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Chemical Biological Radiological Nuclear terrorism: Assessing the Threat

By Yaron Schwartz and Ophir Falk

Within the gamut of terrorism’s longtime familiar perils, the events of 11 September 2001 constituted a shift in the paradigm of the character of terrorist attacks: it is currently no longer a speculation whether terrorists are consciously willing to kill thousands of innocent people in the wake of their attacks.

The equation Capabilities + Intentions = Probable Threat has now become less ambiguous, for 9/11 clearly demonstrated that the terrorists’ intentions to cause damage of epic proportions constitute a clear and present danger. In that respect, this paradigm shift is a “wake-up call” for facing the real threat of Chemical, Biological, Radiological and Nuclear (CBRN)-Weapons of Mass Destruction (WMD) terrorism.

In the past, the essence of terrorism was to disseminate fear and make a political statement through violence. It was a political act designed to influence an audience, thus levels of violence were calculated so as to draw attention but not to be so high as to alienate supporters or trigger overwhelming response from authorities. That continues to be a main theme of “common” or “old-school” terrorism. However, in so-called postmodern or mega-terrorism, the aim is to maximize the number of casualties.[1]

This reflects a fundamental shift in the goal of terrorists, from trying to make a political statement through violence, to combining that pretext with the maximization of damage to the target as an additional or often primary goal. Such terrorists may be motivated by nihilistic ethnic or religious considerations, among others.

A Department of Defense report suggested that as many as 25 countries have or are in the process of acquiring weapons of mass destruction.[2] CIA Director George Tenet testified before the US congress that terrorists currently rely on conventional explosives by-and-large, but that a number of groups are seeking chemical, biological, radiological strike capacity (al-Qaida stands out as the most familiar example).[3]

Conversely, Dr. David Franz—former Commander of the U.S. Army Medical Institution for Infectious Diseases—argued that “an effective, mass-casualty producing attack would require either a fairly large, very technically competent, well funded terrorist program or state sponsorship.”[4] Ominously, this strand of terrorism is no longer a question of will, but a matter of means and opportunity. On the other hand, the threat must be kept in perspective, based on the capabilities of the perpetrators and the abilities to mitigate the threat.

Among types of WMD, chemical weapons are the ones previously most used in wars as in non-conventional terror attacks. Perhaps the most notorious case of a lethal chemical terror attack is the 1995 Aum Shinrikyo use of Sarin gas in Tokyo’s subway.

Chemical terror incidents are characterized by the rapid onset of medical symptoms (minutes to hours) and usually easily observed marks (colored residue, dead foliage, pungent odor, and dead insect and animal life).

In the case of biological weapons, rarely used in combat in comparison to chemical weapons, the onset of symptoms caused by many of the pathogens and toxins comes hours or even days after an exposure, with typically no palpable characteristic signatures. Because of the delayed symptoms of most biological attacks and the importance of weather conditions, especially winds, have in spreading the agents from the epicenter of the attack, as well as due to the movement of infected individuals, especially in a busy metropolitan setting and its transportation systems—the area affected and the number of victims may be greater than initially thought and would entail a costly lapse of time, in terms of detection and initial treatment. A high-grade biological agent dispersed in large enough quantities and efficiently, could, in some scenarios, prove to be calamitous: one report suggests that well dispersed Anthrax (in ideal weather conditions) could inflict 20% more casualties than a 12.5 Kiloton nuclear bomb,[5] while another report suggests that 110kg of Anthrax could inflict as much damage on a densely populated metropolis, as a 1 megaton hydrogen bomb.[6]

With respect to radiological weapons, the problem of acknowledging that an attack has taken place is similar: Radiological materials are not recognizable by the senses, being colorless and odorless. Specialized equipment is required to determine the size of the effected area and whether the level of radioactivity poses an immediate or long-term health hazard. Due to the delayed onset of symptoms in a radiological incident and the role of wind conditions (as in biological weapons), the affected area may be very large.

