Effective dose (radiation safety)
Encyclopedia
The concept of effective dose is used in radiation protection as an estimate of the stochastic
effect that a non-uniform radiation
dose has on a human. It should not be confused with equivalent dose
, which is a related but more general concept. For whole-body radiation, the sum of effective doses to each region of the body add up to the whole-body effective dose for the organism. If only part of the body is radiated, then only the regions radiated are used to add up an "effective dose" which can be compared to organisms that receive a whole body "equivalent dose."
Effective dose compares the stochastic
(i.e., probabilistic) risk of a non-uniform exposure of an organism to ionizing radiation
, with the risk caused by a uniform exposure of the whole body. The stochastic risks are carcinogenesis and hereditary effects.
The effective dose is not intended as a measure for acute or threshold effects of radiation exposure such as erythema
, radiation sickness
or death.
The effective dose replaces the former effective dose equivalent (these are the same concept). It compares radiation doses on different body parts on an equivalent basis, because radiation even when corrected by radiation dose equivalent (quality) factors, does not affect different parts of the body in the same way. For example, the gonads and bone marrow are more sensitive healthwise to radiation than their simple equivalent doses suggest.
The effective dose (E) to an individual is found by calculating a weighted average of the whole-body equivalent dose
(H) to different body tissues, with the weighting factors (W) designed to reflect the contribution of different tissue exposures to the danger to the whole organism:
The weighting factors (not to be confused with RBE biological effectiveness factors) are designed to estimate the fraction of health risk, or biological effect, which is attributable to the specific tissue named. The weighting factors add up to 1.0, so that if an entire organism is radiated with uniformally penetrating external radiation, the effective dose for the entire organism is equal to the equivalent dose
for the entire organism.
The unit for effective dose is the sievert
(Sv), the same as for equivalent dose. It is measured in joule
/kilogram
(J/kg).
The International Commission on Radiological Protection
provide guidance on the risk caused by radiation. The concept of effective dose was introduced in 1977. It was then included as “effective dose equivalent” into Publication 26 by ICRP.
Stochastic
Stochastic refers to systems whose behaviour is intrinsically non-deterministic. A stochastic process is one whose behavior is non-deterministic, in that a system's subsequent state is determined both by the process's predictable actions and by a random element. However, according to M. Kac and E...
effect that a non-uniform radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
dose has on a human. It should not be confused with equivalent dose
Equivalent dose
The equivalent absorbed radiation dose, usually shortened to equivalent dose, is a computed average measure of the radiation absorbed by a fixed mass of biological tissue, that attempts to account for the different biological damage potential of different types of ionizing radiation...
, which is a related but more general concept. For whole-body radiation, the sum of effective doses to each region of the body add up to the whole-body effective dose for the organism. If only part of the body is radiated, then only the regions radiated are used to add up an "effective dose" which can be compared to organisms that receive a whole body "equivalent dose."
Effective dose compares the stochastic
Stochastic
Stochastic refers to systems whose behaviour is intrinsically non-deterministic. A stochastic process is one whose behavior is non-deterministic, in that a system's subsequent state is determined both by the process's predictable actions and by a random element. However, according to M. Kac and E...
(i.e., probabilistic) risk of a non-uniform exposure of an organism to ionizing radiation
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
, with the risk caused by a uniform exposure of the whole body. The stochastic risks are carcinogenesis and hereditary effects.
The effective dose is not intended as a measure for acute or threshold effects of radiation exposure such as erythema
Erythema
Erythema is redness of the skin, caused by hyperemia of the capillaries in the lower layers of the skin. It occurs with any skin injury, infection, or inflammation...
, radiation sickness
Radiation Sickness
Radiation Sickness is a VHS by the thrash metal band Nuclear Assault. The video is a recording of a concert at the Hammersmith Odeon, London in 1988. It was released in 1991...
or death.
The effective dose replaces the former effective dose equivalent (these are the same concept). It compares radiation doses on different body parts on an equivalent basis, because radiation even when corrected by radiation dose equivalent (quality) factors, does not affect different parts of the body in the same way. For example, the gonads and bone marrow are more sensitive healthwise to radiation than their simple equivalent doses suggest.
The effective dose (E) to an individual is found by calculating a weighted average of the whole-body equivalent dose
Equivalent dose
The equivalent absorbed radiation dose, usually shortened to equivalent dose, is a computed average measure of the radiation absorbed by a fixed mass of biological tissue, that attempts to account for the different biological damage potential of different types of ionizing radiation...
