Small-scale Terrorist Attacks Using Chemical and Biological Agents: An Assessment Framework and Preliminary Comparisons

Small-scale Terrorist Attacks Using Chemical and Biological Agents: An Assessment Framework and Preliminary Comparisons

Order Code RL32391
CRS Report for Congress
Received through the CRS Web
Small-scale Terrorist Attacks
Using Chemical and Biological Agents:
An Assessment Framework and
Preliminary Comparisons
Updated June 23, 2004
-name redacted-
Analyst in Science and Technology Policy
Resources, Science, and Industry Division
-name redacted-
Analyst in Science and Technology Policy
Resources, Science, and Industry Division
Congressional Research Service ˜ The Library of Congress

Small-scale Terrorist Attacks Using Biological and
Chemical Agents: An Assessment Framework and
Preliminary Comparisons
Summary
This report, which will be updated as necessary, presents a means of assessing
the relative threat from terrorist-use of individual chemical, biological, and toxin
agents. It focuses on small-scale, targeted chemical and biological attacks, rather
than mass-casualty attacks. The framework considers the elements of access, public
health impact, medical treatment, prophylaxis, and dissemination. Other factors that
may affect potential use by terrorists include the range of lethality, covert
employment of an agent, and the availability of dual-use technologies.
The results of this framework may be useful in addressing the threat these agents
pose, for example by indicating priorities for countermeasure funding. Other uses
include weighing the potential effectiveness of policy options, assessing threat
reduction approaches to specific agents, and serving as a resource for developing
other specialized frameworks.
Defense against chemical and biological agents is high on the list of the nation’s
priorities. No clear consensus exists with respect to which agents pose the greatest
threat. Previous analyses of the chemical and biological threat have largely revolved
around historical and comparative treatments or been based in a military framework.
Examination of the chemical and biological threat to civilians is more complicated.
Agents whose characteristics make them poor military weapons may still be powerful
if deployed as weapons of terror. Chemical and biological weapons used in the past
have not always been chosen for the highest potential fatalities, but rather for other
reasons.
Some chemical and biological agents are closely regulated, both domestically
and internationally. Expansion or further refinement of policies controlling these
agents may lower the threat posed by terrorist use of them. Domestic policy options
to reduce the threat posed by these agents include methods to prevent their use,
consequence management after their use, and methods for protecting the public from
them. Specific policies to implement these goals include improving the general
public health system, increasing prophylaxis research, development of new medical
countermeasures treatments, increasing intelligence gathering, and increasing
regulation of dual-use technology. International policy options include development
of new biosecurity agreements and increasing participation in current non-
proliferation organizations.
It is impossible to eliminate the risk of chemical or biological terrorism.
Important issues facing policymakers include balancing the need for increased
security with the potential economic costs associated with increased regulation and
redirected federal resources, determining the relative ratio between general and
specific countermeasures against chemical and biological terrorism, and assessing the
success of federal efforts at reducing chemical and biological terrorism vulnerability.

Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Definition of C/B Terrorism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Probability of a C/B Weapon Attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Historical Acquisition and Use of C/B Agents . . . . . . . . . . . . . . . . . . . . . . . 8
C/B Assessments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Assessments by Government Agencies . . . . . . . . . . . . . . . . . . . . . . . . . 9
Military-use Assessment Compared to Terrorist-use Assessment . . . . 10
How Difficult Is it to Develop C/B Agents for Terrorist Use? . . . . . . 11
Agent Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Chemical Agent Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Choice of Chemical Agents Assessed . . . . . . . . . . . . . . . . . . . . . . . . . 17
Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Biological Agent Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Choice of Biological Agents Assessed . . . . . . . . . . . . . . . . . . . . . . . . 22
Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Toxin Agents Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Choice of Toxin Agents Assessed . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Potential Uses of Framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Deviations From Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Terrorist Motivation-Specific Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Potential for Covert Deployment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Range of Lethality and Impact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Contagious Dissemination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Previous Use of C/B Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Source of C/B Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
From a Manufacturing Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
From a Natural Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
From a Culture Collection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Manufacture and Preparation of C/B Agents . . . . . . . . . . . . . . . . . . . . . . . . 43
Policy Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Current Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
International Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Domestic Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Dual-Use Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
New Multinational Regulation Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Prevention Versus Consequence Management . . . . . . . . . . . . . . . . . . . . . . 47
Law Enforcement Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Health Care Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Separating Assessments of Chemical and Biological Agents . . . . . . . . . . . 49

Acceptable Level of C/B Terrorism Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Advances in Science and Science Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
How Criteria Were Chosen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
The Weighting System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Appendix B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Appendix C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Appendix D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
List of Figures
Figure 1. Comparison of State Chemical WMD and Terrorist Chemical Agent
Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 2. Comparison of State Biological WMD and Terrorist Biological Agent
Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
List of Tables
Table 1. Chemical agent comparison according to barriers to potential
terrorist use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 2. Biological agent comparison according to barriers to potential
terrorist use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Table 3. Toxin agent comparison according to barriers to
potential terrorist use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Table 4. Comparison of chemical agent characteristics . . . . . . . . . . . . . . . . . . . . 57
Table 5. Comparison of biological agent characteristics . . . . . . . . . . . . . . . . . . . 64
Table 6. Comparison of toxin agent characteristics . . . . . . . . . . . . . . . . . . . . . . . 80

Small-scale Terrorist Attacks Using
Biological and Chemical Agents: An
Assessment Framework and Preliminary
Comparisons
Introduction
Public concern about the nation’s vulnerability to chemical and biological (C/B)
terrorism was amplified by the consequences of the anthrax mailings that sickened
22 people and killed 5 between September and November, 2001. Subsequent C/B
terrorism events, such as the ricin mailings to the White House in 2003 and to the
Senate in 2004, have served to highlight the potential for future terrorist attacks using
C/B agents. C/B weapons, previously considered to be of interest mainly to military
planners, are now a topic of public and congressional interest. Compared with most
conventional weapons, C/B weapons are less well understood and have the potential
to cause mass casualties. Even if used in smaller attacks, C/B weapons have the
potential to cause mass terror. Potential effects of a C/B terrorist event vary widely,
depending on the agent used, the effectiveness of its dissemination, the target struck,
and the public reaction to the event.
This report addresses the potential terrorist use of C/B agents, including toxins.
The focus of this report is on small-scale, targeted chemical and biological attacks.
In this framework, manufacture and dissemination of modest amounts of material,
able to cause significant casualties in a building, subway station or other enclosed
space, rather than on a citywide scale, are discussed. This approach attempts to
analyze the threat posed by various agents if used by small, non-state-sponsored
terrorist groups that may lack the technology, expertise, or logistical capability to
mount a large mass-casualty attack. To provide policymakers with background and
analysis for prioritization of federal resources, this framework summarizes the
characteristics of each agent into broad categories with a coarse scale, rather than a
highly differentiated, multidimensional ranking. It is likely that policymakers will
find more detailed analysis than that presented here helpful when refining policy
alternatives.

Reports that discuss chemical and biological agents must be careful not to
provide terrorist groups with information or opportunities that are not already known
to them. This report follows the precedent set by other publications in this field by
not providing detailed information on the C/B agents discussed herein.1 It does not
1 Publications in the C/B arena include Richard A. Falkenrath, Robert D. Newman and
Bradley A. Thayer, America’s Achilles’ Heel: Nuclear, Biological, and Chemical Terrorism
and Covert Attack, Cambridge, MA: MIT Press, 1998; Joshua Lederberg, ed., Biological
(continued...)

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contain any technical information regarding the growth or synthesis of biological or
chemical agents. Furthermore, all information in this report has been compiled solely
from reports in the open literature. No classified information was used in the
preparation of this report. It raises issues expressed by other analysts in disparate
open sources with regard to current terrorist motivational factors. The material in
this report is designed to be used as a potential springboard to assess and prioritize
responses to the various C/B agents that might be used by a terrorist. It provides a
potential policy framework for use by Congress as it considers legislative issues
associated with the potential use of such agents by terrorists.
Some previous assessments of the C/B threat have highlighted the difficulty of
developing and producing agents, but these assessments may ignore significant
advances in the areas of dual-use technology.2 Such technology may significantly
ease C/B agent production by small groups. Additionally, concerns have been raised
about the applicability of previous assessments, especially those developed using a
military framework, to civilian settings and casualties. The classification of C/B
weaponry into the catch-all category of “weapons of mass destruction” (WMD) has
led to consideration of C/B use primarily on a mass-casualty scale.3 This treatment
may misstate the potential civilian vulnerability to a small-scale terrorist C/B attack.
Treatment of terrorist attacks on a mass-casualty scale has produced many worst-case
scenarios, but few assessments of the wide spectrum of potential C/B agents.
The merging of all unconventional, high-consequence/low-probability-of-use
weapons into a single category is advantageous for some military planning, but can
obfuscate assessment of each weapon type or individual agent. All of the weapons
of mass destruction differ from each other significantly in effect, effort required for
development, and production and dissemination. While the impact of nuclear and
radiological devices varies largely depending on the size of the device, the impact of
different chemical and biological agents has wider variation. For example, the agent
used can determine if the result is temporary impairment, injury and disfigurement,
1 (...continued)
Weapons: Limiting the Threat, Cambridge, MA: MIT Press, 1999; Bill Frist, When Every
Moment Counts: What You Need to Know About Terrorism By The Senate’s Only Doctor,
Lanham, MD: Rowman & Littlefield, 2002; National Research Council, Making the Nation
Safer: The Role of Science and Technology in Countering Terrorism, Washington, DC:
National Academies Press, 2002; and Microbial Threats to Health: Emergence, Detection,
and Response, Institute of Medicine, Washington, DC: National Academies Press, 2004.
2 Dual-use technologies have a legitimate civilian use in addition to a military use.
3 This assessment method has been ubiquitous in both governmental and private-sector
assessments. As examples, see the White House Fact Sheet, Combating Terrorism:
Presidential Decision Directive 62, May 22, 1998; Centers for Disease Control and
Prevention, “Biological and Chemical Terrorism: Strategic Plan for Preparedness and
Response: Recommendations of the CDC Strategic Planning Workgroup,” Morbidity and
Mortality Weekly Report 49 RR-4 (2000): 2-3; Jonathan B. Tucker and Amy Sands, “An
Unlikely Threat,” Bulletin of the Atomic Scientists 55 (July-August 1999): 46-52; and World
Health Organization, Health Aspects of Chemical and Biological Weapons, Geneva: World
Health Organization, 1970, 98-99.

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or widespread death. This report treats C/B agents alone, rather than assessing
WMD, to better address the threat posed by individual C/B agents.
Addressing events with small-scale casualties generally has been outside the
purview of previous assessments, though small-scale terrorism is noted as being more
likely than mass-casualty events.4 After the events of October 2001, small-scale
terror events also concern the public. It is a concern for policymakers that analyses
on, and preparations against, large-scale chemical and biological attacks may not be
widely applicable to events occurring on smaller scales. This concern was expressed
in the first annual report of the Advisory Panel to Assess the Domestic Response
Capabilities of the Government for Terrorism Involving Weapons of Mass
Destruction, also known as the Gilmore Commission. Looking at lower
probability/higher consequence scenarios, it stated:
Such scenarios, however, are at odds with the focus of current policy and
preparedness efforts — which have been based on less than comprehensive
information and analysis — which seem to emphasize the
lower-probability/higher-consequence attacks at the expense of
higher-probability/lower-consequence incidents. The guiding assumption has
been that smaller-scale, non-mass-casualty events are a lesser-included
contingency that can be addressed adequately by preparations for the higher-end
mass casualty attacks. This is by no means axiomatic.5
To address these concerns, this report focuses on smaller-scale, targeted terror
attacks, rather than addressing C/B weapons in a mass-casualty framework.
This report establishes an assessment framework for C/B agents to help
policymakers develop risk-management based policies to counter terrorist use of C/B
agents. Vulnerability, threat, and risk are related terms. Vulnerability represents the
impact an event could have, and contains measures of protection and preparedness.
Threat represents the probability that a given event will occur, and contains measures
of both capability and intention. Risk is the combination of vulnerability with threat.
Risk management approaches rely on reducing vulnerability, threat, or both to lower
the overall risk of attack. The assessment framework presented here is generic in the
sense that it does not incorporate the motivations or capability of a specific terrorist
organization. A risk assessment of a specific terrorist organization’s likelihood of
using C/B weapons would incorporate these factors.
Independent think tanks and federal government agencies have developed and
modeled scenarios, through exercises including federal and local officials, to assess
the potential impact of a C/B attack. These exercises provide vulnerability
assessment rather than threat or risk assessment. The potential public threat posed
4 See The Advisory Panel to Assess the Domestic Response Capabilities of the Government
for Terrorism Involving Weapons of Mass Destruction, “The First Annual Report to the
President and the Congress of The Advisory Panel to Assess the Domestic Response
Capabilities of the Government for Terrorism Involving Weapons of Mass Destruction: I.
Assessing the Threat,” Dec. 15, 1999, available on-line from RAND at
[http://www.rand.org/organization/nsrd/terrpanel].
5 Ibid.

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by C/B terrorism is not accurately assessed through the development of worst-case
scenario exercises such as Dark Winter, TOPOFF, TOPOFF 2 and others.6,7 These
exercises are instructive in establishing the United States’ current C/B vulnerability,
but they do not assess many factors needed to understand the C/B risk. For example,
it is unclear whether the pathogens chosen for the exercises (smallpox and
pneumonic plague, respectively) represent agents likely to be chosen by a terrorist.
Without understanding the range of likely C/B agents, rather than the range of
possible C/B agents, it is difficult to convert vulnerability assessments into threat
assessments. Therefore, it is difficult to make effective policy based strictly on
vulnerability assessments. The General Accounting Office (GAO) has advocated
using a risk-management approach, rather than vulnerability assessments, to limit the
potential damage done by a C/B attack.8
Background
Definition of C/B Terrorism
There are several federal definitions of terrorism.9 For example, the U.S.
Department of Defense (DOD) defines terrorism as “The calculated use of unlawful
violence or threat of unlawful violence to inculcate fear; intended to coerce or to
intimidate governments or societies in the pursuit of goals that are generally political,
6 The Johns Hopkins Center for Civilian Biodefense Strategies, in collaboration with the
Center for Strategic and International Studies, the Analytic Services Institute for Homeland
Security, and the Oklahoma National Memorial Institute for the Prevention of Terrorism,
held a senior-level exercise in June, 2001 entitled “Dark Winter” that simulated a covert
smallpox attack on the United States. A review of the Dark Winter exercise can be found
in Tara O’Toole, Michael Mair, and Thomas V. Inglesby, “Shining Light on “Dark Winter,”
Clinical Infectious Diseases 34 (2002): 972-983.
7 The U.S. Department of Justice conducted an exercise, called TOPOFF for its involvement
of top officials, in May 2000, regarding the management of mock radiological, chemical, and
biological attacks in three cities. A review of the TOPOFF 2000 exercise can be found in
Thomas V. Inglesby, Rita Grossman, and Tara O’Toole, “A Plague on Your City:
Observations from TOPOFF,” Clinical Infectious Diseases 32 (2001): 436-445. In May
2003, the U.S. Department of Homeland Security conducted TOPOFF 2 to test the response
to a radiological and biological terrorist attack. See U.S. Government, Top Officials
(TOPOFF) Exercise Series: TOPOFF 2, After Action Summary, U.S. Department of
Homeland Security, Washington DC, December 19, 2003.
8 The GAO has often cited the need for a risk management approach to chemical and
biological terrorism in both testimony before and reports to Congress. For representative
examples, see testimony by Raymond J. Decker before the Senate Committee on
Governmental Affairs. General Accounting Office, Homeland Security: A Risk
Management Approach Can Guide Preparedness Efforts, GAO-02-208T, October 2001, and
General Accounting Office, Bioterrorism: Coordination and Preparedness, GAO-02-129T,
October 2001.
9 For an overview of the statutory language defining terrorism, see CRS Report RS21021
“Terrorism” and Related Terms in Statute and Regulation: Selected Language by (name red
acted).

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religious, or ideological.”10 The U.S. Department of Justice (DOJ) defines terrorism
as “...the unlawful use of force and violence against persons or property to intimidate
or coerce a government, the civilian population, or any segment thereof, in
furtherance of political or social objectives.”11 Because of differences in federal
definitions of terrorism, especially in the areas of threatened use and articulation of
goals, this report uses a more encompassing definition for C/B terrorism. For the
purposes of this report, C/B terrorism refers to the use of chemical or biological
agents by individuals or groups motivated by ideology, but not necessarily
accompanied by a stated political or social agenda.12 By using this definition, attacks
which have a large apparently random component to them may be included as
terrorist events.13 This definition includes several C/B terrorist events to date, such
as the ricin mailings in 2003 and 2004, the anthrax mailings in 2001, the Aum
Shinrikyo sarin gas attack in Tokyo in 1995,14 and the Rajneeshees’ use of salmonella
poisoning in Oregon in 1984.15
Probability of a C/B Weapon Attack
Most experts agree that the probability of a C/B attack on a domestic target
remains much smaller than that of a comparably damaging attack with conventional
arms. The instantaneous consequence of, greater access to, and relative ease of using
conventional weapons all contribute to the likelihood of conventional weapon use.
Additionally, terrorist organizations have historically chosen to use proven attack
methods, rather than attempt attacks with less well-established technologies.16
Experts debate whether C/B agents have become weapons with special value to
potential terrorists due to their psychological effect on the public. Some experts have
10 U.S. Department of Defense, “DOD Dictionary of Military and Associated Terms,” Joint
Publication 1-02, as amended through December 17, 2003.
11 28 C.F.R. 0.85, also see U.S. Department of Justice, Terrorism in the United States,
Federal Bureau of Investigation, 1999.
12 The definition used here closely follows that used by W. Seth Carus in Bioterrorism and
Biocrimes: The Illicit Use of Biological Agents Since 1900, Center for Counterproliferation
Research, Washington, DC: National Defense University, 2001.
13 This definition is not the broadest definition for terrorism, as it excludes actions taken by
nation-states and does not require that the victims of terrorism be noncombatants.
14 For an overview of the Aum Shinrikyo use of sarin in the Tokyo subway system, see
David E. Kaplan, “Aum Shinrikyo (1995)” in Toxic Terror: Assessing Terrorist Use of
Chemical and Biological Weapons, ed. Jonathan B. Tucker, Cambridge, MA, MIT Press,
2000.
15 For an overview of the Rajneeshees’ use of Salmonella Typhimurium in Oregon in 1984,
see W. Seth Carus, “The Rajneeshees (1984)” in Toxic Terror: Assessing Terrorist Use of
Chemical and Biological Weapons, op. cit.
16 See, for example, Bruce Hoffman, “Holy Terror,” the Implications of Terrorism
Motivated by a Religious Imperative, RAND Document P-7834, 1993.

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asserted that terrorist groups will continue to escalate the level of violence employed,
including C/B agents, so that reaction and attention is drawn to their actions.17
Some experts feel that it is simply a matter of time until terrorists begin using
C/B weapons in earnest. In a 1999 Washington Post opinion article, then Defense
Secretary Cohen stated:
Also looming is the chance that these terror weapons will find their way into the
hands of individuals and independent groups — fanatical terrorists and religious
zealots beyond our borders, brooding loners and self-proclaimed apocalyptic
prophets at home. This is not hyperbole. It is reality.18
In May, 2002, Defense Secretary Rumsfeld told the Senate Appropriations
Committee, “... they [terrorists] inevitably will get their hands on them [weapons of
mass destruction] and they will not hesitate to use them.”19 Experts holding this view
believe it is a matter of “when” rather than “if” terrorists will use C/B or other WMD
technology against civilian targets.
Other experts believe that the historical record shows few successful attempts
at C/B terrorism, and that past trends are relevant to future assessments. For
example, Milton Leitenberg, a senior fellow at the Center for International and
Security Studies at the University of Maryland, has written “...the threat assessment,
most particularly regarding “BW terrorism” — the potential for BW use by non-state
actors — has been greatly exaggerated.”20
Some experts claim that the ease of using conventional weapons so heavily
outweighs the potential benefits of using a more challenging, unconventional method
that it makes C/B terrorism unlikely. Anthony H. Cordesman, Arleigh A. Burke
Chair in Strategy at the Center for Strategic and International Studies, stated “Most
terrorist/extremist attacks to date on Americans inside and outside the U.S. have used
conventional explosives, and the [1993] World Trade Center and Oklahoma City
bombings show that such attacks can be very costly.”21
The public’s response to highly visible acts of property destruction may provide
a disincentive for C/B agent usage. Groups accustomed to shocking the populace
17 See, for example, Jeffrey D. Simon, “The Growing Threat of Bioterrorism”, in The Age
of Super and Cyber Terrorism. Selected Papers (Arlington, VA: Potomac Institute for
Policy Studies) 1999.
18 William S. Cohen, “Preparing for a Grave New World,” The Washington Post, July 26,
1999.
19 “Rumsfeld Says Terrorists Inevitably Will Get Chemical, Nuclear or Biological
Weapons,” Associated Press, May 21, 2002. Bracketed information added by CRS.
20 Milton Leitenberg, “Biological Weapons and ‘Bioterrorism’ in the First Years of the 21st
Century,” Center for International and Security Studies, April 3, 2003. Found online at
[http://www.fas.org/bwc/papers/21centurybw.pdf].
21 Anthony H. Cordesman, “Defending America: Asymmetric and Terrorist Attacks with
Biological Weapons,” Center for Strategic and International Studies, February 12, 2001.

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through infrastructure destruction may choose to use conventional weapons rather
than unconventional arms because of the greater visual display of property
destruction. Also, C/B agent development requires greater time and financial
investment than development of conventional explosives, and it demands a higher
degree of training. Groups may not be able or willing to invest such a high
proportion of resources in unconventional weapons given the relative ease of
obtaining and using conventional weapons. Finally, the effects of C/B agents are
more unpredictable than conventional weapons and may be delayed in time. This
uncertainty may make them less likely to be chosen by a terrorist group, especially
a group with limited resources or opportunity.22
In contrast, some analysts point out that the changing nature of terrorist
organizations may lower the barriers for those groups who wish to use chemical or
biological agents.23 Historically, terrorist groups tended to possess clear, defined
political aims and easily identified constituents. These groups’ activities were
constrained by the cultural and moral beliefs of their constituents, including the
general aversion to the use of chemical or biological agents. Additionally, the
potential for disease transmission from an infected terrorist target to a terrorist
supporter was viewed as a barrier to biological terrorism. Recently, terrorist groups
bearing a fundamentalist, extremist view lacking clear political goals and having a
diffuse, less easily identified constituency have become more common. Many
analysts suspect that the taboo against use of C/B agents has weakened, since these
groups may be less susceptible to traditional deterrents and may be less concerned
with maintaining a high level of legitimacy to their constituents. Changes in political
makeup of these groups also may result in a reassessment of the terrorists’ choice
between conventional and unconventional arms.24
Recent advances in dual-use technology may reduce the technological barriers
for terrorist groups who wish to engage in C/B-related attacks. Industries and
academia, especially in the area of microbiology, increasingly employ technologies
that can be converted to C/B agent production with moderate to low effort. These
dual-use technologies provide prospective terrorists with equipment that can be
obtained by theft or purchase. Policymakers may be required to reassess the
likelihood of terrorists using C/B agents, as technical barriers to C/B agent
development may become less of a hindrance.25
22 Another possibility is the use of chemical or biological agents in conjunction with
conventional weapons. The combination of these two attack types presents additional policy
challenges and considerations which are beyond the scope of this report.
23 For an overview of the different factors potentially motivating terrorist groups towards
C/B use, see Jerrold M. Post, “Psychological and Motivational Factors in Terrorist Decision-
Making: Implications for CBW Terrorism” in Toxic Terror: Assessing Terrorist Use of
Chemical and Biological Weapons, op. cit.
24 For an in-depth examination of this issue see, CRS Report RL31831 Terrorist Motivations
for Chemical and Biological Weapons Use: Placing the Threat in Context by (name redact
ed).
25 For more on this topic, see CRS Report RS21422 Dual-Use Biological Equipment:
Difficulties in Domestic Regulation by (name redacted).