In the nuclear realm, ever since the breakup of the former Soviet Union and the deteriorating level of control, regulation and monitoring of nuclear facilities (weapon depots and reactors)—there has been ample cause for concern. The alarm grew as more and more countries defined by the West as “rogue” or “pariah” states (Iraq, Iran, North Korea) had either successfully produced nuclear weapons or are feverishly pursuing that goal. The recent development came in October 2002, when North Korea admitted it had developed and produced nuclear weapons, contrary to its consistent previous denials and guarantees. This concern is now coming to the fore in policy discussions and strategic brainstorming, receiving ever-growing attention from intelligence services and decision-makers.

Trial testimony has revealed that Osama bin Laden’s al-Qaida training camps, for example, offered instruction in ‘urban warfare’ against ‘enemy installations’, including power plants. It is fair to assume, especially after the highly coordinated attacks on the World Trade Center and the Pentagon, that bin Laden’s disciples/operatives have done their homework and must be considered as fully capable of contemplating an attack on nuclear plants for a maximizing effect, using conventional means (for instance, airplanes). More pertinent however, it is also clear that bin Laden was seeking to acquire nuclear fissile materials (plutonium or highly enriched uranium) and the technical know-how for building atomic bombs and what is euphemistically referred to as “dirty bombs” (devices that spread radioactive contamination via the detonation of conventional high-yield explosives). Notwithstanding that, top experts believe Al-Qaida has not realized this capability as of yet.

The likelihood of CBRN-WMD terrorism has increased in the past decade and continues to do so due to a confluence of factors, most importantly the threat of sophisticated and suicidal terrorists who are not hindered by the prospect of mass killings and widespread destruction. When taking into account the willingness of individuals and groups to execute CBRN attacks on the one hand, and the vulnerability, leakage and “black market” access to and feasible production venues of CBRN materials on the other hand, the potential danger of nuclear, radiological, chemical and biological terrorist attacks taking place is not to be taken lightly.

The possibility that nihilist groups (such as al-Qaida and its ilk) could acquire the hardware, means and know-how for the construction of a nuclear device, “dirty bombs”, chemical weapons or biological agents, is of particular concern.

It is imperative to contend with this concern and provide the analysis of these odious threats (provided herein) and the optimal measures and readiness in countering them.

Based on extensive research, which included the evaluation of hundreds of
reported CBRN case studies (many of which were hoaxes), we have reached an
assessment of the threat we are faced with in terms of Chemical, Biological, Radiological and Nuclear terror. The threat is based on the motivation and
capability of perpetrators to carry out such attacks and the consequences of
a successful attack. The CBRN terrorism threat assessment herein discusses the capabilities and additional considerations required to pursue the means and execution of a terrorist attack using these four types of WMD.

The purpose of this research is threefold: to lay out the dangers, obstacles to acquire and potential consequences of CBRN attacks; to identify trends and patterns in CBRN terrorism through the exploration of data of past cases; and to discuss the prospects of these kinds of attacks in the future.

The major findings of this study are that the current motivation to carry out a CBRN incident has almost never been higher, but that the capability of a non-state entity to currently execute a CBRN incident with mass destruction consequence is still questionable.


I. Chemical weapons

Chemical warfare agents are man-made, super-toxic chemicals that can be dispersed as a gas, vapor, liquid, aerosol (a suspension of microscopic droplets), or absorbed onto a fine powder to create “dusty” agents. Basic classes of chemical agents include choking agents that damage lung tissue (e.g., chlorine, phosgene), blood agents that interfere with cellular respiration (e.g., hydrogen cyanide), blister agents that cause severe chemical burns to the skin and lungs (e.g., mustard gas), and nerve agents (e.g., VX, Sarin).

The use of chemical weapons offers many advantages to terrorists. These include the limited capacity of detecting such weapons, the relatively low cost required to develop them, their frightening image and psychological effect on the population, and potential damage (under optimal conditions- i.e., type and quantity of agent, dispersion and weather).

Chemical weapons have long been considered ”the poor man’s atomic bomb” for their relative low cost and ease of manufacture compared to an atomic bomb.


