Recommended citation
ICRP, 2020. Dose coefficients for external exposures to environmental sources. ICRP Publication 144. Ann. ICRP 49(2).
Authors on behalf of ICRP
N. Petoussi-Henss, D. Satoh, A. Endo, K.F. Eckerman, W.E. Bolch, J. Hunt, J.T.M. Jansen, C.H. Kim, C. Lee, K. Saito, H. Schlattl, Y.S. Yeom, S.J. Yoo
Abstract - This publication presents radionuclide-specific organ and effective doserate coefficients for members of the public resulting from environmental external exposures to radionuclide emissions of both photons and electrons, calculated using computational phantoms representing the International Commission on Radiological Protection’s (ICRP) reference newborn, 1-year-old, 5-year-old, 10-year-old, 15-year-old, and adult males and females. Environmental radiation fields of monoenergetic photon and electron sources were first computed using the Monte Carlo radiation transport code PHITS for source geometries representing environmental radionuclide exposures including planar sources on and within the ground at different depths (representing radionuclide ground contamination from fallout or naturally occurring terrestrial sources), volumetric sources in air (representing a radioactive cloud), and uniformly distributed sources in simulated contaminated water. For the above geometries, the exposed reference individual is considered to be completely within the radiation field. Organ equivalent dose-rate coefficients for monoenergetic photons and electrons were next computed employing the PHITS code, thus simulating photon and electron interactions within the tissues and organs of the exposed reference individual. For quality assurance purposes, further cross-check calculations were performed using GEANT4, EGSnrc, MCNPX, MCNP6, and the Visible Monte Carlo radiation transport codes. From the monoenergetic values, nuclide-specific effective and organ equivalent dose-rate coefficients were computed for 1252 radionuclides of 97 elements for the above environmental exposures using the nuclear decay data from ICRP Publication 107. The coefficients are given as dose-rates normalised to radionuclide concentrations in environmental media, such as radioactivity concentration (nSv h-1Bq-1m² or nSv h-1Bq-1m³), and can be renormalised to ambient dose equivalent (Sv Sv-1) or air kerma free in air (Sv Gy-1). The main text provides effective dose-rate coefficients for selected radionuclides; details including age- and sex-dependent organ dose-rate coefficients are provided as an electronic supplement to be downloaded from the ICRP and SAGE websites. The data show that, in general, the smaller the body mass of the phantom, the higher the organ and effective dose due to: (1) closer proximity to the source (in the case of ground contamination); and (2) the smaller amount of body shielding of internal organs in the younger and smaller reference phantoms. The difference in effective dose between an adult and an infant is 60–140% at a photon energy of 0.05 MeV, while it is less than 70% above a photon energy of 0.10 MeV, where smaller differences are observed for air submersion and the largest differences are observed for soil contamination on the surface of the ground. For realistic exposure situations of radionuclide environmental contamination, the difference is found to be more moderate. For example, for radioactive caesium (134Cs, 136Cs, 137Cs/137mBa) deposited on and in the ground, the difference in effective dose between an adult and an infant is in the range of 30–60%, depending on the radioactivity deposition depth within the soil.
© 2020 ICRP. Published by SAGE.
Keywords: External radiation; Environmental; Effective dose; Organ equivalent dose; Dose coefficients; Ambient dose equivalent; Soil contamination; Air submersion; Water immersion.
Key Points
Reference organ and effective dose-rate coefficients are provided for external exposures of members of the public resulting from radionuclide contamination of soil, air, and water. The source profiles for soil contamination include planar sources at various specific depths, and exponential volumetric sources at different relaxation masses per unit area.
The calculations require modelling of the environmental radiation fields, computation of organ and effective dose-rate coefficients for exposures to monoenergetic photons and electrons, and the use of these data to calculate dose-rate coefficients for radionuclides, considering their emissions of gamma rays, conversion electrons, x rays, Auger electrons, and bremsstrahlung x rays. Extensive quality assurance was undertaken for all steps of the calculations.
This publication includes effective dose-rate coefficients for exposures to selected radionuclides at the ages represented by the International Commission on Radiological Protection (ICRP) reference phantoms: newborn, 1-year-old, 5-year-old, 10-year-old, 15-year-old, and adult. Full lists of effective dose-rate coefficients for the radionuclides tabulated in Publication 107 (ICRP, 2008) and the respective organ dose-rate coefficients are provided separately for males and females in an electronic supplement and a data viewer available for download. Ambient dose equivalent and air kerma rates are also given for soil contamination and air submersion.
