An Unlikely Threat

Question: Over the past 100 years, how many people have died in chemical or biological terrorist attacks in the United States?

Answer: One.

In November 1997, Defense Secretary William Cohen told ABC-TV's This Week audience that a supply of anthrax the size of a 5-pound bag of sugar would kill half the population of Washington, D.C.

In a January speech to the National Academy of Sciences, President Clinton warned that “the enemies of peace realize they cannot defeat us with traditional military means” and are therefore working on “new forms of assault,” including chemical and biological weapons (CBW). Responding to this still largely hypothetical threat, the Clinton administration's proposed federal budget for fiscal year 2000 calls for nearly $1.4 billion to protect U.S. citizens against terrorist chemical or biological attacks. That amount would more than double fiscal 1999 spending.

Is such a dramatic increase warranted? Not necessarily. In fact, a variety of factors, including the nerve-gas attack on the Tokyo subway by the Japanese Aum Shinrikyo cult in March 1995, led U.S. officials to overestimate the threat of mass-casualty attacks involving chemical or biological agents. A mid-course correction in U.S. policy is now needed.

At first glance, the threat of chemical and biological terrorism seems to be increasing. Before the late 1980s, the Federal Bureau of Investigation (FBI) typically encountered about a dozen incidents a year involving terrorist threats or actual attempts to acquire or use chemical or biological materials–or (rarely) radiological or nuclear materials.

In 1997, however, the FBI opened 74 investigations involving CBW or nuclear materials, and in 1998, it launched 181 investigations. 1 Nevertheless, about 80 percent of these cases turned out to be hoaxes and the remainder were threats, small-scale attacks, and failed attempts at delivery.

In the United States, a mass-casualty attack with a chemical weapon has never occurred–and only one successful incident of biological terrorism has been reported. In 1984, members of the Oregon-based Rajneeshee cult deliberately contaminated restaurant salad bars in the town of The Dalles with salmonella bacteria, affecting 751 people temporarily with a diarrheal illness. Their objective was not to kill people but rather to sicken voters and keep them at home so as to throw the outcome of a local election in the cult's favor.

A whiff of hysteria

U.S. policy-makers and several outside analysts have predicted catastrophic consequences if a terrorist group or an individual–alone or with state sponsorship–ever mounts a major chemical or biological attack. These alarmist scenarios have been based on the potential vulnerability of U.S. urban centers to chemical or biological attack and the growing availability of relevant technology and materials. But these scenarios have not drawn on a careful assessment of terrorist motivations and patterns of behavior.

With more than a hundred terrorist organizations active in the world today, the challenge is to identify groups or individuals who are both motivated and capable of employing chemical or biological agents against civilians. Yet instead of examining historical cases in which terrorists sought to acquire and use such agents, the Clinton administration, as well as many outside analysts, developed their threat assessments and response strategies in an empirical vacuum. Lacking solid data, they fell back on worst-case scenarios that may be remote from reality.

The tendency of U.S. government officials to exaggerate the threat of chemical and biological terrorism has been reinforced by sensational reporting in the press and an obsessive fascination with catastrophic terrorism in Hollywood films, best-selling books, and other mainstays of pop culture.

Examples include movies such as The Rock, Executive Decision, Outbreak, and Twelve Monkeys; novels such as Tom Clancy's Executive Orders and Rainbow Six, Richard Preston's The Cobra Event, and Stephen King's The Stand; and episodes of popular television series such as The X-Files, Seven Days, Outer Limits, Millennium, Burning Zone, and even Chicago Hope. The sensational depiction of chemical and biological weapons in the popular media seems to have had the unintended effect of making these weapons more attractive to hoaxers, as evidenced by the recent rash of anthrax hoaxes [see “Anthrax Hoaxes: Hot New Hobby,” page 6].

A few critics have recently begun to question the worst-case assumptions underlying the administration's counterterrorism programs. Science policy analyst Daniel S. Greenberg, writing in the Washington Post, criticized what he called “a whiff of hysteria-fanning and budget opportunism in the scary scenarios of the saviors who have stepped forward against the menace of bioterrorism. … While a gullible press echoes [their] frightening warnings, there are no independent assessments of the potential for terrorist attacks or the practicality of the proposed responses.” 2

Using more polite language, the General Accounting Office (GAO), the investigative arm of Congress, made a similar point in a preliminary report published in March. The report said that plans developed by the Department of Health and Human Services for “medical consequence management” after a chemical or biological terrorist attack appear to be “geared toward the worst-possible consequences from a public health perspective and do not match intelligence agencies' judgments on the more likely biological and chemical agents a terrorist group or individual might use.”