In general, terrorists thrive on the shock factor of their activities, and chemical warfare exhibits a high degree of immediate shock factor. Therefore, the use of chemical weapons might “enhance” many terrorist groups’ images (“immortalizing” them in history, as they see it) and provides and extra incentive to the ambition to wreak mass-scale casualties and havoc. This is arguably especially true for nihilistic groups such as al-Qaida. US government sources, among others, note that Osama Bin Laden has shown a strong interest in WMD and that U.S. intelligence detected chemical weapon tests by Bin Laden’s associates (as seen in the Al-Qaida tapes shown on CNN in summer 2002).

The overall efficiency of CW agents, combined with all of the previously mentioned advantages, makes a frighteningly inexpensive, undetectable, and efficient weapon—agreat motivator for those contemplating acts of mass-murder.


The lack of available detection technology makes CW agents ideal to transport and conceal due to their clandestine nature. They can either be purchased from an illegal source, such as from a former Soviet state or a sympathetic third world country, or legally purchased as industrial chemicals and later employed in an attack.

Many industrial chemicals are closely related to chemical weapons; in fact, several industrial chemicals were even employed as chemical weapons during World War I. Chlorine and Phosgene were both used extensively by Germany, Britain and France. Although these substances are far less lethal than the nerve agents, they are quite common and have many legitimate industrial applications (Ammonia is another example). Even more worrisome is that an entire class of industrial chemicals of a highly toxic nature: Organophosphates (also the class of chemicals to which Sarin and VX belong) are commonly used as insecticides and include Parathion, an insecticide notorious for the hazards it poses to those who use it.

The lethal doses required for the industrial chemicals of this class are in general ten to fifty times higher than those of the military agents. Many of these industrial agents are well-suited for use as a weapon, and their legitimate uses make it particularly difficult to regulate them: general chemical compounds suitable for use as a weapon are abundant and easily available, regardless of the method used to acquire them.

Once a terrorist group has decided to use chemical weapons and obtained them, the final hurdle is effectively using them (dissemination) without causing harm to the user. In this age of increasing education and booming technology, it is easier that in the past to find the necessary technical and mechanical assistance for such endeavor, although the barriers themselves are not to be discounted.
The gassing of the Tokyo subway with the nerve agent Sarin by the Aum Shinrikyo cult in 1995 was perhaps the clearest example of the specter and gave renewed credence to the threat of CW terrorism. Aum was an unprecedented terrorist group -both in terms of the technological sophistication and the wealth at its disposal—and its Tokyo attack represented the culmination of an elaborate five-year effort to develop viable chemical and biological weapons capability.

The cult had acquired enough of the chemical agent to kill more than a million people, and a Russian-made helicopter with a chemical sprayer. They recruited scientists from Japan’s leading schools and abroad, while spending millions of dollars exploring nuclear, biological and chemical agents.

Yet the attack, which took place during rush hour in one of the busiest cities in the world, caused 12 deaths. This actual failure to inflict mass-scale casualties is indicative of the enormous obstacles that are inherent in weaponizing and dispersing chemical agents over wide areas and affect large numbers of people (something that applies equally to biological organisms—Aum’s attempts to disseminate anthrax slurries and botulinum toxin were equally unsuccessful).

Despite this, the attack underscored intelligence failures, the relative ease with which materials can be acquired and the dangers of underestimating the imagination of terrorists. Supposedly, the group only needed a few extra hours to remix some fresh nerve agent or to have more efficiently disseminated the Sarin they had used, to have potentially killed thousands. It could be argued though, and the authors are inclined to support this view, that the Aum case may ironically be a source for optimism, in that such a well-organized and multi-resourced group was not able to execute an attack of mass destruction and that more than seven years have elapsed since that attack, with no other such unconventional incident occurring.

Additionally, recent reports that terrorists planned to disseminate hydrogen cyanide in London’s subway, serves a source for great concern. On the other hand, the fact that lethal nerve agents (such as VX and Sarin) were not obtained by the perpetrators may imply something concerning the current capability level of the said terrorists and their cronies.

