Radiological Terrorism and Public Health Lecture 13: Survey of Isotopes Steffan Puwal, PhD Source: CDC Fact Sheets, available at

Likely Isotopes for a Radiological Dispersion Device The following isotopes have been identified as primary hazards for use in a radiological dispersal device (RDD), or “dirty bomb” or release from an attack on a nuclear power facility ▫Cesium-137 ▫Iodine-131 ▫Strontium-90 ▫Cobalt-60 ▫Iridium-192 ▫Americium-241

Likely Isotopes for a Radiological Dispersion Device The risk they present derives mainly from their wide-spread use for industrial and medical purposes (ease of access) and relatively high dose rate

Cesium-137 Decays by  and  modes with a half life of 30.2 years Normally a liquid at room temperature, readily binds with chloride to form a powder the consistency of talc ▫In powder form is easily dispersed in the air ▫Very rarely found in pure, liquid form Used for calibration of radiation detectors, cancer therapy, and industrial radiography Produced by uranium fission Accidental exposure can lead to skin burns, acute radiation syndrome, and death in high doses

Cesium-137 Cs-137 is easily inhaled in powder form and is physiologically mobile ▫Leading to a whole body dose of radiation Treatment for inhalation usually involves oral administration Prussian Blue, an insoluble molecule that binds to cesium resulting in an insoluble complex

Iodine-131 I-131 decays by  and  modes with a half life of 8.06 days Sublimates at room temperature (directly from solid to gas phase) Readily soluble (dissolves easily in water, milk) Used for medical therapy to treat thyroid tumors, industrial radiography Produced as a byproduct in fission reactors Treatment involves oral administration of stable iodine

Iodine-131 Iodine is an essential dietary component for the synthesis of thyroid hormones Naturally occurring radioiodine is exceedingly rare (usually stable I-127) The National Research Council guidelines recommend no more than 150 micrograms per day consumption of iodine

Strontium-90 Decays by  mode with a half life of 29.1 years Chemically reactive in salt compounds Used as a thermal source for power generation in satellites, probes, navigational beacons, and weather stations; sometimes to treat bone cancer Pure Sr-90 is a soft, shiny silver metal usually present in powder form after a nuclear power accident or uranium fission weapon incident Ingestion is the primary route of entry Once ingested it behaves similar to calcium – and is primarily concentrated in the bone leading to bone cancers, cancers of the marrow, tumors in the soft tissue surrounding the bone, and hematopoietic symptoms

Cobalt-60 Decays by  and  modes with a half life of 5.27 years A hard, gray-blue metallic solid (that can be magnetized) Used for cancer therapy, industrial radiography, food irradiation and sterilization Non-radioactive cobalt has long been included as a blue coloring agent in ceramics and glass Co-60 is produced in accelerators for medical uses and is also a byproduct of fission reactors Exposure effects include skin burns and limited bioaccumulation in the liver, kidneys, and bones; also, acute radiation syndrome and death

Iridium-192 Decays by  and  modes with a half life of days A dense, shiny, silvery-white metal; reactive with fluorine gas to form compounds Used in industrial radiography and some cancer therapy uses Medical isotopes come in tiny seeds about the size of a grain of rice Skin burns and acute radiation syndrome are expected after exposure; ingestion is unlikely but if ingested can cause burns in the stomach and intestines

Americium-241 Decays primarily by  mode with a half life of days A solid, silver-white crystalline metal Used in medical diagnostic kits, smoke detectors, and density measurement devices Man-made from plutonium reactors Found in the environment from past nuclear testing As a dust, or fine powder it can be inhaled So, even though an  emitter, we can still get a significant internal dose

Irradiation And just so we don’t think all radioisotopes have harmful uses…

Food Irradiation FoodApproved UseDose (kGy) Recommended Spices and dry vegetable seasoning Decontaminates and controls insects and microorganisms 30 Dry or dehydrated enzyme preparations Controls insects and microorganisms 10 All foodsControls insects1 Fresh foodsDelays maturation1 PoultryControls disease-causing microorganisms 3 Red meat (beef, lamb, pork) Controls spoilage and disease causing microorganisms 4.5 (fresh) 7 (frozen)

Postal Irradiation LD 50 for inhalational anthrax is between 8,000 and 10,000 spores Postal irradiation assumes an initial population in a letter of spores AFRRI recommends a dose of 56 kGy to kill off a sufficient percentage of the population to be below LD A 3 MCi Co-60 source is typically used, and a standard letter envelope is irradiated from both sides