The GAO report concluded: “A sound threat and risk assessment could provide a cohesive roadmap to justify and target spending for medical and other countermeasures to deal with a biological and/or chemical terrorist threat.” 3

Examining the data

It is paradoxical that chemical and biological terrorism has come to occupy such a high position on the worry list of top U.S. government officials when so little is known about the actual threat.

At the Center for Nonproliferation Studies at the Monterey Institute of International Studies in Monterey, California, the authors have sought to bridge the gap between anecdote and empirical knowledge. With research assistance from Jason Pate and Diana McCauley, we have compiled a database of 520 global CBW incidents that occurred between 1900 and May 1999.

November 1985: Members of the Rajneeshee sect—which perpetrated the largest biological attack in U.S. history—protest the arrest of their leader, the Bhagwan Shree Rajneeshee.

Our goal in building the database was to help identify which types of terrorist groups were most likely to acquire and use chemical and biological agents, the motives underlying attacks, the choice of agent and target, and other aspects of terrorist behavior.

Although caution is in order when extrapolating from the past to the future, much can be learned from examining actual cases. The Monterey database also permits statistical analysis of the historical record, making it possible to discern patterns over time in the incidence of chemical and biological terrorism. This information should assist policy-makers in developing prudent, cost-effective programs for prevention and response.

The incidents involving chemical or biological agents in the Monterey database include hoaxes, plots, efforts to acquire toxic materials, proven possession of materials, and actual attacks. The incidents have been grouped in two basic categories, terrorist or criminal. There were 282 terrorist cases (54 percent) and 238 criminal cases (46 percent).

We define terrorism as “the instrumental use or threatened use of violence by an organization or individual against innocent civilian targets in furtherance of a political, religious, or ideological objective.” Criminal incidents, in contrast, involve extortion, murder, or some other non-political objective. They are not addressed in this article.

Of the 282 incidents grouped in the terrorist category, 263 were selected for analysis because they contained sufficient information to permit cross-case comparison. While most of these incidents took place overseas, 40 percent occurred in the United States.

Contrary to the conventional wisdom about the catastrophic nature of chemical and biological terrorism, actual attacks were few in number, small in scale, and generally produced fewer casualties than conventional bombs.

A breakdown of the 263 cases between 1900 and last May is eye-opening: 26 percent were hoaxes or pranks, eight percent involved an apparent conspiracy that did not proceed far, four percent involved the attempted acquisition of dangerous materials, 10 percent involved the actual possession of dangerous materials, 21 percent concerned a threatened attack that did not materialize, and only 27 percent (71 incidents) included the actual use of a chemical or biological agent.

Of the actual attacks, 83 percent (59) occurred outside the United States. The largest number of incidents took place in 1995 (16, all non-U.S.) and in 1998 (15, one-third in the United States). In very few cases did the perpetrators seek to inflict mass casualties–defined as 1,000 or more deaths–and in none did they occur.

Among the 71 actual attacks–and again, the coverage is global and the timeframe is 1900 to May of this year–the choice of agent and method of delivery varied considerably. Chemical agents employed included cyanide (by far the most popular), rat poison, VX nerve agent, sarin nerve agent, butyric acid, mercury, and insecticide. Biological agents included anthrax, botulinum toxin, salmonella bacteria, and the HIV virus.

The 71 attacks produced 123 fatalities and 3,774 injuries. Of these totals, the sole U.S. fatality was caused by the use of cyanide-tipped bullets by the Symbionese Liberation Army to assassinate an Oakland, California school superintendent in 1973.

The foreign incidents that inflicted the largest numbers of fatalities were the contamination of drinking water with pesticide by an unknown terrorist group in the Philippines in 1987, causing 19 deaths among new recruits to the Philippine Constabulary on the island of Mindanao, and the use of an unknown poison gas against a Turkish village in 1994, possibly by Kurdish Workers Party (PKK) terrorists, causing 21 deaths.

Of the nonfatal casualties, 1,038 were associated with Aum Shinrikyo's release of sarin nerve agent on the Tokyo subway in 1995. 4

To date, incidents of chemical or biological terrorism in the United States have inflicted a total of 784 nonfatal injuries, of which 751 were associated with the Rajneeshee food poisoning case. Other major U.S. incidents involving casualties include the 1989 delivery by racial extremists of a package containing a tear-gas bomb to the Atlanta office of the National Association for the Advancement of Colored People, which injured eight; and attacks with butyric acid against abortion clinics in Houston and Florida in 1998, injuring 14 people.

