Biochemical Factors
Intake of radioactive material can occur through four pathways:
- inhalation of airborne contaminants such as radon,
- ingestion of contaminated food or liquids,
- absorption of vapours such as tritium oxide through the skin, or
- injection of medical radioisotopes such as technetium-99m.
An accurate evaluation of committed dose must take into account a variety of biochemical effects. The rate of biological uptake and elimination of the material will depend on its chemical nature, which is not necessarily defined by the radioisotope. The radioactive material may enter the body as part of a chemical compound, which might have very different biochemical properties from the element, and it may breakdown or undergo chemical reactions before leaving the body. Some artificial radioisotopes such as iodine-131 are chemically identical to natural isotopes needed by the body, and may be more readily absorbed if the individual has a deficit. Others have an affinity for particular tissues, such as plutonium into bone, and may be retained there for years in spite of their foreign nature.
Potassium iodide (KI), administered orally immediately after exposure, may be used to protect the thyroid from ingested radioactive iodine in the event of an accident or attack at a nuclear power plant, or the detonation of a nuclear explosive. KI would not be effective against a dirty bomb unless the bomb happened to contain radioactive iodine.
Read more about this topic: Committed Effective Dose Equivalent (CEDE)
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