materials.1,2 The government agency charged with responsibility for the implementation of technology for countering such threats is the Transportation Security Administration (TSA) in the Department of Homeland Security. The TSA, and the Federal Aviation Administration before it, have invested extensively in the development and deployment of technological and procedural systems designed to protect the traveling public. In support of its mission, TSA has tasked the National Research Council (NRC) with assessing a variety of technological opportunities for protecting the U.S. transportation system, with a focus on the air transportation system. STATEMENT OF TASK AND COMMITTEE APPROACH The TSA has given the NRC the following statement of task for this study: This study will explore opportunities for technology to address national needs for transportation security. While the primary role of the committee is to respond to the government’s request for assessments in particular applications, the committee may offer advice on specific matters as required. The committee will: (1) identify potential applications for technology in transportation security with a focus on likely threats; (2) evaluate technology approaches to threat detection, effect mitigation, and consequence management; and (3) assess the need for research, development, and deployment to enable implementation of new security technologies. These tasks will be done in the context of current, near-term, and long-term requirements. The committee will perform the following specific tasks: Identify potential applications for technology in transportation security with a focus on likely threats derived from threat analyses that drive security system requirements. Review security system developments structured to meet the changing threat environment. Assess government and commercial industry plans designed to address these threats. Evaluate technology approaches to threat detection, effect mitigation, and consequence management. Delineate the benefits of the insertion of new technologies into existing security systems. Evaluate the trade-offs between effectiveness and cost, including the cost of changing the security system architectures. 1   The President’s Homeland Security Department Proposal, available online at http://www.whitehouse.gov/deptofhomeland/bill/index.html. Accessed October 3, 2005. 2   National Research Council, Making the Nation Safer: The Role of Science and Technology in Countering Terrorism, Washington, D.C.: The National Academies Press, 2002.

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Defending the U.S. Air Transportation System Against Chemical and Biological Threats Assess the need for research, development, and deployment to enable implementation of new security technologies. Review and assess the potential benefit of existing and advanced detection technologies, including scanning technologies, sensing technologies, and the use of computer modeling and databases. Review and assess emerging approaches to effect mitigation and consequence management. An overarching goal of the Committee on Assessment of Security Technologies for Transportation is to provide timely reports that meet TSA’s priorities for defeating terrorist threats. The committee judged that this could best be done by issuing a series of short reports on chosen technological applications. In consultation with TSA, the committee selected four topics for review, of which this report is the second: Mass spectrometry for enhanced trace chemical detection,3 Chemical/biological sensors and mitigation of threats, Millimeter wave imaging for explosives detection, and Data fusion and integration for airport terminals. By mutual agreement between the committee and the sponsor, the broad focus on “transportation security” in the statement of task was narrowed to the threat of chemical and biological attacks on the U.S. air transportation system. The committee approached its charge by focusing on two attack settings: air terminals and aircraft. Of all the different transportation environments, the air transportation environment is perhaps the best controlled, with its checkpoints, orderly passenger flows, controlled access areas, relatively clean air, and so on. Therefore, it is likely to be the most favorable transportation environment for the application of defensive measures and technologies against terrorist attacks. Although the defensive measures and technologies discussed here may not have application to all transportation modes (e.g., containerized ships, bridges, highway tunnels), the committee believes that the air transportation security arena provides a relatively well controlled testbed for gaining experience with defensive strategies that could be adapted to other transportation spaces, such as high-value buildings, bus terminals, train stations, and cruise ships, with appropriate modifications. As suggested by the wording of the topic of this report in the list above, this study is concerned not only with technologies for detecting the presence of chemical or biological threat agents in the air transportation context, but also with the mitigation of the impacts of their potential release. Given the very large number of technologies that are currently being investigated—both for the detection of chemical and biological agents and for the mitigation of the impact of attacks involving these agents—it was not feasible for the committee to evaluate each technology in detail. Rather, the committee chose to take a higher-level view, focusing on options for defensive strategies, as well as on the role that TSA might play in implementing these strategies. Thus, this report contains neither in-depth technical analyses nor cost-benefit analyses of specific detection systems; instead, it explores defensive strategies and options to inform the choices available to policy makers. SCOPE OF THE REPORT One can imagine a very large number of scenarios for attacks on the U.S. air transportation system with chemical/ biological agents. This report focuses on the dispersal of threat agents in air, either in airport terminals and their boarding areas or in aircraft, as illustrated in Figure 1-1. Two kinds of agent releases are considered: point releases of agent into open spaces and releases of agent into the inlets of terminal or aircraft heating, ventilation, and air conditioning (HVAC) systems. Chapter 2 discusses the threat posed by chemical and biological agents to the air transportation system and describes a range of attack scenarios that should be considered by government and private-sector planners. Concepts for defense against chemical/biological attacks—including those that depend on the detection of an attack before action is taken and those that do not—are explored in Chapter 3. Finally, Chapter 4 presents the committee’s findings and recommendations regarding the role that TSA should play in the defense of air transportation spaces against chemical/biological attack. 3   National Research Council, Opportunities to Improve Airport Passenger Screening with Mass Spectrometry, Washington, D.C.: The National Academies Press, 2004.

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Defending the U.S. Air Transportation System Against Chemical and Biological Threats FIGURE 1-1 Generic airport diagram showing various airport spaces and some likely sites for chemical/biological attacks.