Defending the U.S. Air Transportation System Against Chemical and Biological Threats (2006)

This chapter briefly outlines some of the current institutional and programmatic responses of government agencies, universities, and private industry to the threat posed by terrorist attacks using chemical/biological agents. It also presents the committee’s findings and recommendations regarding the role that the Transportation Security Administration (TSA) should play in defending the U.S. air transportation system against such attacks.

Many federal agencies are actively involved in both funding and conducting research to develop defensive strategies and technologies for dealing with chemical/biological threats. These agencies include the Department of Defense (DOD), the Department of Energy’s (DOE’s) national laboratories, the Department of Homeland Security (DHS), the National Science Foundation (NSF), the Centers for Disease Control and Prevention, and many others. Interagency groups such as the Technical Support Working Group (TSWG) have also been formed to solicit ideas for solving homeland security problems and to provide grants for further research.

The committee reviewed several federal chemical/biological research programs that appeared to have application to the U.S. air transportation environment. Two programs that are perhaps most relevant in this context are the Program for Response Options and Technology Enhancements for Chemical/Biological Terrorism (PROTECT) and Protective and Response Options for Airport Counter-Terrorism (PROACT). These programs, which originated in the late 1990s under DOE’s Chemical and Biological National Security Program, focus on the protection of transportation facilities against chemical/biological attacks. Partnerships to protect subway systems—and later, airports—began under PROTECT, and these programs later diverged, with subway work continuing under PROTECT and airport work shifting to PROACT. PROACT is now funded by DHS.

Under PROTECT, the subway system in Washington, D.C., has been a focus for tests involving the use of sensor technology to detect chemical agents; about half of the city’s underground stations have been outfitted with chemical sensors.¹ PROACT has focused on a collaboration with the San Francisco International Airport (SFIA) to determine how threat agent simulants² released into the air in various airport spaces would spread and to assess what air-handling and evacuation response strategies would be most effective in limiting exposures of airport patrons.^3,4 As part of this effort, a war-game-type exercise was held in November 2003, that brought together key airport authorities and local decision makers to explore how response decisions would be made during a real attack.⁵ The exercise showed the difficulty of developing an effective and timely response to a threat that cuts across so many diverse jurisdictions and areas of responsibility (airport operations, security, fire con-

trol and prevention, public health and safety, environment, and so on) and illustrated the importance of having response plans in place ahead of time with clearly defined roles for the relevant actors. The PROACT program has published a guidance document that draws together the lessons learned from the collaboration with SFIA to help other airports develop response plans to counter future chemical/biological attacks.⁶

Guidance is also available from a number of government sources on steps that building owners or managers can take to help protect occupants from airborne chemical, biological, or radiological attacks,⁷ and on how they can choose the most appropriate air filtration and/or cleaning systems.⁸ The Defense Advanced Research Projects Agency (DARPA) has had an Immune Building Program under way for several years to develop effective strategies for protecting military buildings from chemical/biological attacks. The DARPA program had the goal of developing an integrated set of models and analysis tools to help users understand the vulnerabilities of their buildings and to predict the performance of various defensive architectures. However, DARPA has found that theoretical models are not sufficient; rather, empirical testing in full-scale building areas is essential for addressing these issues with confidence.⁹ The committee notes that the options and procedures available for the protection of the occupants of military buildings may be rather different from those available for protecting civilian spaces such as airport terminals.

The committee received briefings that provided an overview of the very large number of research efforts to develop detection technologies (Figure 4-1) and of the range of specific technology approaches (Figure 4-2) being investigated. The Department of Defense (DOD) has provided much of the funding for current systems, and DOD has fielded a number of detector prototypes as indicated in Figure 4-1. Near-term research is also being funded by the Department of Energy (DOE), Department of Homeland Security (DHS), Defense Threat Reduction Agency, and TSWG, whereas longer-term projects are being funded by DARPA, the Soldier Biological and Chemical Command (SBCCOM), Naval Research Laboratory, Army Research Laboratory, and National Science Foundation (NSF).

