In This Issue
Nuclear Dangers
June 15, 2010 Volume 40 Issue 2

Radiological Terrorism: First Responders and Communicating Risk

Tuesday, June 15, 2010

Author: John F. Ahearne


Effective communication is essential to informed decision making about radiological risks.

During the cold war, school children were taught what to do in case of a nuclear attack, and some people built underground shelters to enable them to outlast the long-term effects of such an attack. When the cold war ended, so did the exercises and the digging. However, since 2001, the public has again heard a great deal about the dangers of nuclear and radiological terrorism. In 2008, the National Academy of Engineering published Grand Challenges for Engineering in which 14 grand challenges were identified, including nuclear terror (NAE, 2008). That report states:

Long before 2001, defenders of national security worried about the possible immediate death[s] of 300,000 people and the loss of thousands of square miles of land to productive use through an act of terror. From the beginning of the nuclear age, the materials suitable for making a weapon have been accumulating around the world. Even some actual bombs may not be adequately secure against theft or sale in certain countries. Nuclear reactors for research or power are scattered about the globe, capable of producing the raw material for nuclear devices. And the instructions for building explosive devices have been widely published, suggesting that access to the ingredients would make a bomb a realistic possibility.

In the event of such an attack, responders will be called upon to go into areas where they may be exposed to radiation. In addressing potential exposures of soldiers on the battlefield, an Institute of Medicine report cautioned that although “there is a general ethical principle that one should not put individuals at risk of harm, . . . [c]ertain roles . . . carry with them an obligation to bear risk for the benefit of others.” In those cases, there “must be an analysis that supports . . . that no more risk than . . . necessary is . . . imposed or placed on the individual. . . . This includes disclosure of the risks to the person both before and after the exposure . . . .” (IOM, 1999).

The same applies to responders to a radioactive event, who should be trained to explain radiation, measure exposures, and understand the risk of entering contaminated areas following a radiological attack. Responders must also be aware of public fears of chemicals and radiation.  Studies have shown that as many as 60 to 75 percent of people believe that if an individual is exposed to a chemical that can cause cancer, that person will someday develop cancer. A similar number believe that exposure to radiation will probably lead to cancer (e.g., Slovic, 1996).

Communicating Risk

The definition of “risk” depends on culture and context. Risk in the financial world is different from risk in bridge construction and from risk in the world of religion. According to a recent definition, the factors that determine risk in the context of radiological terrorism include “(1) the hazardousness of the material, (2) its quantity, (3) the probability of release, (4) the dispersion of the hazard, (5) the population exposed, (6) organism uptake, and (7) [the] response of officials to the hazard before, during, and after release” (Greenberg et al., 2009). That description, although probably too complex to be of use for the average person, can serve as a framework for educating responders.

In addition to learning the framework for risk analysis, effective risk communication requires understanding the audience. Officials often believe the public does not and cannot understand complex situations. While the general public may not have an understanding when a crisis arises, according to Professor Baruch Fischhoff of Car-negie Mellon University, “...lay risk perceptions may be judged unfairly, leading professionals to be unduly critical of lay-people’s decision-making capabilities” (Fischhoff, 2009). He notes that “Citizens can, typically, acquire the understanding to reach reasonable conclusions, given well-prepared communications, presented at appropriate times” (personal communication). The key is having well prepared communications ready when needed.

More than two decades ago, the National Research Council recognized the necessity of taking special care when communicating risk during a crisis (NRC, 1989):

Risk managers should ensure that (1) where there is a foreseeable potential for emergency, advance plans for communication are drafted, and (2) there is provision for coordination among the various authorities that might be involved and, to the extent feasible, a single place where the public and the media can obtain authoritative and current information.

In the aftermath of the Three Mile Island accident, it became apparent that these principles should be incorporated into regulations for all nuclear power reactors, and the U.S. Nuclear Regulatory Commission has since done so.

The likelihood of panic following a radiological terrorist attack should be a strong motivator for federal, state, and local authorities to develop and practice using a communication hub. The National Council on Radiation Protection and Measurements advises that: “In preparing for or responding to terrorist incidents involving radioactive releases, it is crucial to recognize the centrality of social and psychological issues” (NCRP, 2001).

There are many other sources of information on addressing stressed individuals in a radiation incident. The International Radiation Protection Association, for example, has identified the most important issues that should be addressed in planning with responders (IRPA, 2008):

  • initiation of the process as early as possible
  • seeking out and involving relevant stakeholders and experts
  • ensuring that the roles and responsibilities of all participants are well understood and that the rules for cooperation are clearly defined

Effective risk communication is central to informed decision making about radiological risks because it establishes public confidence in the ability of individuals and organizations to deal with a radiological emergency. The keys to successful risk communication are anticipation, preparation, and practice.