(H) to different body tissues, with the weighting factors (W) designed to reflect the contribution of different tissue exposures to the danger to the whole organism:
The weighting factors (not to be confused with RBE biological effectiveness factors) are designed to estimate the fraction of health risk, or biological effect, which is attributable to the specific tissue named. The weighting factors add up to 1.0, so that if an entire organism is radiated with uniformally penetrating external radiation, the effective dose for the entire organism is equal to the equivalent dose
Equivalent dose
The equivalent absorbed radiation dose, usually shortened to equivalent dose, is a computed average measure of the radiation absorbed by a fixed mass of biological tissue, that attempts to account for the different biological damage potential of different types of ionizing radiation...
for the entire organism.
The unit for effective dose is the sievert
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...
(Sv), the same as for equivalent dose. It is measured in joule
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...
/kilogram
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
(J/kg).
The International Commission on Radiological Protection
International Commission on Radiological Protection
The International Commission on Radiological Protection is an advisory body providing recommendations and guidance on radiation protection; It was founded in 1928 by the International Society of Radiology and was then called the ‘International X-ray and Radium Protection Committee’...
provide guidance on the risk caused by radiation. The concept of effective dose was introduced in 1977. It was then included as “effective dose equivalent” into Publication 26 by ICRP.
| Organs | |Tissue weighting factors | ||
|---|---|---|---|
| ICRP30(I36) 1979 | ICRP60(I3) 1991 | ICRP103(I6) 2008 |
|
| Gonads | 0.25 | 0.20 | 0.08 |
| Red Bone Marrow Bone marrow Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg... |
0.12 | 0.12 | 0.12 |
| Colon Colón Colón is a Spanish and Portuguese surname, comparable to the Italian and Portuguese Colombo . It may refer to:People:* Cristóbal Colón, the Spanish language name for the explorer Christopher Columbus... |
- | 0.12 | 0.12 |
| Lung Lung The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart... |
0.12 | 0.12 | 0.12 |
| Stomach Stomach The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is... |
- | 0.12 | 0.12 |
| Breast Breast The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues... s |
0.15 | 0.05 | 0.12 |
| Bladder Bladder Bladder usually refers to an anatomical hollow organBladder may also refer to:-Biology:* Urinary bladder in humans** Urinary bladder ** Bladder control; see Urinary incontinence** Artificial urinary bladder, in humans... |
- | 0.05 | 0.04 |
| Liver Liver The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion... |
- | 0.05 | 0.04 |
| Oesophagus | - | 0.05 | 0.04 |
| Thyroid Thyroid The thyroid gland or simply, the thyroid , in vertebrate anatomy, is one of the largest endocrine glands. The thyroid gland is found in the neck, below the thyroid cartilage... |
0.03 | 0.05 | 0.04 |
| Skin Skin -Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat... |
- | 0.01 | 0.01 |
| Bone Bone Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue... surface |
0.03 | 0.01 | 0.01 |
| Salivary glands | - | - | 0.01 |
| Brain Brain The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,... |
- | - | 0.01 |
| Remainder of body | 0.30 | 0.05 | 0.12 |
See also
- Radioactivity
- Radiation poisoningRadiation poisoningAcute radiation syndrome also known as radiation poisoning, radiation sickness or radiation toxicity, is a constellation of health effects which occur within several months of exposure to high amounts of ionizing radiation...
- Ionizing radiationIonizing radiationIonizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
- Collective doseCollective doseCollective dose is a measure of the total amount of effective dose multiplied by the size of the exposed population. Collective dose is usually measured in units of person-rem or person-sieverts, or man-rem or man-sievert.-References:**-See also:...
- Total effective dose equivalentTotal effective dose equivalentThe Total effective dose equivalent is a dosimetric quantity used for comparing the health effects of radiation to the human body.TEDE is used by the United States Nuclear Regulatory Commission to define dose limits for occupationally exposed individuals and members of the general public...
- Deep-dose equivalentDeep-dose equivalentThe Deep-dose equivalent is the external whole-body exposure dose equivalent at a tissue depth of 1 cm .-References:*-See also:*Radioactivity*Radiation poisoning*Ionizing radiation*Total effective dose equivalent*Collective dose...
- Cumulative doseCumulative doseCumulative dose is the total dose resulting from repeated exposures of ionizing radiation to an occupationally exposed worker to the same portion of the body, or to the whole body, over a period of time.-References:*-See also:*Radioactivity...
- Committed dose equivalent
- Certain safety factorCertain safety factorThe Certain Safety Factor is the ratio of the lethal dose to 1% of population to the effective dose to 99% of the population . This is a better safety index than the LD50 for materials that have both desirable and undesirable effects, because it factors in the ends of the spectrum where doses may...