Effects of a Dirty Bomb

Perhaps the biggest misconception about dirty bombs -- and there are many -- has to do with their effects. Although radioactive material is utilized in constructing them, they are not nuclear or atomic weapons. They do not produce a nuclear chain reaction and, therefore, the employment of such a device will not produce an "American Hiroshima." In fact, there can be a wide range of effects produced by a dirty bomb depending on the size of the IED and the amount and type of radioactive material involved. Environmental factors such as terrain, weather conditions and population density would also play an important role in determining the effects of such a device.

Generally, a dirty bomb that uses a large quantity of highly dangerous radioactive material such as plutonium-238 or cesium-137 will produce more (and stronger) contamination than a device that uses less material or material that is not as radioactive. However, the most highly radioactive materials are the hardest to obtain and the most difficult to work with. Some materials are so dangerous that even suicide bombers would die before they could use one if they were not properly shielded. For example, in September 1999, two Chechen militants who attempted to steal highly radioactive materials from a chemical plant in the Chechen capital of Grozny were incapacitated after carrying the container for only a few minutes each; one reportedly died.

There are, however, many more-common, less-dangerous materials, such as americium-241 or strontium-90, that would be easier to obtain and work with. It is therefore widely believed that terrorists wanting to construct a dirty bomb would be more likely to use one of them.

According to experts from organizations such as the National Council on Radiation Protection and Measurements, unless a large quantity of a very highly radioactive material is used, not many people will be immediately killed by the radiation released by a dirty bomb. Rather, the initial casualties will be a result of the explosive effects of the IED, just as they would be in a conventional IED attack without a radiological component. While exposure to very strong sources of radiation at close range could cause fatalities, a dirty bomb by design disperses its radiation over a larger area. Therefore, most of the deaths caused by the radiation in a dirty bomb will most likely be from causes like cancer that will take years to develop. Most people who quickly leave the area contaminated by the dirty bomb will have minimum exposure to radioactivity and should not suffer permanent health consequences.

Keep in mind, however, that a dirty bomb is intended to cause a panic -- and the explosion of such a device in a heavily populated urban area could very well result in a panic that could kill more people than the IED or the radiation it disperses.

It should also be noted that the radiological effects of a dirty bomb will be larger than the killing radius of the IED itself, and will persist for far longer. The explosion from a conventional IED is over in an instant, but radiation from a RDD can persist for decades. While the radiation level may not be strong enough to affect people who are exposed briefly in the initial explosion, the radiation will persist in the contaminated area and the cumulative effects of such radiation could prove very hazardous. (Here again, the area contaminated will depend on the type and quantity of the radioactive material used. Materials in a fine powdered form are easier to disperse than solid blocks of material and some radioactive materials possess a far longer half-life than others.) Due to this contamination, it will be necessary to evacuate people from the contaminated area in many, if not most, cases involving a dirty bomb. People will need to stay out of the area until it can be decontaminated, a process that can be lengthy and expensive.

Therefore, while a dirty bomb is not truly a weapon of mass destruction (WMD) like a nuclear device, many authorities refer to them as "weapons of mass disruption" or "weapons of mass dislocation" because of the fact that they temporarily render the contaminated areas uninhabitable. The vast expense of decontaminating a large, densely populated area, such as a section of Manhattan or Washington, would also make a dirty bomb a type of economic weapon.

The Actors

Due to the ease of constructing a dirty bomb -- which is really just an IED plus a source of radioactivity -- such a device could be employed by almost any terrorist actor ranging from a "lone-wolf" domestic terrorist to a transnational militant organization such as al Qaeda. However, when considering that the effects of such a device are more likely to be symbolic and economic, the equation begins to shift toward the al Qaeda side, as symbolic targets that harm the U.S. economy are dead in the center of the jihadist network's targeting sweet spot. Al Qaeda also has a history of planning to use such weapons.