Many of the terrorists implicated in the 71 actual attacks were not traditional terrorist organizations like the Irish Republican Army. Twenty-four attacks were perpetrated by religiously motivated groups, 15 by nationalist-separatist groups, and 12 by single-issue groups such as anti-abortion or animal-rights advocates. The rest were committed by lone terrorists, right-wing or left-wing groups, and unknown actors.

What factors might account for these patterns? Historically, traditional terrorist organizations have eschewed chemical or biological agents for several reasons, including unfamiliarity with the relevant technologies, the hazards and unpredictability of toxic agents, moral constraints, concern that indiscriminate casualties could alienate current or future supporters, and fear that a mass-casualty attack could bring down the full repressive power of the affected government on their heads.

In contrast, individuals and nontraditional groups that have sought to acquire chemical or biological agents tend to be motivated by religious fanaticism, supremacist or anti-government ideology, or millenarian prophecy, and they often have a paranoid, conspiratorial worldview.

Such individuals and groups may view chemical or biological terrorism as a means to destroy a corrupt social structure, to fulfill an apocalyptic prophecy, to exact revenge against evil-doers or oppressors, or as a form of “defensive aggression” against outsiders seen as threats to the group's survival.

Terrorists who contemplate chemical or biological attacks typically lack outside supporters or other moderating influences that might restrain them from engaging in indiscriminate violence. Religiously motivated cults, for example, are cut off from the outside world and are often guided by a charismatic and all-powerful leader, making them less subject to societal norms.

Most of the incidents of chemical or biological terrorism in the United States were grossly ill-conceived and ineffective. Two typical examples: In 1972, an ecoterrorist group called R.I.S.E., led by two students at a community college in Chicago, plotted to wipe out the entire human race with eight different microbial pathogens and then repopulate the world with their own genes.

Chemical or biological terrorism in the United States has inflicted a total of 784 nonfatal injuries, 751 as a result of the Rajneeshee food poisoning case.

Their initial scheme was to use aircraft to disperse the disease agents on a global basis, but they eventually scaled down their vision to killing the residents of the five states around Chicago by contaminating urban water supplies. Group members informed the FBI about the plot before it could be carried out, however, and the two ringleaders fled to Cuba.

In 1986, a white supremacist Christian Identity group known as the Covenant, the Sword, and the Arm of the Lord sought to overthrow the federal government and hasten the return of the Messiah. They acquired 30 gallons of potassium cyanide to poison urban water supplies, believing that God would direct the poison to kill only the targeted individuals–non-believers, Jews, and blacks living in major cities. Before they could act, however, the FBI penetrated the group and arrested its leaders.

Why toxic weapons?

What specific factors might motivate terrorists to employ chemical or biological agents, as opposed to conventional guns and explosives? Although the desire to inflict mass casualties is one factor, there may be others.

Bombs are appealing to terrorists because of the shock, drama, and cathartic effect of the explosion. Chemical and biological weapons, in contrast, are generally invisible, odorless, tasteless, silent, and insidious. Despite their lack of cathartic power, these weapons evoke deep human anxieties and instill a qualitatively different type of terror.

Nerve agents attack the central nervous system, resulting in seizures, loss of voluntary control, and a gruesome death by respiratory paralysis. Biological agents such as anthrax elicit horrific symptoms of disease such as disfiguring skin eruptions.

These manifestations, and the pervasive threat of contamination with an invisible yet deadly agent, may be more frightening than the sudden trauma of an explosion. Even a chemical or biological attack that killed fewer people than a conventional bomb could have a disproportionate psychological impact.

From an operational standpoint, chemical weapons have both advantages and disadvantages compared with conventional guns and bombs. Nerve agents such as sarin can kill in minutes, and the ability of persistent agents such as mustard or VX to contaminate buildings and people creates the potential for sowing disruption and chaos in an affected urban area.

To be successful, a biological or chemical attack must overcome a series of major technical hurdles.

Disadvantages of chemical weapons are that they are hazardous to handle, unpredictable to disperse in open areas, and can be countered with timely medical intervention such as the administration of antidotes.

With respect to biological agents, terrorists might wish to exploit the ability of certain microorganisms to incapacitate temporarily rather than kill, as in the Rajneeshee cult's use of food-poisoning bacteria. At the other extreme, apocalyptic terrorists seeking to inflict a catastrophic blow against society might employ a highly contagious and lethal agent such as the Ebola virus, which the Aum Shinrikyo cult reportedly sought to acquire in Zaire. 5

The time lag associated with biological weapons effects also makes them well suited to covert delivery. In recent years, no one has claimed responsibility for the most lethal attacks, in part because countries are pursuing terrorists more aggressively. 6 Te rrorists seeking to conceal their involvement and avoid arrest or repression might therefore have a greater incentive to employ biological agents.

