Emerging Infectious Diseases
[Volume 5 No.4 / July - August 1999]
Special Issue
Historical Trends Related to Bioterrorism: An Empirical Analysis
Jonathan B. Tucker
Monterey Institute of International Studies, Monterey, California,
USA
Since the Japanese doomsday cult Aum Shinrikyo released sarin
nerve gas on the Tokyo subway in March 1995, killing 12 people,
terrorist incidents and hoaxes involving toxic or infectious agents
have been on the rise. Before the late 1990s, the Federal Bureau of
Investigation (FBI) typically investigated a dozen cases per year
involving the acquisition or use of chemical, biological, radiologic,
or nuclear materials; however, FBI opened 74 such investigations in
1997 and 181 in 1998 (1). Although 80% of these incidents have
been hoaxes, some were unsuccessful attacks (2).
The vulnerability of civilian populations to chemical, biological,
radiologic, or nuclear terrorism has been widely discussed, but
information on historical cases is anecdotal and often inaccurate
(3). Without a realistic threat assessment based on solid empirical
data, government policymakers lack the knowledge they need to
design prudent and cost-effective programs for preventing or
mitigating future incidents.
Responding to this knowledge gap, the Chemical and Biological
Weapons Nonproliferation Project at the Monterey Institute's
Center for Nonproliferation Studies has compiled an open-source
database of all publicly known cases from 1900 to the present in
which domestic or international criminals or terrorists sought to
acquire or use chemical, biological, radiologic, or nuclear materials.
As of January 31, 1999, the database contained 415 incidents, both
domestic and international. Each entry draws on multiple sources
and includes a detailed description of the event and a list of
citations.
The project has conducted a preliminary analysis of the data to
discern patterns over time in the frequency of such incidents, the
underlying motives, and the choice of agent and target. The
ultimate goal is to identify which types of individuals or groups are
most likely to acquire and use toxic or infectious materials and for
what purposes.
Since the Monterey Database has been compiled from journalistic
accounts and other unclassified sources, it may not be
comprehensive or fully accurate. Incidents have been recorded only
if they came to the attention of law enforcement or the news media,
so the database does not include events that were not detected or
whose existence remains secret. Despite these limitations, the
information in the database indicates trends and patterns of
behavior that may assist intelligence and law-enforcement personnel
in focusing their monitoring efforts.
Database Findings
Most of the incidents in the Monterey Database involve chemical or
biological agents rather than radiologic or nuclear materials (Figure
1). The cases have been divided into three categories: terrorist
events, criminal events, and state-sponsored assassinations. To be
classified as a terrorist event, an incident must involve an
organization or person that conspires to use violence instrumentally
to advance a political, ideologic, or religious goal. Criminal
incidents, in contrast, involve extortion, murder, or some other
nonpolitical objective. Of the 415 incidents involving chemical,
biological, radiologic, or nuclear materials, 151 cases are terrorist
events for which information is sufficient to permit cross-case
comparison. These incidents have been classified according to type
of agent, event, target, motive, and group (Figure 2).
"Type of event" includes the following categories: 1) conspiracy to
acquire and use an agent, 2) attempted acquisition, 3) possession,
4) threatened use, 5) actual use, and 6) hoax or prank. Most of the
151 incidents involve threatened or actual use, although rarely with
the intent of inflicting mass casualties. Of the 151 terrorist
incidents, a subset of 33 involves biological agents (22 alleged
biological cases were dropped from the analysis because they
lacked key pieces of information). Many of the biological-agent
cases are hoaxes.
Since 1985, the number of terrorist incidents involving the
threatened or actual use of chemical, biological, radiologic, or
nuclear materials has risen sharply; a more modest increase has
occurred in efforts to acquire such agents. When criminal and
terrorist incidents involving chemical or biological agents are
examined, two large peaks become apparent (Figure 3a). The 1995
peak was associated primarily with Aum Shinrikyo and related
copycat attacks in Japan; in 1998, incidents of actual use again
increased abruptly (Figure 3a).