To sum up, a chemical weapons attack can be potentially very harmful, depending on a matrix of location, population affected, weather conditions, material employed, dispersal techniques, civil authorities’ biohazard capabilities and the public’s education/readiness. That range is very wide – from a few injured/dead to as many as thousands and upwards.

II. Biological weapons

Subject to optimal dissemination conditions, biological weapons are more destructive than chemical weapons, including nerve gas. Under certain circumstances, biological weapons can be as devastating as nuclear ones — a few military-grade, efficiently disseminated kilograms of anthrax can kill as many people as a Hiroshima-size nuclear attack.

Of particular concern is the threat of biological agents clandestinely dispersed by terrorists. For all the horrific damage caused on September 11th via the rather unconventional use of conventional means, a biological incident would be several times worse.

Biological weapons can range in lethality, from salmonella used to temporarily incapacitate to bubonic plague engineered for mass casualties or even pneumonic plague. Biological weapons include Ricin, which an individual may use to assassinate a single targeted official/VIP, as well as pathogens such as Smallpox, with high transmissibility and broad potential impact. Biological agents may be used to kill or disable humans (more likely) or to attack plants or animals to harm a nation’s economy (less probable).

Given that broad scope, biological attacks have already taken place and continue to be a probability for the foreseeable future.[7]


Why would anyone wish to use biological weapons? A leading entity with a motive to perpetrate a biological attack could be a rogue state (as an act of clandestine warfare). The very strength of a superpower may provide an incentive for adversaries to challenge it unconventionally.

If a rogue regime were to mount such an unconventional asymmetric attack, it might choose biological weapons because of their extreme destructive potential is concentrated in a relatively small and difficult to trace package, with virtually no detectable sensor signature. Because of the agent’s incubation period, the perpetrators might be gone before anyone knew that an attack had been made. Finally, biological agents, unlike ballistic missiles, lend themselves to clandestine dissemination.

Warfare itself may be becoming more total and losing much of its political character in some situations. Biological weapons, which kill people but leave infrastructure intact, could become the “poor man’s neutron bomb.”

From a motivational perspective, such agents offer a psychologically powerful tool to instigate disorder and mayhem. Biological agents and infectious diseases are not well understood, and their use would bring about the panic, dislocation and mass casualties that characterize modern terrorism. Any group seeking to escalate violence, achieve maximum notoriety or prestige, or seriously impair a superpower, would see biological warfare as a useful instrument.


From a capability perspective, there are several operational reasons biological agents are desirable (providing the technical hurdles are surmounted):

Covert delivery averts attribution, postpones retaliation, and the delayed nature of the outbreak of an attack facilitates the escape of the perpetrators. Such weapons are relatively cheap, easy to hid, and extremely lethal, and as previously mentioned, biological agents can be as or more lethal than a nuclear bomb (a World Health Organization study indicated that five-hundred kilograms of anthrax powder, delivered by airplane over a city of 500,000 residents under favorable weather conditions, could produce 95,000 deaths). Science has enhanced the potency of pathogens, made them more stable in delivery, and more resistant to antibiotics, which could increase lethality and allow their use under less than ideal weather conditions. But again, this is much more pertinent to those actors that can actually manufacture and effectively disseminate biological weapons, i.e., states and not terrorists.

Fortunately, few groups have such resources. But were a state to provide assistance or completed products to a non-state actor, the chance of a biological disaster is much higher. Clandestine, inadvertent or indirect assistance should not be entirely ignored.

The dual nature of biological processes used in agriculture, medicinal products, breweries and pharmaceutical firms, will diffuse competence and technical skills and complicate the detection of illicit programs or suspicious activity. Ongoing developments in commercial biotechnology, biomaterials and genetic engineering will stimulate vast new developments and advances, but also complicate security concerns and unintended consequences.

Even conventional terrorism tends to escalate levels of violence to keep garnering attention. The threat of biological weapons imparts high levels of fear that may make them desirable to perpetrators who wish to terrorize, even more than kill. Threats have to become increasingly credible after the initial shock of specious threats has diminished. Even a minor biological attack, made to demonstrate credibility, could have a disproportionate impact. Thus, a certain subset of terrorists may be motivated to commit mass casualty terrorism, including biological terrorism.