In a previous report,¹⁰ this committee evaluated one of the technologies cited in Figure 4-2—mass spectrometry—for its potential to improve on current capabilities to detect trace quantities of explosives, chemical agents, and biological agents that might adhere to potential terrorists or their luggage. Another National Research Council (NRC) committee evaluated a wide range of technologies for their potential to rapidly detect and/or identify biological agents.¹¹ That committee found that within the next 10 years, a number of promising detection systems should become available that can substantially improve the defenses of high-value buildings and extended military bases against chemical/biological attacks. Nevertheless, on the basis of its earlier work on mass spectrometry, the wide range of presentations made to the committee by various technology analysts, and the expertise of its current members, it is this committee’s judgment that, although there is great potential for several of these technologies in the future, there is currently no detection system that can operate for long periods of time and reliably detect a wide range of agents in an airport context with few false alarms.

Despite widespread recognition that the U.S. air transportation system remains an attractive target for terrorists to attack with chemical/biological agents and despite the large federal investment in detection technologies, no federal agency has been assigned clear responsibility for the defense of U.S. air transportation spaces against such an attack. Although some preliminary studies have considered various threat scenarios and contingency plans, at this writing these studies have involved a limited number of spaces¹² within a

FIGURE 4-1 Partial list of chemical/biological detection system developers. NOTE: JBPDS, Joint Biological Point Detection System; RAPID, Ruggedized Advanced Pathogen Identification Device; APDS, Autonomous Pathogen Detection System; LLNL, Lawrence Livermore National Laboratory; HANAA, Handheld Advanced Nucleic Acid Analyzer; SRI, SRI International; UC, Upconverting. SOURCE: Briefing presented to the committee by Thomas Austin, Boeing Phantom Works, Woods Hole, Massachusetts, October 14, 2003.

single airport (SFIA). Clearly, much remains to be done to expand this effort and to encourage airports across the country to assess the threat and develop defensive architectures that make sense for their own particular facilities.

Finding 1: The U.S. air transportation system is an attractive target for attacks with chemical or biological weapons, yet no federal agency has been assigned clear responsibility for developing a strategy for defense against such attacks.

Based on its recent experience in facilitating the deployment of explosives-detection equipment at airports around the country, DHS’s Transportation Security Administration (TSA) has established relationships with local airport authorities and is the agency most knowledgeable about U.S. air transportation spaces. It is therefore well positioned to contribute to helping airports develop defenses against chemical/biological threats.¹³

Recommendation 1: The Transportation Security Administration, with its responsibility for the federal oversight of security operations at U.S. airports, should integrate strategies for defense against chemical/biological attacks into its broader security plan for protecting the U.S. air transportation system. The line of authority and accountability for implementing these strategies should be clearly defined.

FIGURE 4-2 Partial list of technologies being investigated for various stages of chemical/biological detection systems. NOTE: MEMS, microelectromechanical systems; LIF, laser-induced fluorescence; UV LIDAR, ultraviolet light detection and ranging. SOURCE: Briefing presented to the committee by Thomas Austin, Boeing Phantom Works, Woods Hole, Massachusetts, October 14, 2003.

The committee does not suggest that TSA should be given a lead role in the development of chemical/biological-detection technologies, nor should it attempt to duplicate other agencies’ programs. However, TSA can be assigned a coordinating and oversight role in the development and implementation of defensive strategies for transportation spaces.

Finding 2: No specific strategies, approaches, or procedures have been developed to defend the U.S. air transportation system against chemical/biological attacks.

The Department of Homeland Security has funded preliminary studies to elaborate specific chemical/biological threat vectors and to increase understanding of airflows in several terminals and boarding areas of San Francisco International Airport and Albuquerque Airport. It has also conducted an exercise in which the many airport decision makers (e.g., in areas of operations, security, fire control and prevention, public health and safety, and environmental issues) come together to try to formulate a coordinated response to a simulated chemical/biological attack. Such studies and exercises are valuable and should result in useful guidance that can help airports throughout the country begin to think about their own response plans. However, the work thus far is preliminary and of limited scope, and TSA itself appears to have had little involvement.

Recommendation 2: The Transportation Security Administration, in collaboration with other appropriate entities within the Department of Homeland Security,¹⁴ should create a high-level task force to perform the following functions:

• Create a validated threat assessment document for air transportation spaces and keep it updated;

• Take advantage of ongoing research aimed at the de velopment of models of the airflow within aircraft, terminals, and so forth, based on empirical studies of specific facilities, and explore the dispersal of chemical/biological simulants under various release scenarios;

• Create guidance to help air transportation facilities develop a threat defense strategy; and

• Determine unique air transportation requirements for dealing with chemical/biological threats and coordinate closely with other agencies that are active in the chemical/biological threats area to ensure that these requirements are given visibility in their programs.