CRS-8
Historical Acquisition and Use of C/B Agents
Many chemical and biological agents have been used in the past, both during
times of war and through terrorist action. The former Soviet Union and the United
States both possessed active chemical and biological weapons programs that
attempted to develop new, more deadly weapons.26 Currently, international treaties
restrict research to that for defensive purposes only. Other nations have, at various
times, also developed their own biological and chemical programs, though some of
these programs are no longer supported.27
Chemical and biological weapons were initially developed in a military context,
as weapons with potential strategic and tactical use. Chemical agents were widely
used in Europe during World War I, and biological agents were reportedly used in
sabotage actions against animals in World War I.28 Also, Japan has been cited as
using plague as an antipersonnel weapon against China during World War II.29 The
former Soviet Union has been accused of providing toxin agents to allies in Vietnam
and Laos and using these toxins during its war in Afghanistan.30 During the 1980-
1988 Iraq-Iran war, both Iran and Iraq reportedly used chemical agents, with both
26 The Russian Federation and the United States have ratified the Chemical Weapon
Convention which went into force in 1997. On November 25, 1969, President Nixon ended
the U.S. offensive biological weapons program. The former Soviet Union’s offensive
biological weapons program persisted into at least the 1990's; an account of which is in Ken
Alibek’s Biohazard: The Chilling True Story of the Largest Covert Biological Weapons
Program in the World — Told from Inside by the Man Who Ran It, New York: Random
House, 1999.
27 For an overview of the historical development and wartime use of C/B agents, see Javed
Ali, Leslie Rodrigues and (name redacted), U.S. Chemical-Biological Defense Guidebook,
Alexandria, VA: Jane’s Information Group, 1998; Stockholm International Peace Research
Institute, The Problem of Chemical and Biological Warfare, Volume I: The Rise of CB
Weapons, Stockholm: Almqvist & Wiksell, 1971; and Stockholm International Peace
Research Institute, The Problem of Chemical and Biological Warfare, Volume II: CB
Weapons Today, Stockholm: Almqvist & Wiksell, 1973. For more information regarding
national weapons programs, see CRS Report RL30699 Nuclear, Biological, and Chemical
Weapons and Missiles: The Current Situation and Trends, by (name redacted) and
Chemical and Biological Weapons: Possession and Programs Past and Present, Monterey
I n s t i t u t e f o r I n t e r n a t i o n a l S t u d i e s , f o u n d o n l i n e a t
[http://cns.miis.edu/research/cbw/possess.htm].
28 W. Seth Carus, Bioterrorism and Biocrimes: The Illicit Use of Biological Agents Since
1900, op. cit.
29 See “Chronology of State Use and Biological and Chemical Weapons Control” compiled
by Center for Nonproliferation Studies, Monterey Institute of International Studies, updated:
October, 2001, found online at [http://cns.miis.edu/research/cbw/pastuse.htm].
30 Jonathan B. Tucker, “The ‘Yellow Rain’ Controversy: Lessons for Arms Control
Compliance,” The Nonproliferation Review, Spring, 2001. Other analysts have disputed this
interpretation of the “yellow rain” event. See Julian Robinson, Jeanne Harley Guillemin,
and Matthew Meselson, “Yellow Rain: The Story Collapses,” Foreign Policy, 68 (1987):
100-117.

CRS-9
countries using vesicants and Iraq purportedly employing nerve agents.31 It has also
been widely reported that Iraq used chemical agents against Kurdish civilians to quell
an insurgency.32
Some terrorist groups have adopted C/B agents to further their aims. In 1984,
the Rajneeshees sickened hundreds of people in Oregon by producing and deploying
Salmonella Typhimurium, a bacterium which normally causes non-fatal food
poisoning.33 Aum Shinrikyo attempted to develop an array of chemical and
biological agents to be used against the Japanese civilian populace in the early
1990s.34 There are also many reports of small groups or individuals producing toxin
agents.35 While it is difficult to determine the extent to which terrorist groups are
researching potential chemical and biological weapon use, it has been reported that
some known terrorist groups have an interest in acquiring such weapons.36
C/B Assessments
Assessments by Government Agencies. An assessment of terrorist
threat is difficult to quantify, since many of the variables involved are not reliably
known. Some of these variables include the skill level of various terrorist groups, the
location and size of terrorist assets, and the possession of any particular C/B agent.
As a consequence, the exact threat faced is indeterminable from the open literature
and the risk involved can only be estimated. Vulnerability can be assessed through
the development of scenarios, including worst-case scenarios. Vulnerability studies
do not address the likelihood of an attack occurring; they only assess possible
outcomes if an attack very similar to the one modeled occurs. It is commonly
thought that a worst-case scenario is unlikely to occur, since many low-probability
events must occur for the worst to happen. However, given the nature of some C/B
agents, even non-worst-case events could have huge psychological effects, public
health impacts and economic costs for the nation.
31 Julian Perry Robinson and Jozef Goldblat, Chemical Warfare in the Iraq-Iran War,
Stockholm International Peace Research Institute, May 1984.
32 For example see, Staff Report, U.S. Congress, Senate, Committee on Foreign Relations,
Chemical Weapons Use in Kurdistan: Iraq’s Final Offensive, 100th Congress, 2nd session,
U.S. Government Printing Office, 1988.
33 W. Seth Carus, “The Rajneeshees” in Toxic Terror: Assessing Terrorist Use of Chemical
and Biological Weapons, op. cit.
34 David Kaplan, “Aum Shinrikyo” in Toxic Terror: Assessing Terrorist Use of Chemical
and Biological Weapons, op. cit.
35 For an extensive overview of the use of chemical, biological, and toxin agents by non-state
actors see Ron Purver, Chemical and Biological Terrorism: The Threat According to the
Open Literature, Canadian Security Intelligence Service, 1995. A comprehensive
compilation of biological agent use and its context can be found in W. Seth Carus,
Bioterrorism and Biocrimes: The Illicit Use of Biological Agents Since 1900, op. cit.
36 Central Intelligence Agency, Unclassified Report to Congress on the Acquisition of
Technology Relating to Weapons of Mass Destruction and Advanced Conventional
Munitions, 1 January Through 30 June 2003, November 2003.

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With few historical precedents for C/B terrorism, determining the current risk
of C/B terrorism from past events is difficult and perhaps misleading. To assess the
threat from other nations, the U.S. intelligence community has prepared several
National Intelligence Estimates on the biological and chemical capabilities of foreign
states.37 Within these classified estimates, reportedly, the C/B agents that have the
highest relative probability of use have been described, but these reports are not
available in the open literature.38 Presumably, the Directorate for Information
Analysis and Infrastructure Protection in the Department of Homeland Security and
the Terrorist Threat Integration Center have developed or are in the process of
developing similar C/B threat assessments.39
Several other federal agencies have developed, or are in the process of
developing, biological agent threat lists, to determine the agents which have the
highest relative probability of use.40 The Centers for Disease Control and Prevention
(CDC), in collaboration with law enforcement, intelligence and defense agencies,
have developed a list of agents that would have the greatest impact on the public
health.41 The U.S. Department of Agriculture has developed two biological threat
lists through a collaborative, international process.42 The Environmental Protection
Agency, under provisions of the Clean Air Act, has collected worst-case scenario
plans and information regarding catastrophic toxic releases from chemical plants
adjacent to or within communities.43 As each agency has different requirements and
perspectives, each has generated individualized C/B threat lists. There is a lack of
consensus on the contents of a definitive, unified C/B threat list.
Military-use Assessment Compared to Terrorist-use Assessment.
Military-use analyses predominantly revolve around military management of C/B
37 A National Intelligence Estimate is the most authoritative written judgment concerning
a national security issue by the major agencies comprising the U.S. intelligence community.
Most National Intelligence Estimates forecast future developments and many address their
implications for the United States. National Intelligence Estimates cover a wide range of
issues including military, technological, economic, and political trends. They are prepared
by the Director of Central Intelligence with the participation of intelligence community
agencies. See General Accounting Office, Combating Terrorism: Need for Comprehensive
Threat and Risk Assessments of Chemical and Biological Attacks, GAO/NSIAD-99-163,
September, 1999.
38 The accuracy of some NIEs have been questioned. For example, see John Barry and Mark
Hosenball, “What Went Wrong,” Newsweek, February 9, 2004, 24-31.
39 For more on these entities, see CRS Report RS21283 Homeland Security: Intelligence
Support by Richard A. Best, Jr.
40 As cited by General Accounting Office, Bioterrorism: Coordination and Preparedness,
GAO-02-129T, October 2001, 10.
41 Lisa D. Rotz, et al., “Public Health Assessment of Potential Biological Terrorism Agents,”
Emerging Infectious Diseases 8 (2002): 225-230.
42 As cited by General Accounting Office, Bioterrorism: Coordination and Preparedness,
GAO-02-129T, October 2001.
43 More information on the Risk Management Program of the EPA can be found online at
[http://yosemite.epa.gov/oswer/CeppoWeb.nsf/content/index.html].

CRS-11
weapons and battlefield casualties. These analyses may inadequately address terrorist
use of C/B agents against civilian populations. Several key factors cited as necessary
conditions for military use would not be required in a smaller-scale assault on
civilian targets using limited dispersal of C/B agents. For example, military
assessments include factors such as stabilization of the C/B agent for storage and
transport purposes, dispersal technologies for maximum airborne dissemination,
timeliness of agent effectiveness, and integration within the battle plan. Additionally,
many of the military assessments, especially those relating to chemical agents, are
made specifically in relation to use by an opposing military, with considerations of
chemical prophylaxis and protective equipment being included. Finally, a recurring
theme in military assessments is the difficulties involved in disseminating an agent
against a target in the open, a tactic requiring training in meteorology and engineering
in addition to chemical and/or biological training.
Concerns of storage, stability and mass dissemination are examples of why a
military assessment may differ from one using a terrorism framework. While it is
likely true that only a state-funded biological or chemical weapons program could
successfully develop the technology necessary to make bulk C/B agents that are
stable under long-term storage in munition form, a terrorist who wishes to make gram
quantities of a C/B agent and disseminate it, for example with a modified pesticide
sprayer, would be unconstrained by these criteria. This underscores the Gilmore
Commission’s concern that large-scale WMD analysis may be inappropriate when
applied to terrorist events.44 Agents whose characteristics make them poor military
weapons may still be powerful if deployed as weapons of terror.
How Difficult Is it to Develop C/B Agents for Terrorist Use? Experts
disagree on the difficulty of C/B agent manufacture. Many experts believe that it is
relatively easy to manufacture some chemical agents,45 while others point to the
apparent difficulties that state actors have had in developing chemical weapons
programs. Some experts claim that development of weaponized biological agents
presents remarkably high hurdles, particularly in mass dissemination, which would
require teams of scientists with state backing to overcome.46 Other experts believe
that a single, moderately well funded individual could develop a biological weapon
in a home basement.47 Richard Danzig, while he was Under Secretary of the Navy,
stated the opinion that, “[A] small pharmaceutical industry or even moderately
sophisticated university or medical research laboratory can generate a significant
44 Some terrorist-use assessments of biological weapon use focus significantly on mass
casualty threats. See, for example, Centers for Disease Control and Prevention, “Public
Health Assessment of Potential Biological Terrorism Agents,” Emerging Infectious Diseases
8 (2002): 225.
45 For a representative opinion, see Robert K. Mullen, “Mass Destruction and Terrorism,”
Journal of International Affairs 32 (1978): 62-89.
46 For a representative opinion, see Milton Leitenberg, “An Assessment of the Biological
Weapons Threat to the United States,” Conference on Emerging Threats Assessment:
Biological Terrorism, Dartmouth College, July, 2000, found online at
[http://www.homelanddefense.org/journal/Articles/Leitenberg.htm].
47 For a representative opinion, see Jeffrey D. Simon, “Terrorists and the Potential Use of
Biological Weapons: A Discussion of Possibilities,” RAND Corporation, December 1989.

CRS-12
offensive capability.”48 Some experts reportedly claim that very pure, high quality
anthrax spores similar to those used in the anthrax mailings could be made with “a
very simple, nonindustrial process — a very primitive process — that could let you
get a trillion spores in one gram.”49 Other experts dispute this assertion.50
One explanation for some of the differences among expert views lies in
assumptions of event size. Experts who opine that terrorist use of biological and
chemical weapons is difficult tend to consider such agents in the framework of mass
destruction, with fatalities numbering in the thousands and casualties in the tens of
thousands of people, which would require mass production of agents and the
independent development of efficient, effective distribution systems.51 In contrast,
others argue that the small batches required for a targeted, low-casualty attack would
be relatively ease to produce. The Aum Shinrikyo sarin gas attack in Tokyo and the
anthrax mailings demonstrated that an attack utilizing either a chemical or biological
agent need not inflict mass casualties to cause widespread disruption.
Figure 1 provides a comparison between the steps necessary to develop a mass-
casualty chemical weapon and those required for the same agent to be used on a
smaller scale in a terrorist attack. Figure 2 shows a similar comparison for
biological weapons. While the exact criteria needed to develop a C/B agent vary
with the agent, the primary difference between the two flowcharts is that for terrorist
distribution of a C/B agent, many steps considered to have high practical difficulties
may be nonexistent in the case of terrorist groups that wish to launch only a small-
scale attack and that have low regard for their personal safety.52 Such steps include
developing agents that have a long storage shelf life, optimizing a large-scale
dissemination device, developing rigorous prophylaxis, and optimizing the
manufacturing process so as to make mass quantities of the C/B agent. These steps,
indicated by italics in the flowchart for military use, are not necessarily required for
terrorist group use and therefore have been removed from the flowchart for terrorist
programs.
48 See Richard Danzig, “Biological Warfare: A Nation at Risk - A Time to Act,” Strategic
Forum, Institute for National Strategic Studies, January 1996.
49 Ken Alibek quoted by Jonathan Rauch, “Does Al Qaeda Have Anthrax? Better Assume
So,” National Journal, May 31, 2002.
50 Gary Matsumoto, “Anthrax Powder: State of the Art?” Science 302 (2003): 1492-1497.
51 The Office of Technology Assessment produced several comprehensive analyses of
chemical and biological agents in terms of mass destruction. While dated, the majority of
the information contained in these reports continues to be applicable. See U.S. Congress,
Office of Technology Assessment, Technologies Underlying Weapons of Mass Destruction,
OTA-BP-ISC-115, Washington, DC: Government Printing Office, 1993; U.S. Congress,
Office of Technology Assessment, Proliferation of Weapons of Mass Destruction: Assessing
the Risks, OTA-ISC-559, Washington, DC: Government Printing Office, 1993; U.S.
Congress, Office of Technology Assessment, Technology Against Terrorism: Structuring
Security, OTA-ISC-511, Washington, DC: Government Printing Office, 1992; and U.S.
Congress, Office of Technology Assessment Technology Against Terrorism: The Federal
Effort, OTA-ISC-487, Washington, DC: Government Printing Office, 1991.
52 For an overview of motivations leading to terrorist use of suicide tactics, see CRS Report
RL32058 Terrorists and Suicide Attacks by (name redacted).

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Experts contend that for large scale attacks these steps represent barriers of
comparable importance to a terrorist organization. If terrorist groups focus on
smaller scale distribution of C/B agents, the amount of agent necessary to inflict
dozens to thousands of casualties can be made using only research-scale, rather than
mass-production, facilities. If a terrorist group decides that small-scale distribution
is acceptable, disseminating agents either as a crude aerosol or solution through the
use of converted industrial equipment would become a viable, if inefficient,
distribution method. The problem of long-term agent storage is bypassed if only
enough material for each use is prepared shortly before being used. These
compromises reduce the effective lethality of a given amount of agent, as several
non-optimized steps are involved, but this could be addressed through production of
more agent. These compromises result in removing many of the hurdles cited as
being of maximal difficulty in nation-state-level C/B development.

CRS-14
Figure 1. Comparison of State Chemical WMD and Terrorist Chemical Agent Development
Source: Adapted by CRS, 2002 from Technologies Underlying Weapons of Mass Destruction, Office of Technology Assessment, December, 1993.
Note: The process required for a nation-state level capability is found on the left, that for a terrorist capability is found on the right. Italics reflect differences between programs.

CRS-15
Figure 2. Comparison of State Biological WMD and Terrorist Biological Agent Development
Source: Adapted by CRS, 2002 from Technologies Underlying Weapons of Mass Destruction, Office of Technology Assessment, December, 1993.
Note: The process required for a nation-state level capability is found on the left, that for a terrorist capability is found on the right. Italics reflect differences between programs.

CRS-16
Agent Analysis
C/B agents are presented in a matrix framework in this section, with the agents
ranked by number of barriers to their use in small scale terrorist attacks, rather than
use in mass-casualty attacks or military use. Because of the differences among the
agents, they are divided into three categories: chemical agents, biological agents, and
toxins. Toxins are separated from biological agents because they do not reproduce
in a host, and are separated from chemical agents because of their biological origin.
Each C/B agent type is analyzed according to criteria specific to its category. A
negative sign ( — ) denotes an aspect that poses a significant barrier to terrorist use
or that is a negative influence to terrorist use. A positive sign (+) refers to an aspect
that does not pose a significant barrier to terrorist use or that is a positive influence
to terrorist use. The O rank represents an intermediate state. The matrices present
agents for comparison within a category, but agents should not be compared across
different matrices, as the criteria used vary for each matrix. Appendix A contains
a detailed description of the methodology used to develop these matrices.
The successful development of a C/B agent requires a certain level of individual
competence and training.53 The analysis here applies only to cases where terrorist
groups possess such levels of skill. Also, reasonable financial means on the part of
the terrorist is assumed. Since this report focuses on the ability of groups or
individuals to develop small-scale production capacity, it is also assumed that there
is no overt state-sponsorship of the terrorist group, and, as a consequence, there has
been no documented technology transfer to the terrorist group from a national
biological or chemical weapons program. In order to compare the impact of different
C/B agents, the target is assumed to be the same in each case: a medium-sized
enclosed space, such as an office building or subway station. The effect of changing
these assumptions is explored in the Discussion section.
Chemical Agent Comparison
Most chemical agents, unlike biological or toxin agents, do not naturally occur.
Typically, a larger amount of chemical agent is required for equivalent effect than a
biological or toxin agent. Some chemical agents were discovered during research in
chemical warfare and others in civilian research areas, such as pesticide development.
Chemical agents have widely varying effects and forms; some chemical agents are
toxic or corrosive gases commonly found in industrial processes.54 Other chemical
agents are not used in manufacturing processes and are used only as a weapon.
Finally, some chemical weapons have found civilian applications in other areas and
are manufactured for those purposes, for example, nitrogen mustard has been used
for cancer chemotherapy.
53 Many experts agree that a graduate education in chemistry or biology provides the
necessary skills to produce laboratory quantities of a chemical, biological, or toxin agent
respectively. Others believe that some agents might be within the capabilities of intelligent
and dedicated high school students.
54 Toxic chemicals such as chlorine, phosgene, hydrogen cyanide, and anhydrous ammonia
are often used in chemical manufacturing processes.

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Choice of Chemical Agents Assessed. There are many toxic chemicals,
but most are ill-suited for terrorist use because of their physical properties. The
chemical agents discussed in this report are a subset of all available toxic chemicals.
Criteria for selecting these agents include their coverage by the Chemical Weapons
Convention (CWC),55 their inclusion on the CDC’s chemical agent list,56 their
inclusion in North Atlantic Treaty Organization (NATO)57 and U.S. military medical
fieldbooks,58 their inclusion in the U.S. DOJ Guide for the Selection of Chemical and
Biological Decontamination Equipment for Emergency First Responders,59 and
finally their reported presence in the former Soviet Union’s or the United States’
chemical weapons program.60 Agents found on a preponderance of these lists were
chosen to be included for assessment. Agents with purely psychological effects, such
as LSD (lysergic acid diethylamide) or the compound BZ, were omitted.
Criteria. Table 1 categorizes chemical agents according to four criteria: ease
of acquisition, public health impact, resistance to medical treatment, and ease of
dissemination. Agents are listed in descending order of combined ranking with
respect to the criteria. For further information on the methodology regarding criteria
choice, ranking, and weighting, see Appendix A. See Table 4 in Appendix B for
technical data used to rate each agent.
55 The list of chemicals found on the three schedules of the Chemical Weapons Convention
can be found online at
[http://www.opcw.org/html/db/cwc/eng/cwc_annex_on_chemicals.html].
56 The Centers for Disease Control and Prevention list of chemical agents of concern is
found at [http://www.bt.cdc.gov/Agent/AgentlistChem.asp].
57 NATO Handbook on the Medical Aspects of NBC Defensive Operations AmedP-6(B),
Departments of the Army, the Navy and the Air Force, 1996, found online at
[http://www.vnh.org/MedAspNBCDef/toc.htm].
58 Field Manual: Treatment of Chemical Agent Casualties and Conventional Military
Chemical Injuries, Departments of the Army, the Navy, and the Air Force, and
Commandant, Marine Corps, July, 2000, found online at
[http://www.vnh.org/FM8285/cover.html].
59 Guide for the Selection of Chemical and Biological Decontamination Equipment for
Emergency First Responders, NIJ Guide 103 — 00, October, 2001, found online at
[http://www.ncjrs.org/pdffiles1/nij/189724.pdf].
60 Chemical agents found in the former Soviet Union’s and the United States’ chemical
weapons program are taken from a summary developed by the Monterey Institute of
International Studies from sources in the open literature. The summary is found online at
[http://cns.miis.edu/research/cbw/possess.htm].

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Table 1. Chemical agent comparison according to barriers to potential terrorist use
Chemical Agent
Ease of Acquisition
Public Health Impact
Resistance to Medical Treatment
Ease of Dissemination
Nitrogen Mustard
+
+
+
+
Sulfur Mustard
+
+
+
+
Phosgene Oxime
O
+
+
+
Lewisite
O
+
O
+
Cyclohexyl Sarin
O
+
O
O
Sarin
O
+
O
O
Tabun
O
+
O
O
VX
—
+
+
+
Ammonia
+
O
+
—
Chlorine
+
O
+
—
Chloropicrin
+
O
+
—
Phosgene
+
O
+
—
Diphosgene
+
O
+
—
Soman
—
+
+
O
Cyanogen Chloride
+
O
—
—
Hydrogen Cyanide
+
O
—
—
Perfluoro-isobutylene
—
O
+
—
Source: This table was prepared from compiled open source data. Congressional Research Service, 2002 (Updated 2004). See Appendix B for detailed data used to generate rating.
Note: See text for explanation of symbols. Breaks within the table group agents with roughly comparable rank.

CRS-19
Ease of Acquisition. Most chemical agents require artificial synthesis and
manufacture, so a prospective terrorist would be concerned with their relative ease
of production. While dual-use chemical agents are potentially available by theft or
purchase in large quantity, many chemical agents require a dedicated synthetic effort
to acquire in bulk. In some cases, precursor chemicals required to synthesize agents
can be purchased on a research scale without undue difficulty.61
The technology necessary to manufacture most chemical agents is known
through the open literature. The safety and efficiency of chemical synthesis and
manufacturing practices have increased substantially since the early manufacture of
chemical agents. While the equipment necessary for large-scale manufacture of these
agents is regulated through export controls, equipment necessary to create small-scale
amounts of chemical agents at home, in makeshift laboratory facilities, can be
purchased through many chemical distributors. Attempting to manufacture chemical
agents under such circumstances comes with increased risk of discovery and
inadvertent exposure to the agent.
In the ease of acquisition column of Table 1, the symbol + denotes chemical
agents that are created via processes that are technically straightforward and have few
noxious side products, or those chemicals that have industrial dual-uses and therefore
might be obtained rather than manufactured. The symbol O denotes chemical agents
that generate significant toxic side products during manufacture, endangering the
person manufacturing the agents.62 The symbol — denotes chemical agents that
require closely monitored precursor chemicals for manufacture, create significant
lethal side products, or require sophisticated synthesis equipment.
Public Health Impact. This report combines morbidity, mortality and load
placed on the public health care system to describe this aspect of an agent’s
effectiveness. Effects of a chemical agent are agent-specific. Some agents kill
exposed people. Other agents primarily incapacitate victims; these agents,
predominantly choking agents, tend to have a wide range of effects, from temporary
tightness of chest and difficulty breathing to life-threatening pulmonary edema.
Finally, some agents incapacitate those exposed through painful tissue damage.
These agents, called blister agents or vesicants, cause damage on contact with the
skin and do not need to be inhaled for effect. A single scale of impact, such as
lethality, would strongly under-report the impact of a blister agent, which requires
relatively large quantities to kill, but little to cause intense pain and disfigurement.
On the other hand, using lethality as the only scale would over-report the impact of
a nerve agent, which can be lethal, but generally causes much less harm at sub-lethal
dosages.
Because of the above factors, this report uses a more general criterion to
describe an agent’s effectiveness, namely impact on the health care system. Mortality
61 “Special Report: Better Killing Through Chemistry,” Scientific American, December,
2001.
62 The synthesis of some agents involves the generation of toxic side products. These side
products could significantly complicate the production of chemical agents, as they increase
the level of danger to the person making the compound.

CRS-20
and morbidity from the release of nerve agent would have a high impact on the health
care system, as would cases of extensive chemical burns from the release of blister
agents, and cases of pulmonary edema from choking agents. By using this more
indirect gauge of effectiveness, useful comparisons can be made between agents with
different mechanisms of causing harm.
In the public health impact column of Table 1, the symbol + denotes chemical
agents whose use would create a high, deleterious public health consequence. The
symbol O denotes chemical agents whose use would create a more moderate,
deleterious public health consequence. The symbol — denotes chemical agents
whose use would create a relatively low, deleterious public health consequence.63
Resistance to Medical Treatment. The degree to which treatment can
ameliorate or prevent symptoms is a primary concern in treating chemical casualties.
This factor is essential to defusing the impact of a chemical attack. Injuries from
some chemical agents cannot be reversed. Injuries from other agents may be
successfully reversed through treatment immediately after the attack. Depending on
the agent and the quantity of agent to which a victim is exposed, the time frame in
which these treatments are effective varies from minutes to hours.64
In the resistance to medical treatment column of Table 1, the symbol + denotes
chemical agents that lack any treatment to prevent the onset of symptoms. The
symbol O denotes chemical agents that first responders would likely be able to treat.
The symbol — denotes chemical agents which can be treated after a significant time
delay.
Ease of Dissemination. Chemical agents are typically dispersed as a gas or
liquid, depending on the ambient temperature and the agent. Gases dilute themselves
into the surrounding atmosphere, limiting their effectiveness. In most cases,
chemical agent effects arise from some form of interaction with the vapors or the
aerosols of these agents. Liquids that are not volatile do not provide enough vapor
for inhalation and must either be aerosolized or heated to maintain their effect.
In the ease of dissemination column of Table 1, the symbol + denotes chemical
agents which do not require inhalation to inflict damage, the vapors or aerosol cause
an effect upon skin contact. The symbol O denotes chemical agents which require
inhalation of small quantities of vapor or aerosol. The symbol — denotes chemical
agents that require inhalation of large volumes of vapor or aerosol.
Examples. Chlorine is a chemical commonly used in many manufacturing and
industrial processes, ranging from the pharmaceutical industry to water treatment
facilities. Because of its wide availability, chlorine receives a + in the ease of
63 No — symbols appear in this column, as chemicals with low public health impact did
not pass the selection criteria for inclusion in this framework.
64 For information on the aging times of various nerve agents, see Frederick R. Sidell,
“Nerve Agents,” in Medical Aspects of Chemical and Biological Warfare, eds. Frederick R.
Sidell, Ernest T. Takafuji, and David R. Franz, Washington, DC: TMM Publications, 1997,
129-179.

