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Biological and Chemical Weapons

Frequently Asked Questions: Likelihood of Terrorists Acquiring and Using Chemical or Biological Weapons

Since the September 11th attacks on the World Trade Center and the Pentagon, the Stimson Center's Chemical and Biological Weapons Nonproliferation Project has received numerous inquiries from citizens and the media about whether terrorists could execute a chemical or biological attack. Such queries are understandable given concerns about subsequent attacks on US soil, so the project's director, Amy E. Smithson, Ph.D., answers below the most frequently asked questions. She discusses these matters in much more detail in Chapter 2 of the project's publication Ataxia: The Chemical and Biological Terrorism Threat and the US Response. Chapter 3 of Ataxia details what Aum Shinrikyo, the Japanese group responsible for the 1995 attack on the Tokyo subway system, was and was not able to achieve in its extensive efforts to acquire and use chemical weapons. While she has never made chemical or biological weapons herself, Dr. Smithson has spent a great deal of time in the company of weaponeers and defense specialists, as well as hazardous materials experts. Her responses draw from their first-hand knowledge and authoritative reference books, not speculation or hypotheses. A separate page of frequently asked questions titled "Personal Protection & Chemical or Biological Terrorism" provides information for individuals looking for ways to protect themselves and their families.

Have terrorists been actively seeking chemical and biological weapons capabilities? If so, what have they been doing with them?

Media reports that a handful of terrorist organizations have been exploring chemical and biological weapons are accurate, including the terrorist organization Al Qaeda. The terrorist group headed by Usama bin Laden may well have acquired a rudimentary chemical weapons capability, but that does not automatically translate into an ability to conduct a mass casualty attack with a chemical warfare agent. When all is said and done, there are no guarantees that terrorists groups may not overcome the technical hurdles involved. However, for the reasons discussed below, the technical hurdles to actually developing an effective large-scale chemical or biological weapons program---as opposed to investigating or experimenting with them---may well turn out to be so sizeable that terrorists would choose to remain reliant on more conventional means of attack.

Would it be easy for terrorists to acquire chemical agents?

Chemical weapons formulas have been published and publicly available for decades. Mustard agents came of age during World War I, and nerve agents were discovered in the mid-1930s. The production processes used over seventy years ago are still viable. The ingredients and equipment a group would need to produce these agents are readily available because they are also the same items that are used to make various commercial items that we use everyday---from ballpoint pens to plastics to ceramics to fireworks. Scientists with a solid chemical background could likely make certain agents in small quantities.

However, two factors stand in the way of manufacturing chemical agents for the purpose of mass casualty. First, the chemical reactions involved with the production of agents are dangerous: precursor chemicals can be volatile and corrosive, and minor misjudgments or mistakes in processing could easily result in the deaths of would-be weaponeers. Second, this danger grows when the amount of agent that would be needed to successfully mount a mass casualty attack is considered. Attempting to make sufficient quantities would require either a large, well-financed operation that would increase the likelihood of discovery or, alternatively, a long, drawn-out process of making small amounts incrementally. These small quantities would then need to be stored safely in a manner that would not weaken the agent's toxicity before being released. It would take 18 years for a basement-sized operation to produce the more than two tons of sarin gas that the Pentagon estimates would be necessary to kill 10,000 people, assuming the sarin was manufactured correctly at its top lethality.

How easy would it be for terrorists to disperse a chemical agent effectively?

The options for delivering poison gas range from high to low tech. Theoretically, super toxic chemicals could be employed to foul food or water supplies, put into munitions, or distributed by an aerosol or spray method. Because of safeguards on both our food and water supplies as well as the difficulty of covertly disbursing sufficient quantities of agent, this method is unlikely to be an effective means to achieving terrorist aims. Chemical agents could also be the payload of any number of specially designed or modified conventional munitions, from bombs and grenades to artillery shells and mines. However designing munitions that reliably produce vapor and liquid droplets requires a certain amount of engineering skill. Finally, commercial sprayers could be mounted on planes or other vehicles. In an outdoor attack such as this, however, 90 percent of the agent is likely to dissipate before ever reaching its target. Effective delivery, which entails getting the right concentration of agent and maintaining it long enough for inhalation to occur, is quite difficult to achieve because chemical agents are highly susceptible to weather conditions.