The data show that the smaller body mass of young children will result in higher dose-rate coefficients due to smaller masses of overlying tissues shielding doses to internal organs, and increased proximity to the source in the case of soil contamination. However, age-related differences in effective dose-rate coefficients are generally not large for important radionuclides.
Executive Summary
(a) External irradiation from environmental sources of radionuclides is an important pathway of exposure to members of the public which may result from both routine discharges and major accidental releases from nuclear facilities, regions of high naturally occurring radionuclide soil concentrations, or environmental contamination following radiological terrorist events involving radioactive materials.
(b) Age-dependent dose coefficients for internal exposures have been evaluated comprehensively by the International Commission on Radiological Protection (ICRP) in Publications 56, 67, 69, 71, and 72 (ICRP, 1990, 1993, 1995a,c,d), with updates published for the reference adults in the Occupational Intakes of Radionuclides series (ICRP, 2015, 2016a,b, 2017a, 2019). However, age-dependent dose coefficients for external environmental exposures have not been evaluated previously by ICRP. These data are especially important for dose evaluation in the environment where individuals across a wide range of age groups can be potentially exposed. The purpose of this publication is, therefore, to provide reference agedependent dose-rate coefficients for external environmental exposures for members of the general public.
(c) Dose-rate coefficients are needed to evaluate effective dose from measured or evaluated data on environmental radioactivity concentrations, air kerma rates, absorbed dose-rates in air, or ambient dose equivalent rates. Calculation of dose-rate coefficients requires evaluation of the environmental field (such as exposure geometry, density and composition of soil, and radionuclide concentration distribution in the environmental media), information on the emitted radiations, anatomic computational models of the human body (such as reference voxel phantoms representing exposed members of the general public), and transport simulations of emitted radiations within both the environmental media and anatomy of the exposed individuals. Organ equivalent doses depend on body size as, in external photon exposures, increasing amounts of overlying tissue (skeletal muscle and subcutaneous fats in particular) enhance the shielding of deeper radiosensitive organs (ICRP, 2010). Resultantly, this publication considers the full range of ICRP reference individuals (newborn to adult) in these calculations.
(d) The most probable exposure scenarios were identified: exposure to contamination on or below the ground surface and at different depths (ground exposure); submersion in a contaminated atmospheric cloud (air submersion); and immersion in contaminated water (water immersion). In the first two scenarios, air-over-ground geometry and a human body standing upright above the ground surface were assumed.
(e) Organ and effective dose-rate coefficients for environmental exposures were computed for the ICRP voxel-based adult male and female reference computational phantoms in Publication 110 (ICRP, 2009a), as well as for the 10 ICRP Reference Male and Female paediatric phantoms (ICRP, 2020). These phantoms have been formally adopted by ICRP for use by Committee 2 in the development of agedependent dose coefficients following the 2007 Recommendations (ICRP, 2007).
(f) ICRP establishes, for the first time, reference dose-rate coefficients for exposure to radionuclides in the environment in ground, air, and water. Radiations considered include direct photons from radionuclide decays, scattered photons in the environment, beta particles and electrons, and bremsstrahlung x rays from beta particles and from conversion and Auger electrons. For contaminated ground and air, computations were performed in three steps. In Step 1, radiation transport of monoenergetic particles (photons and electrons) from the contaminated environment was conducted and the resulting radiation field (particle type, energy, and direction) was recorded on the surface of a virtual cylinder surrounding the exposed individual (a so-called ‘coupling cylinder’). In Step 2, the recorded particles on the surface of the coupling cylinder were transported, in turn, within the body of each of the 12 reference phantoms and monoenergetic source particles. In Step 3, values of organ equivalent dose rate for monoenergetic particles were spectrum-weighted to yield radionuclide-specific dose-rate coefficients. Additional simulations under Step 2 included the placement of an air sphere for tallying ambient dose equivalent rate and air kerma rate at a height of 1 m from the surface of the ground in order to report organ and effective dose-rate coefficients normalised to either the environmental radionuclide concentration, or measured values of ambient dose equivalent rate or air kerma rate, where the latter might be obtained from radiation environmental monitoring data.