The threat assessment document should include the best intelligence on the most likely sources and sites of terrorist attacks against the system and should be updated continuously. The TSA should also build on modeling work conducted under DARPA’s Immune Building Program and earlier DHS work with two airports to facilitate the development of defensive strategies and to help evaluate their efficacy. Models must include explicit consideration of the behavior of people as decision makers and as members of crowds, although research is lacking in both areas in the context of terrorism.

The TSA should build on work already being done within DHS to help airports develop an effective concept of operations for a threat defense strategy, including contingency plans for the following: scenarios involving the release of various threat agents, plans for limiting the spread of agents once released, plans for the evacuation of personnel to safe areas, plans for the isolation of contaminated areas, strategies for the early notification and treatment of potentially exposed individuals, and timely remediation of affected areas. The guidance should stress the importance of having well-defined roles and responsibilities for the many local, state, and federal authorities and airport decision makers in responding to a future attack.

The TSA should ensure that the requirements of detection systems in the transportation environment (for example, probability of detection, probability of false alarms, ruggedness, system footprint, operator interface) are considered in the relevant programs of other agencies. While TSA does participate in interagency groups that discuss homeland security issues (e.g., the Technical Support Working Group), the specific requirements of transportation systems have not been given a high priority according to briefings to the committee by TSA personnel who have attended these meetings.

As discussed in Chapter 3, a detection-based defensive strategy could complement the non-detection-based strategy in some scenarios, particularly those involving the release of slow-acting biological agents. However, it is likely to be some years before technological detection systems become available that are sufficiently affordable, effective, and robust for deployment in air transportation spaces.

Finding 3: Many alternative chemical/biological detection technologies are being investigated in university, industry, and government laboratories, and various military prototype systems have been developed; however, it is very difficult to independently evaluate all of the performance claims for these technologies.

A staggering number of papers is published each year in the literature on various candidate chemical/biological-detection systems. Researchers and manufacturers make diverse claims of detection limits, sensitivity, false-alarm rates, and robustness for these systems. The committee believes that in many cases, researchers emphasize the strengths of their particular detection systems while minimizing or ignoring their flaws. This practice makes it virtually impossible to evaluate the likely performance of a detection system in real-world transportation environments.

Recommendation 3: The Transportation Security Administration should keep abreast of ongoing research on chemical/biological detector technologies without starting an in-house research and development activity. Rather, it should seek to leverage the research programs of other agencies, and it should consider supporting a vendor-independent testing capability in order to verify performance claims made for chemical/biological detection systems.

The TSA has been concerned with the deployment of technologies for the detection of small arms and explosives; it has neither the resources nor the expertise to conduct its own research programs in the chemical/biological area. However, TSA’s technology-monitoring effort might involve maintaining a close liaison with the efforts of other agencies, as well as funding a third party to survey the spectrum of detection technologies being developed in the private sector in order to identify those that might be most appropriate for the transportation environment.

Given the very large number of candidate detection technologies and the many (often overly optimistic) performance claims for them, TSA should also consider supporting an independent body to develop test criteria and conduct standard tests to evaluate the performance of chemical/ biological detection systems and to verify the claims of prospective manufacturers. Such an independent testing body would benefit the ongoing research efforts of many government agencies.

Finding 4: Although the rapid detection of a chemical/ biological attack and identification of the agent used are worthwhile objectives, a defensive strategy that depends exclusively on a detection-system alarm before action is

taken (i.e., employment of a “detect and react” strategy) has several serious limitations.

As discussed in Chapters 2 and 3, chemical/biological agent detectors can play a valuable role in defensive architectures for air transportation spaces, especially for the scenario of an attack with a delayed- or slow-acting agent. Videocamera surveillance of air transportation spaces, which can be considered a kind of functional detection technology for attacks with fast-acting agents, is available today. Technological detection systems with acceptable cost and performance are not likely to be available for some years. In the meantime, much can be done to improve the defenses of transportation spaces by blending elements of the detection-based and non-detection-based strategies that are available today.

Recommendation 4: Given the limitations of sensor- and assay-based chemical/biological agent detection and identification technologies, the Transportation Security Administration should pursue a baseline defensive strategy against chemical/biological attacks that does not depend solely on the technological detection of threat agents to initiate action. Such a strategy would be based on elements such as the following:

• Protective and preventative steps and enhanced security;

• Improved visual surveillance of air transportation spaces;

• The establishment of a separate air supply for spaces that have a critical function (e.g., cockpits, flight-control towers, emergency-response centers); and

• Continuous air treatment to neutralize and/or remove agents or contaminants.