CRS-21
acquisition category. Because chlorine can cause serious lung damage but is rarely
lethal, chlorine receives a O in the public health impact category. These injuries
cannot be cured, and can only be treated with supportive care; therefore chlorine
receives a + in the resistance to medical treatment category. Finally, for chlorine to
cause harm, large volumes of the gas must be inhaled, and therefore chlorine receives
a — in the ease of dissemination category.
In contrast to chlorine, the nerve agent VX is much harder to acquire.65 There
is no industrial use for VX and the known existing sources are under military guard.
A terrorist bent on using VX would most likely need to manufacture it from
precursor chemicals. However, these chemicals are controlled under the CWC and
would not be easy to obtain. Additionally, the synthesis of VX produces highly toxic
side products, so VX receives a — for ease of acquisition. VX is deadly at
relatively low concentration and many people could be affected by a small-scale
attack, therefore VX receives a + in public health impact. Treatment is available for
victims of VX exposure, especially those who receive lower doses and prompt
attention. However, VX’s persistent nature requires first responders to don
specialized equipment to enter and treat victims in the contaminated area. This time
delay may significantly complicate effective treatment. Therefore, VX receives a +
for resistance to medical treatment. Although VX is a liquid at room temperature,
it need not be inhaled; skin contact with small quantities is lethal. VX receives a +
for ease of dissemination.
The most effective known use of a chemical weapon in a terrorist attack
occurred in 1995 when the Aum Shinrikyo cult released sarin into the Tokyo subway.
Sarin is not widely available like chlorine gas, but is technically easier to
manufacture than VX. It receives a O for ease of acquisition. Twelve people died
in the attack, more than one thousand were injured, and more than five thousand
sought treatment.66 Sarin is deadly at relatively low concentration and many people
could be affected by a small-scale attack. Therefore, sarin receives a + for public
health impact. Treatment is available for victims of sarin exposure, especially those
who receive lower doses and prompt attention. Therefore sarin receives a O in
resistance to medical treatment. Because sarin is a liquid at room temperature and
must be inhaled to injure, it receives a O for ease of dissemination.67 Sarin reportedly
was not the original agent of choice for Aum Shinrikyo, as previous attempts were
made to develop botulinum toxin and anthrax. The cult reportedly developed other
chemical agents, such as phosgene and VX, but for various internal political and
technical reasons was unable to effectively use these weapons to inflict mass
casualties.68
65 VX is the common name for O-Ethyl S-Diisopropylaminomethyl
Methylphosphonothiolate, a toxic nerve agent.
66 Tim Ballard et al., “Chronology of Aum Shinrikyo’s CBW Activities,” Monterey Institute
of International Studies, March 15, 2001.
67 Liquid sarin can be a deadly upon prolonged skin contact, but its predominant threat is
through inhalation of sarin vapor.
68 David Kaplan, “Aum Shinrikyo” in Toxic Terror: Assessing Terrorist Use of Chemical
(continued...)

CRS-22
Biological Agent Comparison
Potential biological agents include the many bacteria and viruses that induce
disease in human beings. Many pathogens are not suitable biological agents because
of their fragility, long incubation time, or other characteristics. Biological agents
differ from chemical agents in that large amounts of agent can be grown from a tiny
initial supply. Biological agents may be considered especially insidious compared
to other agents, because the pathogens can multiply within infected individuals.
Thus, the dosage needed to induce illness can be very low, an amount much smaller
by weight than required of chemical or toxin agents.
Choice of Biological Agents Assessed. The biological agents chosen for
inclusion in Table 2 were compiled from several sources including the Biological
Weapons Convention (BWC) draft Compliance Protocol Annex A list,69 the CDC
Select Agent list,70 the CDC Biological Diseases/Agents Listing,71 the NATO
Handbook on the Medical Aspects of NBC Defensive Operations,72 the U.S. DOD
Field Manual: Treatment of Biological Warfare Agent Casualties,73 the Australia
Group List of biological agents for export control,74 the World Health Organization’s
Preparedness for the Deliberate Use of Biological Agents,75 the U.S. DOJ An
Introduction to Biological Agent Detection Equipment for Emergency First
Responders,76 the former Soviet Union’s bioweapons program, and the United States’
former biological weapons program.77 Biological agents found on a preponderance
of these lists were selected for assessment.
68 (...continued)
and Biological Weapons, op. cit.
69 The rolling text for the draft Biological Weapons Convention Protocol from February,
2001 was used, found online at [http://www.fas.org/bwc/papers/febannexI.htm#aann].
70 The Select Agent list is defined in 42 C.F.R. 73.4.
71 The CDC Biological Diseases/Agents Listing can be found online at
[http://www.bt.cdc.gov/Agent/Agentlist.asp].
72 NATO Handbook on the Medical Aspects of NBC Defensive Operations AmedP-6(B), op.
cit.
73 Field Manual: Treatment of Biological Warfare Agent Casualties, op. cit.
74 The Australia Group List of Biological Agents for Export Control can be found online at
[http://www.australiagroup.net/en/control_list/bio_agents.htm].
75 World Health Organization, Preparedness for the Deliberate Use of Biological Agents:
A rational approach to the unthinkable, World Health Organization, Geneva, May, 2002,
found online at [http://whqlibdoc.who.int/hq/2002/WHO_CDS_CSR_EPH_2002.16.pdf].
76 An Introduction to Biological Agent Detection Equipment for Emergency First
Responders, NIJ Guide 101-00, December, 2001, found online at
[http://www.ncjrs.org/pdffiles1/nij/190747.pdf].
77 Biological agents found in the former Soviet Union’s and United States’ former biological
weapons program can be found in a summary developed by the Monterey Institute of
International Studies from sources in the open literature. The summary is found online at
[http://cns.miis.edu/research/cbw/possess.htm].

CRS-23
Criteria. Table 2 categorizes biological agents based on six criteria: ease of
acquisition, public health impact, prophylaxis, resistance to medical treatment, ease
of dissemination, and whether the pathogen has been developed for use in a military
setting (“weaponized”). Agents are listed in descending order of combined ranking
with respect to the criteria. For further information on the methodology regarding
criteria choice, ranking, and weighting, see Appendix A. See Table 5 in Appendix
C for technical data used to rate each agent.
Ease of Acquisition. In marked contrast to chemical agents, most biological
agents can be obtained from natural sources, but natural strains vary widely in their
virulence. In some cases, biological agents are endemic in an animal reservoir
population, simplifying access and development. This availability provides terrorists
with options in developing a self-contained biological agent capacity. Terrorists
could attempt to isolate a pathogen found in nature, obtain a sample from a natural
human outbreak, or purchase or steal a sample from a commercial culture collection
or hospital. This would provide enough source material for a small-scale production
facility, using liter-sized fermenters, or even petri dishes, to grow enough material
for a small-scale attack.
In assessing the ease of a pathogen’s acquisition, several factors were weighed.
The first is whether the biological agent is available in an accessible area. Biological
agents which are rare cannot be readily or reasonably obtained from nature and would
need to be acquired from preexisting samples. For example, Marburg virus would
be very difficult to obtain from nature.78 It could be obtained from a culture
collection, but such transfers are closely regulated and observed. There would be
large practical barriers to their acquisition, regardless of the legality of such a
transfer. In contrast, salmonella bacteria would be easy to obtain from natural
sources and are available in many culture collections.
In the ease of acquisition column of Table 2, the symbol + denotes biological
agents that are endemic in nature, have well documented outbreaks, or are routinely
disseminated from culture collections. The symbol O denotes biological agents that
are available in nature only in very localized or remote areas, have small or poorly
documented outbreaks, or are obtained primarily through culture banks. The symbol
— denotes biological agents that are located predominantly in restricted culture
banks and are rarely documented in the wild.
78 Marburg virus causes a rare hemorrhagic fever with high lethality. The location of the
natural reservoir for Marburg virus is not well established.

CRS-24
Table 2. Biological agent comparison according to barriers to potential terrorist use
Ease of
Public Health
Resistance to
Ease of
Disease (Biological Agent)
Prophylaxis
Weaponized
Acquisition
Impact
Medical Treatment
Dissemination
Glanders (Burkholderia mallei)
+
+
+
O
+
Weapon
Crimean-Congo hemorrhagic fever
+
+
+
O
+
Unknown
Pneumonic Plague (Yersinia pestis)
+
+
O
O
+
Weapon
Hantavirus
+
+
+
O
O
Research
Dengue hemorrhagic fever
O
+
O
+
O
Research
Eastern equine encephalitis
O
+
O
+
O
Research
Lassa fever
O
O
+
O
+
Research
Russian spring-summer encephalitis
O
O
O
+
+
Research
Western equine encephalitis
O
O
O
+
O
Research
Rift Valley fever
O
O
O
O
O
Research
Marburg hemorrhagic fever
—
+
+
+
+
Weapon
Ebola hemorrhagic fever
—
+
+
+
+
Research
Melioidosis
+
+
+
—
+
Research
(Burkholderia pseudomallei)
Yellow fever
+
+
—
+
+
Research
Anthrax (Bacillus anthracis)
+
+
—
O
+
Weapon
Q fever (Coxiella burnetti)
+
+
O
—
+
Weapon

CRS-25
Ease of
Public Health
Resistance to
Ease of
Disease (Biological Agent)
Prophylaxis
Weaponized
Acquisition
Impact
Medical Treatment
Dissemination
Machupo hemorrhagic fever
—
+
+
O
+
Research
Tularemia (Francisella tularensis)
O
+
O
—
+
Weapon
Junin hemorrhagic fever
—
+
O
O
+
Research
Venezuelan equine encephalitis
O
—
O
+
O
Weapon
Typhus (Rickettsia prowazekii)
+
O
O
—
O
Research
Rocky Mountain spotted fever
O
+
O
—
O
Unknown
(Rickettsia rickettsiae)
Escherichia coli O157:H7
+
—
+
+
—
Unknown
Smallpox (Variola major)
—
+
—
O
+
Weapon
Monkeypox
—
+
—
O
+
Unknown
Brucellosis (Brucella abortus,
+
—
O
—
+
Research
B. melitensis, B. suis)
Shigella dysenteriae
O
+
+
—
—
Unknown
Cholera (Vibrio cholerae)
+
—
—
—
+
Unknown
Salmonella Typhimurium
+
—
+
—
—
Unknown
Typhoid fever (Salmonella Typhi)
+
O
—
—
—
Unknown
Source: This table was prepared from compiled open source data. Congressional Research Service, 2002 (Updated 2004). See Appendix C for detailed data used to generate rating.
Note: See text for explanation of symbols. Breaks within the table group agents with roughly comparable rank.

CRS-26
Public Health Impact. Biological agents, like chemical agents, can induce
a range of effects. Some agents are primarily incapacitating in nature, while other
agents are acutely lethal.79 The public health impact criterion used here is the same
as used above for chemical agents.
In the public health impact column of Table 2, the symbol + denotes biological
agents that have high, deleterious public health impact. The symbol O denotes
biological agents that have a more moderate, deleterious public health impact. The
symbol — denotes biological agents that have a relatively low, deleterious public
health impact.
Prophylaxis. Vaccines and other prophylactic measures are important factors
in assessing whether a particular agent would be a useful weapon in either military
or terrorist terms. The availability of a vaccine could provide civilian targets with
high protection from particular agents if the vaccine is routinely administered. The
presence of a widely used vaccine might significantly deter terrorist use of that
biological agent.80 Biological agents against which the population is routinely
vaccinated have been removed from this analysis.81
In the prophylaxis column of Table 2, the symbol + denotes biological agents
with no established prophylaxis. The symbol O denotes biological agents with
experimental prophylaxis lacking Food and Drug Administration approval. The
symbol — denotes biological agents with an approved vaccine.
Resistance to Medical Treatment. There is no uniform medical treatment
for biological agents. Some diseases are not curable and can only be treated with
generalized supportive care to limit symptoms. Other diseases can be cured through
the use of specific medicines. Furthermore, some diseases are treatable at any time
in the progression of the illness, while others can only be successfully treated during
onset. Treatment potential is likely to be an important consideration for a terrorist.
An agent which is easily treated has little offensive utility, while an agent which is
not curable might have a high value even if it only leads to an incapacitating disease.
Additionally, the chance for self-infection with an incurable pathogen may also factor
into the terrorist decision-making process.
In the resistance to medical treatment column of Table 2, the symbol + denotes
biological agents which have no specific treatment outside of supportive care. The
symbol O denotes biological agents which can be treated with agent-specific
medicine in a narrow time frame, or have a potential, but unproven, treatment. The
symbol — denotes biological agents which can be cured without restriction.
79 Incapacitating agents may still result in fatalities depending on the infectious dose, the
individual’s immune system strength, and other complicating factors.
80 The existence of effective prophylaxis may conversely enhance a prospective terrorist’s
ability to use an agent, if the terrorists place a premium on their own safety. The level of
external, mechanical protection required to handle and produce biological agents is
decreased when effective prophylaxis is available.
81 Polio is an example of a disease against which the population is routinely vaccinated. A
terrorist attack using this pathogen would likely cause little harm.

CRS-27
Ease of Dissemination. Unlike chemical agents, biological agents can
reproduce and are generally grown suspended in liquid solutions. They are more
difficult than chemical agents to effectively disseminate in the air. They may be
disseminated via other media (see below). Some biological agents can be dried and
ground into small particles which can be released as aerosols, but this is a fairly
advanced technique. Because of the natural filtering capacity of the human airways,
there is an optimal range of particle size that will deeply penetrate the lungs. Many
experts cite the difficulty of preparing or disseminating biological agents in such a
particle size range as a primary barrier to terrorist use. Other experts counter that
commercial dissemination equipment, namely technologies similar to yard foggers
and crop dusters, can be adapted to provide aerosols that, while not optimal in size,
will still be infectious. Additionally, not all biological agents must be lodged deep
in the lungs to cause infection.
Some biological agents are contagious from person to person. Each person
infected with a biological agent which is contagious by casual contact can become
a new dissemination vector. These highly contagious agents might be viewed by
terrorists as more useful than other types of biological agents, as people not in the
original exposed area may fall ill through such contact. All other factors being equal,
contagious agents that require close contact may be viewed by a terrorist as less
useful than those needing only casual contact, due to the lower probability of
secondary infection.
Another common infectious pathway is through ingestion via contaminated
water, beverages, or food, but some pathogens are less virulent by this route than by
inhalation. It is logistically complex to affect large numbers of people with a
significantly lethal pathogen through contaminating the food or water supply. Still,
as shown by the Rajneeshees’ use of Salmonella Typhimurium to contaminate
restaurant salad bars in Oregon, low-technology approaches, such as food
contamination, may be effective.
In the ease of dissemination column of Table 2, the symbol + denotes biological
agents that are amenable to dissemination as an aerosol and through ingestion, or are
contagious through close contact.82 The symbol O denotes biological agents that can
be disseminated as an aerosol. The symbol — denotes biological agents that require
ingestion or dissemination using a animal vector, such as a mosquito, tick, or other
insect.
Weaponization. Some biological agents were reportedly developed by either
the Soviet Union’s or the United States’ former biological weapons program. While
most of these agents were only research targets, several pathogens were successfully
converted into military grade weapons. Due to these research efforts, the knowledge
necessary to convert a naturally occurring disease into an optimized weapon may be
82 For the purposes of this report, close contact refers to situations in which infected body
fluids may come in contact with others. This includes health care professionals and family
members who may provide care for those infected.

CRS-28
available for purchase.83 In assessing the degree to which these agents have been
studied in a munitions framework, agents are categorized in Table 2 as weapon,
research, or unknown. If an agent has been reported as successfully weaponized, it
is listed as weapon. If an agent was a known target of a weapons program, but it is
not reported as successfully weaponized, it is listed as research. If it is unknown
whether an agent was the target of a weapons program, it is listed as unknown.
Examples. The bacterium Yersinia pestis causes the disease commonly
known as plague. This bacterium is found naturally in many locations, with
reservoirs in rodent populations. It causes publicized outbreaks in locations around
the world (the United States averages 10 to 15 cases each year).84 Thus, plague is
considered easy to acquire by a terrorist and receives a + in this category in Table 2.
There are several subcategories of plague, depending mostly upon the method of
infection. Naturally occurring plague is usually transmitted by flea bites and has a
mortality rate of 5% — 12% despite the availability of effective antibiotics.85
Pneumonic plague is a more serious type of plague caused when the bacteria infect
the lungs. Pneumonic plague is much more lethal than that caused by flea bites; the
victims require isolation and intensive hospital care. Therefore plague receives a +
for public health impact. There is a vaccine against plague, but it has not been shown
to be effective against pneumonic plague. If an outbreak is detected, antibiotics can
be taken prophylactically to prevent infection. Thus, plague receives a O for
prophylaxis. Because pneumonic plague responds well to antibiotics only within the
first 24 hours after symptom onset, it receives a O for resistance to medical
treatment. In contrast to the type of plague transmitted by fleas, pneumonic plague
is contagious through casual person-to-person contact.86 Therefore, each initially
infected individual could eventually infect several others. This would allow a
terrorist to bypass the technically challenging development of an aerosolizing device.
Each infected person becomes a potential vector for the spread of the disease.
Because of this, plague receives a + for ease of dissemination. Plague was reportedly
studied by both the U.S. and former U.S.S.R. weapons programs.87 The former
83 Ken Alibek, a former high ranking official in the Soviet weapons program and a widely
quoted expert on biological weapons, claims that many scientists who worked for the former
Soviet Union’s biological weapons program have been approached by groups interested in
purchasing their expertise. See, for example, Ken Alibek, Biohazard: The Chilling True
Story of the Largest Covert Biological Weapons Program in the World — Told from Inside
by the Man Who Ran It, op. cit. pp. 271-272.
84 Centers for Disease Control and Prevention, Plague Fact Sheet, available online at
[http://www.cdc.gov/ncidod/dvbid/plague/index.htm].
85 Thomas W. McGovern and Arthur M. Friedlander, “Plague,” in Medical Aspects of
Chemical and Biological Warfare, op. cit.
86 Raymond Gani and Steve Leach, “Epidemiologic Determinants for Modeling Pneumonic
Plague Outbreaks,” Emerging Infectious Diseases, 10 (2004): 608-614.
87 The United States former biological weapons program reportedly did not weaponize
plague, but only studied it as a research target. Stockholm International Peace Research
Institute, The Problem of Chemical and Biological Warfare, Volume I: The Rise of CB
Weapons, Stockholm: Almqvist & Wiksell, 1971.

CRS-29
U.S.S.R. reportedly successfully weaponized plague and is rumored to have
developed antibiotic-resistant strains.88
Anthrax is caused by the bacterium Bacillus anthracis. This bacterium occurs
naturally in many locations around the world. Therefore in Table 2, anthrax receives
a + for ease of acquisition. Untreated inhalational anthrax is nearly always fatal. The
aggressive medical treatment victims received during the 2001 anthrax outbreak
reduced the mortality rate to approximately 50% (five of eleven). Because of the
high mortality rate and the need for hospitalization for treatment, inhalational anthrax
rates a + for public health impact. Because the anthrax vaccine and antibiotics work
prophylactically, anthrax receives a — in the prophylaxis category. Antibiotics are
used against anthrax, but the success of this treatment depends on diagnosis shortly
after onset of symptoms. Therefore anthrax receives a O for resistance to medical
treatment in Table 2. Traditionally, it is considered difficult to produce the very fine
particle size necessary to inflict mass casualties. However, to inflict causalities on
a more modest scale (tens to hundreds), a cruder preparation with non-optimal
particle size distribution may be sufficient. Therefore, for a small-scale attack,
anthrax receives a + for ease of dissemination. Anthrax was reportedly successfully
weaponized by both the U.S. and former U.S.S.R. programs. Antibiotic resistant
strains could be developed. While this would increase the public health impact, the
technical ability required to do this would decrease the ease of acquisition.
In 1984, the Rajneeshee cult successfully employed Salmonella Typhimurium
in Oregon restaurants, sickening 751 people. This bacterium is ubiquitous, causing
an estimated 40,000 cases of food poisoning in the United States each year.
Therefore, salmonella receives a + for ease of acquisition in Table 2. Because
salmonella usually does not require hospitalization, it receives a — for public health
impact. There is no vaccine for salmonella. Because of the lack of a vaccine,
salmonella receives a + for prophylaxis. Since antibiotic treatment for salmonella is
well established, salmonella receives a — under resistance to medical treatment.
Salmonella needs to be ingested, so the only effective route for dissemination would
be through deliberate food, beverage, or water contamination. Therefore, Salmonella
Typhimurium receives a — for ease of dissemination.
Toxin Agents Comparison
Toxins are poisonous substances that are produced by living organisms,
including plants, animals, algae, and bacteria. These substances cause damage when
introduced into the body. Often, toxin is the lethal agent in a bacterial infection,
rather than the bacteria themselves. For example, intestinal infection with
Clostridium botulinum is lethal due to the toxins that are exuded into the body, not
simply because of the presence of bacteria. In some cases, these toxins can be
produced in sufficient quantities and isolated from the organisms that produce them.
Unlike living pathogens, toxins do not replicate. The human body is capable of
developing antibodies to neutralize many toxins.
88 Ken Alibek, Biohazard: The Chilling True Story of the Largest Covert Biological
Weapons Program in the World — Told from Inside by the Man Who Ran It, op. cit.

CRS-30
Toxins are intermediate between biological and chemical agents in efficacy as
weapons; requiring a greater amount of material than in the case of a biological
agent, but less than required for a chemical agent. Toxins generally cause injury
within hours of an attack. Therefore toxins may act more quickly than biological
agents, which may take days or weeks to incubate, but more slowly than chemical
agents, which generally act immediately. Toxins often have effects similar to
chemical nerve agents, such as paralysis and nerve-related damage. Countermeasures
for toxins resemble those for biological agents. Toxoid vaccines are used for
prophylaxis and anti-toxins for patients after exposure.
Choice of Toxin Agents Assessed. The toxins chosen for inclusion in the
matrix were compiled by comparing several sources including the BWC draft
Compliance Protocol Annex A list,89 the CDC Select Agent List,90 the CDC
Biological Diseases/Agents Listing,91 the NATO Handbook on the Medical Aspects
of NBC Defensive Operations,92 the U.S. DOD’s Medical Aspects of Chemical and
Biological Warfare,93 the Australia Group List of biological agents for export
control,94 the World Health Organization’s Preparedness for the Deliberate Use of
Biological Agents,95 the U.S. DOJ’s An Introduction to Biological Agent Detection
Equipment for Emergency First Responders,96 the former Soviet Union’s bioweapons
program, and the United States’ former biological weapons program.97 Toxins that
appear on most lists were selected from the initial compilation, and then ranked.
Table 3 presents the toxins with the highest relative rank according to this analysis.
Criteria. Table 3 categorizes toxin agents based on six criteria: ease of
acquisition, public health impact, prophylaxis, resistance to medical treatment, ease
of dissemination, and whether the toxin has been weaponized. Agents are listed in
descending order of combined ranking with respect to the criteria. For further
information on the methodology regarding criteria choice, ranking, and weighting,
89 The rolling text for the draft BWC Protocol from February, 2001 was used. It can be
found online at [http://www.fas.org/bwc/papers/febannexI.htm#aann].
90 The Select Agent list is defined in 42 C.F.R. 73.4.
91 The CDC Biological Diseases/Agents Listing can be found online at
[http://www.bt.cdc.gov/Agent/Agentlist.asp].
92 NATO Handbook on the Medical Aspects of NBC Defensive Operations AmedP-6(B), op.
cit.
93 Medical Aspects of Chemical and Biological Warfare, op. cit.
94 The Australia Group List of Biological Agents for Export Control can be found online at
[http://www.australiagroup.net/en/control_list/bio_agents.htm].
95 Found online at [http://whqlibdoc.who.int/hq/2002/WHO_CDS_CSR_EPH_2002.16.pdf].
96 An Introduction to Biological Agent Detection Equipment for Emergency First
Responders, op. cit.
97 Toxins found in the former Soviet Union’s and United States’ former biological weapons
program can be found in a summary developed by the Monterey Institute of International
Studies from sources in the open literature. The summary is found online at
[http://cns.miis.edu/research/cbw/possess.htm].