(g) Section 1 provides an introduction and Section 2 describes the schema for dose assessment from environmental exposures. Section 3 gives a brief description of the quantities used currently in radiation protection for external environmental dosimetry. Section 4 is a brief summary of the ICRP adult and paediatric voxel phantoms employed in the calculations. Section 5 illustrates the characteristics of the environmental fields simulated, as well as the main aspects of their simulation (Step 1). Section 6 highlights the organ dose-rate simulations in the computational phantoms (Step 2). Section 7 depicts the estimation of dose-rate coefficients for radionuclides (Step 3), and Section 8 depicts the estimation of nuclide-specific dose-rate coefficients for planar sources in specific depths and volumetric sources. Section 9 gives some concluding remarks on the use and limitations of the given dose-rate coefficients.
(h) Annex A gives the reference coefficient rates for effective dose for all ages considered, ambient dose equivalent, and air kerma for selected radionuclides for soil contamination at a depth of 0.5 g cm-2, air submersion, and water immersion. Tables for all radionuclides as well as for further planar sources and exponential volumetric sources can be found in the electronic supplement which may be downloaded from the ICRP and SAGE websites.
(i) Annexes B and C discuss the special considerations for skeletal and skin dosimetry, respectively, and Annex D gives some examples of calculations of the dose-rate coefficients tabulated in this publication.
(j) The electronic supplement presents reference dose-rate coefficients for effective dose and organ equivalent doses for those organs for which tissue weighting factors are assigned in Publication 103 (ICRP, 2007) (red bone marrow, colon, lungs, stomach, breast, stomach wall, gonads, bladder wall, liver, oesophagus, thyroid, endosteum, brain, salivary glands, and skin). The organ equivalent dose-rate coefficients are given separately for the adult male and female models. In addition, dose-rate coefficients are given for ambient dose equivalent and air kerma for soil contamination and submersion in contaminated air. For description of the content of the electronic supplement, please see Annex E.
(k) A data viewer code is provided which allows interactive, comfortable viewing and downloading of the dose-rate coefficient data.
ICRP, 2020. Dose coefficients for external exposures to environmental sources. ICRP Publication 144. Ann. ICRP 49(2).
Authors on behalf of ICRP
N. Petoussi-Henss, D. Satoh, A. Endo, K.F. Eckerman, W.E. Bolch, J. Hunt, J.T.M. Jansen, C.H. Kim, C. Lee, K. Saito, H. Schlattl, Y.S. Yeom, S.J. Yoo
Abstract - This publication presents radionuclide-specific organ and effective doserate coefficients for members of the public resulting from environmental external exposures to radionuclide emissions of both photons and electrons, calculated using computational phantoms representing the International Commission on Radiological Protection’s (ICRP) reference newborn, 1-year-old, 5-year-old, 10-year-old, 15-year-old, and adult males and females. Environmental radiation fields of monoenergetic photon and electron sources were first computed using the Monte Carlo radiation transport code PHITS for source geometries representing environmental radionuclide exposures including planar sources on and within the ground at different depths (representing radionuclide ground contamination from fallout or naturally occurring terrestrial sources), volumetric sources in air (representing a radioactive cloud), and uniformly distributed sources in simulated contaminated water. For the above geometries, the exposed reference individual is considered to be completely within the radiation field. Organ equivalent dose-rate coefficients for monoenergetic photons and electrons were next computed employing the PHITS code, thus simulating photon and electron interactions within the tissues and organs of the exposed reference individual. For quality assurance purposes, further cross-check calculations were performed using GEANT4, EGSnrc, MCNPX, MCNP6, and the Visible Monte Carlo radiation transport codes. From the monoenergetic values, nuclide-specific effective and organ equivalent dose-rate coefficients were computed for 1252 radionuclides of 97 elements for the above environmental exposures using the nuclear decay data from ICRP Publication 107. The coefficients are given as dose-rates normalised to radionuclide concentrations in environmental media, such as radioactivity concentration (nSv h-1Bq-1m² or nSv h-1Bq-1m³), and can be renormalised to ambient dose equivalent (Sv Sv-1) or air kerma free in air (Sv Gy-1). The main text provides effective dose-rate coefficients for selected radionuclides; details including age- and sex-dependent organ dose-rate coefficients are provided as an electronic supplement to be downloaded from the ICRP and SAGE websites. The data show that, in general, the smaller the body mass of the phantom, the higher the organ and effective dose due to: (1) closer proximity to the source (in the case of ground contamination); and (2) the smaller amount of body shielding of internal organs in the younger and smaller reference phantoms. The difference in effective dose between an adult and an infant is 60–140% at a photon energy of 0.05 MeV, while it is less than 70% above a photon energy of 0.10 MeV, where smaller differences are observed for air submersion and the largest differences are observed for soil contamination on the surface of the ground. For realistic exposure situations of radionuclide environmental contamination, the difference is found to be more moderate. For example, for radioactive caesium (134Cs, 136Cs, 137Cs/137mBa) deposited on and in the ground, the difference in effective dose between an adult and an infant is in the range of 30–60%, depending on the radioactivity deposition depth within the soil.