It is the judgment of this committee that the very large number of candidate sensor-based and assay-based detection systems have received a great deal of attention and research money but that none currently has the effectiveness, technical maturity, reliability, sensitivity, and selectivity to many different agents and the low-cost characteristics needed for deployment in the air transportation environment. In contrast, there are a variety of technologies that do not involve the detection of an agent that can prevent or mitigate the consequences of a chemical/biological attack, are available today, and would be arguably less costly to deploy. These non-technological-detector-based defensive measures have not received the attention and analysis that the committee believes they deserve.

Generally, the committee believes that technologies associated with non-detection-based strategies (e.g., air cleaning, better security, better control of airflows) are nearer term, while technologies associated with detection-based strategies (with the exception of videocamera surveillance) are longer term or more speculative. Guided by the threat defense strategy described above, TSA should work with individual airports to explore security enhancements such as limiting access to identified areas of vulnerability—for example, the inlets of the terminal heating, ventilation, and air conditioning (HVAC) systems or the ventilation system for aircraft on the ground. Using experimental testing of the dispersion of released agent simulants, TSA should also work with the facilities to explore methods for limiting the spread of chemical/biological agents once they are released, such as automatic shut down of HVAC systems balancing of adjacent air-handling regions, and so on.

To combat the threat of an attack with fast-acting agent, TSA should explore the feasibility of the widespread deployment of surveillance cameras throughout transportation spaces that would enable a monitor to quickly determine that such an attack had occurred. Such cameras could also provide a dual-use value in improving the overall security environment. The TSA should fund the creation of computer models of crowd behavior during such an attack that would enable pattern-recognition software to monitor the surveillance cameras so as to provide backup for human monitors. This software should not be seen as a stand-alone system but as part of a hybrid human/software solution that recognizes the complementary capabilities of human and machine. In addition, many critical nodes in the air transportation system (control rooms, emergency-response centers, and so on) are supplied with air that is recirculated from publicly accessible areas; this makes them vulnerable to being disabled by the release of chemical/biological agents in these public areas. Thus, it may be prudent to ensure that these critical nodes have an independent air supply and are kept at a positive pressure with respect to surrounding areas.

Finally, to mitigate the impacts of a release involving either fast- or slow-acting agents, TSA should explore the feasibility of a program to use the HVAC system in a terminal or the Environmental Control System in an aircraft to continuously treat the air in transportation spaces in order to remove harmful chemicals and biological particles. This approach could involve improved air filtration and cleaning, ultraviolet irradiation of filters to kill biological organisms, plasma cleaning of air, or other technologies that are widely used to clean the air in hospitals, biology research laboratories, and industrial clean rooms. A feasibility study would include the costs (both first cost and maintenance/replacement cost), number, and optimum placement of air-cleaning units required, their effectiveness in removing threat agents from the air under various release scenarios, the number of likely exposures prevented, and so on. Such a “clean air” approach would also likely be appealing to the traveling public that is concerned about the transmission of common diseases such as colds, flu, and even severe acute respiratory syndrome (SARS), in densely populated, enclosed transportation spaces.

In the event that chemical/biological detection systems become available with appropriate cost and performance at-

tributes and demonstrated benefits for defending against the attack scenarios of interest, TSA should consider deploying them to augment the effectiveness of the baseline non-detection-based strategy.

It appears that, given the need to maintain convenient public access to an efficient transportation system, a terrorist attack on the system with chemical/biological agents would be difficult to prevent and would likely result in a significant number of casualties. Because there are a very large number of possible chemical and biological agents that might be used in a future terrorist attack, and because the specific type of agent to be used will not, in general, be known in advance, the development and deployment of chemical sensors and bioassays for arbitrarily selected specific agents offer little real protection. By contrast, the deployment of video monitors and/or biology-based “functional” detectors (analogous to the canary in the mine) that indicate the effects of any fast-acting toxic chemical agents would be beneficial in some attack scenarios, and these systems could be deployed in a complementary way with non-detection-based defensive strategies. Thus, the overall impact of such an attack may depend less on the development of technologies for the detection of threat agents than on prudent protective measures that can be implemented before the attack ever takes place. The TSA should explore the feasibility of these options and should help local authorities and facilities develop contingency plans for responding to chemical/biological attacks on the U.S. air transportation system.