CRS-31
see Appendix A. See Table 6 in Appendix D for technical data used to rate each
agent.
Ease of Acquisition. Toxins must be extracted from the material in which
the toxin was formed. Thus, acquiring toxins is more complicated than growing
biological agents, but can be less complicated than synthesizing chemical agents.
The production capacity needed to make enough agent for a terror event within a
medium-sized, enclosed space could be developed in a basement lab, without access
to a manufacturing plant.
A limiting factor is how ubiquitous the source of a toxin is. Some toxins are
commercially available due to their dual-use nature;98 the source plants or bacteria
for other toxins are commercially available. In a few cases, neither the toxin nor its
source is commercially available. To obtain these toxins one would need to find the
plant, animal, bacteria or algae that produces the toxin in nature.
In the ease of acquisition column of Table 3, the symbol + denotes toxins for
which the source of the compound can be found widely in nature, easily purchased
or grown. The symbol O denotes toxins for which the source of the compound is
purchased or grown with some difficulty. The symbol — denotes toxins for which
the source of the compound cannot be purchased, is found only in few locations, or
is grown with great difficulty.
Public Health Impact. Toxins can be incapacitating or lethal.99 The variety
of effects and methods of dispersal necessitate a more indirect estimation of the
agent’s impact. Again, the burden placed on the medical system will be used as the
measurement for effect on the target. As an example, a toxin may have a low
lethality but a high public health impact due to its effects.
In the public health impact column of Table 3, the symbol + denotes toxins that
have a high, deleterious public health impact. The symbol O denotes toxins that
have a more moderate, deleterious public health impact. The symbol — denotes
toxins that have a relatively low, deleterious public health impact.
98 Botulinum toxin is used commercially in dilute solutions as a medical treatment; several
other toxins are commonly used in biomedical research.
99 This distinction is made between different toxins, not between different types of C/B
agents. For example, although Staphylococcus aureus enterotoxin B is generally considered
to be an incapacitating agent, it is lethal at a concentration comparable to that necessary for
the most lethal nerve gas, VX.

CRS-32
Table 3. Toxin agent comparison according to barriers to potential terrorist use
Ease of
Public Health
Resistance to
Ease of
Toxins
Prophylaxis
Weaponized
Acquisition
Impact
Medical Treatment
Dissemination
Abrin
+
+
+
+
O
Unknown
Shigatoxin
+
+
+
+
O
Unknown
Ricin
+
+
O
+
O
Weapon
Clostridium perfringens
O
+
O
+
O
Weapon
epsilon toxin
Staphylococcus aureus
O
+
O
+
O
Weapon
enterotoxin B
Trichothecene mycotoxins
—
O
+
+
+
Research
Aflatoxins
O
—
+
+
O
Weapon
Clostridium botulinum toxins
+
+
O
—
O
Weapon
Saxitoxin
—
+
+
O
O
Research
Tetrodotoxin
—
+
O
—
O
Unknown
Source: This table was prepared from compiled open source data. Congressional Research Service, 2002 (Updated 2004). See Appendix D for detailed data used to generate rating.
Note: See text for explanation of symbols. Breaks within the table group agents with roughly comparable rank.

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Prophylaxis. Toxoid vaccines can be used to protect people against specific
toxins. While many toxoid vaccines are available, few are licensed for general use,
and supplies of these toxoid vaccines are generally small. Toxins against which the
population is routinely vaccinated pose little threat and therefore have been removed
from the analysis.100
In the prophylaxis column of Table 3, the symbol + denotes toxins which have
no prophylaxis. The symbol O denotes toxins with experimental prophylaxis lacking
Food and Drug Administration approval. The symbol — denotes toxins which have
licensed prophylaxis.
Resistance to Medical Treatment. Not all toxins have effective treatment.
For some toxins, anti-toxin injections or other treatments are effective. Other toxins
have no specific treatment available, but can be treated with supportive care such as
mechanical ventilation or treatment for shock.
In the resistance to medical treatment column of Table 3, the symbol + denotes
toxins that can only be treated using supportive care. The symbol O denotes toxins
whose effects can be successfully ameliorated by a specific, established medical
treatment. The symbol — denotes toxins that have documented anti-toxins
available.
Ease of Dissemination. Toxins, like biological agents, can be weaponized
in liquid or solid form, with the inherent difficulties of generating aerosols of
appropriate particle size for efficient inhalation. Toxins can be delivered through
contaminated food or drink or by aerosolization. Most toxin aerosols must enter the
body through the lungs, eyes or broken skin to cause damage, although trichothecene
mycotoxins can cause damage through intact skin. Toxins vary in their stability,
which can complicate the ease with which they are disseminated.
In the ease of dissemination column of Table 3, the symbol + denotes toxins
that can be delivered by skin contact. The symbol O denotes toxins that can be
disseminated through both aerosolization and contamination of food or drink. The
symbol — denotes toxins that only can be disseminated through either
aerosolization or contamination of food or drink.
Weaponization. Some toxins were reportedly developed by either the Soviet
Union’s or the United States’ former biological weapons program. While most of the
toxin agents were only research targets, several toxins were successfully converted
into military grade agents. Due to this research, the knowledge necessary to produce
toxins efficiently and formulate them into warfare agents may be available for
purchase. In assessing the degree to which these agents have been studied in a
munitions framework, agents were categorized as weapon, research, or unknown. If
an agent has been reported as successfully weaponized, it is listed as weapon. If an
agent was a known target of a weapons program, but has not reported as successfully
100 Tetanus toxin is an example of a toxin against which the population is routinely
vaccinated. A terrorist attack using tetanus toxin would likely cause little harm.

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weaponized, it is listed as research. If it is unknown whether an agent was the target
of a weapons program, it is listed as unknown.
Examples. Botulinum toxin is the most poisonous substance known.101 It is
produced by Clostridium botulinum, a ubiquitous soil bacterium. Therefore, in
Table 3, it receives a + for ease of acquisition. Persons affected by botulinum toxin
suffer nerve damage and paralysis, leading to asphyxiation and death. Although
deaths rarely occur from naturally occurring botulism outbreaks, victims require
intensive hospital care. Additionally even a small terrorist attack may overwhelm the
capacity of local health facilities, resulting in many deaths. Therefore, it receives a
+ for public health impact. Because there is a toxoid vaccine for botulinum toxin,
available in limited supply from the Centers for Disease Control and Prevention, it
receives a O for prophylaxis. Botulism antitoxin can mitigate the effects of
exposure, but there are limited available supplies. Supportive care including
mechanical ventilation can also prevent death. Because of its well established
medical treatment, it receives a — for resistance to medical treatment. Botulinum
toxin is fairly stable, existing for extended periods at room temperature, but is
inactivated by cooking. It can therefore be aerosolized or delivered via uncooked
food or drink. It receives a O for ease of dissemination. Both the Soviet Union’s and
the United States’ weapons program reportedly successfully weaponized this toxin.
Ricin is a very toxic compound found in castor beans. During the production
of castor oil, bean mash with a 5 percent ricin content is produced. Recipes for
extracting the ricin from this mash are available on the Internet.102 Because of the
ready availability of both the raw material and the necessary information to refine the
toxin, ricin receives a + for ease of acquisition in Table 3. Persons exposed to ricin
exhibit different symptoms depending on the exposure route. Ingestion of ricin
causes nausea, diarrhea, gastric hemorrhaging and shock, leading eventually to death.
Injection of ricin produces severe internal necrosis and hemorrhage, which usually
culminates in systemic collapse. Inhalation of ricin leads to irritation of airways and
lungs, causing pulmonary edema and pneumonia. Because the progressive nature of
the toxin’s effects requires continual hospitalization and care, ricin receives a + for
public health impact. An Investigational New Drug (IND) ricin toxoid could be
made available. Consequently, ricin receives a O for prophylaxis. Exposure to large
amounts of ricin is almost invariably lethal, as ricin acts rapidly and irreversibly, and
lacks known treatment. Ricin receives a + for resistance to medical treatment. Ricin
is very stable and can be stored in either purified or impure forms. Ricin can be used
either as an aerosol or as a food or drink contaminant. It receives a O for ease of
101 The Working Group on Civilian Biodefense, “Botulinum Toxin as a Biological Weapon,”
Journal of the American Medical Association, Vol. 285, Feb. 28, 2001, pp. 1059-1070.
102 The quality of recipes available on the Internet ranges from those that would produce
only crude preparations to those that would produce nearly pure ricin. One such crude
recipe is examined by George Smith in “The Recipe for Ricin: Examining the Legend,”
National Security Notes (formerly The Crypt), February 20, 2004.

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dissemination. The United States reportedly researched ricin under its former
biological weapons program, and Iraq reportedly attempted to weaponized ricin.103
Saxitoxin is a very toxic compound best known for its role in paralytic shellfish
poisoning. It is produced by dinoflagellate marine algae. Because of the difficulties
growing and collecting large amounts of toxin from the algae or from shellfish in
which the toxin has concentrated, saxitoxin receives a — for ease of acquisition in
Table 3. Persons who ingest saxitoxin suffer nerve damage and slow paralysis
similar to botulinum toxin. Inhalation of saxitoxin causes a fast blockage of nerve
impulses, leading to death within minutes. Saxitoxin receives a + for public health
impact. There is no toxoid vaccine available for saxitoxin, and so it receives a + for
prophylaxis. It is difficult to successfully treat victims within the necessary time
window dictated by inhalation of aerosolized saxitoxin. Supportive care including
mechanical ventilation can prevent death. Because of this established treatment,
saxitoxin receives a O for resistance to medical treatment. It can be used to
contaminate food or drink or as an aerosol. This flexibility gives saxitoxin a O for
ease of dissemination. The U.S. Central Intelligence Agency researched the use of
saxitoxin as a covert weapon, but it is unlikely to have been developed as a weapon
for military use.104
Discussion
Potential Uses of Framework
Many expert analyses focus on the use of C/B agents to cause mass casualties
through catastrophic terrorism. In this view, C/B agents that can be mass produced,
are contagious, or are markedly stabile are identified as the greatest threats.
Therefore, government policy towards C/B terrorism has been designed to reduce the
impact of C/B agents, such as nerve agents, smallpox, and anthrax, that possess these
specific qualities. While some of these agents have been used in terror attacks, this
analysis of the potential for small-scale use leads to a different assessment of C/B
agent threat. C/B agents that were considered high threats in other frameworks
appear to present a lesser threat when viewed in the small scale attack context.
Conversely, C/B agents that were considered of lesser threat when considering mass
casualty attacks may be ranked more highly in the small scale context, as barriers to
mass use may be missing when the agent is used on a small scale. Because of these
differences, policies designed to protect against catastrophic C/B attack may not
provide equivalent protection against small scale C/B attack.
A potential use for the above framework is to help prioritize approaches to
address the threat presented by small scale use of C/B agents. This analysis provides
103 Iraq reportedly performed field tests of munitions filled with ricin in November, 1990.
UNSCOM, Reports to the Security Council, January 25, 1999, Annex C.
104 U.S. Senate. Unauthorized Storage of Toxic Agents: Hearings before U.S. Senate
Intelligence Committee, 94th Cong, 1st Sess., Washington, DC: U.S. Senate, September
16-18, 1975.

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information relevant to the formation of general approaches to reduce the threat from
terrorist use of different C/B agents, as well as information that may allow
policymakers to reduce the dangers from specific agents. For example, policymakers
may wish to develop specific remedies, via research targeted towards developing
cures, prophylaxis, and detection equipment, or more efficient public health
mechanisms for detecting and treating the agents towards the tops of these matrices.
Because the agents analyzed in this framework are those which appear in a
preponderance of past assessments, they represent a subset of potential C/B agents.
Other dangerous agents which may be amenable to similar analysis have not been
included. For example, newly emerging diseases, such as Nipah virus and SARS,
may pose a future threat, but have not been included in past assessments. Therefore
while policymakers may find this framework useful in formulating policy, more
detailed analysis may be required when refining policy alternatives.
Another potential use of this framework is to qualitatively highlight the effects
that different policies may have in reducing C/B vulnerability. This overview
indicates which agents of concern might be amenable to particular countermeasures.
For example, policymakers may wish to focus on prophylaxis of toxins to reduce the
threat that their use by terrorists would present. By reviewing the data presented in
this assessment framework, policymakers might identify toxins for which no
approved vaccine exists. This might aid in prioritizing regulatory review or directing
research funds to develop new toxoid vaccines. Similarly, by weighing and
considering the ease of acquisition of C/B agents, for example, it may become
apparent which agents are susceptible to regulatory control, perhaps because of their
development for industrial use, and which agents might not be, perhaps because of
their endemic nature. This may aid in developing additional policy against C/B
terrorism.
Another application for this framework might be to develop threat-reduction
approaches for specific agents. Depending on the agent, funding for research and
development, regulation, or directed advances in public health may lower the threat
posed. For example, regulation regarding the sale of the source of the toxin abrin
might be considered an effective approach to reducing its ease of access, thereby
lowering the threat posed by this toxin.
The data presented in this framework, and in the appendices, may also serve as
a resource to develop other more specialized frameworks. Policymakers might
reorder agents based on specific criteria, for example, response to medical treatment,
based on the data provided in this report. Some may wish to emphasize certain
criteria over others, providing a nonequivalent weighting to the different criteria.
These manipulations might provide legislators with more tailored matrices for use
in exploring policy options.
For example, while the agents in this assessment have been sorted by
considering the difficulties a terrorist group might encounter in developing an agent,
sorting according to specific priorities might present a different final product.
Especially in the cases where specific knowledge is held about criteria presented
here, sorting the agents while excluding certain criteria would provide other insights.
For example, Marburg hemorrhagic fever is ranked lower on Table 2 because of the
difficulty in obtaining the causative virus. In the current sorting algorithm, this

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significant disadvantage to its use determines its ranking below other agents which
lack any comparable disadvantage. If, for reasons outside the confines of this
assessment, it was known that Marburg virus was available to a terrorist organization,
resorting this matrix without regard to the ease of acquisition would place Marburg
hemorrhagic fever at the top of this matrix. Thus, the risk posed by Marburg
hemorrhagic fever would be increased under those conditions.
Whether an agent has been weaponized, or was the target of a weapons program,
was not used as a primary ranking factor. Rather it was used to adjust the relative
ranking of agents that are comparably rated. Thus, two agents that have the same
relative numbers of — , +, and O in the matrix would be equally rated. If one of
these agents was known to be successfully weaponized, while the other was never
studied, then the agent known to be weaponized would be ranked higher on the
matrix. The exclusion of weaponization status as an independent category might be
seen as inappropriate if there are credible reports of information or technology
transfer from a bioweapons program to a terrorist group. In such an event, it might
be more appropriate to directly include the weaponization status into the ranking and
sorting procedure.
Deviations From Assumptions
Several assumptions, mainly about the resources and skills of the groups
attempting to develop C/B agents, have been made in developing this framework.
If these assumptions are invalid, then the results of this report will be less applicable.
For example, if a terrorist group is unable to recruit or train members to the degree
necessary to reproducibly and repeatedly synthesize or grow C/B agents, then the
effort expended in acquiring sufficient amounts of the C/B agent may be much higher
than estimated through this framework. If a terrorist group lacks financial means, a
similar increase in the difficulty of manufacture might occur. This could cause the
criteria to have distinctly unequal weights, where the ease of acquisition would
dominate all other criteria.
If a terrorist group is sponsored by a nation-state, then the capabilities of the
terrorist group may be much greater than those assumed here. For instance, ease of
acquisition and ease of dissemination could be drastically different, as technology
transfer from the sponsor to the terrorist group could remove these barriers and thus
remove the influence of these criteria from the ranking. A terrorist group planning
a mass, city-wide assault using a C/B agent might face difficulties in the scale of
material and logistics necessary, and the threat might more closely parallel previous
assessments of mass-dissemination.105
One policy issue regarding C/B defense is that threat assessments rely on
probability estimates. This means that while analysts may speak of a likelihood of
an agent being used, no one, besides terrorists who use them, can speak with
authority about the agents that will be used. Terrorists may act opportunistically; if
presented with an agent, either purchased or stolen, they may use that agent even if
105 See U.S. Congress, Office of Technology Assessment, Technologies Underlying
Weapons of Mass Destruction, op. cit.

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it is not optimal for their purposes. Purchase or theft of a C/B agent alters relative
threat assessments, as many of the factors contributing to the relative threat are
weighted differently. Consequently, while a relative threat assessment is a useful
framework for rational discussion, it cannot be used as a definitive statement on the
likelihood of future C/B use.
Terrorist Motivation-Specific Factors
The above analysis assumes a terrorist group has decided to use a chemical,
biological, or toxin weapon and is considering the relative potential of all of these
agents equally. However, this analysis does not necessarily reflect all factors that
may contribute to the choice of a particular agent. The following section explores
other factors that a specific terrorist group might consider, based on its objectives or
motivations.106
Potential for Covert Deployment
Some experts claim that it is increasingly likely that a terrorist group would not
claim responsibility for a C/B attack.107 The incidence of catastrophic, anonymous
terrorist attacks is projected to increase, as terrorist groups organize around issues
that have less local, concrete political goals, but instead are more ideologically
driven.108 This tendency complicates analysis of the bioterror threat, as terrorists may
successfully covertly attack using a disease found within the United States. With a
small outbreak, a lack of any claim of responsibility could raise the question of
whether the outbreak was a terrorist act or a simply an unusual natural epidemic. For
example, releasing Ebola virus in a building in New York City would immediately
be treated as a terrorist attack, regardless of whether any group claimed
responsibility. On the other hand, the salmonella attacks perpetrated by the
Rajneeshees were not identified as a deliberate release until over a year after the
event when a member of the cult confessed to the crime. One of the factors that led
the cult leaders to choose salmonella was that it was a less traceable agent, in the
hopes that their act would remain undiscovered.109 Since the probability that a
terrorist group will opt for covert, rather than open, deployment may not be known,
it is difficult to factor this choice into an analysis.
A terrorist group could choose to deploy a biological agent covertly because of
the advantages the group would gain. An agent release disguised as a natural
106 For more on this topic, see CRS Report RL31831 Terrorist Motivations for Chemical and
Biological Weapons Use: Placing the Threat in Context by (name redacted).
107 National Commission on Terrorism, Countering the Changing Threat of International
Terrorism, August 2, 2000, Chapter 3.
108 National Intelligence Council, Global Trends 2015: A Dialogue About the Future with
Nongovernment Experts, December 2002.
109 Another factor involved in the Rajneeshee attack was their reported wish to influence
local elections by incapacitating, rather than killing, the electorate. W. Seth Carus, “The
Rajneeshees (1984)” in Toxic Terror: Assessing Terrorist Use of Chemical and Biological
Weapons, op. cit.

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outbreak could allow for trial runs to be conducted before a large attack as was done
by the Rajneeshees. Such trials could test the government response to an apparently
natural outbreak, possibly allowing terrorists to further refine attack plans to exploit
weaknesses uncovered during the trials. By using a local pathogen, there may be
serious, though reasonable, disagreement between public health and law enforcement
officials with respect to the outbreak’s origin, leading to over- or under-reaction to
the outbreak. Finally, during a small-scale outbreak, questions over the magnitude
of local, state, or federal response may arise, to the potential advantage of a terrorist
wishing to instill confusion at low cost.110
The Department of Homeland Security has developed and deployed a system of
biological weapon detectors called BioWatch.111 The BioWatch program has
installed detectors in more than thirty cities. They are primarily designed to detect
the catastrophic release of biological weapons, not the release of small amounts of
biological weapons. In October 2003, the BioWatch system in Houston, TX detected
aerosols of Francisella tularensis. Subsequent analysis revealed that this signal arose
from detection of naturally occurring bacteria.112 Considering the apparent sensitivity
of this detection system, it is possible that small-scale releases might be detected.
Determining whether such a signal was from naturally occurring bacteria, or from a
small-scale act of terrorism, may be challenging. Since the federal response to an act
of terrorism will likely be substantially different than to detection of naturally
occurring bacteria, quickly differentiating between the two events is important.
Range of Lethality and Impact
The media attention given to civilian deaths may induce a terrorist to prefer an
agent with high fatalities over agents that inflict a high number of casualties, but low
fatalities, if they believed that this would garner more media attention. Terrorists
may believe that such media coverage of terror events may further recognition of
their cause or increase the impact of their actions.
A potential C/B agent user is also faced with the possibility that the C/B agent
may kill the user either during an accident in the preparation stage or during
dissemination. The events of September 11, 2001 have shown that there are
individuals motivated enough to die for their beliefs who wish to strike at assets
within the United States.113 Consequently, the idea that a C/B agent might be too
110 Coordination between federal agencies and the preparedness of state and local responders
have been highlighted in testimony by the GAO. Testimony of Janet Heinrich, Director,
Health Care — Public Health Issues, before the House Committee on Government Reform,
October 5, 2001. U.S. Congress, General Accounting Office, Bioterrorism: Coordination
and Preparedness, GAO-02-129T, October 5, 2001.
111 For more information about the BioWatch program, see CRS Report RL32152 The
BioWatch Program: Detection of Bioterrorism by (name redacted) and (name redacted).
112 Robert Roos, “Signs of Tularemia Agent Detected in Houston Air,” CIDRAP News,
October 10, 2003.
113 Not all terrorists who might be willing to die committing an act of terrorism would be
(continued...)

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lethal or too toxic to be used, a belief held in some previous treatments of this
subject, should be reexamined. If one assumes that the user of the C/B agent is
willing to die during its use, casualties and fatalities from an agent’s dissemination
can be maximized, because an agent lacking both treatment and prophylaxis can be
used.
Similarly, an organization with a supply of members willing to be placed at risk
during the manufacture of a biological agent can produce large amounts of an
incurable pathogen by training members in the specific techniques necessary to grow
that agent. The threat of self-infection combined with the need for advanced
technical knowledge is often cited as another barrier to terrorist development of
biological agents. The use of trained technicians willing to die would allow
production of agents under improvised safety conditions. By training others to act
as technicians, a terrorist organization could reduce the danger to its knowledgeable
scientists, distribute the techniques for developing a pathogen program among the
members of the organization, and increase the rate of pathogen production.
It is not necessary for members of a terrorist group to be without regard for their
lives to develop C/B agents. Terrorist groups with access to prophylaxis, especially
prophylaxis with limited distribution, could develop biological agents at less personal
risk. Alternately, effective mechanical protection might guard terrorists
manufacturing chemical agents. Even if the civilian population has some access to
the vaccine or other prophylaxis, the impact of dissemination would still be very high
if these materials are uncommon. Some biological and toxin agents have vaccines
available to select individuals, such as troops or research scientists, but not the
general public.
Therefore, some terrorists may find highly lethal, incurable agents to be most
effective in achieving their objectives. However, as seen in the salmonella attack, not
all terrorists choose the most lethal agent available. The cult leaders chose
salmonella because a nonlethal agent was deemed sufficient to achieve the desired
outcome of decreasing voter turnout in a local election.114
Contagious Dissemination
Pathogens contagious through casual contact may be preferred by some
terrorists. One scenario could involve dissemination of a contagious pathogen
through self-infection. Self-infection is especially important to consider because it
is a low-technology method for highly selective targeting of initial infection points.
A terrorist who is contagious could choose to fly through multiple airports in a single
day, potentially causing many different foci of infection to erupt. While the terrorist
113 (...continued)
likely to commit an act of chemical or biological terrorism. Cultural and religious norms
regarding chemical or biological weapons’ use, as well as the potential for significant
suffering from self-infection or exposure, may limit the number of individuals willing to
engage in chemical or biological terrorism.
114 This case study shows the importance of developing further refined risk assessment based
on the known goals, motivations, and capabilities of specific terrorist organizations.

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would have to endure the full effects of the untreated illness, the consequences of
such a method of distribution could be high. Some experts claim that the progression
of the illness would prevent the terrorist from being well enough to proceed with
such a plan. Other experts have cited historical natural outbreaks on public
transportation, such as trains, as evidence that individuals with diseases in the
contagious stage have been able to travel and infect others.115
The lack of controllability of contagious pathogens in comparison to other
biological agents may serve as a deterrent to groups unwilling to engage in
indiscriminate infection. For example, terrorist groups that have a constituency in
or near the exposure area might not be willing to risk infection of their constituents.
Alternately, apocalyptic groups or terrorist groups acting geographically distant from
their support may not view the lack of controllability as a significant drawback.
Previous Use of C/B Agents
Some terrorists, lacking knowledge of potential agents, may choose C/B agents
because they have been used in the past. Terrorists may look to previous attacks to
learn which C/B agents were effective and how the C/B agents were dispersed. The
difficulties in performing a successful C/B attack are illustrated through the examples
of the Rajneeshees’ 1984 salmonella attack and Aum Shinrikyo’s 1995 sarin attack.
Both groups attempted to develop several different C/B agents before being
successful.116 A terrorist could view past examples as decreasing the need to
extensively test their C/B agent, since successful use had already been previously
demonstrated.
Significant media attention may influence C/B agent choice. In the case where
the media has reported widely on a C/B agent, more information is available
regarding the strengths and weaknesses of an agent’s use. While the C/B agent may
not be optimal for the terrorist group’s purpose, easily available information may
provide a lower barrier than that provided by the group investing its resources in
independent research for a more optimal C/B agent. Thus, there may be bias towards
choosing those C/B agents which receive publicity.
Some C/B agents have garnered a reputation among extremist groups. Such a
reputation, regardless of its basis in fact, may influence choice of agents. For
example, ricin has been promoted by domestic paramilitary groups as a “silent tool
of Justice.”117 One of the factors that led members of the Minnesota Patriots Council
to choose ricin over other alternatives was apparently such promotion.118
115 Dr. William Bicknell at “Bioterrorism and Smallpox: Ring Containment, Mass
Vaccination, or Individual Choice?” Cato Institute, June 4, 2002.
116 Toxic Terror: Assessing Terrorist Use of Chemical and Biological Weapons, op. cit.
117 Jonathan B. Tucker and Jason Pate, “The Minnesota Patriots Council” in Toxic Terror:
Assessing Terrorist Use of Chemical and Biological Weapons, op. cit.
118 Ibid.