Reliable and effective biological weapons are not, contrary to common belief, readily adaptable to “cookbook”-type recipes that can be implemented by novices. Nevertheless, technical expertise and sophistication vis-?-vis biological processes are more common than in the past. Moreover, technical expertise is required to produce high-quality, military-grade biological weapons and reliable means of disseminating them, especially in terrorist applications.

There is a substantial difference between the theory and practice of bioterrorism. The technical obstacles associated with the use and dissemination of biological agents are considerable and should not be underestimated. The central technical problems for bioterrorism arise when the objective is to cause mass casualties through the aerosolization of an agent.

A complicated process, aerosolization is subject to factors that are difficult to assess. For example, most of the “wet” agents (as much as 99 percent) die during the spraying process. In contrast, a dry agent is relatively simple to disseminate, but most experts agree producing it is a dangerous process almost certainly beyond the capabilities of non-state actors.

Biological agents disseminated through the air must be released in particles 1-5 microns in size so as to be retained in the lungs. Particles larger than 10 microns fall out of the air relatively quickly. Moreover, the size of the dose required for inducing illness climbs substantially as the size of the particles grows. Producing aerosol particles of the wrong size might reduce an attack to complete ineffectiveness. In addition, the particles must be released in the correct location to have the desired effect. [8]

Hence, to actually be able to improve their chances if inflicting mass casualties, a dry form of powder (with small enough particles) has to be produced/acquired by the terrorists. On the one hand, these fine powders are difficult to produce. Yet on the other hand, aerosolization and effective dispersal mechanisms are improving (although dissemination is the biggest impediment), as the terrorists themselves become more knowledgeable and potentially capable of executing mass-casualty biological weapons. News reports that al-Qaida was exploring using crop-duster planes, should be seen as an alarming notice.

Making biological weapons requires sample cultures, the means to grow, purify, and stabilize them and the means to reliably disseminate them. All these tasks pose substantial but not insurmountable challenges. There are over 1,500 biological culture “libraries” worldwide, as well as numerous research institutions that maintain sample cultures. Biological production and weapon-producing facilities can be small, inexpensive, and even inconspicuous (which is where the weight of good intelligence capabilities for detecting them is crucial). Equipment to develop BW may have legitimate commercial and research purposes, as well as nefarious ones. Unlike nuclear weapons, biological weapons do not require unique ingredients that are themselves subject to stringent arms control treaties (the Biological Weapons Convention only prohibits USE, not research or production). However, as noted, there is a great degree of difficulty is achieving the required efficient dissemination capability for the infliction of mass-scale casualties.

Cost is not much of an issue for advanced groups, since the equipment used to produce such weapons is not unique, expensive or difficult to acquire. A well-stocked bio-weapon facility can be built for as little as $2M and experts believe simpler BW can be produced for less than $1M. This is not beyond the capacity of some terrorist groups. However, pulling together all these resources and creating the multidisciplinary team of technical personnel needed in various fields (biology, aerosolization physics, etc.) to produce enough agents, stabilize, store and weaponize, not to mention effectively disseminating them, is a formidable challenge. Experts hold it to be the main reason why this capacity is currently out of the reach of non-state actors.

State-Actor Capability

Hypothetically, terrorist groups—depending on their level of sophistication and resources—may achieve the capability to build broad-impact biological weapons. The writers’ view is that currently, terror groups do not have the capability to disseminate broad-impact biological weapons, but that this situation may not last for long.

Many nations have the capability to make biological weapons, should they decide to do so. Some eighteen countries are believed to have done so, including the former Soviet Union and several nations the US State Department lists as supporting terrorism.[9]

Leakage of State Bio-Warfare Technologies

Unlike nuclear weapons and the related technology, a very small portion of the threat reduction effort in post-USSR Russia was devoted to containing biological weapons.