Hoaxes involving chemical or biological agents have shown two
peaks in frequency over the past 30 years (Figure 3b). The 1986
peak in chemical hoaxes was inspired by the second series of
Tylenol poisonings, while the dramatic rise in biological hoaxes in
1998 is attributable to the flurry of anthrax threats in the United
States. The first wave of anthrax hoaxes followed the
well-publicized arrest on February 18, 1998, of Larry Wayne
Harris, a microbiologist linked to white-supremacist groups, after
he allegedly threatened to release "military-grade anthrax" in Las
Vegas (4). Although Harris's anthrax turned out to be a harmless
veterinary vaccine strain, sensational media coverage appears to
have had the unintended effect of popularizing this agent among
potential perpetrators.
The categories of terrorist organizations involved in the acquisition
and use of chemical, biological, radiologic, or nuclear materials
have changed over time. Omitting incidents involving lone
terrorists, recent years have seen a rise in cases involving three
types of terrorist organizations: single-issue groups such as those
dealing with abortion and animal rights; nationalist and separatist
groups such as Chechen rebel organizations, the Kurdistan Workers
Party, and the Tamil Tigers of Sri Lanka; and apocalyptic religious
cults such as Aum Shinrikyo (although Aum accounts for nearly all
the latter cases). No clear pattern is apparent in the types of groups
involved in biological incidents, although religious fundamentalism
as a motivation has emerged within the past 5 years.
The preferred choice of target has also changed over time. If one
examines 135 terrorist incidents for which the target is known, two
types of targets have increased in frequency: the general civilian
population (with the apparent intent of inflicting indiscriminate
casualties) and a symbolic building or organization.
Motivations for the terrorist use of chemical, biological, radiologic,
or nuclear materials appear to encompass a wide range of
objectives. (For each case, two analysts separately determined the
"best fit" to a menu of motivations.) In descending order, the main
motivations are: 1) to promote nationalist or separatist objectives;
2) to retaliate or take revenge for a real or perceived injury; 3) to
protest government policies; and 4) to defend animal rights (Figure
4). A similar breakdown of motivations is found in the incidents
involving biological agents, except for the greater prominence of
apocalyptic prophecy (Figure 5). Nearly all the latter cases are
linked to Aum Shinrikyo, which may be either an outlier or a
trend-setter.
The motivations underlying terrorist incidents with chemical,
biological, radiologic, or nuclear materials appear to have shifted
over time. The predominant motivation from 1975 to 1989 was to
protest government policies. Since 1990, however, the leading
motivations have been to further nationalist or separatist objectives
and for retaliation or revenge. In 1993, because of Aum Shinrikyo,
apocalyptic prophecy also emerged as an important motivation. The
prominence of these three motivations becomes even greater when
only incidents involving biological agents are examined.
In addition to compiling the incidents database, the project
commissioned historical case studies of seven terrorist groups or
individuals that acquired or employed biological agents (Table 1).
Two of the cases appear to be apocryphal, but the five confirmed
cases share a number of characteristics that may be diagnostic of
groups and individuals most likely to engage in bioterrorism (Table
2). These characteristics include diffuse objectives, a sense of
grandiosity, and a paranoid, conspiratorial, or apocalyptic world
view that may lead to "defensive aggression." Such terrorists also
lack a domestic political constituency that might restrain them from
engaging in indiscriminate violence. Religiously motivated cults
such as Aum Shinrikyo and the Rajneeshees are cut off from the
outside world and are often guided by a charismatic, all-powerful
leader, making them less subject to societal norms. Other factors
not listed in the table include a tendency to escalate terrorist
violence over time and to use innovative weapons and tactics.
[fig]
Figure 1.  Overall  database:  Distribution of  incident by  type,
1960 Jan.  31, 1999 (415  cases).
[fig]
Figure 2.  Standardized  typology used in  analysis of  politically or
ideologically  motivated  incidents.
[fig]
Figure 3. (A)  Actual chemical  and biological  incidents vs.
hoaxes,  1960 1998 (278  cases). (B)  Chemical and  biological
hoaxes over  time, 1960 1998  (93 cases: 43  chemical, 50
biological).
[fig]
Figure 4.  Distribution of  motivations for  chemical and  biological
terrorism  incidents,  1960 Jan. 31,  1999 (147  cases).
[fig]
Figure 5.  Distribution of  motivations for  biological  terrorism
incidents,  1960 Jan. 31,  1999 (33 cases).