High-concern situations change the rules of communication. At a recent conference the director of the Center for Risk Communication provided 12 templates for crafting messages, such as, “When responding to any high stress or emotionally charged question: provide information at four or more grade levels below the average grade level of the audience [and] be brief and concise in your first response: no more than 27 words, 9 seconds, and 3 messages” (Covello, 2010).

For examples of what not to do, we need only look back to the weeks and months following the 1986 Chernobyl accident in the Ukraine. Communication after the event was summed up by Slovic (1996): “Communication about Chernobyl was dreadful in Europe. Information messages were peppered with different terms (roentgens, curies, bequerels, rads, rems, sieverts, grays) which were explained poorly or not at all.”

A recent review of research on public understanding of issues important in a radiological emergency reported that only about 50 percent know the difference between a nuclear bomb and a “dirty” bomb and that common terms for protective action, such as “shelter in place,” are not always understood (Becker, 2010). Among responders, the review found low levels of technical knowledge and a low comfort level with radiation, which raises “serious concerns about individual and organizational preparedness for a terrorist event involving radioactive materials.” “Top Hat” exercises have been conducted to test the ability of responders.

Understanding Radiation and Hazards

Radiological terrorism is not just a theory. Attacks have been carried out in Russia and have been defined in a study by the Nuclear Safety Institute of the Russian Academy of Sciences (2005): “Radiological terrorism is carrying out technological terrorism where ionizing sources are used as defeating agents.” The Russian study describes a broad range of possible methods and devices for dispersing radioactive substances over a city or infrastructure, including placing sources of ionizing radiation in the public transport system, in subway stations or stadiums, in air flow intakes in buildings, in water supply systems, and so on.

In the same study, some possible scenarios (which could be realized in the United States as well) were analyzed:

  • the planting of a cobalt-60 gamma radiation source under a seat in a subway car
  • the detonation of a strontium-90-based dirty bomb in a subway station during rush hour (This high, but not nuclear, explosive was used in the two subway attacks in the Moscow metro in late March 2010, demonstrating terrorists’ ability to carry out such attacks.)
  • contamination of an asphalt roadway, before it enters a highway, with a liquid solution of cesium-137

The fear and stigma associated with radiation and the term “nuclear” underlies opposition to nuclear power plants. The same fears have led to the well known public-relations name change from “nuclear magnetic resonance,” an accurate description, to the more palatable “magnetic resonance imaging” (MRI); the closing of a Brookhaven research reactor after very small amounts of tritium were detected in groundwater; and opposition to the proposed Yucca Mountain nuclear spent fuel repository (Slovic, 1996). The fear of tritium, which has a 13.7 year half-life, also led the Vermont senate to vote overwhelmingly to shut down the Vermont Yankee nuclear plant after tritium leaks were found in ground measurements. The utility compounded the problem by issuing inaccurate and misleading statements.

Box 1 

Radiation Exposure

In a radiological event, first responders and later responders will face a serious obstacle. Although the average American is exposed to radiation every day, half of which is unavoidable, most people, including some responders, fear radioactivity and do not understand it. Table 1 shows the effective dose per individual in the United States in 2006.

Table 1

The total for an individual is 6.2 milliSieverts (mSv). As a reference point, a typical dental x-ray gives a patient about 0.005 mSv per image, or about 0.02 mSv—or 2 mR—for a four-image examination (NCRP, 2010). Not every individual is subject to medical exposures, but everyone is subject to background exposures. Nevertheless, as anyone who has tried to argue the insignificance of an extra milliSievert of exposure knows, routine exposures do not seem to make the general public more understanding of, or more willing to tolerate radiation.

“Dirty Bombs”

Constructing a nuclear weapon requires well trained personnel and careful construction, of course, but, most of all, it requires either plutonium or highly enriched uranium (special nuclear materials [SNMs]), which are quite difficult to obtain. Plutonium must be chemically separated from nuclear fuel that has been used in a nuclear reactor. Highly enriched uranium (HEU) can be obtained by enriching natural uranium. (The enriching process, in which Iran is currently engaged, is the reason for international concern.)

As mined, uranium is less than 1 percent U235, the fissionable isotope. The uranium used in most reactors has been enriched to 3 to 5 percent U235. The uranium most useful for a nuclear weapon (weapon-grade uranium) requires more than 90 percent U235.

Whereas SNMs to make a nuclear weapon are extremely difficult to obtain, radioactive material for a dirty bomb is not. The capability of packaging conventional explosives with radioactive material and detonating a radiological dispersal device to kill and terrorize people—the “dirty bomb” scenario—is, unfortunately, within the means of some terrorist groups (NRC, 2007). Strong ionizing radiation sources (IRSs), such as cobalt used in medical devices and cesium used to power remote devices (e.g., navigation beacons in isolated locations), are but a few of the sources of radiological materials.