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Source of C/B Agents
Among the most important variables to a terrorist choosing an agent is what
agents are available to the group. Regardless of the ideal preference of a terrorist
group, if the C/B agents available to it are limited, the group will choose from among
those available.
From a Manufacturing Site. Some chemical agents are used commercially
in manufacturing, water treatment and other industries. Theft of such agents in bulk
from such a facility is of special concern to law enforcement officials. Due to the
large volumes of agents used in many industrial processes, the regular rail and truck
shipments of chemicals are also potential sources for terrorists. Before September
11, 2001, the chemical industry had been heavily criticized for its low plant security.
The American Chemistry Council, a chemical trade organization dedicated to best
practices, has increased its member security requirements in response to recent
events. For further information on chemical plant security, see CRS Report
RL31530, Chemical Plant Security, by (name redacted).
From a Natural Source. The ease with which naturally occurring pathogens
and toxins can be recovered from nature is a topic of much debate. Their natural
prevalence is one of the most important criteria in determining the relative threat.
There are strong differences in opinion regarding how easy it is to isolate microbial
pathogens from nature. Because many biological agents are widely found in nature,
covertly collecting these agents is not viewed as difficult. However, some experts
claim that it is difficult to isolate pathogens with high virulence from these
environmental samples.
Disease epidemics, either among humans or animals, may also be sources for
pathogens. Some experts assert that obtaining pathogens from a disease outbreak
would be difficult. They point to the efforts public health officials exert to identify
the source of the disease during an outbreak.119 Other experts contend that the
availability of pathogens during an outbreak is high, as any victim of the epidemic
is a plentiful source of pathogens, not just the initial case. Further complicating
debate on the topic is the prevalence of viral outbreaks in countries with limited
health care systems. In 2002, an outbreak of Crimean-Congo hemorrhagic fever on
the Afghanistan-Iran border occurred over a three-month period with multiple
outbreaks among humans and animals.120 Epidemics such as this could be an ample
source of pathogenic material, provided that the terrorist group was international in
scope or had support among hospital staff in the outbreak region. Terrorist groups
which infiltrate into hospital infrastructure, laboratory production, and other medical
positions is an area of great concern. Laboratory workers handle many tissue and
119 Public comments of Jonathan B. Tucker at “The Case for a Biosecurity Treaty” briefing
for congressional staff, June 3, 2002. See also, Jonathan B. Tucker, “Preventing Terrorist
Access to Dangerous Pathogens: The Need for International Biosecurity Standards,”
Disarmament Diplomacy, No. 66, September 2002.
120 See “Virus of Deadly Disease Spreads in Iran,” The Associated Press, May 23, 2002 and
Ted Anthony, “Outbreak of Hemorrhagic Fever Reported at Afghan-Iran Border,” The
Associated Press, June 6, 2002.

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blood samples containing potential pathogens. These samples could be used as a
starting point for growing biological agents.
From a Culture Collection. Culture collections are repositories of bacteria
and viruses maintained typically for scientific research.121 In the past, culture
collections have been largely unregulated. For example in 1995, Larry Wayne Harris
was able to fraudulently purchase plague bacteria from a private germ bank, the
American Type Culture Collection. This event caused great concern among health
and law enforcement officials, and resulted in greater oversight and regulation of the
transfer of pathogens.122 This higher level of oversight has not been duplicated
worldwide. The World Federation of Culture Collections, an international
organization that indexes culture collections, has established member guidelines to
adopt best practices and follow domestic and international regulation with respect to
pathogens.123 However, approximately two-thirds of the world culture collections are
not members of this federation.124 Additionally, many culture collections are not
financially secure. This situation may provide the opportunity for a wealthy terrorist
group to acquire seed microbes from a culture collection which has well-
characterized pathogens.
Manufacture and Preparation of C/B Agents
Most experts agree that terrorist groups lacking specialized training and
knowledge in the weaponization of C/B agents will likely produce sub-optimal
quality agents. These C/B agents may be more likely to degrade during storage than
C/B weapons produced by nation-states. This degradation may lead terrorist groups
to produce the agent immediately before the attack or to plan smaller scale attacks,
so as to minimize agent loss.
The preparation of C/B agents for dissemination will also play a significant role
in the effectiveness of a terror attack. Terrorist groups lacking experience and
specialized knowledge will likely be unable to generate weaponized C/B agents, and
instead will be forced to utilize cruder, less refined mixtures of C/B agent and other
material, such as non-viable pathogens and media or residual solvent. Dissemination
of C/B agents using adapted technologies, such as improvised aerosolization
121 There are also toxin collections. Toxins do not reproduce, and so the purchase of small
amounts of toxins from a collection is not as potentially dangerous as the purchase of small
amounts of microbial pathogens. On the other hand, the availability of toxin-producing
agents, such as aflatoxin-producing mold strains, through such a collection would raise
concerns similar to those surrounding culture collections.
122 The Antiterrorism and Effective Death Penalty Act of 1996 (P. L. 104-132) requires the
Secretary of Health and Human Services to create the Select Agent list and regulate these
agents’ transfer within the United States. This part of this act closed the loophole allowing
Harris’s purchase of a Select Agent pathogen.
123 For more information about the World Federation of Culture Collections see their website
at [http://www.wfcc.info].
124 Michael Barletta, Amy Sands and Jonathan B. Tucker, “Keeping Track of Anthrax: The
Case for a Biosecurity Convention,” Bulletin of the Atomic Scientists, May/June 2002.

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devices, is unlikely to produce optimal particle size distributions, thereby limiting
their effect. Therefore, the effectiveness of a C/B attack by terrorists is likely to be
significantly lower than that predicted under optimal conditions. These factors may
lead to the appearance of a smaller scale attack, even if a catastrophic, mass casualty
attack is attempted.
The above considerations may significantly influence the C/B agent choice of
a terrorist group. C/B agents which lack well documented storage procedures or
manufacturing information may be avoided by a terrorist group even if the C/B agent
would otherwise be more highly ranked. Similarly, reduced dissemination
effectiveness may dissuade terrorist groups from selecting C/B agents difficult to
manufacture or store, due to concerns about producing and stockpiling enough C/B
agent.
Policy Issues
Current Regulation
International Regulation. The development, proliferation, and use of
chemical and biological weaponry are closely regulated. The United States is a
signatory to both the Biological Weapons Convention (BWC) and the Chemical
Weapons Convention (CWC), and is actively involved in their implementation.125
Both the BWC and CWC prohibit offensive C/B development, as well as provide
proliferation barriers to states not possessing a C/B capability. CWC international
implementation is overseen by the Organization for the Prohibition of Chemical
Weapons.126 Additionally, the United States and 32 other nations participate in the
Australia Group, an organization developed to voluntarily harmonize national export
controls on chemical weapon precursor compounds, dual-use equipment, and
biological agents that could be used to develop chemical and/or biological weapons
capability.127
Domestic Regulation. The use or threatened use of a weapon of mass
destruction is illegal. More specific restrictions apply to chemical and biological
weapons.128 It is unlawful to knowingly develop, produce, possess, use, or threaten
125 For an overview of the United States’ implementation of the CWC and BWC provisions,
see CRS Report RL30033, Arms Control and Nonproliferation Activities: A Catalog of
Recent Events, coordinated by (name redacted).
126 More information on the Organization for the Prohibition of Chemical Weapons can be
found at [http://www.opcw.org].
127 More information on the Australia Group can be found at
[http://www.australiagroup.net/index_en.htm].
128 For an overview of the laws surrounding chemical and biological agents see CRS Report
RL32220 Biological and Chemical Weapons: Criminal Sanctions and Federal Regulations
by Michael J. Garcia, CRS Report RL32158 Chemical Weapons Convention: Issues for
Congress, by Steven R. Bowman, and CRS Report RL31059 Biological Weapons: A Primer
by Steven R. Bowman.

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to use a chemical weapon. However, various governmental agencies and
departments are exempted, as are research and possession for peaceful purposes.
In the U.S., it is a criminal offense to use or threaten to use, develop, produce,
stockpile, acquire, or retain biological weapons, or transfer biological agents without
registration. Exceptions are made for bona fide research, prophylactic, medical, and
diagnostic activities. Also, the Department of Health and Human Services is required
to create and maintain a list of those agents (the Select Agent list) dangerous to the
public health.129
The Public Health Security and Bioterrorism Preparedness and Response Act
of 2002 (P.L. 107-188) requires the Secretary of Health and Human Services to create
a registry of all persons possessing agents on the Select Agent list and a registry
containing identifying characteristics of the agents possessed. It also requires the
Secretary of Agriculture to create a similar registry regarding agents deemed to be an
agricultural hazard. For more on P. L. 107-188, and specifically on the new Select
Agent requirements in that law, see CRS Report RL31263, Bioterrorism: Legislation
to Improve Public Health Preparedness and Response Capacity, by (name reda
cted), (name redacted) and Mary E. Tiemann.
Dual-Use Concerns
Dual-use technologies are technologies that have legitimate uses, but are
adaptable for terrorist purposes and can provide terrorist groups with ready-made,
proven technology to aid in their C/B agent production. An issue of great concern
to anti-proliferation agencies is the potential of dual-use technology to jump-start
access to C/B production. The export and import of dual-use technologies is
primarily addressed through trade regulation. The U.S. Department of Defense, the
U.S. Department of State, and the U.S. Department of Commerce are all involved in
determining, regulating, and implementing export controls for dual-use technology.
Additionally, the United States supports and participates in the Australia Group’s
anti-proliferation campaign. These policies are directed primarily at nation-level
programs and only partially block an individual’s access to dual-use technology,
especially when the purchases do not cross national borders.130
Addressing the issue of dual-use technology is complicated for analysts,
regulators, and policymakers. Strict control of C/B dual-use technology could
provide an accurate accounting of such sales, but this level of control may greatly
impact both the business and health sectors. Pharmaceutical and chemical industries
would likely fall under any regulations dealing with chemical threats, while hospitals,
medical laboratories and biotechnology firms would likely become further regulated.
Academic research into a number of fields, including molecular biology, chemistry,
microbiology, virology, neuroscience and others, might be significantly affected as
129 The Select Agent list is defined in 42 C.F.R. 73.4.
130 Under Project BACUS, the Defense Threat Reduction Agency successfully built a C/B
agent production facility in Nevada from dual-use technology without drawing regulatory
attention. As reported in Judith Miller, Stephan Engelberg, and William Broad, Germs:
Biological Weapons and America’s Secret War, New York: Simon and Schuster, 2001, 121.

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well.131 The addition of such technology regulation might be successful at lowering
the risk of C/B terror, but could come at a high regulatory burden and economic
cost.132
New Multinational Regulation Options
Some experts advocate, as a means of controlling C/B terror, a biosecurity treaty
to further enhance the transparency of national biodefense and industrial
biotechnology programs.133 One aspect of this proposed, evolving framework is a
harmonization of internal national standards to regulate the handling, storage and
transfer of biological pathogens. Signatories would determine a list of covered
pathogens and set general guidelines. Each signatory would then develop specific
methods to implement the guidelines. In theory, this would lower the probability
that a terrorist could acquire a dangerous pathogen from a foreign germ bank for use
in the United States. Proponents of such a treaty point to the largely successful use
of regulatory inspections and control of raw starting materials in stemming transfer
of radiological and nuclear materials from nation states to terrorist groups. They also
cite the short travel time between distant points as a factor which requires
international cooperation and attention to combat potential bioterrorism.134
It is not clear whether regulation on the nation-state level could provide
significant barriers to small-scale production. Nation-state-level mechanisms have
been relatively successful at stemming nuclear proliferation because of the technical
difficulties involved in developing an infrastructure capable of manufacturing a
nuclear bomb, combined with the need for localized, easily detected and tracked
nuclear material. However, revelations regarding the dissemination of nuclear
weapon technology from Pakistan highlight some of the difficulties in this approach
even with nuclear weapons. Proliferation of chemical and biological agents is not as
limited by required technology as nuclear weapons, and source material is much more
readily available. Also, because of the dual-use nature of the technologies used with
C/B agents, export control of chemical and biological weapons development is
difficult. For example, Iraq was able to significantly expand its chemical and
biological weapon capabilities before the first Gulf War through the purchase of
dual-use technology. Opponents of further regulation by treaty emphasize the ease
131 After the anthrax letters were typed as an Ames strain, the veterinary school at Iowa State
University decided to destroy its collection of anthrax strains, which had been collected
since 1928. See Katie Norris, “Iowa State U. Officials Don’t Regret Destroying Their
Anthrax Sample,” Iowa State Daily, November 27, 2001. Other researchers in the field also
have encountered more complicating factors in their work as CDC oversight and FBI inquiry
are now more pronounced. See Melinda Deslatte, “Anthrax Researcher Finds More
Complications in Work Since October,” Associated Press, January 31, 2002.
132 See CRS Report RS21422 Dual-Use Biological Equipment: Difficulties in Domestic
Regulation by (name redacted).
133 See Michael Barletta, Amy Sands and Jonathan B. Tucker, “Keeping Track of Anthrax:
The Case for a Biosecurity Convention,” op. cit. and Jonathan B. Tucker, “Preventing
Terrorist Access to Dangerous Pathogens: The Need for International Biosecurity
Standards,” op. cit.
134 Christopher Chyba, “Toward Biological Security,” Foreign Affairs, May/June 2002.

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in obscuring the purpose of dual-use technology and the difficulty in conclusively
identifying a C/B program. Additionally, there are serious concerns with
international regulatory inspections, including the transparency of on-site inspections,
the degree to which inspectors should be allowed to document and access
commercial sites, because of concerns over protecting proprietary information, and
the practicality of a challenge inspection system.135
There is also concern that multinational regulation would not adequately address
the C/B terrorist threat. Some analysts point out that export and import controls
prevent only the transfer of such items or technology over international borders, and
do little to address C/B agent development within the country. They contend that
domestic terrorist groups, or international groups which establish themselves within
the United States, would be unaffected by enhanced multinational cooperation and
transparency.
Prevention Versus Consequence Management
Law Enforcement Options. The approach that U.S. law enforcement
agencies take towards counterterrorism is still evolving. FBI Director Mueller has
stated that the FBI is shifting its counterterrorism efforts from a reactive philosophy
to a proactive one.136 As examples of this shift, Director Mueller pointed to efforts
to restrict fund-raising efforts of terrorist groups and increased counterterrorism
intelligence gathering. This approach is based on preventing future terrorist attacks,
but it is unlikely that all possible attacks can be discovered, prevented, or planned for.
Secretary of Defense Rumsfeld is reported to have stated, “It is physically impossible
to defend at every time, in every place, against every conceivable technique.” Vice
President Cheney and FBI Director Mueller have reportedly stated that another
terrorist attack is inevitable.137
A related approach is deterrence. This approach has generally worked well at
a nation-state level. For example, during the first Gulf War, coalition forces faced
an adversary who apparently chose not to use the chemical, biological, and toxin
weapons in its possession. It has been argued that Iraq was deterred from using these
weapons by a veiled threat of massive retaliation.138 It is less clear that deterrence
would be effective against a terrorist group. In particular, international agreements
and threats of massive retaliation are unlikely to deter a terrorist group that is willing
to deploy a C/B agent anonymously and has no identifiable infrastructure vulnerable
to counterattack.
135 For an overview of the issues surrounding international inspections, see CRS Report
RL31559, Proliferation Control Regimes: Background and Status by Sharon A. Squassoni,
Steven R. Bowman, and (name redacted).
136 Robert Mueller, Testimony before the Senate Judiciary Committee, June 6, 2002.
137 David Westphal, “Rumsfeld: Terrorists’ Access to Deadlier Weapons Inevitable,” Scripps
Howard News Service, May 21, 2002.
138 Judith Miller, Stephan Engelberg, and William Broad, Germs: Biological Weapons and
America’s Secret War, op. cit.

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Some policymakers may suggest increasing the resources devoted to
investigating the incidents and prosecuting the perpetrators. This approach of
deterrence on an individual scale is common in law enforcement. In the case of bank
robberies, for example, it is widely believed that identifying, arresting, and punishing
bank robbers is effective at deterring others who might be contemplating a similar
crime. Criminal prosecution derives its deterrence value from the wish of the
assailant to succeed at the event and escape. This approach may be adequate against
some terrorist groups; however, it is unlikely to deter groups with members willing
to die during action or groups that insulate the leaders and planners from those
carrying out the attack. Hence, normal forms of policing may be inadequate to deal
with those terrorists who choose suicide or place low value on escape. Proactive
measures, such as intelligence gathering or infiltration of terrorist groups, may be the
more effective approach to prevent suicide attacks.
Health Care Options. Policymakers may want to address whether to focus
on prophylaxis against specific diseases or to address the bioterror threat through a
broader approach. The targeted approach is illustrated by Secretary of Health and
Human Services Thompson, who is reported as saying that the government’s position
with respect to smallpox vaccine is that “every man, woman and child will have a
vaccine they can say has their name on it.”139 Vaccines for many diseases are
available under Investigational New Drug protocols, and there has been legislative
interest in spurring private sector research into the development of new vaccines and
treatments.140 With development and large-scale availability of vaccines for bioterror
agents, the threat posed by those specific agents is diminished.
Proponents of a targeted approach claim that additional vaccines will
appreciably lower the global threat as fewer pathogens become viable mass-casualty
agents. Critics argue that the vulnerability to agents lacking a vaccine would be
fundamentally unchanged under the targeted approach. Furthermore, the decision of
what agents to protect against may reflect the ease of vaccine production or other
factors rather than the risk an agent will be used. It is not certain that a vaccine can
be produced in a timely manner for the highest threat agents. A further criticism of
the specific vaccine approach is the logistical effort required to vaccinate the
population. The cost of repeatedly vaccinating large populations may offset the
economic benefit of providing specific prophylaxis for many agents. Finally, as seen
in the smallpox vaccination efforts, the perceived risk from vaccination must be
weighed against the potential risk of biological attack.
139 Susan Okie and Justin Gillis, “U.S. Mounts Smallpox Vaccine Push; Officials Want a
Dose for Every Person in the Country by the End of 2002,” The Washington Post, October
28, 2001.
140 For example, in 108th Congress, S. 15, S. 1504, and H.R. 2122 (The Project BioShield
Act of 2003, Sen. Judd and Rep. Tauzin) would guarantee a government market for certain
biomedical countermeasures against potential bioterror agents and S. 666 (the Biological,
Chemical, and Radiological Weapons Countermeasures Research Act, Sen. Lieberman)
would provide tax and market based incentives to encourage companies to develop
treatments for bioterror agents.

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A broader approach is advocated by other experts, who claim that the best
defense against a bioterror attack is to increase the capacity of the public health sector
to treat ill people, track emerging diseases, and provide care to those made ill during
a bioterror attack. Proponents of an increase in public health advocate that this
approach provides an equal and general application to most naturally occurring
diseases and accidents.141 Yet critics contend that increasing the nationwide quality
of public health care would be too expensive to implement at the required level and
to sustain indefinitely. Furthermore, the threat posed by untreatable agents would
remain unchanged, as this approach would not attempt to discover new specific
treatments.
Separating Assessments of Chemical and Biological Agents
The concept of WMD, while useful in a military framework, may obscure some
dangers of a terrorist threat. Policymakers may want to consider whether continuing
attempts to treat all non-conventional weapons within the same framework is
adequate for the terrorist threat. An alternative is to treat the different threats in
separate frameworks.
Methods for controlling proliferation and production of C/B agents are often
assumed to be equally applicable to both types of agents. Policymakers may want to
determine whether it is valid to regulate biological (including toxins) and chemical
agents jointly. Since inhibition of C/B proliferation involves similar issues, namely
large volumes of dual-use machinery, a similar educational and financial component,
and a sliding production scale, a combined regulatory approach may be a reasonable
solution. It may provide for clear, uniform standards, and simplify the regulatory
process.
Alternatively, policymakers may wish to regulate chemical and biological agents
separately, focusing on areas where they differ technically. For example, biological
agents lack signatures which can be detected from a distance, while chemical agents
have signatures unique to these agents; laser remote sensing has been used to
determine if clouds contain nerve agents. Detecting biological agents requires
sensitive, agent-specific detectors, and this difficulty in detecting biological agents
complicates remote monitoring of potential biological agent laboratories. Also, since
most biological agents, unlike most chemical agents, are available in nature,
preventing access to seed stocks of biological material is more difficult than blocking
access to chemical precursors. Detection methods for biological agents need to be
able to differentiate between naturally occurring and anthropogenic pathogens.142 For
example, to find a hidden terrorist anthrax laboratory, a sensor would need to
distinguish between the background, naturally occurring levels of anthrax spores and
141 For example see, Greg Seigle, “Feds Could Make Bioterror ‘Impossible’, Expert Says,”
Global Security Newswire, April 9, 2002.
142 See CRS Report RL32152 The BioWatch Program: Detection of Bioterrorism by (nam
e redacted) and (name redacted).

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those coming from the covert facility.143 Creating regulations addressing chemical
and biological agents in separate frameworks may provide a more rigorous control
of these agents.
Acceptable Level of C/B Terrorism Risk
A further issue policymakers may consider is how to balance an acceptable
degree of risk from C/B terrorism against the amount of security required to address
this risk. Viewed from a statutory and regulatory perspective, the C/B terrorism risk
appears to be reduced from the 2001 level. Current laws limit access to, record
possession of, and limit the transfer of pathogens on the Select Agent list.144
Congress has allocated funding to improve aspects of the public health system,
including research into agent detectors and epidemiological surveillance, to reduce
the vulnerability level. Increased law enforcement efforts designed to reduce the
general terrorist threat also reduce the probability of a C/B terror attack. There
appears to be a concerted attempt to significantly lower the risk of C/B terrorism.
A complete removal of domestic C/B vulnerability is probably impossible. A
maximum effort would likely require, among other measures, in-depth searches of
all materials entering the country, strict purchasing controls on all dual-use
technologies, and industrial controls, such as registration, increased security
procedures, and regular inspection of sites engaged in chemical or biological
manufacture. The cost of such a program could be high, both in economic terms and
civil liberties. Policymakers may likely consider the balance between further
decreasing vulnerability and the continued success of industry and research when
crafting additional legislation and regulation.
Advances in Science and Science Policy
Scientific advances may alter some of the conclusions of the above analysis,
which addresses naturally occurring strains of pathogens, their natural distribution,
and the known methods of treatment for them. It does not, for example, address
intentionally induced antibiotic resistance; pathogen strains designed to evade current
vaccines; Novichok-type chemical agents;145 or the expression of toxins from
143 U. S. forces in Afghanistan reportedly have found traces of anthrax at several al Qaeda
sites, but have been unable to determine its origin. Niles Latham, “Al Qaeda Lab Hunt
Reveals Anthrax,” The New York Post, March 26, 2002.
144 The Antiterrorism and Effective Death Penalty Act of 1996 (P. L. 104-132) requires any
institution or person transferring listed agents to register with CDC. The USA PATRIOT
Act (P. L. 107-56) places additional limitations on the status of persons who may knowingly
possess, transport or receive such agents. The Public Health Security and Bioterrorism
Preparedness and Response Act of 2002 (P. L. 107-188) requires registration with the
Secretary of Health and Human Services of the possession, use, and transfer of listed agents
and toxins.
145 Novichok-type agents are a reported, though not confirmed, chemical agent type which
is created without using any chemicals listed by the verification schedules of the CWC.
Novichok-type agents are reported to be more lethal than VX. For more information on
(continued...)

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genetically-modified organisms. While all of these items are reportedly possible with
current technology, their production requires a greater degree of knowledge and
experience than that needed to produce pathogens, chemical agents, and toxins
addressed in this report. The successful synthesis of polio virus146 and the
development of a genetically engineered strain of mousepox highly lethal to even
vaccinated mice147 stand as stark examples of how advances in relevant research can
potentially change fundamental assumptions underlying an analysis.
Conclusions
This report is designed to provide a framework for legislators to use in
developing risk-management-based policies, rather than vulnerability-based policies,
to protect against chemical, biological, and toxin attacks. This analysis addresses
relatively small-scale attacks that could be accomplished by determined, non-state-
sponsored terrorists.
The analysis presented in this report is consistent with the findings of the
Gilmore Commission, which stated that preparation against a large-scale chemical
or biological attack would not necessarily simultaneously protect against smaller-
scale attacks. This analysis suggests that agents that are effective for small-scale
attacks are not necessarily the agents of choice for massive-scale attacks. This is in
part explained by the higher availability of commercial equipment to prepare, store,
and disseminate an agent, and in part explained by the less restrictive safety and
logistical requirements of a small attack in comparison to a large attack. Small
attacks require amounts of equipment and supplies that are less likely to trigger
regulatory notice. The presence of dual-use equipment in industrial settings may
mean that obtaining the required technology for C/B production may be less difficult
than previously thought.
Another potential use for this analysis is to determine a possible priority with
which the threat presented by specific agents should be addressed. This analysis
provides information on the general approaches to reduce the threat from terrorist use
of different C/B agents, as well as information that may allow policymakers to reduce
the dangers from specific agents. The analysis could be useful in decisions related
to policy options, such as developing specific remedies (e.g. cures, prophylaxis,
detection equipment) and more efficient public health mechanisms for detecting and
treating the agents towards the tops of these matrices.
145 (...continued)
Novichok agents, see Vil Mirzayanov, “Dismantling the Soviet/Russian Chemical Weapons
Complex: An Insider’s View,” in Chemical Weapons Disarmament in Russia: Problems and
Prospects, Washington, D.C.: Henry L. Stimson Center, 1995.
146 Jeronimo Cello, Aniko V. Paul, and Eckard Wimmer, “Chemical Synthesis of Poliovirus
cDNA: Generation of Infectious Virus in the Absence of Natural Template,” Science 297
(2002): 1016-1018. See CRS Report RS21369 Synthetic Poliovirus: Bioterrorism and
Science Policy Implications by (name redacted).
147 Ronald J. Jackson et al., “Expression of Mouse Interleukin-4 by a Recombinant
Ectromelia Virus Suppresses Cytolytic Lymphocyte Responses and Overcomes Genetic
Resistance to Mousepox,” Journal of Virology 75 (2001): 1205-1210.