The scope of the biological weapons program was vast and undetected.[10] By the early 1990’s, Russian labs had weaponized plague, smallpox, anthrax, equine encephalitis, tularemia, and brucellosis. They explored the deadly Ebola virus and variations of Marburg hemorrhagic fever. Russian scientists also worked on genetically modified viral strains to make them more deadly and resistant to vaccines.

According to defectors, the USSR produced twenty tons of plague, the same of smallpox, and almost one hundred tons of anthrax. The security of these biological materials and the production knowledge behind them is extremely questionable. Sources suggest Iran and Iraq recruited assistance for biological projects from Russia, that former Soviet Union personnel are marketing their skills in Europe and that North Korea may have smallpox samples. Curtailed programs such as the one in South Africa, may have been diffused to other states or to the highest bidder. However, no open source states that any possible products of these state-rub programs have reached terrorists’ hands and leaves it as a matter for speculation for the open-source researcher. A recent event that strengthens this assessment is the uncovering of a terror cell in Europe that planned to disseminate Ricin, a relatively easily accessible biological agent and much less lethal than smallpox and other types of very lethal biological agents.

Keeping the Threat in Perspective

The disparity between threat assessments—which are often unfocused or emphasize single factors—and contingency preparedness efforts, can be partly accounted for by deficient methodologies of threat assessing, which fails to take into account all of the factors that make up the threat that is being assessed. For example, some threat assessments focus on the motivation and goals of terrorists or the potential effects of a WMD attack, yet they fail to designate which scenarios are more plausible or address their likelihood in comparison to other scenarios.

Consider, for example, a terrorist attack involving smallpox, which is often cited as the worst-case scenario, for several reasons:

First, smallpox is a highly contagious disease.

Second, the population has little or no immunity to the disease.

Third, even with large stockpiles of smallpox vaccine, given our highly mobile modern lifestyle, it would be difficult to contain an outbreak – naturally occurring or deliberate.

This threat, however, should be kept in perspective. The catastrophic effects of a smallpox attack notwithstanding, the probability of such an attack is low, especially compared to other scenarios. Smallpox, as a naturally occurring disease has been eradicated. Second, the virus that causes smallpox is openly known to exist in only two high-security laboratories (one in the US and the other in Russia, although it has been recently reported that France and North Korea possess samples of the virus as well). Hence, it would be extremely difficult for terrorists to acquire the virus. Moreover, the effects of a smallpox attack would be virtually uncontrollable and, therefore, could also affect the terrorists and their supporting constituencies. Reviewing all these factors, we conclude that a smallpox attack is a potential contingency, even, perhaps, the most damaging potential BW contingency, but the probability of occurrence is not high.

Nevertheless, smallpox has received the lion’s share of attention and has drawn attention away from the wide range of other agents that could be used (botulinum, Ricin).

Rather than solely focusing on vulnerability to a particular organism or looking to history to determine what is to come, policy makers must recognize that the bioterrorism threat is not one-dimensional.

Four key elements of the threat should be considered: the Who (the actor), the What (the agent), the Where (the target), and the How (mode of attack). The impact of a bioterrorist attack will be determined by the interaction of these components.

The more casualties bioterrorists seek to inflict, the more difficult it will be for them to assemble the necessary combination of these components. Hence, it is rational to believe that the level of probability declines as the level of desired casualties increases, because the mode of attack becomes more challenging.

Mostly due to the often-insurmountable list of technical difficulties, a catastrophic-scale bioterrorist incident is currently not a high contingency. Only the release of a very contagious or very high-quality agent by a highly efficient dissemination technique could result in thousands or more casualties. In reality, the number of pathways open to terrorists resulting in catastrophic numbers of casualties is limited, and those that do exist are technically challenging.

In contrast, based on the case studies we examined and the levels of capability, it is apparent that the number of technical pathways for the production of a low to mid-level BW incident is higher, less technically challenging and more suited to the motivations and constraints of traditional concepts of terrorism. The “WMD-terrorist” is thus left with relatively few, very challenging contingencies for inflicting mass casualties.

The Bottom line

It would be comforting to conclude that bioterrorism is beyond the pale of any terroris