Committed dose effect

Schlenker RA. 1986. Comparison of intake and committed dose equivalent permitted by radiation protection systems based on annual dose equivalent and committed dose equivalent for a nuclide of intermediate effective half-life. Health Phys 51 207-213. 

Kendall, G.M., Kennedy, B.W., Greenhalgh, J.R., Adams, N. Fell, T.P. (1987) Committed doses to selected organs and committed effective doses from intake of radionuclides. Report GS7. National Radiological Protection Board. Chilton, Oxon. 

Current federal and state regulations limit radiation workers doses to a total effective dose equivalent (TEDE) of 5 rem/year and a committed dose equivalent to any organ, other than the lens of the eye, of 50 rem/year (EPA 1988c USNRC 1995a). These limits apply to the sum of external and internal doses. The limits are upper limits, and an important philosophy in radiahon protection is to keep radiation doses as low as reasonably achievable (ALARA). 

The ALI is the activity of a radionuclide that can be taken into the body in a year, by inhalation or ingestion, without exceeding a committed effective dose equivalent (CEDE) of 5 rem/year or a committed dose equivalent to any organ of 50 rem/year, whichever is more limiting. The total effective dose equivalent TEDE is the sum of the CEDE and any penetrating external dose (10 CFR 20). If any external dose is present the ALI must be reduced by a proportional amount to ensure that the dose limits are not exceeded. For example, if a worker received an external dose of 1 rem/year, the ALI would have to be reduced by 20% to ensure that the TEDE did not exceed 5 rem/year. 

F. Radiation Dose (committed dose equivalent, committed effective dose)... 

Absorbed dose, organ dose, equivalent dose, effective dose, committed equivalent dose, or committed effective dose, depending on the context. The modifying terms are often omitted when they are not necessary for defining the quantity of interest. 

Effective dose equivalent (He) is the sum of the products of the tissue weighting factors (Wr) applicable to each of the body organs or tissues that are irradiated and the committed dose equivalent to the corresponding organ... 

The annual occupational dose limit to an adult radiation worker is the more limiting of (1) total effective dose of 5 rem (0.05 Sv) or (2) the sum of deep-dose equivalent and the committed dose equivalent to any individual organ or tissue, other than the lens of the eye, being equal to 50 rem (0.5 Sv). 

The Food and Drug Administration (FDA) develops standards for radioactive material concentrations in food (FDA 1998), and medical devices used in radiation therapy (FDA 1997). The FDA recently updated its guidance document that presents recommended action levels for radionuclides in foods, both domestic and imported (FDA 1998). These derived intervention levels (DILs) are estimated levels in food that could lead to individuals receiving a radiation equivalent dose equal to the FDA protection action guide (PAG) that is set as the more limiting of either 0.5 rem (5 mSv) for committed effective dose or 5 rem (50 mSv) committed dose equivalent to any individual tissue or organ. Table 8-2 presents the most restrictive DILs for strontium. 

Annual limit of intake (ALI) the amount of a radioactive material taken into the body of an adult worker in one year, by inhalation or ingestion, that would result in an effective committed dose equivalent of 0.05 Sv (5 rem) or a committed dose equivalent of 0.5 Sv (50 rem) to any single tissue or organ. 

The ICRP and the IAEA regularly issue recommendations for proper handling of radiation sources. The purposes of the recommended system of dose limitations are to ensure that no exposure is unjustified in relation to its benefits, that all necessary exposure is kept as iow as is reasonably achievable (the ALARA principle), and that the doses received do not exceed the specified limits. The ICRP stresses the values given in Table 18.11 they apply to the sum of the relevant doses from external exposure in die specified period and the SO-year committed dose (for children 70 years see also next ) in the same period. These values must be respected. They are intended to limit somatic effects in individuals, hereditary effects in the immediate offspring of irradiated individuals, and hereditary and somatic effects in the population as a whole. 

In order to relate the emissions of radioactivity from nuclear power installations or the accumulation of radioactivity in the body from fall-out to a resulting dose to the population, the ICRP has introduced the committed dose concept (equival t or effective), S... 

Radiotoxicity depends on energy deposition in tissue or organs by the radionuclide, the specific tissue exposed to the radionuclide, and the tissue radiation sensitivity. Energy deposition by a radionuclide is a function of its emitted radiations and half-life. Biokinetic studies have identified for most radionuclides of interest the pattern of movement through the body and the effective turnover rate (the sum of the biological and radioactive turnover rates). Biokinetic information also identifies the appropriate type of sample to be collected among blood, urine, feces, saliva, breath, hair, teeth, nasal swipes, and tissue obtained incidental to unrelated operations, and collection frequency. The measured radionuclide concentrations are combined with biokinetic information to calculate the committed dose equivalent, the indicator of radiation impact on the subject (NCRP 1987b). 

Figure 7-1 gives a first impression of possible effective committed doses. It shows data from the Chernobyl, Windscale and Three Mile Island accidents (collected by G. Santarossa), together with a subjective evaluation of the effects of a maximum... 

The fundamental dosimetric quantity used is the absorbed dose. The equivalent dose and the effective dose are also important quantities. Special circumstances might be characterized by committed dose, kerma dose, and some other dose quantities and factors. 

Committed doses are defined in cases of intakes of radioactive materials, mainly by ingestion, inhalation, or absorption through the skin, in terms of internal radiation impact. In most cases, the quantities of committed absorbed dose, committed equivalent dose, and committed effective... 

The SI unit of committed effective dose is Sv, the same as for effective dose. Similarly, one can derive a committed equivalent dose. The quantity of dose commitment differs from the committed dose only by the upper integration limit. It is defined as the infinite time integral (t = oo) of the per caput dose rate Hi or E) ofthe population due to a specified event. The unit of the dose commitment is the same as for committed dose. Both individual dose commitment and collective dose commitment can be defined. 

The limits apply to the sum of the relevant doses from the external exposure in the specified period and the 50- (for children 70-) year committed dose from intakes in the same period. The limitation on the effective dose to the public provides sufficient protection for the extremities (hands and feet) against stochastic effects therefore, no limitations are established for them. ... 

Accidents resulting in deterministic health effects will be very rare, and usually this will occur among employees or other professionals. However, in the case of a lost or stolen source, limited number of the general public may receive doses that can lead to deterministic health effects. Such a situation requires special medical care and supportive treatment for the early effects of acute radiation. In the event of internal exposure, especially by long-lived ra onuclides, decorporation might be considered, even if the dose is below the threshold for deterministic health effects. The decision about decorporation levels should be based on committed equivalent dose to the organs and the effective committed dose. 

The sum of the effective dose equivalent resulting from exposure to external sources and the committed effective dose equivalent incurred from all significant inhalation pathways during the early phase. Committed dose equivalents to the thyroid and to the skin may be 5 and 50 times larger respectively. 

Food item Transfer factors 241 Am concentration4 Committed effective dose ( lSv) from241 Amb ... 

Regional total effective human dose-equivalent commitment from the Chernobyl accident... 

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