This is an interesting discussion, and to be perfectly honest, I don't know a lot about dirty bombs or their potential for destruction; so I looked it up.... I'll share if you care to bear with me.
The term dirty bomb is most often used to refer to a Radiological Dispersal Device (RDD), a radiological weapon which combines radioactive material with conventional explosives. Though an RDD is designed to disperse radioactive material over a large area, the conventional explosive would likely have more immediate lethal effect than the radioactive material. At levels created from most probable sources, not enough radiation would be present to cause severe illness or death. A test explosion and subsequent calculations done by the United States Department of Energy found that assuming nothing is done to clean up the affected area and everyone stays in the affected area for 1 year, the radiation exposure would be "fairly high". However, recent analysis of the Chernobyl fallout seems to show that many people are hardly affected over 5 years and more.
Because a terrorist dirty bomb is unlikely to cause many deaths, many do not consider this to be a weapon of mass destruction. Its purpose would presumably be to create psychological, not physical, harm through ignorance, mass panic, and terror (for this reason they are sometimes called "weapons of mass disruption"). Additionally, decontamination of the affected area might require considerable time and expense, rendering affected areas partly unusable and causing economic damage.
Government "Fact Sheet":
In order to better inform the public on what a dirty bomb is and what terrorists might intend to try to accomplish in setting off such a weapon, the following information is provided. Given the scores of exercises–federal, state and local–being staged to assure that all emergency response organizations are properly equipped, trained and exercised to respond to terrorist chemical, biological or radiological attack, we believe members of the public, as well as news organizations, will value some concise, straightforward information.
Basically, the principal type of dirty bomb, or Radiological Dispersal Device (RDD), combines a conventional explosive, such as dynamite, with radioactive material. In most instances, the conventional explosive itself would have more immediate lethality than the radioactive material. At the levels created by most probable sources, not enough radiation would be present in a dirty bomb to kill people or cause severe illness. For example, most radioactive material employed in hospitals for diagnosis or treatment of cancer is sufficiently benign that about 100,000 patients a day are released with this material in their bodies.
However, certain other radioactive materials, dispersed in the air, could contaminate up to several city blocks, creating fear and possibly panic and requiring potentially costly cleanup. Prompt, accurate, non-emotional public information might prevent the panic sought by terrorists.
A second type of RDD might involve a powerful radioactive source hidden in a public place, such as a trash receptacle in a busy train or subway station, where people passing close to the source might get a significant dose of radiation.
A dirty bomb is in no way similar to a nuclear weapon. The presumed purpose of its use would be therefore not as a Weapon of Mass Destruction but rather as a Weapon of Mass Disruption.
Impact of a Dirty Bomb
The extent of local contamination would depend on a number of factors, including the size of the explosive, the amount and type of radioactive material used, and weather conditions. Prompt detectability of the kind of radioactive material employed would greatly assist local authorities in advising the community on protective measures, such as quickly leaving the immediate area, or going inside until being further advised. Subsequent decontamination of the affected area could involve considerable time and expense.
Sources of Radioactive Material
Past experience suggests there has not been a pattern of collecting such sources for the purpose of assembling a dirty bomb. Only one high-risk radioactive source has not been recovered in the last five years in the United States. However, this source (Iridium-192) would no longer be considered a high-risk source because much of the radioactivity has decayed away since it was reported stolen in 1999. In fact, the combined total of all unrecovered sources over a 5-year time span would barely reach the threshold for one high-risk radioactive source. Unfortunately, the same cannot be said world-wide. The U.S. Government is working to strengthen controls on high-risk radioactive sources both at home and abroad.
What People Should Do Following an Explosion
* Move away from the immediate area--at least several blocks from the explosion--and go inside. This will reduce exposure to any radioactive airborne dust.
* Turn on local radio or TV channels for advisories from emergency response and health authorities.
* If facilities are available, remove clothes and place them in a sealed plastic bag. Saving contaminated clothing will allow testing for radiation exposure.
* Take a shower to wash off dust and dirt. This will reduce total radiation exposure, if the explosive device contained radioactive material.
* If radioactive material was released, local news broadcasts will advise people where to report for radiation monitoring and blood and other tests to determine whether they were in fact exposed and what steps to take to protect their health.
Federation of American Scientists:
Significant amounts of radioactive materials are stored in laboratories, food irradiation plants, oil drilling facilities, medical centers, and many other sites. Cobalt-60 and cesium-137 are used in food disinfection, medical equipment sterilization, and cancer treatments. During the 1960s and 1970s the federal government encouraged the use of plutonium in university facilities studying nuclear engineering and nuclear physics. Americium is used in smoke detectors and in devices that find oil sources.
With the exception of nuclear power reactors, commercial facilities do not have the types or volumes of materials usable for making nuclear weapons. Facility owners provide adequate security when they have a vested interest in protecting commercially valuable material. However, once radioactive materials are no longer needed and costs of appropriate disposal are high, security measures become lax, and the likelihood of abandonment or theft increases.
We must wrestle with the possibility that sophisticated terrorist groups may be interested in obtaining these materials and with the enormous danger to society that such thefts might present. Significant quantities of radioactive material have been lost or stolen from US facilities during the past few years and thefts of foreign sources have led to fatalities. In the US, sources have been found abandoned in scrap yards, vehicles, and residential buildings.
If these materials were dispersed in an urban area, they would pose a serious health hazard. Intense sources of gamma rays can cause acute radiation poisoning, or even fatalities at high doses. Long-term exposure to low levels of gamma rays can cause cancer. If alpha emitters, such as plutonium, americium or other elements, are present in the environment in particles small enough to be inhaled, these particles can become lodged in the lungs and damage tissue, leading to long-term cancers.
Radiological attacks constitute a credible threat. Radioactive materials that could be used for such attacks are stored in thousands of facilities around the US, many of which may not be adequately protected against theft by determined terrorists. Some of this material could be easily dispersed in urban areas by using conventional explosives or by other methods.
Radiological attacks would not result in the hundreds of thousands of fatalities that could be caused by a crude nuclear weapon, though they could contaminate large urban areas.
Materials that could easily be lost or stolen could contaminate tens of city blocks at a level that would require prompt evacuation and create terror in large communities even if radiation casualties were low. But, since there are often no effective ways to decontaminate buildings that have been exposed at these levels, demolition may be the only practical solution.
It's the chaos, not the chemicals, that likely would cause the most harm should a "dirty bomb" explode, experts say. Heart attacks, not radiation poisoning, might claim more victims.
People within a half-mile radius of even a particularly potent dirty bomb would be exposed to less than the average dose of radiation a person receives naturally within a year, according to the American Institute of Physics' Web site. Most people who work in radiation environments annually receive 10 times the exposure of a person within a half-mile of a dirty bomb, the site states.
Stress and fear-induced heart attacks are more likely to cause deaths after a dirty bomb explosion than the radioactive material.
It's the ignorance of the actual threat that produces the most harm. People may mistakenly envision a small-scale version of the nuclear devastation experienced at Hiroshima, Japan. But the radioactive material in dirty bombs would not likely cause any more harm than that of the explosion itself, according to the Council on Foreign Relations. The size of the explosive device would dictate the extent of any death toll.
Information is the best way to combat the terror a dirty bomb would create, according to the American Institute of Physics. The site advises using radiation officers to quickly measure radiation levels, provide a realistic risk assessment and curtail public panic.
If you're a battery, you're either working or you're dead....