Would it be easy for terrorists to acquire biological agents?

Oftentimes, obtaining biological agents is portrayed as being as easy as taking a trip to the country. The experience of the Japanese cult Aum Shinrikyo proves that this is not the case. Isolating a particularly virulent strain in nature---out of, for example, the roughly 675 strains of botulinum toxin that have been identified---is no easy task. Despite having skilled scientists among its members, Aum was unable to do so. Terrorists could also approach one of the five hundred culture collections worldwide, some of which carry lethal strains. Within the United States, however, much tighter controls have been placed on the shipment of dangerous pathogens from these collections in recent years.

How easy would it be for terrorists to disperse a biological agent effectively?

Terrorists cannot count on just filling the delivery system with agent, pointing the device, and flipping the switch to activate it. Facets that must be deciphered include the concentration of agent in the delivery system, the ways in which the delivery system degrades the potency of the agent, and the right dosage to incapacitate or kill human or animal targets. For open-air delivery, the meteorological conditions must be taken into account. Biological agents have extreme sensitivity to sunlight, humidity, pollutants in the atmosphere, temperature, and even exposure to oxygen, all of which can kill the microbes.

Biological agents can be dispersed in either dry or wet forms. Using a dry agent can boost effectiveness because drying and milling the agent can make the particles very fine, a key factor since particles must range between 1 to 10 ten microns, ideally to 1 to 5, to be breathed into the lungs. Drying an agent, however, is done through a complex and challenging process that requires a sophistication of equipment and know-how that terrorist organizations are unlikely to possess. The alternative is to develop a wet slurry, which is much easier to produce but a great deal harder to disperse effectively. Wet slurries can clog sprayers and undergo mechanical stresses that can kill 95 percent or more of the microorganisms.

Are terrorists trying to create genetically engineered biological agents to target certain ethnic groups?

While it is impossible to know what is happening behind closed laboratory doors worldwide, anyone trying to genetically engineer a weapon to attack Americans would encounter an incredibly tall technical challenge. America, like many other nations, is populated by a wide range of ethnic groups and there is a long history of interracial marriages that makes it extremely difficult to target just one group, much less the entire country. While some governments may attempt genetic engineering of biowarfare agents, as the USSR did by hardening some agents against antibiotic treatment, terrorists just beginning to explore bioweapons would probably find this type of advanced work to be extremely difficult.

What places are terrorists likely to target for a chemical or biological agent attack?

Part of what terrorists count on to "terrorize" is that it is never really possible to know where they will strike next. Conventional wisdom says that terrorists intent on causing mass casualties would target large buildings, sporting arenas, or transit systems. Given my knowledge of how difficult it would be for terrorists to successfully execute a poison gas or germ attack, I have no concern about frequenting such locations.

Could terrorists poison the water supply?

The "pill in the water supply" is a myth about chemical terrorism that is not true. All metropolitan water supplies have certain safeguards in place between their citizens and the reservoir. Everyday, water goes through various purification processes and is tested repeatedly. If terrorists were to attempt to poison a reservoir, they would need to disperse truly huge amounts of agent into the water---smaller amounts would be diluted---and the vessels required for such a feat would be difficult to miss. Many cities have implemented heightened security around their reservoirs in order to further monitor any questionable activities.

Can crop dusters be used to disperse chemical agents?

Crop dusters are routinely employed in the agricultural industry to spread fertilizers, pesticides, and seeds. Indeed, crop dusters could be employed to spread a chemical warfare agent. However, anyone trying to commandeer a crop duster for this purpose would have to understand a multitude of factors in order to execute a chemical weapons attack. First, they would have to know how to load the spreader. Second, they would have to be able to actually take-off in a loaded crop duster, a difficult task given that the heavy weight of the loaded spreading apparatus makes take-off in a crop duster quite challenging. To use a basic analogy, the difference between taking off in a regular small aircraft versus a crop duster is similar to the difference between handling a nimble sports car versus a fully loaded double-trailer truck. Pilots of crop dusters are required to have a one-year apprenticeship to learn how to operate and fly the aircraft safely. Someone with limited piloting experience in light aircraft would be considerably challenged to translate those basic skills into an ability to get a loaded crop duster successfully off the ground.