© 2020 ICRP. Published by SAGE.
Keywords: External radiation; Environmental; Effective dose; Organ equivalent dose; Dose coefficients; Ambient dose equivalent; Soil contamination; Air submersion; Water immersion.
Key Points
Reference organ and effective dose-rate coefficients are provided for external exposures of members of the public resulting from radionuclide contamination of soil, air, and water. The source profiles for soil contamination include planar sources at various specific depths, and exponential volumetric sources at different relaxation masses per unit area.
The calculations require modelling of the environmental radiation fields, computation of organ and effective dose-rate coefficients for exposures to monoenergetic photons and electrons, and the use of these data to calculate dose-rate coefficients for radionuclides, considering their emissions of gamma rays, conversion electrons, x rays, Auger electrons, and bremsstrahlung x rays. Extensive quality assurance was undertaken for all steps of the calculations.
This publication includes effective dose-rate coefficients for exposures to selected radionuclides at the ages represented by the International Commission on Radiological Protection (ICRP) reference phantoms: newborn, 1-year-old, 5-year-old, 10-year-old, 15-year-old, and adult. Full lists of effective dose-rate coefficients for the radionuclides tabulated in Publication 107 (ICRP, 2008) and the respective organ dose-rate coefficients are provided separately for males and females in an electronic supplement and a data viewer available for download. Ambient dose equivalent and air kerma rates are also given for soil contamination and air submersion.
The data show that the smaller body mass of young children will result in higher dose-rate coefficients due to smaller masses of overlying tissues shielding doses to internal organs, and increased proximity to the source in the case of soil contamination. However, age-related differences in effective dose-rate coefficients are generally not large for important radionuclides.
Executive Summary
(a) External irradiation from environmental sources of radionuclides is an important pathway of exposure to members of the public which may result from both routine discharges and major accidental releases from nuclear facilities, regions of high naturally occurring radionuclide soil concentrations, or environmental contamination following radiological terrorist events involving radioactive materials.
(b) Age-dependent dose coefficients for internal exposures have been evaluated comprehensively by the International Commission on Radiological Protection (ICRP) in Publications 56, 67, 69, 71, and 72 (ICRP, 1990, 1993, 1995a,c,d), with updates published for the reference adults in the Occupational Intakes of Radionuclides series (ICRP, 2015, 2016a,b, 2017a, 2019). However, age-dependent dose coefficients for external environmental exposures have not been evaluated previously by ICRP. These data are especially important for dose evaluation in the environment where individuals across a wide range of age groups can be potentially exposed. The purpose of this publication is, therefore, to provide reference agedependent dose-rate coefficients for external environmental exposures for members of the general public.
(c) Dose-rate coefficients are needed to evaluate effective dose from measured or evaluated data on environmental radioactivity concentrations, air kerma rates, absorbed dose-rates in air, or ambient dose equivalent rates. Calculation of dose-rate coefficients requires evaluation of the environmental field (such as exposure geometry, density and composition of soil, and radionuclide concentration distribution in the environmental media), information on the emitted radiations, anatomic computational models of the human body (such as reference voxel phantoms representing exposed members of the general public), and transport simulations of emitted radiations within both the environmental media and anatomy of the exposed individuals. Organ equivalent doses depend on body size as, in external photon exposures, increasing amounts of overlying tissue (skeletal muscle and subcutaneous fats in particular) enhance the shielding of deeper radiosensitive organs (ICRP, 2010). Resultantly, this publication considers the full range of ICRP reference individuals (newborn to adult) in these calculations.