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The terrorist attacks of 2001 increased the awareness of the vulnerabilities of the
United States to asymmetric attacks. Policymakers are carefully re-examining many
policies to reduce the threat of future attacks. Some policies already changed include
an increase in public health funding; an increase in C/B related research funding; an
increase in regulatory oversight of C/B agents; and greater limitations on access to
potential C/B agents. While some steps have been taken towards increasing the
robustness of the public health system, how increased funding will translate into
greater preparedness for and response to a C/B attack is still an open question.148
Efforts to limit the risk of bioterrorism through greater physical control of certain
pathogens have elicited concerns regarding unexpected costs.149
Other issues that may be of interest to policymakers in the future include
limiting access to C/B related scientific data,150 and increasing electronic and
physical surveillance to discover C/B use at an early stage.151 The Department of
Health and Human Services has established a National Science Advisory Board for
Biosecurity to aid in determining whether unclassified, federally funded, fundamental
research may pose a threat to national security, while the Department of Homeland
Security is supporting the BioWatch program for early detection of catastrophic
bioterrorism. Whether these programs are successful in addressing the threat posed
by C/B terrorism, including small scale C/B terrorism, will likely be an area of
congressional interest.
148 See CRS Report RL31719 An Overview of the U.S. Public Health System in the Context
of Bioterrorism by (name redacted) and Sarah Lister.
149 See CRS Report RL31354 Possible Impacts of Major Counter Terrorism Security Actions
on Research, Development, and Higher Education by (name redacted)
150 See CRS Report RL31695 Balancing Scientific Publication and National Security
Concerns: Issues for Congress by (name redacted).
151 For more information about the BioWatch program, see CRS Report RL32152 The
BioWatch Program: Detection of Bioterrorism by (name redacted) and (name redacted).

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Appendix A
Methodology
How Criteria Were Chosen. The matrix approach is derived from that used
by the Centers for Disease Control and Prevention (CDC) in prioritizing potential
biological terrorism agents.152 It should be emphasized that there are many different
ways to develop an assessment framework for terror agents. The approach taken here
is not the only valid approach, and different results may occur if different criteria and
weighting systems are chosen. A military assessment, a public health assessment,
and an assessment focusing on terrorist use may have different criteria and relative
weighting depending on the assumptions and needs of each assessment type.
The CDC assessed biological agents in a public health framework, using criteria
appropriate for considering public health response. These criteria included the public
health impact, the dissemination potential, public perception, and special public
health preparedness needs. This report contains modified criteria to address qualities
that terrorist groups planning a small scale attack might consider. For example, a
more general criterion than used by the CDC of public health impact was developed
for use in this report. As defined for this report, public health impact refers to a more
general impact on the health care system, incorporating both casualties and fatalities.
This criterion allows, for example, a more direct comparison of agents which are
lethal with those that predominantly injure.
In contrast to the CDC approach, this report provides a framework that separates
ease in making and disseminating into separate criteria (ease of acquisition and ease
of dissemination). Since both acquisition and dissemination may pose a significant
barrier to the use of a C/B agent, it was deemed important to separate these two
criteria. Additionally, the person-to-person contagiousness of a pathogen was not
considered as a distinct category in contrast to the CDC assessment. From a public
health perspective, a massive attack using contagious pathogens could quickly
overwhelm the surge capacity of the public health system. However, in assessing
distribution of such an agent, contagiousness may be considered as making the agents
easier to disseminate. Contagion may leverage the dissemination of a pathogen. For
example, the initial release may need only to successfully infect a single individual
to be effective. This infected individual might now further disseminate the pathogen
inadvertently, infecting others. For this reason, this report considers contagion as a
positive in terms of ease of dissemination if a pathogen is transmissible through
casual contact. In contrast, agents that are contagious only through close contact or
by exchange of bodily fluids may be less effective means of dissemination.
This report addresses small-scale terror attacks, and so does not postulate any
enhanced requirements for preparation. The number of casualties and fatalities
arising from a small-scale attack may have a large public health impact, but the
mechanisms already in place to provide rush pharmaceuticals (if available), track and
locate affected people, and perform required diagnostics should be sufficient for
152 Centers for Disease Control and Prevention, “Public Health Assessment of Potential
Biological Terrorism Agents,” Emerging Infectious Diseases 8 (2002): 225.

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events of this scale. Consequently, the CDC assessment of special preparation has
been reduced to two remaining components, the response to medical treatment of
various agents and the pre-event prophylaxis which may be available to the
population to ameliorate the impact of the event. These two criteria may have equal
weight to a terrorist, as either would reduce the effects of a terror agent
dissemination.
The final criterion used in this report is the degree to which various agents have
been investigated by military weapons programs. Agents which reportedly have been
weaponized or were research targets for a weapons program may be available for
purchase or theft by terrorist groups. Additionally, records of the weaponization
process, information about successful or unsuccessful research routes, and knowledge
of optimized processes for these agents may be available. While there are few data
available in the open literature about the level of information available to terrorist
groups from these weapons programs, the possibility that there could be technology
transfer from a state program to a terrorist group factors into the relative threat
analysis. Additionally, the fact that an agent may not be explicitly cited as being part
of a weapons program does not preclude its presence in one. Instead, this merely
means that it is unknown from open sources whether any weapons-related research
has been performed regarding it.
These criteria were originally developed for pathogens, and since this report also
considers chemical and toxin agents, the criteria were further adapted for use with
toxin and chemical agents. Since the chemical agents considered in this report have
been considered as chemical weapons for many years, a chemical agent’s status in
a weapons program seemed superfluous and was omitted from the assessment. Also,
prophylaxis for chemical agents, in general, refers to physical protection comprised
of impermeable suits and barriers to personal exposure. Since this report focuses on
the threat to an unprepared civilian population, it was considered unlikely that
prophylaxis would be available for such a surprise attack. Consequently, this
criterion was removed.
The Weighting System.
Between Criteria. In this analysis, each individual criterion is given equal
weighting. This was done to imply that each of the criteria can be viewed from a
generic perspective of use to have roughly equal importance. As discussed elsewhere
in this report, some terrorist groups, because of specific aims, ideology or expertise,
may place more importance on some categories than on others. For example, a group
with extensive practical experience in dissemination technology may place much less
importance on this category than a group lacking this specialized knowledge. By
weighting all the criteria equally, this limited analysis attempts to rate the domestic
risk of potential terrorist use of these agents to a first approximation. The criteria
have been made equivalent in the absence of information requiring a different
weighting. Other weighting systems using these data may be useful for other
purposes.
Within Criteria. Each criterion was divided into three segments to develop a
relative scale of influence. Consequently, a — refers to an aspect that is a negative
influence to terrorist use, while a + refers to an aspect that is a positive influence to

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terrorist use. The O rank represents an intermediate state. For example, in the
prophylaxis criterion, a — denotes licensed prophylaxis while a + denotes no
prophylaxis at all. A O denotes an experimental prophylaxis lacking Food and Drug
Administration approval.
In defining the scale within criteria, an effort was made to logically group the
range of possibilities into three segments. The separation between segments is more
distinct in some categories than in others. Because of the coarseness of this scale,
agents that receive the same symbol within a criterion do not necessarily possess the
same exact properties, but instead should be considered roughly comparable. The
full scale of potential response may not be presented in these categories, as the agents
presented here are those agents which have been identified as having the potential to
be used as a bioweapon. These agents have, generally, been preselected to possess
appropriate characteristics for use. As a consequence, the definitions developed
address the characteristics of bioweapons rather than C/B agents in general.
The full spectrum of potential agents is not represented in these matrices. The
selection process for agents described in the text requires that potential agents be
identified by multiple lists of agents of concern. This process removes many agents
which appear to have low terrorism potential and agents not considered a threat to the
populace at large. Because of this truncation, there are few examples of very poor
C/B agents found on the matrices.
Ranking. Agents were ranked based on the symbols assigned within each
criterion. Agents were first sorted by the number of barriers to their successful
terrorist use: the incidence of — symbols for a given agent initially determined the
ranking of an agent. Agents with equivalent numbers of — symbols were then
sorted according to the number of O symbols present. In the case of further
equivalency, the number of + symbols were considered. If equivalent rankings result,
agents which have been successfully weaponized are presented above those which
have been research targets. Agents which are fully equivalent in ranking and
weaponization status are presented in alphabetical order.
Agents are presented in the matrices in inverse order to the number of barriers
to their successful terrorist use. Thus, agents which possess the greatest number of
barriers are presented at the bottom of the matrix. Agents with equivalent ranking
are presented grouped together within the matrices. This type of analysis is not
designed to produce a highly differentiated ranking of agents, but a qualitative
understanding of relative dangers. Therefore, this list does not attempt to
discriminate agents of roughly equal ranking.
The sorting mechanism used here is not the only mechanism which might be
applied to this framework, but it was felt that sorting according to the number of
barriers would more properly address criteria which might block successful use of a
given agent. This implies that a terrorist may use an agent which is less well-suited,
but lacks significant barriers, rather than an highly effective agent, which has a
significant barrier to its use. Further refinement of the range of characteristics
involved in a given symbol or criterion or reranking agents using other methods may
lead to a different assessment of each agent and its relative threat. For example,

CRS-56
some may wish to sort this framework according to positive factors. This changes
the order of some agents, although the overall ordering of the matrix remains similar.

CRS-57
Appendix B
Table 4. Comparison of chemical agent characteristics
Chemical Agent
Ease of Acquisition
Public Health Impact
Resistance to Medical
Ease of
Treatment
Dissemination
Nitrogen Mustard a
Nitrogen mustard has been
Exposure to nitrogen mustard produces effects
Other than supportive care,
Nitrogen mustard
used as a chemotherapy
similar to sulfur mustard. Skin exposure causes
there is no specific treatment
is both a vapor
agent. Its synthesis
blistering, while inhalation causes severe airway
for nitrogen mustard
and a liquid
produces few toxic
damage. The lethal concentration over time
exposure.
threat to skin and
byproducts and is not
which will kill 50% of those exposed (LCt ) is
lungs.
50
technically complex.
1,500 (milligrams * minutes) per meter3 [or
(mg*min)/m3] . The lethal dosage which will
kill 50% of those exposed (LD ) is10 mg per
50
kilogram (or mg/kg). (See Table Note).
Sulfur Mustard b
Sulfur mustard was first
Skin exposure to sulfur mustard causes blisters
Other than supportive care,
Sulfur mustard is
synthesized in the early
on the skin several hours after exposure.
there is no specific treatment
both a vapor and
1800s. Its synthesis
Inhalation of sulfur mustard causes severe
for sulfur mustard exposure.
a liquid threat to
produces few toxic
airway damage. Exposure to large amounts of
skin and lungs.
byproducts and is not
sulfur mustard by either method causes
technically complex. It has
gastrointestinal and bone marrow damage. The
no commercial uses.
LCt is 1,500 (mg * min)/m3. The LD is 100
50
50
mg/kg. Amounts as small as 10 microgram
(mcg) will cause blistering.
Phosgene Oxime c
Phosgene oxime has no
Skin exposure to phosgene oxime vapor results
Other than supportive care,
Phosgene oxime
industrial use. Its synthesis
in immediate burning and pain, followed by
there is no specific treatment
is a solid, but the
generates significant toxic
wheal-like skin lesions. Inhalation causes
for phosgene oxime
vapor pressure of
side products.
severe pulmonary edema. The extreme pain
exposure.
the solid is high
from phosgene oxime exposure may persist for
enough to make
days. The LCt is 3,200 (mg * min)/m3. The
it a contact and
50
LD is 25 mg/kg.
inhalation threat.
50

CRS-58
Chemical Agent
Ease of Acquisition
Public Health Impact
Resistance to Medical
Ease of
Treatment
Dissemination
Lewisite d
Lewisite has no industrial
Skin exposure to Lewisite causes immediate
A specific antidote,
Lewisite is both
use. Its synthesis has
pain and a grayish area of dead skin, followed
British-Anti-Lewisite (BAL,
a vapor and a
significant toxic side
by blister formation. Lewisite causes more skin
dimercaprol), will alleviate
liquid threat to
products, but is not
damage than mustard. Inhalation of Lewisite
some effects of Lewisite, but
skin and lungs.
technically complex.
causes immediate burning pain, profuse nasal
is no longer in production.
secretions, cough and lung edema. The LCt is
Otherwise, treatment is
50
1,200 (mg * min)/m3. The LD is 40 mg/kg.
symptom based.
50
Amounts as small as 10-15 mcg will cause
blistering.
Cyclohexyl Sarin e
Cyclohexyl sarin has no
Inhalation exposure to cyclohexyl sarin causes
Atropine and pralidoxime
Cyclohexyl sarin
industrial use. Its synthesis
runny nose, pin-point pupils, difficulty
chloride are recommended
is a threat by
produces significant toxic
breathing, nausea, and muscle seizure. Death
for treatment of cyclohexyl
inhalation, and
side products.
usually occurs quickly after absorption of a fatal
sarin exposure. For severe
secondarily
dosage. The LD is 30 mg/kg.
cases, diazepam is given to
through skin
50
limit seizures.
contact.
Sarin f
Sarin has no industrial use.
Inhalation exposure to sarin causes runny nose,
Atropine and pralidoxime
Sarin is a threat
Its synthesis produces
pin-point pupils, difficulty breathing, nausea,
chloride are recommended
by inhalation,
significant toxic side
and muscle seizure. Death usually occurs
for treatment of sarin
and secondarily
products.
quickly after absorption of a fatal dosage. The
exposure. For severe cases,
through skin
LCt is 100 (mg * min)/m3. The LD is 24
diazepam is given to limit
contact.
50
50
mg/kg.
seizures.
Tabun g
Tabun has no industrial use. Inhalation exposure to tabun causes runny nose,
Atropine and pralidoxime
Tabun is a threat
Its synthesis produces
pin-point pupils, difficulty breathing, nausea,
chloride are recommended
by inhalation,
significant toxic side
and muscle seizure. Death usually occurs
for treatment of tabun
and secondarily
products.
quickly after absorption of a fatal dosage. The
exposure. For severe cases,
through skin
LCt is 400 (mg * min)/m3. The LD is 14
diazepam is given to limit
contact.
50
50
mg/kg.
seizures.

CRS-59
Chemical Agent
Ease of Acquisition
Public Health Impact
Resistance to Medical
Ease of
Treatment
Dissemination
VX h
VX has no industrial use.
Inhalation exposure to VX causes runny nose,
Atropine and pralidoxime
VX is a threat
The synthesis of VX
pin-point pupils, difficulty breathing, nausea,
chloride are recommended
both by skin
generates lethal side
and muscle seizure. Death usually occurs
for treatment of VX
contact and
products.
quickly after absorption of a fatal dosage. The
exposure. For severe cases,
inhalation.
LCt is 10 (mg * min)/m3. The LD is 140
diazepam is given to limit
50
50
mcg/kg.
seizures.
Ammonia i
Ammonia is widely used in
Exposure to ammonia causes irritation of the
Other than supportive care,
Ammonia is an
industrial processes,
eyes, nose and throat. Exposure to large
there is no specific treatment
inhalation threat.
including petroleum, pulp
amounts of ammonia causes pulmonary edema.
for ammonia exposure.
and paper, and food and
Death is a rare consequence of ammonia
beverage industries.
exposure.
Chlorine j
Chlorine is used in varied
Chlorine inhalation causes irritation of the eyes,
Other than supportive care,
Chlorine is an
industrial processes,
nose and throat, with pulmonary edema and
there is no specific treatment
inhalation threat.
including water
airway swelling and obstruction after exposure
for chlorine exposure.
purification,
to high-concentrations. Death is a rare
pharmaceutical, and
consequence.
chemical industries.
Chloropicrin k
Chloropicrin is a soil
Inhalation of chloropicrin causes coughing,
Other than supportive care,
Chloropicrin is a
fumigant used for its broad
dizziness, bluish skin, vomiting, and pulmonary
there is no specific treatment
threat both by
biocidal and fungicidal
edema. Contact with chloropicrin can lead to
for chloropicrin exposure.
inhalation and
properties. It is
chemical burns or dermatitis. The LCt is
contact.
50
commercially available.
16,000 (mg * min)/m3. The LD is 250 mg/kg.
50
Phosgene l
Phosgene was first
Inhalation of phosgene causes extensive cellular
Other than supportive care,
Phosgene, with
synthesized in 1812. It is
damage to the lung membrane. Victims may
there is no specific treatment
its high
used in industrial processes,
suffer cough, and pulmonary edema. Death
for phosgene exposure.
volatility, is an
such as dye and plastic
from phosgene inhalation can occur. The LCt
inhalation threat.
50
manufacturing.
is 3,200 (mg * min)/m3.

CRS-60
Chemical Agent
Ease of Acquisition
Public Health Impact
Resistance to Medical
Ease of
Treatment
Dissemination
Diphosgene m
Diphosgene is used in
Diphosgene causes irritation of the respiratory
Other than supportive care,
Diphosgene, with
industrial processes. Its
tract and delayed pulmonary edema. The LCt
there is no specific treatment
its high
50
synthesis has significant
is 3000 (mg * min)/m3.
for diphosgene exposure.
volatility, is an
toxic side products.
inhalation threat.
Soman n
Soman has no industrial
Inhalation exposure to soman causes runny
Atropine and pralidoxime
Soman is a threat
use. Its synthesis produces
nose, pin-point pupils, difficulty breathing,
chloride are recommended
by inhalation,
significant toxic side
nausea, and muscle seizure. Death usually
for treatment of soman
and secondarily
products.
occurs quickly after absorption of a fatal
exposure. Pralidoxime
through skin
dosage. The LCt is 50 (mg * min)/m3. The
chloride treatment must be
contact.
50
LD is 5 mg/kg.
given within two minutes of
50
exposure to be effective
against soman. For severe
cases, diazepam is given to
limit seizures.
Cyanogen Chloride o
Cyanogen chloride is used
After inhalation of a high concentration of
Sodium nitrite and sodium
Cyanogen
in varied industrial
cyanogen chloride, there is the onset of
thiosulfate are effective
chloride, with its
processes, including mining
convulsions, as well as heavy irritation of the
antidotes in a two-step
high volatility, is
and metalworking.
eyes and respiratory tract, similar to chlorine
process. This combination
an inhalation
exposure. Death occurs as quickly as six to
may save those exposed to up
threat.
eight minutes. The LCt is 11,000 (mg *
to 20 times the lethal dose,
50
min)/m3.
and is effective even after
breathing has stopped.
General supportive care is
given if specific antidotal
treatment is not available.
Several alternative therapies
are experimental antidotes
used in other countries.

CRS-61
Chemical Agent
Ease of Acquisition
Public Health Impact
Resistance to Medical
Ease of
Treatment
Dissemination
Hydrogen Cyanide p
Hydrogen cyanide is widely
Exposure to a sublethal dose of hydrogen
Sodium nitrite and sodium
Hydrogen
used in industry. The U.S.
cyanide tends to not cause marked symptoms.
thiosulfate are effective
cyanide, with its
manufactures over 300,000
After inhalation of a high concentration of
antidotes in a two-step
high volatility, is
tons of hydrogen cyanide
hydrogen cyanide, there is the onset of
process. This combination
an inhalation
annually for use in
convulsions. Death occurs as quickly as six to
may save those exposed to up
threat.
chemical syntheses,
eight minutes after exposure. The LCt is
to 20 times the lethal dose,
50
electroplating, mineral
2,500 - 5,000 (mg min)/m3.
and is effective even after
extraction, dyeing, printing,
breathing has stopped.
photography, paper, textile,
General supportive care is
and plastic manufacture.
given if specific antidotal
treatment is not available.
Several alternative therapies
are experimental antidotes
used in other countries.
Perfluoroisobutylene q
Perfluoroisobutylene was
Inhalation of perfluoroisobutylene causes a
Other than supportive care,
Perfluoro-
used as an industrial
rapid toxic effect on pulmonary tissues. Edema
there is no specific treatment
isobutylene is an
chemical, but is no longer
occurs within 5 minutes. Cough productive of
for perfluoroisobutylene
inhalation threat.
manufactured due to its
bloody sputum occasionally is seen. Death is a
exposure.
toxicity.
rare consequence of exposure.
Source: These data were prepared by the authors from the open literature.
Note: The LD is the dosage of agent per unit body weight required to kill 50% of those exposed. It is expressed here in micrograms (mcg) per kilogram (kg). A microgram weighs
50
approximately as much as the ink used to print a single character on this sheet of paper. A 155 lb. person weighs approximately 70 kilograms. The LCt is the concentration
50
of chemical agent lethal over time to 50% of those exposed. It is expressed in units of (mg * min)/m3. LD values commonly refer to liquid exposure, while LCt commonly
50
50
refer to gaseous exposure.

CRS-62
a Information on nitrogen mustard is taken from “Vesicants,” by Frederick R. Sidell et al., in Medical Aspects of Chemical and Biological Warfare, eds. Frederick R. Sidell, Ernest
T. Takafuji, and David R. Franz, Washington, DC: TMM Publications, 1997; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, Boca Raton, FL: CRC
Press, 2000; Frederick R. Sidell, William C. Patrick, III, and Thomas R. Dashiell, Jane’s Chem-Bio Handbook, Alexandria, VA: Jane’s Information Group, 1998; and the
Federation of American Scientists Special Weapons Primer, found online at [http://www.fas.org/nuke/intro/cw/index.html].
b Information on sulfur mustard is taken from the U.S. Army, Medical Management of Chemical Casualties Handbook, Medical Research Institute of Chemical Defense Chemical
Casualty Care Division, Aberdeen, MD, 1999; Frederick R. Sidell, et al. “Vesicants,” Medical Aspects of Chemical and Biological Warfare, op cit.; and Frederick R. Sidell,
William C. Patrick, III, and Thomas R. Dashiell, Jane’s Chem-Bio Handbook, op. cit.
c Information on phosgene oxime is taken from U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit.; Frederick R. Sidell, et al. “Vesicants,” Medical Aspects
of Chemical and Biological Warfare, op cit.; and Frederick R. Sidell, William C. Patrick, III, and Thomas R. Dashiell, Jane’s Chem-Bio Handbook, op. cit.
d Information on lewisite is taken from the Agency for Toxic Substances & Disease Registry, “Medical Management Guidelines — Blister Agents,” Centers for Disease Control and
Prevention, Washington DC; Frederick R. Sidell, et al. “Vesicants,” Medical Aspects of Chemical and Biological Warfare, op cit; Frederick R. Sidell, William C. Patrick, III,
and Thomas R. Dashiell, Jane’s Chem-Bio Handbook, op. cit; and the U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit.
e Information on cyclohexyl sarin is taken from the U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit. and “Nerve Agents,” by Frederick R. Sidell, Medical
Aspects of Chemical and Biological Warfare, op. cit.
f Information on sarin is taken from the U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit; “Nerve Agents,” by Frederick R. Sidell, Medical Aspects of
Chemical and Biological Warfare, op. cit.; and Frederick R. Sidell, William C. Patrick, III, and Thomas R. Dashiell, Jane’s Chem-Bio Handbook, op. cit.
g Information on tabun is taken from the Agency for Toxic Substances & Disease Registry, “Medical Management Guidelines — Nerve Agents,” op. cit.; “Nerve Agents,” by Frederick
R. Sidell, Medical Aspects of Chemical and Biological Warfare, op. cit; and Frederick R. Sidell, William C. Patrick, III, and Thomas R. Dashiell, Jane’s Chem-Bio Handbook,
op. cit.; the U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit.
h Information on VX is taken from the Agency for Toxic Substances & Disease Registry, “Medical Management Guidelines — Nerve Agents,” op. cit.; “Nerve Agents,” by Frederick
R. Sidell, Medical Aspects of Chemical and Biological Warfare, op. cit; and Frederick R. Sidell, William C. Patrick, III, and Thomas R. Dashiell, Jane’s Chem-Bio Handbook,
op. cit.; the U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit.
i Information on ammonia is taken from the Agency for Toxic Substances & Disease Registry, “Medical Management Guidelines — Ammonia,” op. cit. and “Toxicity, Ammonia,”
by Steven Issley and Eddy Lang, eMedicine Knowledge base, found online at [http://www.emedicine.com/EMERG/topic846.htm].
j Information on chlorine is taken from the Agency for Toxic Substances & Disease Registry, “Medical Management Guidelines — Chlorine,” op. cit. “CBRNE - Lung-Damaging
Agents, Chlorine,” by Daniel Noltkamper and Gerald F. O’Malley, eMedicine Knowledge base, found online at [http://www.emedicine.com/EMERG/topic904.htm].
k Information on chloropicrin is taken from “CBRNE - Lung-Damaging Agents, Chloropicrin,” by Joanne Williams, eMedicine Knowledge base, found online at
[http://www.emedicine.com/emerg/topic907.htm]; the Fisher Scientific Material Safety Data Sheet for Chloropicrin; and the National Institutes of Health National Toxicology
Program fact sheet for chloropicrin.
l Information on phosgene is taken from Strategies to Protect the Health of Deployed U.S. Forces: Detecting, Characterizing, and Documenting Exposures, eds. Thomas E. McKone,
et al., Washington, D.C.: National Academy Press, 2000; Agency for Toxic Substances & Disease Registry, “Medical Management Guidelines — Phosgene,” op. cit.; and
“CBRNE - Lung-Damaging Agents, Phosgene,” by Jeffrey L. Arnold, eMedicine Knowledge base, found online at [http://www.emedicine.com/EMERG/topic905.htm].
m Information on diphosgene is taken from Suresh Damle, “Safe Handling of Diphosgene, Triphosgene,” Chemical and Engineering News, 71 (1993):4; Strategies to Protect the Health
of Deployed U.S. Forces: Detecting, Characterizing, and Documenting Exposures, op. cit. and “CBRNE - Lung-Damaging Agents, Diphosgene,” by Eric Mowatt-Larssen and
Paul P. Rega, eMedicine Knowledge base, found online at [http://www.emedicine.com/emerg/topic906.htm].
n Information on soman is taken from the Agency for Toxic Substances & Disease Registry, “Medical Management Guidelines — Nerve Agents,” op. cit.; “Nerve Agents,” by Frederick
R. Sidell, Medical Aspects of Chemical and Biological Warfare, op. cit; Frederick R. Sidell, William C. Patrick, III, and Thomas R. Dashiell, Jane’s Chem-Bio Handbook, op.

