Responding to 'Dirty Bombs'

The lowdown on Radiological Dispersal Devices: what, why, and how to respond.

SINCE the 9/11 attacks, there have been many media reports on "Dirty Bombs." The U.S. Nuclear Regulatory Commission, the Federal Emergency Management Agency, and the Department of Homeland Security have fact sheets regarding Dirty Bombs on their Web sites. The reality is that a Dirty Bomb is only one of a number of methods (explosives, aerosol spray, mechanical, etc.) that may be used to spread radioactive contamination over a large area as part of a terrorist attack. The inclusive term for these various methods is Radiological Dispersal Device, or RDD.

Media hype aside, there is a real threat an RDD may be used against the United States because the terrorist networks under the Al Qaeda umbrella need to overcome the image the United States and its allies are winning the war against terror. The threat is real, so the need to prepare for such an attack is real.

RDDs are devices or methods that spread radioactive contamination over a large area or adulterate a food/water supply. The media and various government agencies usually characterize this threat as being a "Dirty Bomb"--where an explosive device is salted with radioactive material. The intent is to use the force of the explosion to spread the radioactive material over a target area. Depending on the physical form of the radioactive material, other RDDs can be crop dusters, insecticide sprayers, or even the simple act of dumping material out on the streets. Recently the NOVA science TV series on the Public Broadcasting Service aired a program on Dirty Bombs and discussed the other methods. Information from the program and additional material are posted at, which is a good starting point for learning about this form of attack.

Materials and Rationale
The only essential ingredient for an RDD is a source of radioactive materials. There are thousands of small sources of radioactivity used by industry and medicine throughout the United States. Examples of these are radiography sources, cancer therapy devices, density gauges, and smoke detectors. Most of the sources are too small to cause any concern, but there is a significant number that would be strong enough to use in an RDD.

These sources were not closely regulated previously because they could not be used to make a nuclear weapon, but now it is realized they could be the basis for an RDD. A common isotope used in industry and medicine is Cesium 137 (Cs-137). Cs-137 is normally found in a powdered form as Cesium Chloride and is water-soluble. The Nuclear Regulatory Commission and the Department of Energy are developing programs to identify the sources that would be sought for the construction of an RDD and are establishing tracking systems, but these will not be fully in effect for some time.

So an RDD can be a simple device where all the components can be purchased or stolen within the United States. But its only real effect is as a weapon of fear. Why would a terrorist group use an RDD as a method of attack if it cannot cause direct damage? RDDs are often called weapons of disruption, due to the fear that people in the United States have of radioactivity. It is assumed this fear will cause panic and mass hysteria; this is the value in using an RDD as a method of attack. It would be assumed to cause to economic damage by causing a shutdown of business in the area affected and from the costs of decontaminating the affected area. The fear factor regarding radioactivity makes this form of attack something spectacular, although no major casualties or damage would occur.

Oddly enough, a recent enemy of the United States proved the lack of direct casualties resulting from a Dirty Bomb attack. One of the items United Nations weapons inspectors discovered after the Gulf War was that Iraq conducted a series of tests in 1987 to determine whether a Dirty Bomb was a viable military weapon. The Iraqi tests determined a Dirty Bomb had no value as a military weapon because the levels of contamination would at best increase the incremental cancer risk of personnel in the target area. The levels of contamination were too low to produce acute effects. That RDDs are incapable of producing acute health effects is a key point for responders to note.

The Al Qaeda network has suffered a number of serious setbacks since the 9-11 attacks, with its sanctuary in Afghanistan lost and many of its leaders killed or captured. The network has been unable to launch attacks that really compare to the terrible damage of the 9/11 attacks. Therefore, Al Qaeda and its associates are looking for something to regain prestige. The FBI stated in a recent bulletin that sources suggest the network "may favor spectacular attacks that meet several criteria: High symbolic value, mass casualties, severe damage to the U.S. economy and maximum psychological trauma." In a recent briefing to Congress, the director of the Central Intelligence Agency stated: "If given the choice, Al Qaeda terrorists will choose attacks that achieve multiple objectives--striking prominent landmarks, inflicting mass casualties, causing economic disruption, rallying support through shows of strength."

Both of these statements speak of causing economic disruption, and both refer to the need for Al Qaeda to do something spectacular to show supporters it is still a threat. Given that the construction of an RDD is simple and the materials are available throughout the United States, the probability increases for its use by Al Qaeda.

How Responders Should Prepare
What can first responders do to counter this threat? First, local emergency response agencies, in concert with their state authorities, should determine whether their community is a possible target. Symbolic landmarks, transportation hubs, and key business are the most obvious targets. Size alone does not make a target; Al Qaeda desperately needs the next attack to be successful and will not go against our strength. So a small city may be selected, if an attack there could have the impacts the CIA and the FBI have stated would be the objectives of an Al Qaeda attack.

If the community is a potential target for an RDD, what should first responders do to prepare? In order to respond effectively, first responders need to understand the relative hazards of radioactive contamination. Many first responders are not trained to any great extent on radioactive material response and have little knowledge of the effects of radioactive materials. They also are very concerned by the potential for exposure to radioactivity. The radiation exposure limits for emergency responders and the potential dose that requires an off-site emergency plan for a facility using radioactive materials are based on incremental cancer risk, not acute effects.