Table 1. Comparison of Values Across Selected Bioterrorist
Incidents
----------------------------------------------------------------------
                Motivation/
Case            Objective           Ideology          Target(s)
----------------------------------------------------------------------
Weather       Temporarily           Revolutionary     Urban
Underground   incapacitate          movement opposed  populations
incapacitate  U.S. cities to        to American       the United States
              demonstrate           imperialism and
              impotence of the      the Vietnam War
              Federal government
R.I.S.E.      Kill off most of      Perpetrators were Initially entire
(1972)        humanity to prevent   college students  world population,
              the destruction of    influenced by     later narrowed to
              nature, then start    ecoterrorist      residents of five
              human race over with  ideology and      states around
              a select few          1960s drug        Chicago
Red Army      Allegedly planned BW  Marxist-          Specific targets
Faction       attacks against West  revolutionary     unknown
(1980)        German officials and  ideology
              business leaders
Rajneeshee    Scheme to             Indian            Residents of the
Cult (1984)   incapacitate voters   religious cult    town of The Dalles
              to win local          headed by a       and Wasco County,
              election, seize       charismatic       Oregon
              political control     guru
              of county
Minnesota     Cause harm to the     Anti-government   IRS officials,
Planned       federal government,   tax protesters;   U.S. deputy
Patriots      obtain personal       right-wing        marshal, local
Council       revenge               "patriot"         law enforcement
(1991)                              movement
Aum           Prove an              New Age doomsday  Mass civilian
Shinrikyo     apocalyptic           cult seeking to   populations,
(1995)        prophecy, eliminate   establish a       individual
              enemies and rivals,   theocratic state  opponents of
              halt an adverse court in Japan, with a  cult, judges
              ruling, seize control charismatic,      ruling against
              of Japanese           power-hungry      and police
              government            leader            investigating
                                                      cult
Larry Wayne   To alert Americans    Links to          Made vague threats
Harris        to the Iraqi BW       Christian         against U.S.
(1998)        threat; seeks         Identity and      federal officials
              separate homeland     white             on behalf of right-
              for whites in the     supremacist       wing "patriot"
              United States         groups (e.g.,     groups
                                    the Aryan Nation)
-------------------------------------------------------------------------
Table 1, cont'd
--------------------------------------------------------------------
Agent(s)                  Delivery              Outcome
--------------------------------------------------------------------
Reportedly sought to    Reportedly planned to   Report originated with
obtain agents at Ft.    put incapacitaing CW/BW U.S. Customs informant;
Detrick by blackmail    agents in urban water   case probably
of gay soldier                                  apocryphal
Eight microbial         Planned BW aerosol      Attack aborted when
pathogens including     attacks (dispersed by   cultures were
agents of typhoid       aircraft) and           discovered; the two
fever, diphtheria,      contamination of        main perpetrators
dysentery, and          urban water             then fled to Cuba
meningitis              supplies
Group members           Unknown                 Probably an erroneous
allegedly cultivated                            report, later
botulinum toxin in a                            repudiated by German
Paris safe-house                                government (BKA)
Salmonella              Multiple methods,       Plot revealed when
Typhimurium             mainly contamination    the cult collapsed and
                        of restaurant salad     members turned
                        bars                    informant
Ricin extracted from    Planned to deliver      Group was penetrated
castor beans obtained   ricin through skin      by FBI informants;
by mail-order           with DMSO and aloe      four key members
                        vera or as dry          arrested
                        aerosol
Biological agents       Attempted on at         Multiple CW attacks
(anthrax, botulinum     least 10 occasions      (in Matsumoto, Tokyo,
toxin, Q fever,         to disperse BW agents   and assassination
Ebola virus) and        in aerosol form;        campaign) killed at
chemical agents         all known attacks       20 people and injured
(sarin, VX, hydrogen    failed                  more than 1,000
cyanide
Obtained plague and     Discussed the           Arrested when he
anthrax (vaccine        dissemination of BW     talked openly about
strain), reportedly     agents with crop-       BW terrorism and
isolated several        duster aircraft         made threatening
other bacteria          and other methods       remarks to U.S.
                                                officials
-----------------------------------------------------------------------
BW, biological weapons; CW, chemical weapons; DMSO, dimethylsulfoxide;
IRS, Internal Revenue Service; FBI, Federal Bureau of Investigation.
