The committed dose in radiological protection is a measure of the stochastic health risk due to an intake of radioactive material into the human body.
Stochastic in this context is defined as the probability of cancer induction and genetic damage, due to low levels of radiation.
The radiation risk proposed by the International Commission on Radiological Protection (ICRP) predicts that an effective dose of one sievert carries a 5.5% chance of developing cancer.
The ICRP further states "For internal exposure, committed effective doses are generally determined from an assessment of the intakes of radionuclides from bioassay measurements or other quantities (e.g., activity retained in the body or in daily excreta).
[5] The intake of radioactive material can occur through four pathways: 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 of that element.
For instance, 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 which would release radioactive iodine.
Whole body counting (WBC) is the most direct approach, but has some limitations: it cannot detect beta emitters such as tritium; it provides no chemical information about any compound that the radioisotope may be bound to; it may be inconclusive regarding the nature of the radioisotope detected; and it is a complex measurement subject to many sources of measurement and calibration error.
In occupational or accident scenarios, approximate estimates can be based on measurements of the environment that people were exposed to, but this cannot take into account factors such as breathing rate and adherence to hygiene practices.
Exact information about the intake and its biochemical impact is usually only available in medical situations where radiopharmaceuticals are measured in a radioisotope dose calibrator prior to injection.
[7] Intake of radioactive materials into the body tends to increase the risk of cancer, and possibly other stochastic effects.
The International Commission on Radiological Protection has proposed a model whereby the incidence of cancers increases linearly with effective dose at a rate of 5.5% per sievert.
Intake of very large amounts of radioactive material can cause acute radiation syndrome (ARS) in rare instances.