For other terrorists, however, the very ambiguity of a biological attack might be perceived as a disadvantage. A sudden epidemic of illness resulting from the deliberate release of a microbial agent–particularly an indigenous strain–could be misinterpreted as a natural outbreak of disease, reducing or eliminating its ability to terrorize. (Public health officials believed that the salmonella outbreak in The Dalles was of natural origin until a former member of the Rajneeshee cult confessed.)

Beyond operational considerations, the choice of poison weapons may be related to deep psychological needs on the part of individual terrorists. From a psychoanalytic perspective, the use of chemical and biological agents may involve the symbolic projection of “poisoned” thoughts and feelings onto “out-group” targets. 7

On the other hand, the delayed effects of biological agents may reduce the psychological gratification associated with a terrorist attack by creating anxiety and tension until the outcome is known. The Rajneeshees, for example, waited in suspense for two weeks before they learned that the restaurant contaminations had been successful.

Terrorists may also have ideological motivations for employing toxic weapons. Aum Shinrikyo's Shoko Asahara was attracted to sarin because he was an admirer of Nazi Germany, the first country to develop and manufacture nerve agents during World War II.

Quasi-religious terrorist organizations may also have a mystical fascination with poisons and disease. Some Christian Identity extremists, for example, might seek to employ biological agents against their enemies in imitation of biblical descriptions of God's use of plagues–including boils, cattle diseases, and the death of the firstborn son–to punish Pharaoh for stopping the Israelites from leaving Egypt. 8

Finally, some members of the right-wing patriot movement are fascinated with the protein toxin ricin because it has the glamorous aura of a powerful, “spy weapon” (having been used in 1978 by the Bulgarian Secret Service to assassinate a dissident living in London). Ricin is also mistakenly believed to be an untraceable poison that will enable perpetrators to evade arrest and prosecution. In 1991, for example, four members of the Minnesota Patriots Council acquired ricin and discussed assassinating Internal Revenue Service officials, a U.S. deputy marshal, and local law enforcement officers. The FBI had penetrated the group, however, and arrests were made before any attacks were carried out.

It is also important to distinguish between discrete and indiscriminate CBW attacks. Just because chemical and germ agents are often described as “weapons of mass destruction,” it does not follow that the ability to inflict mass casualties is an intrinsic property. Key variables in determining the impact of a CBW terrorist attack are the quantity of agent employed and the means of dissemination.

Members of Aum Shinrikyo, for example, used VX to assassinate enemies of the cult by spraying the nerve agent from a hypodermic syringe into the victim's face. This small-scale use of a chemical weapon for assassination is clearly different from releasing a ton of nerve agent from an aircraft over a major city.

Technical hurdles

One reason there have been so few successful examples of chemical or biological terrorism is that carrying out an attack requires overcoming a series of major technical hurdles: gaining access to specialized chemical-weapon ingredients or virulent microbial strains; acquiring equipment and know-how for agent production and dispersal; and creating an organizational structure capable of resisting infiltration or early detection by law enforcement.

Many of the microorganisms best suited to catastrophic terrorism–virulent strains of anthrax or deadly viruses such as smallpox and Ebola–are difficult to acquire. Further, nearly all viral and rickettsial agents are hard to produce, and bacteria such as plague are difficult to “weaponize” so that they will survive the process of delivery.

As former Soviet bioweapons scientist Ken Alibek wrote in his recent memoir, Biohazard, “The most virulent culture in a test tube is useless as an offensive weapon until it has been put through a process that gives it stability and predictability. The manufacturing technique is, in a sense, the real weapon, and it is harder to develop than individual agents.” 9

The capability to disperse microbes and toxins over a wide area as an inhalable aerosol–the form best suited for inflicting mass casualties–requires a delivery system whose development would outstrip the technical capabilities of all but the most sophisticated terrorists. Not only is the dissemination process for biological agents inherently complex, requiring specialized equipment and expertise, but effective dispersal is easily disrupted by environmental and meteorological conditions.

A large-scale attack with anthrax spores against a city, for example, would require the use of a crop duster with custom-built spray nozzles that could generate a high-concentration aerosol cloud containing particles of agent between one and five microns in size. Particles smaller than one micron would not lodge in the victims' lungs, while particles much larger than five microns would not remain suspended for long in the atmosphere.