(d) The most probable exposure scenarios were identified: exposure to contamination on or below the ground surface and at different depths (ground exposure); submersion in a contaminated atmospheric cloud (air submersion); and immersion in contaminated water (water immersion). In the first two scenarios, air-over-ground geometry and a human body standing upright above the ground surface were assumed.
(e) Organ and effective dose-rate coefficients for environmental exposures were computed for the ICRP voxel-based adult male and female reference computational phantoms in Publication 110 (ICRP, 2009a), as well as for the 10 ICRP Reference Male and Female paediatric phantoms (ICRP, 2020). These phantoms have been formally adopted by ICRP for use by Committee 2 in the development of agedependent dose coefficients following the 2007 Recommendations (ICRP, 2007).
(f) ICRP establishes, for the first time, reference dose-rate coefficients for exposure to radionuclides in the environment in ground, air, and water. Radiations considered include direct photons from radionuclide decays, scattered photons in the environment, beta particles and electrons, and bremsstrahlung x rays from beta particles and from conversion and Auger electrons. For contaminated ground and air, computations were performed in three steps. In Step 1, radiation transport of monoenergetic particles (photons and electrons) from the contaminated environment was conducted and the resulting radiation field (particle type, energy, and direction) was recorded on the surface of a virtual cylinder surrounding the exposed individual (a so-called ‘coupling cylinder’). In Step 2, the recorded particles on the surface of the coupling cylinder were transported, in turn, within the body of each of the 12 reference phantoms and monoenergetic source particles. In Step 3, values of organ equivalent dose rate for monoenergetic particles were spectrum-weighted to yield radionuclide-specific dose-rate coefficients. Additional simulations under Step 2 included the placement of an air sphere for tallying ambient dose equivalent rate and air kerma rate at a height of 1 m from the surface of the ground in order to report organ and effective dose-rate coefficients normalised to either the environmental radionuclide concentration, or measured values of ambient dose equivalent rate or air kerma rate, where the latter might be obtained from radiation environmental monitoring data.
(g) Section 1 provides an introduction and Section 2 describes the schema for dose assessment from environmental exposures. Section 3 gives a brief description of the quantities used currently in radiation protection for external environmental dosimetry. Section 4 is a brief summary of the ICRP adult and paediatric voxel phantoms employed in the calculations. Section 5 illustrates the characteristics of the environmental fields simulated, as well as the main aspects of their simulation (Step 1). Section 6 highlights the organ dose-rate simulations in the computational phantoms (Step 2). Section 7 depicts the estimation of dose-rate coefficients for radionuclides (Step 3), and Section 8 depicts the estimation of nuclide-specific dose-rate coefficients for planar sources in specific depths and volumetric sources. Section 9 gives some concluding remarks on the use and limitations of the given dose-rate coefficients.
(h) Annex A gives the reference coefficient rates for effective dose for all ages considered, ambient dose equivalent, and air kerma for selected radionuclides for soil contamination at a depth of 0.5 g cm-2, air submersion, and water immersion. Tables for all radionuclides as well as for further planar sources and exponential volumetric sources can be found in the electronic supplement which may be downloaded from the ICRP and SAGE websites.
(i) Annexes B and C discuss the special considerations for skeletal and skin dosimetry, respectively, and Annex D gives some examples of calculations of the dose-rate coefficients tabulated in this publication.
(j) The electronic supplement presents reference dose-rate coefficients for effective dose and organ equivalent doses for those organs for which tissue weighting factors are assigned in Publication 103 (ICRP, 2007) (red bone marrow, colon, lungs, stomach, breast, stomach wall, gonads, bladder wall, liver, oesophagus, thyroid, endosteum, brain, salivary glands, and skin). The organ equivalent dose-rate coefficients are given separately for the adult male and female models. In addition, dose-rate coefficients are given for ambient dose equivalent and air kerma for soil contamination and submersion in contaminated air. For description of the content of the electronic supplement, please see Annex E.
(k) A data viewer code is provided which allows interactive, comfortable viewing and downloading of the dose-rate coefficient data.