On average, crop dusters carry between 300 to 600 gallons of material, although there are some that have an 800-gallon capacity. A 300-gallon tank could hold more than a ton of the nerve agent sarin. According to Pentagon calculations, a ton of sarin is enough to kill 10,000 people outdoors. Chemical agents, however, are very susceptible to the wind. Once in the air, the pilot would have to know how to operate the spreader and understand the meteorological patterns in the intended target area. The pilot would have to know the correct altitude over the target area to fly in order to disperse the agent effectively. In cities, where meteorological conditions can vary from block to block-with the wind whipping in currents between and around tall buildings-spreading the agent in a manner that would achieve a lethal dose would not be a simple task.
Among other individuals, I have spoken at length about the ability of crop dusters to disperse chemical or biological agents with an experienced pilot and spokesperson for an aerial application business.

Can crop dusters be used to disperse biological warfare agents?

The sprayers of crop dusters are geared to spread their materials over fields in an efficient manner, laying down fertilizer, for example, so that it settles on the crop. The key to effective biological weapons agent dispersal is exactly the opposite, to achieve a superfine aerosol spray that lingers in the air instead of settling on the ground. To infect the human lung, the required particle size of a biological warfare agent is 1 to 10 ten microns, ideally to 1 to 5. Yet, the sprayers on the average crop dusters aim to disperse in 100 micron particle sizes or greater, a heavier weight that improves the chances of the materials settling on the target area. These sprayers cannot be "dialed down," so to speak, to consistently disperse the payload in the necessary micron size.

Anyone hijacking a crop duster with the intent of spreading biowarfare agents would have to reconfigure the spraying apparatus to achieve the smaller particle size. Put another way, the nozzles would have to be changed. This changeover is, of course, technically possible, but it rules out a grab the-plane-and-go scenario. Prior to an attempted attack, the adjusted spraying apparatus would need to be tested to ensure that it would perform properly. In addition, anyone attempting this type of an attack would have to understand the correct throughput rate for the biowarfare agent involved. If the agent to be dispersed was in a wet form, the operation of the sprayer could be problematic. Wet slurries tend to clog spray nozzles. Moreover, the sheer mechanical forces of putting a wet slurry through a sprayer can kill 95 percent or more of the agent. In varying degrees, biowarfare agents are susceptible to meteorological conditions, such that once released, the microscopic particles will begin to die. In order to be effective, not only must the biowarfare agent be in a microscopic particle size, it must also be alive when it reaches the human lung.

If the individual(s) have overcome the technical hurdles involved in producing a dry biowarfare agent, dispersal from an adjusted crop duster would not be as difficult. Dry biowarfare agents do not tend to clog sprayers and are hardened against environmental conditions.
Governments, such as the former Soviet Union and the United States, when its now-defunct offensive biowarfare was operative, developed spraying equipment suitable for the dispersal of biowarfare agents. Roughly a dozen nations are now thought to be harboring offensive biological warfare weapons programs.
Among other individuals, I have spoken at length about the ability of crop dusters to disperse chemical or biological agents with an experienced pilot and spokesperson for an aerial application business.

FINAL THOUGHT:

The Japanese cult Aum Shinrikyo was brimming with highly educated scientists, yet the cult's biological weapons program turned out to be a lemon. While its poison gas program certainly made more headway, it was rife with life-threatening production and dissemination accidents. After all of Aum's extensive financial and intellectual investment, the Tokyo subway attack killed a dozen people, seriously injured just over fifty more, and mildly injured just under 1,000.

In 96 percent of the cases worldwide where chemical or biological substances have been used since 1975, three or fewer people were injured or killed.