CRS-63
cit.; the U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit.; and “CBRNE - Chemical Warfare Agents,” by Jeffrey L. Arnold, eMedicine Knowledge
base, found online at [http://www.emedicine.com/EMERG/topic852.htm].
o Information on cyanogen chloride is taken from the U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit.; Frederick R. Sidell, William C. Patrick, III, and
Thomas R. Dashiell, Jane’s Chem-Bio Handbook, op. cit.; Steven I. Baskin and Thomas G. Brewer,”Cyanide Poisoning,” in Medical Aspects of Chemical and Biological Warfare,
op. cit.; and “CBRNE - Cyanides, Cyanogen Chloride,” by Heather Murphy-Lavoie, eMedicine Knowledge base, found online at [http://www.emedicine.com/emerg/topic910.htm].
p Information on hydrogen cyanide is taken from U.S. Army, Medical Management of Chemical Casualties Handbook, op. cit.; Frederick R. Sidell, William C. Patrick, III, and Thomas
R. Dashiell, Jane’s Chem-Bio Handbook, op. cit.; Steven I. Baskin and Thomas G. Brewer,”Cyanide Poisoning,” in Medical Aspects of Chemical and Biological Warfare, op.
cit.
q Information on perfluoroisobutylene is taken from John S. Urbanetti, “Toxic Inhalational Injury,” in Medical Aspects of Chemical and Biological Warfare, op. cit. and “CBRNE -
Lung-Damaging Agents, Toxic Smokes: Nox, Hc, Rp, Fs, Fm, Sgf2, Teflon,” by Daniel T. Smith and Andrea M. DuPont, eMedicine Knowledge base, found online at
[http://www.emedicine.com/emerg/topic908.htm].

CRS-64
Appendix C
Table 5. Comparison of biological agent characteristics
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Glanders a
Burkholderia mallei is
In pulmonary infections,
There is no
Because of the rarity
Glanders could be
(Burkholderia mallei)
endemic in a number of
pneumonia, pulmonary
vaccine for
of human infection,
disseminated via
species including horses,
abscesses, and pleural effusion
glanders.
the response to
aerosol or through
dogs and sheep in Africa,
can occur. The fatality rate is
many antibiotics is
contaminated food
Asia, the Middle East, and
over 50% even with treatment.
not known.
or drink.
Central and South America.
Skin lesions and ulcers occur
from the contact form of
glanders.
Crimean-Congo
Crimean-Congo
Crimean-Congo hemorrhagic
There is no
Specific treatment
Crimean- Congo
hemorrhagic fever b
hemorrhagic fever has been
fever causes malaise,
vaccine for
with the anti-viral
hemorrhagic fever
observed in western Crimea,
weakness, irritability,
Crimean- Congo
drug, ribavirin may
could be
Central Asia, the Balkan
headache, severe pain, and
hemorrhagic fever.
be effective if
disseminated via
region, Iraq, the Arabian
marked anorexia. Vomiting,
promptly given.
aerosol. It is
Peninsula, western China,
and diarrhea may also occur.
contagious
tropical Africa and South
In severe cases, bleeding from
through close
Africa. Recent well
the gums, nose, lungs, and
contact.
publicized outbreaks have
intestine can occur, leading to
occurred on the Iran —
death due to loss of blood. The
Pakistan border. Several
case fatality rate is
bird and rodent species
approximately 30%.
serve as hosts.

CRS-65
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Pneumonic Plague c
Yersinia pestis, the
Pneumonic plague causes
There is no
Plague can often be
Pneumonic plague
(Yersinia pestis)
causative agent of both
fever, headache, weakness, and
publically
treated with
could be
bubonic and pneumonic
rapidly developing pneumonia
available vaccine
antibiotics, but only
disseminated via
plague, is found world wide,
with shortness of breath, chest
for plague in the
if given in the first
aerosol. It is
with several animal
pain, and cough. The
United States,
24 hours.
contagious
reservoirs. Cases of plague,
pneumonia progresses for 2 to
although several
through casual
usually in bubonic rather
four days and may cause
have IND status.
person-to-person
than pneumonic form, occur
respiratory failure and shock.
contact.
in the United States each
Without early treatment, 90%
year. Large plague
of the patients die.
outbreaks occur less
frequently, but are more
widely reported.
Hantavirus d
Hantavirus is found in
Hantavirus can cause either
There is no
Specific treatment
Hantavirus could
nature, with rodents as a
hantavirus pulmonary
vaccine for
with the anti-viral
be disseminated
natural reservoir within the
syndrome or a hemorrhagic
hantavirus.
drug, ribavirin may
via aerosol.
United States. Outbreaks of
fever with renal syndrome.
be effective if
hantavirus are widely
Hantavirus pulmonary
promptly given.
reported in the media
syndrome consists of fever,
fatigue, muscle aches,
coughing and shortness of
breath. In advanced cases,
heavy pulmonary edema
occurs. The fatality rate for
hantavirus pulmonary
syndrome is 37%.
Hemorrhagic fever with renal
syndrome has a fatality rate of
10%.

CRS-66
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Dengue hemorrhagic
Although dengue fever is
Dengue hemorrhagic fever
There is no
Other than
Dengue
fever e
endemic in most regions of
causes a sudden onset of fever,
licensed vaccine
supportive care,
hemorrhagic fever
the tropics, causing
severe headache, muscle pain,
for dengue
there is no specific
could be
epidemic outbreaks among
and hemorrhagic
hemorrhagic fever.
treatment for dengue
disseminated by
humans, dengue
manifestations. The fatality
Several unlicenced
hemorrhagic fever.
insect vector.
hemorrhagic fever is one of
rate of dengue hemorrhagic
vaccines are under
the less common virus
fever is about 5%.
testing.
strains and would be more
difficult to acquire.
Eastern equine
Eastern equine encephalitis
Symptoms range from mild
There is no
Other than
Eastern equine
encephalitis f
is endemic to the United
flu-like illness to encephalitis,
licensed vaccine
supportive care,
encephalitis could
States. It most commonly
coma and death. The average
for human use.
there is no specific
be disseminated
occurs east of the
duration of hospitalization is
Several IND
treatment for eastern
by insect vector or
Mississippi.
16-20 days. 50-70% of
vaccines exist.
equine encephalitis.
via aerosol.
patients die within a few days.
Only 10% of patients fully
recover. 200 human cases have
been confirmed in the U.S.
since 1964.
Lassa fever g
Lassa fever is endemic in
Lassa fever causes fever,
There is no
Specific treatment
Lassa fever could
Guinea, Liberia, Sierra
malaise, headache, sore throat,
licensed vaccine
with the anti-viral
be disseminated
Leone and regions of
cough, nausea, vomiting,
for lassa fever.
drug, ribavirin may
via aerosol. It is
Nigeria. It has a reservoir in
diarrhea, and muscle pain. In
be effective if given
contagious
the mouse and rat
severe cases, shock,
within the first six
through close
population.
hemorrhage, seizures, and
days of illness.
contact.
encephalopathy are frequent.
Lassa fever has a fatality rate
of 1%.

CRS-67
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Russian spring-summer
Russian spring-summer
Russian spring-summer
There is no
There is no specific
Russian spring-
encephalitis h
encephalitis, occurs in
encephalitis causes a flu-like
licensed vaccine
treatments for
summer
China, Korea, Japan, and
illness, including fever,
available in the
Russian spring-
encephalitis could
eastern areas of Russia.
headache, vomiting, and
United States, but
summer
be disseminated
neurologic symptoms.
some effective
encephalitis.
either by tick
Neurologic damage may be
vaccines are
Supportive care is
vector or via
permanent, causing chronic
available in
provided.
aerosol.
headaches, difficulty
Europe.
concentrating, muscle
weakness or loss of balance. A
small percentage of cases are
fatal.
Western equine
Western equine encephalitis
Symptoms consists of fever,
There is no
Other than
Western equine
encephalitis i
occurs within the United
headache, chills, nausea, and
licensed vaccine
supportive care,
encephalitis could
States. It is endemic in some
vomiting. The morbidity of
for western equine
there is no specific
be disseminated
states west of the
such illnesses is higher in
encephalitis.
treatment for
by insect vector or
Mississippi River and in the
infants than in adults. The
Several IND
Western equine
via aerosol.
corresponding Canadian
fatality rate is 3-4%. 639
vaccines exist.
encephalitis.
provinces. Birds are a
human cases have been
natural reservoir for the
confirmed in the U.S. since
virus.
1964.

CRS-68
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Rift Valley fever j
Rift Valley fever is
People with Rift Valley fever
An experimental,
Specific treatment
Rift Valley fever
generally found in regions
typically have either no
unlicenced Rift
with the anti-viral
could be
of eastern and southern
symptoms or a mild illness
Valley fever
drug, ribavirin may
disseminated
Africa, but the virus also
associated with fever. Some
vaccine has been
be effective if
either by insect
exists in most countries of
victims progress to
developed for
promptly given.
vector or via
sub-Saharan Africa and in
hemorrhagic fever. These
human use, but is
aerosol.
Madagascar.
victims experience fever,
not commercially
generalized weakness, back
available. Other
pain, dizziness, and extreme
candidate vaccines
weight loss at the onset of the
are under
illness. The fatality rate of Rift
investigation.
Valley fever is 1%.
Marburg hemorrhagic
Recorded cases of the
Marburg hemorrhagic fever
There is no
Other than
Marburg virus
fever k
disease are rare, and have
causes fever, chills, headache,
vaccine against
supportive care,
could be
appeared in only a few
nausea, vomiting, chest and
Marburg virus.
there is no specific
disseminated via
locations. Primary locations
abdominal pain, and diarrhea.
treatment for
aerosol. It is
of virus sources are in
Symptoms become
Marburg
contagious
Africa. Sporadic cases
increasingly severe and may
hemorrhagic fever.
through close
occur in that region.
include delirium, shock, liver
contact.
failure, massive hemorrhaging,
and multi-organ dysfunction.
Hospitalization is required.
Recovery from Marburg
hemorrhagic fever may be
prolonged and accompanied by
serious complications. The
fatality rate for treated
Marburg hemorrhagic fever is
between 23-25%.

CRS-69
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Ebola hemorrhagic fever l
Ebola virus is not widely
Ebola hemorrhagic fever
There is no
Ebola hemorrhagic
Ebola
available. Ebola occurs in
causes fever, headache, joint
vaccine for Ebola
fever has no specific
hemorrhagic fever
nature in parts of Africa, but
and muscle aches, sore throat,
virus.
treatment.
could be
the vector of infection is
and weakness, followed by
Supportive care is
disseminated via
unknown, and the barrier to
diarrhea, vomiting, and
provided.
aerosol. It is
successful collection is
stomach pain. A rash, red eyes,
contagious
likely to be high.
hiccups, and internal and
through close
external bleeding may be seen
contact.
in some patients. Ebola
hemorrhagic fever has a 50 -
90% fatality rate.
Melioidosis m
Burkholderia pseudomallei
Pulmonary melioidosis is
There is no
Melioidosis can
Melioidosis could
(Burkholderia
thrive in tropical climates,
accompanied by a high fever,
vaccine for
often be successfully
be disseminated
pseudomallei)
and the disease is endemic
chest pain, and cough.
melioidosis.
treated with long
via aerosol or
in Southeast Asia and
Pneumonia and pulmonary
term antibiotic
through
northern Australia.
abscesses occur, leading to
treatment regimens.
contaminated food
Naturally occurring
death. Fatalities occur in 10%
or drink.
outbreaks have been
of naturally occurring cases.
observed in Africa, the
Middle East, and Central
and South America.

CRS-70
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Yellow fever n
Yellow fever is endemic in
Yellow fever causes fever,
There is a widely
Other than
Yellow fever
some tropical areas of
muscle pain, headache, shivers,
available, tested
supportive care,
could be
Africa and the Americas,
loss of appetite, nausea and/or
vaccine against
there is no specific
disseminated by
and causes regular
vomiting. 15% of the infected
yellow fever.
treatment for yellow
insect vector or
epidemics. There are
enter a “toxic phase” within 24
fever.
via aerosol.
200,000 estimated cases of
hours, which requires
yellow fever per year
hospitalization, as massive
reported worldwide.
bleeding can occur, and kidney
function deteriorates. Half of
the patients in the “toxic
phase” die within 10-14 days.
Yellow fever has 8-10%
fatality rate.
Anthrax o
Anthrax is available both in
Anthrax has a 1-7 day
An anthrax
Anthrax responds
Anthrax could be
(Bacillus anthracis)
nature and through a
incubation period. Onset of
vaccine is
well to combination
disseminated via
number of culture
severe symptoms occurs within
available in
antibiotic therapy.
aerosol.
collections. Anthrax is
2-5 days of incubation.
limited quantities.
The recovery rate is
found in spore form in the
Hospitalization is often
~70% if antibiotic
soil and causes illness
required for those showing
treatment is started
among animals regularly.
disease symptoms.
early.
Numerous anthrax strains,
Unvaccinated, untreated
of varying toxicity, exist.
individuals with inhalation
anthrax suffer up to 90%
fatalities.

CRS-71
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Q fever p
Coxiella burnetti is found
Q fever causes sudden onset of
An IND vaccine
Acute and chronic Q
Q fever could be
(Coxiella burnetti)
worldwide. Cattle, sheep,
high fever, severe headache,
for Q fever is
fever can often be
disseminated via
and goats are the primary
pain, confusion, chills, sweats,
available from
treated with
aerosol.
animal reservoirs of C.
cough, nausea, vomiting,
USAMRIID.
antibiotics. Q fever
burnetii.
and/or diarrhea. Fever usually
Australia also has
is resistant to many
lasts for 1 to two weeks. 30 -
an effective
antibiotics.
50% of patients with a
vaccine, which is
symptomatic infection will
unavailable in the
develop pneumonia. Many
United States.
patients may recover to good
health within several months
without any treatment. Only
1%-2% of people with acute Q
fever die of the disease.
Machupo hemorrhagic
Machupo virus is found in
Machupo hemorrhagic fever
There is no
Specific treatment
Machupo
fever q
remote areas of Bolivia.
causes fever, malaise,
licensed vaccine
with the anti-viral
hemorrhagic fever
headache, and muscle pains.
for Machupo
drug, ribavirin may
could be
Bleeding may occur from the
virus.
be effective if
disseminated via
nose, gums, stomach, and
promptly given.
aerosol. It is
intestine. The fatality rate is
contagious
5-30%.
through close
contact.

CRS-72
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Tularemia r
Tularemia is found in many
Pulmonary tularemia causes
An IND vaccine of
Tularemia is treated
Tularemia could
(Francisella tularensis)
countries including the
respiratory failure, shock and
live, attenuated
with antibiotics.
be disseminated
United States. Francisella
death. The mortality rate for
organisms has
via aerosol.
tularensis is a hardy
pulmonic or septicemic cases
been used to
non-spore forming organism
of tularemia without antibiotics
prevent laboratory
that is capable of surviving
treatment has been as high as
infections.
for weeks at low
30-60%. With treatment, the
temperatures in water, moist
fatality rate in the United States
soil, hay, straw or decaying
is 2%. Between 1990 and
animal carcasses.
2000, a total of 1,368 human
cases of tularemia were
diagnosed in the U.S.
Junin hemorrhagic fever s
Junin virus, is found in a
Symptoms are similar to
There is no
Specific treatment
Junin virus could
small area of Argentina.
Machupo hemorrhagic fever.
licensed vaccine
with the anti-viral
be disseminated
Junin has a fatality rate of
for Junin virus.
drug, ribavirin may
via aerosol. It is
5-30%.
There is an
be effective if
contagious
unlicenced vaccine
promptly given.
through close
under testing.
contact.
Venezuelan equine
Venezuelan equine
Venezuelan equine encephalitis
An IND vaccine,
Other than
Venezuelan
encephalitis t
encephalitis is endemic in
causes malaise, spiking fevers,
designated TC-83,
supportive care,
equine
northern South America,
severe headache, photophobia,
is a live,
there is no specific
encephalitis could
Trinidad, Central America,
and muscle pains. Nausea,
attenuated
treatment for
be disseminated
Florida, and Mexico.
vomiting, cough, sore throat,
organism vaccine
Venezuelan equine
either by insect
and diarrhea may follow. Full
which has been
encephalitis.
vector or via
recovery takes 1-2 weeks. The
used to prevent
aerosol.
fatality rate is less than 1%.
laboratory
Nearly 100% of those infected
infections.
suffer an overt illness.

CRS-73
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Typhus u
Epidemic typhus is common
Typhus causes headaches,
There is no
Typhus is treated
Typhus could be
(Rickettsia prowazekii)
during periods when normal
chills, prostration, high fever,
licensed vaccine
with antibiotics.
disseminated
hygiene is extremely
coughing and severe muscular
for typhus fever.
either by insect
disrupted, as in refugee
pain. A dark rash spreads to the
Several unlicenced
vector or via
camps, war, or natural
entire body excepting, usually,
experimental
aerosol.
disasters.
the face, palms and soles of the
vaccines exist.
feet. The fatality rate is
between 1% and 20%.
Rocky Mountain spotted
Naturally occurring Rocky
Rocky Mountain spotted fever
An experimental
Rocky Mountain
Rocky Mountain
fever v
Mountain spotted fever is
can cause fever, rash,
Rocky Mountain
spotted fever can be
spotted fever
(Rickettsia rickettsiae)
the most common
headache, muscle pain, nausea,
spotted fever
successfully treated
could be
potentially fatal tick borne
vomiting, confusion, lethargy,
vaccine is
with antibiotics.
disseminated
disease in the United States,
seizures and coma. Rocky
available.
either by insect
accounting for between 600
Mountain spotted fever has a
vector or via
- 800 infections per year.
fatality rate of 4%.
aerosol.
Escherichia coli
Enterohaemorrhagic E. coli
E.coli O157:H7 causes
There is no
Other than
E. coli could be
O157:H7 w
are found in animal
abdominal cramps and watery
vaccine for E. coli
supportive care,
disseminated by
reservoirs both within and
diarrhea that can develop into
O157:H7.
there is no specific
contamination of
outside of the United States.
bloody diarrhea. Fever and
treatment for E. coli
food or drink.
Outbreaks of food poisoning
vomiting may occur but most
O157:H7.
related to this E. coli strain
patients recover within 10
are well publicized.
days. The fatality rate is less
than 1%.

CRS-74
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Smallpox x
Only two acknowledged
Smallpox is recognizable by a
There is an
Vaccine given
Smallpox could be
(Variola major)
sources of Variola major
widespread, full body rash.
effective vaccine
within 72 hours of
disseminated via
exist, both in controlled
Treated smallpox has a greater
against Variola
exposure reduces
aerosol. It is
facilities, one in Russia, one
than 30% fatality rate among
major. The U.S.
disease severity.
contagious
in the United States.
unvaccinated populations.
vaccination
There is no other
through casual
program ended in
treatment for
person-to-person
1972. Previously
smallpox.
contact.
vaccinated
individuals may
retain some
residual
protection.
Monkeypox y
Monkeypox occurs in
Symptoms consist of rash and
The smallpox
Vaccine given
Monkeypox could
sporadic outbreaks in
lesions similar to that of
vaccine protects
within 72 hours of
be disseminated
Africa. Squirrels appear to
smallpox. Monkeypox has a
against
exposure reduces
via aerosol. It is
be a reservoir for the virus.
fatality rate of 10%.
monkeypox.
disease severity.
contagious
There is no other
through person-to-
treatment for
person contact.
monkeypox.
Brucellosis z
Brucellosis is found
Brucellosis causes fever,
There is no
Brucellosis can be
Brucellosis could
(Brucella abortus,
worldwide, and is endemic
sweats, malaise, loss of
licensed vaccine
successfully treated
be disseminated
B. melitensis, B. suis)
in the Western United
appetite, headache, and muscle
for brucellosis.
with antibiotics.
by contamination
States.
pain. Neurologic symptoms
Experimental
Treatment regimens
of food or drink.
may occur in up to 5% of
vaccines exist.
usually take from a
cases. The fatality rate is less
few weeks to several
than 2%.
months.

CRS-75
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Shigella dysenteriae aa
Shigella dysenteriae is
Shigellosis is an acute
There is no
Severe shigellosis
Shigella
endemic in tropical and
intestinal disease, which causes
vaccine for
can usually be
dysenteriae could
temperate climates.
diarrhea, fever, nausea,
Shigella
treated with
be disseminated
vomiting, and cramps.
dysenteriae.
antibiotics.
by contamination
Shigellosis has a 5 - 15%
Rehydration is
of food or drink.
fatality rate when caused by
necessary for those
Shigella dysenteriae.
made ill.
Cholera bb
Cholera occurs in many of
Most infected persons have no
There is
Cholera is treated
Cholera could be
(Vibrio cholerae)
the developing countries of
symptoms or only mild
discontinued,
with antibiotics to
disseminated via
Africa and Asia, especially
diarrhea. However, persons
licensed cholera
decrease the
aerosol or through
where sanitary conditions
with severe disease can die
vaccine in the
duration of illness.
contaminated food
are not optimal. Cholera
within a few hours after onset
United States.
Supportive
or drink.
outbreaks have also
due to loss of fluid and salts
Other vaccines for
treatment involves
occurred in parts of Latin
through profuse diarrhea and,
cholera are
rehydration.
America.
to a lesser extent, through
licensed and
Antibiotic treatment
vomiting.
available in other
is not necessary to
countries.
cure the disease.
Salmonella
Salmonella Typhimurium is
Salmonella Typhimurium
There is no
Rehydration is
Salmonella
Typhimurium cc
common worldwide.
causes fever, abdominal pain,
vaccine for
necessary for those
Typhimurium
diarrhea, nausea and sometimes
Salmonella
made ill. Antibiotic
could be
vomiting. Serious
Typhimurium.
therapy may be
disseminated by
complications may occur in a
indicated for those
contamination of
small proportion of cases.
who are severely
food or drink.
symptomatic.

CRS-76
Disease
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to
Ease of
(Biological Agent)
Medical Treatment
Dissemination
Typhoid fever dd
Typhoid fever is found
Generalized systemic enteric
There is an
Typhoid fever is
Typhoid fever
(Salmonella Typhi)
worldwide, with sporadic
fever, headache, malaise, and
approved oral
successfully treated
could be
cases in North America.
constipation followed by more
vaccine against
with antibiotics.
disseminated
Most of these cases
severe abdominal symptoms,
Typhoid fever.
through food or
represent importation from
such as abdominal pain,
water
endemic areas.
nausea, vomiting, diarrhea,
contamination.
dehydration may result. The
fatality rate with treatment is
1%.
Source: These data were prepared by the authors from the open literature.
a Information on glanders is taken from the National Center for Infectious Diseases, “Glanders,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dbmd/diseaseinfo/glanders_g.htm]; Dahna Batts-Osborne, et al. “CBRNE - Glanders and Melioidosis,” eMedicine Knowledge base, found online
at [http://www.emedicine.com/emerg/topic884.htm]; U.S. Department of Defense, “Field Manual 8-284: Treatment of Biological Warfare Agent Casualties,” Washington, D.C.,
2000; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, Boca Raton, FL: CRC Press, 2000; and the Health Canada Material Safety Data Sheet - Infectious
Substances for Burkholderia mallei.
b Information on Crimean Congo hemorrhagic fever is taken from the National Center for Infectious Diseases, “Viral Hemorrhagic Fevers,” Centers for Disease Control and Prevention,
found online at [http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/vhf.htm]; the Health Canada Material Safety Data Sheet - Infectious Substances for Crimean Congo
hemorrhagic fever; the World Health Organization, “Crimean Congo Hemorrhagic Fever Fact Sheet”; Handbook of Chemical and Biological Warfare Agents, op. cit.; and Luciana
Borio et al. “Hemorrhagic Fever Viruses as Biological Weapons: Medical and Public Health Management,” Journal of the American Medical Association, 287 (2002): 2391-2405.
c Information on pneumonic plague is taken from the Division of Vector-Borne Infectious Diseases, “CDC Plague Home Page,” Centers for Disease Control and Prevention, found
online at [http://www.cdc.gov/ncidod/dvbid/plague/index.htm]; Thomas Inglesby et al. “Plague as a Biological Weapon,” Journal of the American Medical Association
283(2000):2281-2290; Thomas W. McGovern and Arthur M. Friedlander “Plague,” in Medical Aspects of Chemical and Biological Warfare, op. cit.; D. Hank Ellison, Handbook
of Chemical and Biological Warfare Agents, op. cit.; and the Health Canada Material Safety Data Sheet - Infectious Substances for Yersinia Pestis.
d Information on hantavirus is taken from the National Center for Infectious Diseases, “All About Hantaviruses,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/diseases/hanta/hps/]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and James N. Mills et al., “Hantavirus
Pulmonary Syndrome — United States: Updated Recommendations for Risk Reduction,” Morbidity and Mortality Weekly Report 51(2002):1-12.
e Information on dengue hemorrhagic fever is taken from the National Center for Infectious Diseases, “CDC Dengue Fever Home Page,” Centers for Disease Control and Prevention
found online at [http://www.cdc.gov/ncidod/dvbid/dengue/index.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and the Health Canada
Material Safety Data Sheet - Infectious Substances for dengue fever.
f Information on eastern equine encephalitis is taken from the National Center for Infectious Diseases, “Eastern Equine Encephalitis Fact Sheet ,” Centers for Disease Control and
Prevention, found online at [http://www.cdc.gov/ncidod/dvbid/arbor/eeefact.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Mohan
Nandalur, and Andrew W. Urban, “Eastern Equine Encephalitis,” eMedicine Knowledge base, found online at [http://www.emedicine.com/med/topic3155.htm].

