Pediatric Terrorism and Disaster Preparedness: A ... - PHE Home

explosion, when it is concentrated in one place. The goal of terrorists is to add a
radionuclide to an existing bomb (e.g., truck bomb) to create an RDD that can
contaminate both victims and the surrounding terrain.
First responders can take several steps to avoid injury from a suspected RDD explosion.
RADIAC devices can be used to detect radioactivity at a distance, confirming the RDD.
First responders should don protective gear before entering the site and setting up a safe
perimeter. A health physicist or a nuclear-biological-chemical team can then analyze
samples using specialized laboratory equipment to determine the specific radionuclide.
Isotopes of interest. Internal contamination and casualties are most likely to occur from
common radionuclides linked to improper disposal of radioactive sources or damage to a
medical or commercial facility. Commonly used radioisotopes include high-energy
gamma emitters, such as cesium (Cs)-137, cobalt (Co)-60, and iridium (Ir)-192. These
materials are used in industrial and research applications, medical and commercial
irradiation, tracer units, thickness gauges, and calibration devices. Standard nuclear fuels,
such as uranium and plutonium (Pu) isotopes, are also relatively common. Radioactive
iodines (e.g., I-131), Cs-137, and strontium (Sr)-90 are the most medically important
fission products associated with rupture of a reactor core or radioactive fallout from
nuclear weapon detonations.
Pathophysiology. Radionuclides, their non-radioactive (stable) counterparts, toxins, and
chemicals are all governed by the same principles of toxicology. The same
pharmacokinetics also apply, as all toxic agents must be absorbed, distributed, and
expressed (through toxicological effects on target organs). Factors that determine the
amount of internal hazard are the amount of radionuclide, the energy and type of
radiation, the length of time in the body, the inherent chemical toxicity, and the critical
organ(s) affected. The greatest potential for radiological injury is from large amounts of
very energetic, long-lived radioisotopes that can affect certain critical (target) organs.
Biological half-time. Biological half-time (biological half-life) is defined as the time
required for half of a substance to be removed from the body. This number comprises
both the physical half-life and the metabolic clearance of a radioisotope. A treatment plan
can be developed by combining information on half-life and the amount of nuclide
exposure. This requires knowledge of the exposure and access to reference texts or
experts, because every isotope and chemical formulation has a different half-time. For
example, salts of Cs-137 have a half-time of 68–109 days, while tritium (H-3), Pu-239,
and soluble uranium salts have biological half-times of 8–12 days, 100 years, and 15
days, respectively.
The critical organ. The critical organ is defined as the bodily location where an isotope
exerts its primary effect. A radioisotope is chemically identical to a stable isotope of the
same element. Both are metabolized according to their chemistry, so that the critical
organ is determined by the chemical properties of the isotope.
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