The best comparison is that the EPA guidance for radiological accidents states that evacuation of the public should be considered if the projected dose is from 1-5 roentgen equivalent man (rem); if the projected dose is greater than 5 rem, then evacuation is required.

Compare this to the EPA Risk Management Program (RMP) for non-radioactive hazardous materials. The RMP uses the Emergency Response Planning Guideline Level 2 (ERPG-2) as the basis to determine whether a facility must conduct off-site emergency planning (warning system, evacuation) for the public adjacent to the facility. When acute effects are compared, the ERPG-2 is equivalent to an acute exposure to 100 rem. (The ERPGs do not account for incremental cancer, whereas the radiation exposure limits do account for this.)

So detailed emergency plans are made for facilities that have radioactive materials, but if the same basis as the RMP were used, no plan would be required. The key fact here is that it takes an acute exposure in the 100 rem range before any onset of radiation sickness is likely to been seen. The emphasis on controlling risk is pervasive in that personnel who work with radioactive material on a daily basis literally forget acute doses in the 1-25 rem range will not result in radiation sickness. The direct effects are low and the long-term effects can be avoided or mitigated by the use of standard hazmat response procedures.

The use of an RDD can be compared to someone using a device to spread friable asbestos over a large area. The asbestos will not kill or injure anyone on the day of the event, but it has the potential to cause life-threatening illness later if enough is inhaled. The response to the contamination of a large area by asbestos should be the same given to the spread of radioactive material. Terrorists who would use an RDD are counting on the fear of radioactivity by responders to slow down the response to the attack; they assume the first responders will hesitate.

The protocols responders would use if the hazardous material were friable asbestos are the same ones that should be used if radioactive contamination is present. The real threat from most forms of radioactive contamination is the ingestion or inhalation of the material, just as it is with asbestos. The use of Personal Protective Equipment, control zones, and decontamination are pretty much the same.

The key to a successful response is equipment and training. Because there is a real possibility an RDD may be employed or hoaxes regarding the release of radioactive material may occur, it is important that first responders have the ability to determine the presence of radioactivity. It should be a standard practice to conduct a radiation survey at the scene of any suspicious explosion, particularly if the site meets the criteria mentioned in the FBI bulletin. One of the methods discussed in the NOVA program was an attack where the material is spread and the terrorists do not announce what they have done for several days. The delay in taking credit will allow the dispersion of the material by weather and contact with people and vehicles.

To meet this challenge, first responders need to be equipped and trained on the use of the equipment. The problem is getting the funding for both.

Many emergency response agencies have some radiation detection capability, but often it is old civil defense equipment designed for a much larger amount of radioactivity than probably would be seen after use of an RDD. The Office of Domestic Preparedness has a program in place where the Department of Energy is providing surplus radiation detection equipment to emergency response agencies. This is known as the Homeland Defense Equipment Reuse (HDER) Program, and the Health Physics Society is providing volunteer assistance in training and technical support. Information on this program can be found at ODP's Web site ( and the society's site (

Federal Training & Information Programs
Once first responders have the ability to detect and measure radioactivity, normal hazmat procedures with minor adjustment can be used effectively. FEMA, ODP, and the Department of Energy have hands-on training programs for first responders in radioactive material incident response. FEMA also has a self-study course (available at Once the emergency response organizations have the training and equipment, then plans can be developed.

FEMA offers examples of radiological incident response plans, and the Department of Energy's Transportation Emergency Preparedness Program (TEPP) has developed generic plans and procedures ( for responding to radioactive material incidents. These resources will provide a framework for the development of a plan and procedures.

In the planning process, it is critical to approach the situation as a mass contamination event--not something totally exotic. Most first responders should be able to respond as effectively to an RDD event as any other hazardous material release. The real problem is going to be the reaction of the public to the announcement radioactivity has been released in the community. The only way to overcome the fear that public has is to approach this problem in a similar manner to what the RMP uses for chemical hazards.

The response agencies need to engage the Local Emergency Planning Committee and start an information campaign in the local media demonstrating the training and planning that has been done. The committee needs to be involved because many members are businesses that would be affected and have resources that may be needed. Drills and exercises should be presented in a positive light to increase their confidence in the ability of responders to handle such an event. Evacuation planning needs to be updated and tested, and arrangements made with neighboring communities to provide shelter and assistance if large areas are evacuated.

Public meetings should be held to inform the public about the response to an RDD or other acts of terrorism. If the public is informed and confident the community's emergency responders are prepared, it is more likely people will follow the instructions given to them during an actual event.

Keep the Problem in Perspective
To sum up, an RDD is not just a dirty bomb, it's anything that can spread radioactive contamination across a community. The Al Qaeda terror network has investigated the development and use of these devices. Al Qaeda needs to mount a spectacular attack to regain prestige and gain supporters, so the use of an RDD is a real possibility.

The response to an RDD is similar to any mass contamination event, but it requires personnel trained and equipped to handle the hazards presented. As with any hazardous material incident, if the training, equipment, and plans are not in place before it happens, the response is going to go badly.

An RDD is a weapon based on fear. Both responders and the public must understand the real hazards and how to mitigate them. The response to an RDD is not some exotic event that requires resources way beyond those of most local emergency response organizations.

This article originally appeared in the September 2003 issue of Occupational Health & Safety.

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