In his recent statements about using dirty bombs against U.S. bases in Iraq, al-Muhajer did not present a novel idea. Many in the jihadist universe have a strong fascination with WMDs, and many jihadist Web sites, such as chat rooms and online magazines, regularly post information on how to produce chemical agents, biological toxins, RDDs and even improvised nuclear weapons. Some posts provide instructions on where to obtain radioactive material and, in cases where it cannot be obtained, even purport to provide instruction on how to extract radioactive material from commercial materials, such as distilling radium from luminescent industrial paint.

More specifically to al Qaeda, evidence uncovered in Afghanistan following the U.S. invasion demonstrated that the group was actively pursuing a WMD program that included research on chemical, biological, nuclear and radiological weapons. Based on this evidence, and information obtained from the interrogations of captured high-level al Qaeda members, U.S. intelligence agencies have specifically and repeatedly warned since late 2001 that al Qaeda intends to produce and employ a RDD. When these reports surface, the flow cycle of public concern over RDDs begins anew.

Despite the simplicity of manufacturing dirty bombs, however, they are not often used, possibly due at least in part to their ineffectiveness. Governments such as that of Iraq that experimented with dirty bombs for military purposes abandoned them because they were not effective enough to be militarily significant as a weapon or provide much of a deterrent.

Perhaps the group that has used or attempted to use RDDs the most is the Chechen militants. In November 1995, Chechen militants under commander Shamil Basayev placed a small quantity of cesium-137 in Moscow's Izmailovsky Park. Rather than disperse the material, however, the Chechens used the material as a psychological weapon by directing a television news crew to the location and thus creating a media storm. The material in this incident was thought to have been obtained from a nuclear waste or isotope storage facility in Grozny.

In December 1998, the pro-Russian Chechen Security Service announced it had found a dirty bomb consisting of a land mine combined with radioactive materials next to a railway line. It is believed that Chechen militants planted the device.

The Bottom Line

Analytically, based upon the ease of manufacture and the jihadist interest in dirty bombs, it is only a matter of time before jihadists employ one. Since the contamination created by such a device can be long-lasting, more rational international actors probably would prefer to detonate such a device against a target that is outside of their own country. In other words, they would lean toward attacking a target within the United States or United Kingdom rather than the U.S. or British Embassy in their home country.

Since it is not likely to produce mass casualties, a dirty bomb attack would likely be directed against a highly symbolic target, such as one representing the economy or government, and designed to cause the maximum amount of disruption at the target site. Therefore, it is not out of the question to imagine such an attack aimed at Wall Street or the Pentagon. The bomb would not destroy these sites, but would deny access to them for as long as it takes to clean up the sites.

Due to the history of RDD threats, the U.S. government has invested a great deal of money in radiation detection equipment, and has strategically located that equipment along the border at ports of entry and near critical sites. If the rumors of radioactive materials being smuggled over the Mexican border are true, the terrorists would want to detonate the device in a city close to the border out of fear that this network of detection systems would allow the material to be detected and seized by U.S. authorities before it could be employed.

The Importance of Contingency Plans

The possibility of an RDD attack underscores the importance of having personal contingency plans. This is especially important for those who live or work near one of these potential targets. In the case of a dirty bomb attack, it will be important to stay calm. Panic, as we have said, could potentially kill more people than the dirty bomb itself. The best countermeasure against irrational panic is education. People who understand the capabilities and limitations of dirty bombs are less likely to panic than those who do not.

People caught in close proximity to the detonation site, then, should avoid breathing in the dust as much as possible and then calmly leave the area, paying attention to the instructions given to them by authorities. If possible, they also should bathe and change clothes as soon as possible, and implement their personal or family emergency plan. People not in the immediate vicinity of the dirty bomb should seek shelter where they are -- making sure to close windows and doors and turn off air conditioners -- unless they are instructed to go elsewhere.

However, should communication from the authorities break down or the authorities not provide instruction, the three most important things to remember about protecting oneself from radiation are time, distance and shielding. That means minimizing the time of exposure, maximizing the distance between the person and the radiation source and maximizing the amount of shielding between the person and the radiation source.