According to a 2007 report by the National Research Council, “Hundreds and perhaps thousands of inadequately protected IRSs . . . are present in many countries. Some are in use, some are in storage, and some are awaiting permanent disposal . . . [S]ome IRSs have simply been abandoned . . . because there were no financially affordable disposal pathways for those that had exceeded their useful lifetimes or were no longer needed.”

Radiological material could also be obtained because of lax security. For example, at one facility in Russia two installations contain 27 sources of cobalt-60 and 15 sources of cesium-137. These materials are not being used, only stored, and there are no restrictions on approaching the facility. Another facility in Russia has 42 sources that have not been used for years and are located “in a tumbledown building . . . .” with no closed fence around it. The same report reveals that in the United States, “hundreds of unwanted IRSs have not been under adequate control, but DOE [U.S. Department of Energy], with the assistance of other federal and state agencies, has mounted an aggressive program to find, collect and secure these orphan sources . . . .” (NRC, 2007).

A “dirty bomb” used by terrorists would cause great alarm, even though the physical damage from such a device, caused by the high explosive, might be limited. Placing a radioactive source, such as Cs137, around or on the outside of a high explosive does not make a nuclear weapon, but the message that such a device has exploded may lead to public panic and understandable fear in responders. For these reasons, it is important that police and fire organizations be trained in responding to radiation-laden attacks.


Radiation remains a topic of fear to much of the public, including first responders. While a nuclear weapon detonated in a U.S. city would be catastrophic, a dirty bomb would not be. But unless the public and responders are educated in radioactivity, a dirty bomb could cause havoc.

Planning exercises for responders should include a short course on radioactivity and the use of measurement equipment. Giving responders opportunities to question experts can alleviate understandable concerns. Establishing rules of communication and periodically rehearsing these in table-top exercises can give responders the knowledge and some experience on which they can rely in times of emergency. These exercises should be repeated at least every three years.

Providing a primer on radioactivity would be a useful contribution to public education. A first step would be to provide the primer and a short course for public school teachers. Perhaps one of the National Science Foundation or U.S. Department of Education programs could be adapted for that purpose.


Becker, S.M. 2010. Risk Communication and Radiological/Nuclear Terrorism: A Strategic View. Presentation at Communication of Radiation Benefits and Risks in Decision Making, 46th Annual Meeting of NCRP, March 8–9, 2010, Bethesda, Md.

Covello, V. 2010. Presentation by director of the Center for Risk Communication at Communication of Radiation Benefits and Risks in Decision Making. The 46th NCRP Annual Meeting, March 8–9, 2010, Bethesda, Md.

Fischhoff, B. 2009. Risk Perception and Communication. Pp. 940–952 in Oxford Textbook of Public Health (5th ed.) R. Detels, R. Beaglehole, M.A. Lansang, and M. Gulliford, eds. Oxford, U.K.: Oxford University Press.

Greenberg, M.R., B.M. West, K.W. Lowrie, and H.J. Mayer. 2009. The Reporter’s Handbook on Nuclear Materials, Energy, and Waste Management. Nashville, Tenn.: Vanderbilt University Press.

IOM (Institute of Medicine). 1999. Potential Radiation Exposure in Military Operations: Protecting the Soldier Before, During, and After. Washington, D.C.: National Academy Press.

IRPA (International Radiation Protection Association). 2008. Guiding Principles for Radiation Protection Professionals on Stakeholder Engagement. Available online at

NAE (National Academy of Engineering). 2008. Grand Challenges for Engineering. Available online at  Hard copy available from NAE Program Office, 500 Fifth Street, N.W., Washington, D.C. 20001.

NCRP (National Council on Radiation Protection and Measurements). 2001. Management of Terrorist Events Involving Radioactive Materials. Report No. 138. Beth-esda, Md.: NCRP.

NCRP. 2008. NCRP Composite Glossary. Bethesda, Md.: NCRP. Available online at Composite Glossary.pdf.

NCRP. 2010. Ionizing Radiation Exposure of the Population of the United States. Report No. 160. Bethesda, Md.: NCRP.

NRC (National Research Council). 1989. Improving Risk Communication. Washington, D.C.: National Academy Press.

NRC. 2007. U.S.-Russian Collaboration in Combating Radiological Terrorism. Washington, D.C.: National Academies Press.

Nuclear Safety Institute. 2005. Opportunities for U.S.-Russian Cooperation in Combating Radiological Terrorism. Russian Academy of Sciences, Moscow.

Slovic, P. 1996. Perception of risk from radiation. Radiation Protection Dosimetry 68 (3-4): 165–180.

About the Author:John F. Ahearne is Executive Direc-tor Emeritus, Sigma Xi, The Scientific Research Society, and an NAE member.