CRS-77
g Information on Lassa fever is taken from the National Center for Infectious Diseases, “Lassa Fever,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/lassaf.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; the World Health
Organization, “Lassa Fever,” found online at [http://www.who.int/csr/disease/lassafever/en/]; and Luciana Borio et al. “Hemorrhagic Fever Viruses as Biological Weapons:
Medical and Public Health Management,” op. cit.
h Information on Russian spring-summer encephalitis is taken from the National Center for Infectious Diseases, “Tickborne Encephalitis,” Centers for Disease Control and Prevention,
found online at [http://www.cdc.gov/travel/diseases/tickenceph.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and the Health Canada
fact sheet for European Tick Borne Encephalitis, found online at [http://www.hc-sc.gc.ca/pphb-dgspsp/tmp-pmv/travel/tick_e.html].
i Information on western equine encephalitis is taken from the National Center for Infectious Diseases, “Fact Sheet: Western Equine Encephalitis,” Centers for Disease Control and
Prevention, found online at [http://www.cdc.gov/ncidod/dvbid/arbor/weefact.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Mohan
Nandalur and Andrew W. Urban, “Western Equine Encephalitis,” eMedicine Knowledge base, found online at [http://www.emedicine.com/med/topic3156.htm].
j Information on Rift Valley fever is taken from the National Center for Infectious Diseases, “Rift Valley Fever,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/rvf.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and the World Health
Organization, found online at [http://www.who.int/mediacentre/factsheets/fs207/en/].
k Information on Marburg hemorrhagic fever is taken from the National Center for Infectious Diseases, “Marburg Hemorrhagic Fever,” Centers for Disease Control and Prevention,
found online at [http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/marburg.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and
Luciana Borio et al., “Hemorrhagic Fever Viruses as Biological Weapons: Medical and Public Health Management,” op. cit.
l Information on Ebola hemorrhagic fever is taken from the National Center for Infectious Diseases, “Ebola Hemorrhagic Fever,” Centers for Disease Control and Prevention, found
online at [http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/ebola.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Luciana Borio
et al., “Hemorrhagic Fever Viruses as Biological Weapons: Medical and Public Health Management,” op. cit.
m Information on melioidosis is taken from the National Center for Infectious Diseases, “Melioidosis,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dbmd/diseaseinfo/melioidosis_g.htm]; Dahna Batts-Osborne et al., “CBRNE - Glanders and Melioidosis,” eMedicine Knowledge base, found online
at [http://www.emedicine.com/emerg/topic884.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and the Health Canada Material Safety
Data Sheet - Infectious Substances for Burkholderia pseudomallei, found online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds26e.html].
n Information on yellow fever is taken from the National Center for Infectious Diseases, “Yellow Fever — Disease and Vaccine,” Centers for Disease Control and Prevention, found
online at [http://www.cdc.gov/ncidod/dvbid/yellowfever/index.htm]; the World Health Organization, “Yellow Fever,” found online at
[http://www.who.int/health_topics/yellow_fever/en/]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Luciana Borio et al. “Hemorrhagic
Fever Viruses as Biological Weapons: Medical and Public Health Management,” op. cit.
o Information on anthrax is taken from the Centers for Disease Control and Prevention, “Anthrax,” found online at [http://www.bt.cdc.gov/agent/anthrax/index.asp]; Frederick R. Sidell,
William C. Patrick, III, and Thomas R. Dashiell, Jane’s Chem-Bio Handbook, op. cit.; Arthur M. Friedlander,”Anthrax,”in Medical Aspects of Chemical and Biological Warfare,
op. cit.; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Thomas V. Inglesby et al., “Anthrax as a Biological Weapon: Medical and Public
Health Management,” Journal of the American Medical Association 281(1999):1735-1745.
p Information on Q fever is taken from the National Center for Infectious Diseases, “Q Fever,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dvrd/qfever/]; William R. Byrne, “Q Fever,” in Medical Aspects of Chemical and Biological Warfare op. cit.; the Health Canada Material Safety
Data Sheet - Infectious Substances for Q fever, found online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds43e.html]; D. Hank Ellison, Handbook of Chemical and
Biological Warfare Agents, op. cit.; and Geofrey Nochimson, “CBRNE - QFever,” eMedicine Knowledge base, found online at [http://www.emedicine.com/emerg/topic492.htm].
q Information on Machupo hemorrhagic fever is taken from the National Center for Infectious Diseases, “Arenaviruses,”Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/arena.htm]; the Health Canada Material Safety Data Sheet - Infectious Substances for Machupo hemorrhagic fever, found
online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds89e.html]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Luciana Borio
et al., “Hemorrhagic Fever Viruses as Biological Weapons: Medical and Public Health Management,” op. cit.

CRS-78
r Information on tularemia is taken from the Centers for Disease Control and Prevention, “Tuleremia,” found online at [http://www.bt.cdc.gov/agent/tularemia/index.asp]; David T.
Dennis et al., “Tularemia as a Biological Weapon: Medical and Public Health Management,” Journal of the American Medical Association 285 (2001):2763-2773; D. Hank
Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Martin E. Evans and Arthur M. Friedlander, “Tularemia,”in Medical Aspects of Chemical and
Biological Warfare, op. cit.
s Information on Junin hemorrhagic fever is taken from the National Center for Infectious Diseases, “Arenaviruses,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dvrd/spb/mnpages/dispages/arena.htm]; the Health Canada Material Safety Data Sheet - Infectious Substances for Junin hemorrhagic fever, found
online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds89e.html]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Luciana Borio
et al., “Hemorrhagic Fever Viruses as Biological Weapons: Medical and Public Health Management,” op. cit.
t Information on Venezuelan equine encephalitis is taken from the U.S. Department of Defense, “Field Manual 8-284: Treatment of Biological Warfare Agent Casualties,” op. cit.; D.
Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Robert Derlet, “CBRNE - Venezuelan Equine Encephalitis,” eMedicine Knowledge base, found
online at [http://www.emedicine.com/emerg/topic886.htm].
u Information on typhus is taken from the World Health Organization, “Typhus Fever,” found online at [http://mednet3.who.int/eml/disease_factsheet.asp?diseaseId=352]; D. Hank
Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and Health Canada Material Safety Data Sheet - Infectious Substances for Rickettsia prowazekii, found
online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds128e.html].
v Information on Rocky Mountain spotted fever is taken from the National Center for Infectious Diseases, “Rocky Mountain Spotted Fever,” Centers for Disease Control and Prevention,
found online at [http://www.cdc.gov/ncidod/dvrd/rmsf/]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and the Health Canada Material Safety
Data Sheet - Infectious Substances for Rickettsia rickettsii, found online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds129e.html].
w Information on Escherichia coli O157:H7 is taken from the Center for Food Safety and Applied Nutrition, “Escherichia coli O157:H7,” Foodborne Pathogenic Microorganisms and
Natural Toxins Handbook, Washington, D.C.: U.S. Food and Drug Administration, 1992, found online at [http://vm.cfsan.fda.gov/~mow/chap15.html]; the National Center for
I n f e c t i o u s D i s e a s e s , “ E s c h e r i c h i a c o l i O 1 5 7 : H 7 , ” C e n t e r s f o r D i s e a s e C o n t r o l a n d P r e v e n t i o n , f o u n d o n l i n e a t
[http://www.cdc.gov/ncidod/dbmd/diseaseinfo/escherichiacoli_g.htm]; the Health Canada Material Safety Data Sheet - Infectious Substances for Escherichia coli O157:H7, found
online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds63e.html]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and the World Health
Organization, “Escherichia coli Infections,” found online at [http://www.who.int/health_topics/escherichia_coli_infections/en/].
x Information on smallpox is taken from the Centers for Disease Control and Prevention “Smallpox”, found online at [http://www.bt.cdc.gov/agent/smallpox/index.asp]; D. Hank
Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; David J. McClain, “Smallpox,” in Medical Aspects of Chemical and Biological Warfare, op. cit.; and
Donald A. Henderson et al., “Smallpox as a Biological Weapon: Medical and Public Health Management,” Journal of the American Medical Association 281 (1999):2127-2137.
y Information on monkeypox is taken from National Center for Infectious Diseases, “Monkeypox,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/monkeypox/index.htm] and Yvan J.F. Hutin et al., “Outbreak of Human Monkeypox, Democratic Republic of Congo, 1996 to 1997,” Emerging
Infectious Diseases 17 (2001):434-438.
z Information on brucellosis is taken from the National Center for Infectious Diseases, “Brucellosis,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dbmd/diseaseinfo/brucellosis_g.htm];D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and David L. Hoover and
Arthur M. Friedlander, “Brucellosis,” in Medical Aspects of Chemical and Biological Warfare, op. cit.
aa Information on Shigella dysenteriae is taken from the National Center for Infectious Diseases, “Shigellosis,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dbmd/diseaseinfo/shigellosis_g.htm]; Center for Food Safety and Applied Nutrition, “Shigella Spp.,” Foodborne Pathogenic Microorganisms and
Natural Toxins Handbook, op. cit., found online at [http://vm.cfsan.fda.gov/~mow/chap19.html]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op.
cit.; and the Health Canada Material Safety Data Sheet - Infectious Substances for Shigella spp., found online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds139e.html].
bb Information on cholera is taken from the National Center for Infectious Diseases, “Cholera,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dbmd/diseaseinfo/cholera_g.htm]; the Health Canada Material Safety Data Sheet - Infectious Substances for Vibrio cholerae, found online at
[http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds164e.html]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and the World Health
Organization, “Cholera and Epidemic-prone Diarrhoeal Diseases,” found online at [http://www.who.int/csr/disease/cholera/en/].

CRS-79
cc Information on Salmonella Typhimurium is taken from the National Center for Infectious Diseases, “Salmonellosis,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dbmd/diseaseinfo/salmonellosis_g.htm] and Center for Food Safety and Applied Nutrition, “Salmonella Spp.,” Foodborne Pathogenic
Microorganisms and Natural Toxins Handbook, op. cit.
dd Information on typhoid fever is taken from the National Center for Infectious Diseases, “Typhoid Fever,” Centers for Disease Control and Prevention, found online at
[http://www.cdc.gov/ncidod/dbmd/diseaseinfo/typhoidfever_g.htm]; D. Hank Ellison, Handbook of Chemical and Biological Warfare Agents, op. cit.; and the Health Canada
Material Safety Data Sheet - Infectious Substances for typhoid fever, found online at [http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss/msds134e.html], and Center for Food Safety
and Applied Nutrition, “Salmonella Spp.,” Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, op. cit.

CRS-80
Appendix D
Table 6. Comparison of toxin agent characteristics
Toxins
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to Medical
Ease of
Treatment
Dissemination
Abrin a
Abrin can be isolated
Aerosol abrin exposure causes
There is currently no
Other than supportive
Abrin could be
from seeds of Abrus
weakness, fever, cough, and
vaccine or
care, there is no
disseminated either
precatorius, the
pulmonary edema. Ingestion of abrin
prophylactic
specific treatment for
by aerosol or
rosary pea plant.
causes abdominal pains, vomiting,
antitoxin available
abrin exposure
through
This plant is
diarrhea, and death. The lethal
for human use.
contamination of
commonly found in
dosage which will kill 50% of those
food or water.
many parts of the
exposed (LD ) for aerosol exposure
50
world, including the
is 0.04 micrograms per kilogram
United States.
(mcg/kg). (see Table Note).
Shigatoxin b
Shigatoxin is a potent
Ingestion of shigatoxin can cause
There is currently no
Other than supportive
Shigatoxin could be
toxin produced by
severe intestinal damage and kidney
vaccine or
care, there is no
disseminated either
members of the
failure. Aerosol exposure is expected
prophylactic
specific treatment for
by aerosol or
Shigella bacteria
to cause pneumonic symptoms. The
antitoxin available
shigatoxin exposure.
through
family. This bacteria
LD for aerosol exposure is 0.002
for human use.
contamination of
50
is ubiquitous.
mcg/kg.
food or water.
Ricin c
Ricin can be isolated
Aerosol ricin exposure causes
There is currently no
Other than supportive
Ricin could be
from castor beans
weakness, fever, cough, and
vaccine or
care, there is no
disseminated either
and is a by product of
pulmonary edema within 18-24 hours
prophylactic
specific treatment for
by aerosol or
castor oil production.
and severe respiratory distress and
antitoxin available
ricin exposure
through
Approximately 1
death within 36-72 hours. Ingestion
for human use. A
contamination of
million tons of beans
of ricin causes abdominal pains,
vaccine is in IND
food or water.
are processed
vomiting, diarrhea, and death. The
drug testing.
annually worldwide.
LD for aerosol exposure is 3
50
mcg/kg.

CRS-81
Toxins
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to Medical
Ease of
Treatment
Dissemination
Clostridium
This toxin is one of
Ingestion of Clostridium perfringens
There is currently no
Other than supportive
Clostridium
perfringens epsilon
several toxins
epsilon toxin causes intense
vaccine or
care, there is no
perfringens epsilon
toxin d
produced by
abdominal cramps and diarrhea.
prophylactic
specific treatment for
toxin could be
Clostridium
Aerosol exposure to Clostridium
antitoxin available
Clostridium perfringens
disseminated either
perfringens bacteria.
perfringens epsilon toxin would
for human use.
epsilon toxin.
by aerosol or
These are widely
causes pneumonia-like symptoms.
Antitoxins are in
through
distributed in nature
The LD for aerosol exposure is 0.1 -
animal studies.
contamination of
50
and frequently occur
5.0 mcg/kg.
food or water.
in the intestines of
humans and many
animals.
Staphylococcus
This toxin is one of
Aerosol exposure to Staphylococcal
There is currently no
Other than supportive
Staphylococcus
aureus enterotoxin
several toxins made
aureus enterotoxin B causes fever,
vaccine or
care, there is no
aureus enterotoxin
B e
by many strains of
chills, headache, muscle pain, and
prophylactic
specific treatment for
B could be
the bacterium
cough. The fever may last 2 to five
antitoxin available
Staphylococcus aureus
disseminated either
Staphylococcal
days, and the cough may persist for
for human use.
enterotoxin B exposure.
by aerosol or
aureus. This bacteria
up to four weeks. Victims who ingest
Antitoxins are in
through
is ubiquitous.
the toxin suffer nausea, vomiting, and
animal trials.
contamination of
diarrhea. Higher exposure can lead
food or water.
to septic shock and death. The LD50
for aerosol exposure is 27 mcg/kg.

CRS-82
Toxins
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to Medical
Ease of
Treatment
Dissemination
Trichothecene
The trichothecene
Contact exposure to the mycotoxins
There is currently no
Other than supportive
Trichothecene
mycotoxins f
mycotoxins are
causes burning, tender and reddened
vaccine or
care, there is no
mycotoxins could
produced by molds.
skin, swelling, and blistering, which
prophylactic
specific treatment for
be disseminated
These molds are
progresses to tissue death. In lethal
antitoxin available
trichothecene
either by aerosol or
found in nature, but
cases, sloughing of large skin areas
for human use.
mycotoxin exposure.
through
only produce these
occurs. Aerosol exposure to the
contamination of
toxins under specific
mycotoxins results in nasal itching,
food or water.
conditions.
pain, sneezing, bloody and runny
nose, difficulty breathing, and cough.
Ingestion of the mycotoxins causes
loss of appetite, nausea and vomiting,
abdominal cramping, and bloody
diarrhea. The LD for aerosol
50
exposure 1,210 mcg/kg.
Aflatoxins g
Aflatoxin is a
Exposure to aflatoxins can cause
There is currently no
There is no specific
Aflatoxin could be
naturally occurring
hemorrhage, liver damage, edema,
vaccine or
treatment for aflatoxin
disseminated either
toxin produced by
alteration in digestion, absorption
prophylactic
exposure.
by aerosol or
some molds. These
and/or metabolism of nutrients, and
antitoxin available
through
molds are common in
possibly death. The LD for
for human use.
contamination of
50
nature, and aflatoxin
aflatoxin is 10 mg/kg.
food or water.
is produced when
these molds are
grown under stressful
conditions. Some
foods in the U.S. are
regularly tested for
the presence of
aflatoxins.

CRS-83
Toxins
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to Medical
Ease of
Treatment
Dissemination
Clostridium
There are seven types
Ingestion of botulinum toxin causes
There is currently an
Exposure to botulinum
Clostridium
botulinum toxins h
of toxin produced by
difficulty speaking, seeing and/or
unlicenced
toxin can be treated
botulinum toxins
Clostridium
swallowing, leading to increasing
botulinum toxoid
with antitoxin. This
could be
botulinum bacteria.
paralysis that may include respiratory
vaccine available for
treatment stops further
disseminated either
These bacteria are
paralysis. Recovery from paralysis
human use.
damage, but does not
by aerosol or
ubiquitous in soil and
can take from weeks to months.
reverse current
through
can often be found in
Inhalation of botulinum toxin causes
paralysis. Mechanical
contamination of
poorly preserved,
more rapid onset of symptoms. The
breathing assistance
food or water.
canned food.
LD for aerosol exposure is 0.001
and supportive care are
50
mcg/kg.
required in acute cases.
Saxitoxin i
Saxitoxin is a
Ingestion of saxitoxin is commonly
There is currently no
Other than supportive
Saxitoxin could be
neurotoxin produced
known as paralytic shellfish
vaccine or
care, mechanical
disseminated either
by marine
poisoning. Saxitoxin causes
prophylactic
ventilation to relieve
by aerosol or
dinoflagellates.
numbness of the lips, tongue and
antitoxin available
respiratory distress is
through
These
fingertips, followed by neck and
for human use.
the only treatment for
contamination of
microorganisms live
extremities, and a lack of
saxitoxin exposure.
food or water.
in shellfish.
coordination. Respiratory distress
and paralysis are the terminal stages
and can occur within 2-12 hours.
Death results from respiratory
paralysis. Aerosol exposure to
saxitoxin compresses the onset of
symptoms and death may occur in
minutes. The LD for aerosol
50
exposure is 0.002 mcg/kg.

CRS-84
Toxins
Ease of Acquisition
Public Health Impact
Prophylaxis
Resistance to Medical
Ease of
Treatment
Dissemination
Tetrodotoxin j
Tetrodotoxin is most
Tetrodotoxin ingestion causes a
There is currently no
Other than supportive
Tetrodotoxin could
commonly found in
slight numbness of the lips and
vaccine or
care, mechanical
be disseminated
the pufferfish.
tongue, followed by increasing
prophylactic
ventilation to relieve
either by aerosol or
paralysis. Death usually occurs
antitoxin available
respiratory distress is
through
within 4 to 6 hours. Aerosol
for human use.
the only treatment for
contamination of
exposure is expected to cause more
Antitoxins are in
tetrodotoxin exposure.
food or water.
rapid onset of symptoms. The LD
animal studies.
50
for aerosol exposure is 8.0 mcg/kg.
Source: These data were prepared by the authors from the open literature.
Note: The LD is the dosage of agent per unit body weight required to kill 50% of those exposed. It is expressed here in micrograms (mcg) per kilogram (kg). A microgram weighs
50
approximately as much as the ink used to print a single character on this sheet of paper. A 155 lb. person weighs approximately 70 kilograms.
a Information on abrin is taken from the Ethnobotany Material Safety Data Sheet for precatory pea, found online at
[http://www.smm.org/research/Collections/PrecPea.pdf]; Agriculture and Agri-Food Canada, “Notes on poisoning: Abrus precatorius,” found online at
[http://sis.agr.gc.ca/pls/pp/ppack.info?p_psn=139&p_type=all&p_sci=sci&p_x=px]; and David R. Franz, “Defense Against Toxin Weapons,” in Medical Aspects of Chemical
and Biological Warfare, op. cit.
b Information on shigatoxin is taken from the National Center for Infectious Diseases, “Shigellosis,” Centers for Disease Control and Prevention op. cit.; Center for Food Safety and
Applied Nutrition, “Shigella Spp.,” Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, op. cit.; and David R. Franz, “Defense Against Toxin Weapons,”
in Medical Aspects of Chemical and Biological Warfare, op. cit.
c Information on ricin is taken from U.S. Department of Defense, “Field Manual 8-284: Treatment of Biological Warfare Agent Casualties,” op. cit.; “CBRNE - Ricin,” by Ferdinando
L. Mirarchi and Michael Allswede, eMedicine Knowledge base, found online at [http://www.emedicine.com/emerg/topic889.htm]; and David R. Franz, and Nancy K. Jaax, “Ricin
Toxin,” Medical Aspects of Chemical and Biological Warfare op. cit. For more information on ricin see CRS Report RS21383 Ricin: Technical Background and Potential Role
in Terrorism by Dana Shea and (name redacted).
d Information on Clostridium perfringens epsilon toxin is taken from U.S. Department of Defense, “Field Manual 8-284: Treatment of Biological Warfare Agent Casualties,” op. cit.;
David R. Franz, “Defense Against Toxin Weapons,” in Medical Aspects of Chemical and Biological Warfare, op. cit.; Center for Food Safety and Applied Nutrition, “Clostridium
perfringens” Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, op. cit.
e Information on Staphylococcus aureus enterotoxin B is taken from U.S. Department of Defense, “Field Manual 8-284: Treatment of Biological Warfare Agent Casualties,” op. cit.;
the Federation of American Scientists Special Weapons Primer, found online at [http://www.fas.org/nuke/intro/bw/agent.htm]; David R. Franz, “Defense Against Toxin Weapons,”
in Medical Aspects of Chemical and Biological Warfare, op. cit.; Robert G. Ulrich et al., “Staphylococcal Enterotoxin B and Related Pyrogenic Toxins,” in Medical Aspects
of Chemical and Biological Warfare, op cit.; and Joanne Williams, “CBRNE - Staphylococcal Enterotoxin B,” eMedicine Knowledge base, found online at
[http://www.emedicine.com/emerg/topic888.htm].
f Information on Trichothecene mycotoxins is taken from Robert W. Wannemacher, Jr. and Stanley L. Wiener, “Trichothecene Mycotoxins,” in Medical Aspects of Chemical and
Biological Warfare, op. cit.; and David R. Franz, “Defense Against Toxin Weapons,” in Medical Aspects of Chemical and Biological Warfare, op. cit.

CRS-85
g Information on aflatoxin is taken from the Center for Food Safety and Applied Nutrition, “Aflatoxins,” Foodborne Pathogenic Microorganisms and Natural Toxins Handbook, op.
cit; and from the Office of the Special Assistant to the Deputy Secretary of Defense for Gulf War Illnesses, Medical Readiness, and Military Deployments, “Close-out Report:
Biological Warfare Investigation,” U.S. Department of Defense, February 13, 2001, found on line at [http://www.gulflink.osd.mil/bw_ii/index.html].
h Information on Clostridium botulinum toxins is taken from the Center for Food Safety and Applied Nutrition, “Clostridium botulinum,” Foodborne Pathogenic Microorganisms and
Natural Toxins Handbook, op. cit.; National Center for Infectious Diseases, “Botulism,” Centers for Disease Control and Prevention Centers for Disease Control and Prevention,
found online at [http://www.cdc.gov/ncidod/dbmd/diseaseinfo/botulism_g.htm]; Stephen S. Arnon et al., “Botulinum Toxin as a Biological Weapon: Medical and Public Health
Management,”Journal of the American Medical Association 285 (2001):1059-1070; U.S. Department of Defense, “Field Manual 8-284: Treatment of Biological Warfare Agent
Casualties,” op. cit.; John L. Middlebrook and David R. Franz, “Botulinum Toxins,” in Medical Aspects of Chemical and Biological Warfare, op. cit.; and David R. Franz,
“Defense Against Toxin Weapons,” in Medical Aspects of Chemical and Biological Warfare, op. cit.
i Information on saxitoxin is taken from U.S. Department of Defense, “Field Manual 8-284: Treatment of Biological Warfare Agent Casualties,” op. cit.; David R. Franz, “Defense
Against Toxin Weapons,” in Medical Aspects of Chemical and Biological Warfare, op. cit.; and the Federation of American Scientists Special Weapons Primer, found online
at [http://www.fas.org/nuke/intro/bw/agent.htm].
j Information on tetrodotoxin is taken from the Center for Food Safety and Applied Nutrition, “Tetrodotoxin,” Foodborne Pathogenic Microorganisms and Natural Toxins Handbook,
op. cit.; Theodore Benzer, “Toxicity, Tetrodotoxin,” eMedicine Knowledge base, found online at [http://www.emedicine.com/emerg/topic576.htm]; and David R. Franz, “Defense
Against Toxin Weapons,” in Medical Aspects of Chemical and Biological Warfare, op. cit.

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