Table 2. Selected Motivational Factors Associated with Bioterrorism
----------------------------------------------------------------------
                                            Loner  Sense of
                                    Apoca-    or   paranoia
          Charismatic  No outside   lyptic splinter   and     Defensive
Cases      leadership constituency ideology group grandiosity aggression
------------------------------------------------------------------------
R.I.S.E.       X          X                   X        X          X
Rajneeshee     X          X                   X        X          X
  Cult
Minnesota      X          X            X      X        X          X
  Patriots
  Council
Aum Shinrikyo  X          X            X               X          X
Larry Wayne               X            X      X        X          X
  Harris
Apparently
Apocryphal
Cases
  Weather      X                                       X
   Underground
  Red Army     X                                       X
     Faction
-----------------------------------------------------------------------
Conclusions
The Monterey Database indicates that incidents involving biological
agents have been quite rare, with 66 criminal events and 55 terrorist
events over the 40-year period from 1960 to 1999, although the
frequency of such incidents (mainly hoaxes) has increased sharply in
recent years. The historical record includes few cases in which
criminals or terrorists sought to inflict mass casualties with
biological agents, and none in which they succeeded. Only eight
criminal attacks with biological agents led to casualties, inflicting a
total of 29 deaths and 31 injuries. Of the terrorist attacks with
biological agents, only one resulted in casualties: the use by the
Rajneeshee cult in 1984 of Salmonella Typhimurium bacteria to
contaminate restaurant salad bars in The Dalles, Oregon. This event
caused 751 cases of food poisoning, none fatal (5).
Incidents of bioterrorism in the Monterey Database are extremely
diverse in terms of type of group and motivation. The trend in
recent years has been away from left-wing terrorism and toward
nationalist-separatist groups and individuals or ad hoc groups bent
on revenge. There has also been an apparent rise in incidents
perpetrated by violent sects or cults that believe in apocalyptic
prophecy.
Even if the motivation to inflict mass casualties exists, however,
few terrorist groups possess the scientific-technical resources
required for the successful large-scale release of a biological agent.
Aum Shinrikyo, which had considerable wealth and scientific
expertise, failed in 10 separate attempts to carry out open-air
attacks against urban targets with aerosolized anthrax spores or
botulinum toxin (6).
In summary, the historical record suggests that future incidents of
bioterrorism will probably involve hoaxes and relatively small-scale
attacks, such as food contamination. Nevertheless, the diffusion of
dual-use technologies relevant to the production of biological and
toxin agents, and the potential availability of scientists and
engineers formerly employed in sophisticated biological warfare
programs such as those of the Soviet Union and South Africa,
suggest that the technical barriers to mass-casualty terrorism are
eroding.
--------------------------------------------------------------------
Acknowledgments
The author thanks Jason Pate and Diana McCauley for their
outstanding work in compiling and analyzing the Monterey
Database of chemical, biological, radiologic, and nuclear incidents.
Dr. Tucker is director of the Chemical and Biological Weapons
Nonproliferation Project, Center for Nonproliferation Studies,
Monterey Institute of International Studies.
Address for correspondence: Jonathan B. Tucker, Chemical and
Biological Weapons Nonproliferation Project, Center for
Nonproliferation Studies, Monterey Institute of International
Studies, 425 Van Buren Street, Monterey, CA 93940, USA; fax:
831-647-6534; e-mail: jtucker@miis.edu.
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Pittsburgh Post-Gazette, May 5, 1999.
  2. Weiner T. Reno says U.S. may stockpile medicine for terrorist
attacks. New York Times 1998 Apr 23; Sect. A:12.
  3. For a revealing account of the inconsistencies and inaccuracies
in the secondary literature on CBW terrorism, see Ron Purver,
Chemical and biological terrorism: the threat according to the open
literature (Ottawa, Canada: Canadian Security Intelligence Service,
June 1995).
  4. Edwards TM. Catching a 48-hour bug. Time 1998 Mar 2; p.
56-7.
  5. Torok TJ, Tauxe RV, Wise RP, Livengood JR, Sokolow R,
Mauvais S, et al. A large community outbreak of salmonellosis
caused by intentional contamination of restaurant salad bars. JAMA
1997;278:389-95.
  6. WuDunn S, Miller J, Broad WJ. How Japan germ terror alerted
world. New York Times 1998 May 26; Sect A:1 (col 1), A:10 (col
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