To generate mass casualties, the anthrax would have to be dried and milled into a fine powder. Yet this type of processing requires complex and costly equipment, as well as systems for high biological containment. Anthrax is simpler to handle in a wet form called a “slurry,” but the efficiency of aerosolization is greatly reduced.

(A low-tech terrorist might stage a chemical or biological attack in an enclosed space such as a subway station, as did Aum Shinrikyo, but fewer people would be harmed than in an open-air attack against a city.)

Contamination of an urban water system is also beyond the capability of most terrorists because a huge volume of a chemical or biological agent would be needed to overcome the effects of dilution and chlorination. In contrast, a small-scale attack on restaurant food or a water tank would be more feasible.

Firefighters emerge from the Tokyo subway after cleaning cars contaminated during the Aum Shinrikyo's 1995 sarin gas attack.

So far the FBI has not obtained evidence that any terrorist organization has succeeded in building a device capable of delivering a mass-casualty biological attack. Aum Shinrikyo, for example, failed in 10 known attempts in Japan to conduct biological attacks with either anthrax or botulinum toxin. 10

Despite the cult's vast financial resources (approximately $1 billion) and access to trained scientists, it was unable to overcome the technical hurdles associated with the acquisition of a virulent strain, cultivation of the agent, and efficient delivery.

Terrorists groups must also be capable of evading detection by law enforcement until after they have carried out an attack. While lone psychopaths motivated to use chemical or biological weapons may avoid the notice of the police, their technical and resource limitations make them unlikely to be capable of acts of mass-casualty terrorism.

Conversely, several terrorist organizations that have sought in the past to acquire chemical or biological agents have been infiltrated by the FBI or betrayed by informants before they could implement an effective attack.

As a result of these various constraints, crude or “low-tech” delivery methods, such as those employed by Aum Shinrikyo and the Rajneeshee cult, are likely to remain the most common forms of chemical or biological terrorism. These methods are potentially capable of inflicting at most tens to hundreds of fatalities–within the destructive range of a high-explosive bomb–but not the mass death envisioned by alarmist scenarios.

Assessing the threat

The historical record suggests that only a tiny minority of terrorists will be motivated to carry out an indiscriminate chemical or biological attack, and that few if any of this subset will possess the necessary technology and expertise to actually accomplish it.

Thus, the most likely incidents of chemical or biological terrorism in the future will involve hoaxes and relatively small-scale attacks. Moreover, although chemical or biological agents are often termed “weapons of mass destruction,” some terrorists have sought to employ such agents in a limited manner to assassinate individuals.

Of course, governments cannot afford to be complacent about the potential for high-casualty chemical and biological attacks by terrorists who gain access to military-grade agents and delivery systems–particularly if they receive assistance from a state. A state sponsor that believed it could shield its identity through intermediaries might take the risk, particularly in a crisis or during a war. Incidents of state-sponsored chemical or biological terrorism, however, have been exceedingly rare. All have involved special-operations forces rather than independent terrorist organizations, probably because states fear losing control over proxy groups. States may also be deterred from sponsoring terrorism by the likelihood of severe retaliation if the source of the attack were to become known.

Nevertheless, ad hoc or “transnational” terrorist organizations, such as the group that bombed the World Trade Center, have inspired growing concern because they may be only loosely affiliated with a state sponsor and hence less constrained.

Terrorists with ample financial resources might also seek to purchase technical know-how by recruiting scientists formerly employed by countries with advanced chemical or biological programs, such as the Soviet Union, South Africa, or Iraq.

Further comparative analysis of historical cases should help refine the profile of terrorist groups and individuals most likely to acquire and use chemical and biological agents. If motivations and patterns of behavior associated with this form of terrorism are better understood, it might be possible for intelligence and law enforcement agencies to narrow the “bandwidth” of individuals and organizations considered to be of greatest concern. That, in turn, would permit a more efficient application of intelligence resources, which might otherwise be stretched unproductively over too broad a field of suspects.

The potential threat posed by lone terrorists and small splinter groups, who can easily slip through the surveillance net, may lower confidence in the ability to prevent acts of chemical or biological terrorism before they occur. Even so, better profiling of terrorist groups should enhance the ability of law enforcement officials to assess the credibility of terrorist threats and to manage the current epidemic of anthrax hoaxes.

Historical analysis of patterns of behavior of CBW terrorists, such as the choice of agent and delivery system, can also help improve the effectiveness of medical countermeasures and other consequence-management activities.

Although some planning for worst-case scenarios is justified, the types of chemical and biological terrorism against which federal, state, and local planning should be primarily directed are small- to medium-scale attacks.

Such a threat assessment is not the stuff of newspaper headlines, but the historical record surely justifies it.