1. IAEA International Atomic Energy Agency Lecture 1 – Modes of intake and ICRP biokinetic models Postgraduate Educational Course in radiation protection and the Safety of Radiation sources PART V: ASSESSMENT OF EXTERNAL AND INTERNAL EXPOSURES (OTHER THAN MEDICAL) Module V.2 - Assessment of occupational exposure due intakes of radionuclides

2. IAEA Biokinetic Models – lecture Objectives The objective of this lecture is to provide an overview of principles for development and use of biokinetic and dosimetric models for internal dose assessment. The lecture describes intake, transfer and excretion, and outlines the features of the respiratory tract and gastrointestinal tract models. At the completion of this lecture, the student should understand the principles involved in development and use of biokinetic models, as well as the need for individual specific models when intakes approach relevant limits. V.2 Lecture 1 - Modes of intakes and ICRP models2

3. IAEA Biokinetic Models - lecture Outline l Introduction l Inhalation l Ingestion l Entry through wounds and skin l Systemic activity l Excretion V.2 Lecture 1 - Modes of intakes and ICRP models3

4. IAEA Introduction V.2 Lecture 1 - Modes of intakes and ICRP models4

5. IAEA Metabolic vs. Dosimetric models l Modeling - mathematical descriptions used to describe the processes involved in physical movement of radionuclides in the body following intake, and the deposition of energy that constitutes exposure l Biokinetic modeling includes two types of models u Metabolic models u Dosimetric models V.2 Lecture 1 - Modes of intakes and ICRP models5

6. IAEA l Describe deposition and movement of radioactive material through the body l Depend on the intake mode, element, chemical form and physical form, and particle size (inhalation) l Tissues (including fluids) and organs, termed “Compartments” l Transfer routes l Transfer rates, l Excretion routes Metabolic models A B Intake C Urine Faeces a b V.2 Lecture 1 - Modes of intakes and ICRP models6

7. IAEA Dosimetric models l Address the micro and macro distribution of the radionuclide within the tissues or organs where significant deposition may occur l Take into account the radiosensitivity of source and target tissues or organs - w T l Include consideration of w R, especially for alpha emitting radionuclides l Depend on the decay properties of the radionuclide - particle type and energy l Address contribution to other target organs V.2 Lecture 1 - Modes of intakes and ICRP models7

8. IAEA ICRP recommendations on biokinetics l ICRP Recommendations on: u Assessing radionuclide intake, and u Resulting doses, u From monitoring data. l For occupationally workers, a suite of models to represent radionuclide behaviour after entry by: u Inhalation or u Ingestion V.2 Lecture 1 - Modes of intakes and ICRP models8

9. IAEA Routes of intake, transfers and excretion V.2 Lecture 1 - Modes of intakes and ICRP models9

10. IAEA Other routes of intake l For other routes of exposure, intakes are only likely to occur as a result of accidents l Almost no internationally accepted models for: u Entry through intact skin or u Wounds - see also NCRP report 156 (2006) l Exception - 3 H 2 O u Readily absorbed through intact skin. u Assumed to give additional tritium intake u Equal to 50% of the inhaled tritium V.2 Lecture 1 - Modes of intakes and ICRP models10

11. IAEA Tissue weighting factors, w T l w T introduced to calculate committed effective dose equivalent from individual tissue dose equivalents l Provided a common way of expressing external and internal doses l ICRP used w T in biokinetic models for dose equivalents to organs and tissues from: u Inhalation and u Ingestion l Earlier models didn’t fully describe biokinetics V.2 Lecture 1 - Modes of intakes and ICRP models11

12. IAEA ICRP 103 tissue weighting factors Tissue wTwT Red bone marrow, colon, lung, stomach, breast, remainder 1 0.12 Gonads0.08 Bladder, oesophagus, liver, thyroid0.04 Endosteum, brain, salivary glands, skin0.01 Total1.00 1) Remainder tissues: adrenals, extrathoracic (ET) region, gall bladder, heart, kidneys, lymphatic nodes, muscle, oral mucosa, pancreas, prostate (male), small intestine, spleen, thymus, uterus/cervix (female). V.2 Lecture 1 - Modes of intakes and ICRP models12

13. IAEA General model for radionuclides kinetics V.2 Lecture 1 - Modes of intakes and ICRP models13

14. IAEA ICRP Biokinetic models l ICRP biokinetic models are to be used in normal situations, e.g. doses from routine monitoring measurements. l Evaluation of accident doses needs specific information: u Time and pattern of intake, u Physico-chemical form of the radionuclides, u Individual characteristics (e.g. body mass). V.2 Lecture 1 - Modes of intakes and ICRP models14

15. IAEA Individual specific data Individual specific data may be obtained through special monitoring, i.e. repeated direct measurements of: l Whole body, l Specific sites and/or l Excretion measurements V.2 Lecture 1 - Modes of intakes and ICRP models15

16. IAEA Inhalation V.2 Lecture 1 - Modes of intakes and ICRP models16

17. IAEA Definitions l Aerodynamic diameter The diameter of the unit density sphere that has the same terminal settling velocity in air as the particle of interest l AMAD - Activity median aerodynamic diameter 50% of the activity (aerodynamically classified) in the aerosol is associated with particles of aerodynamic diameter (d ae ) greater that the AMAD. A log-normal distribution is usually assumed V.2 Lecture 1 - Modes of intakes and ICRP models 17

18. IAEA Definitions l Thermodynamic diameter The diameter of a spherical particle that has the same diffusion coefficient in air as the particle of interest (geometric diameter) l AMTD - Activity median thermodynamic diameter 50% of the activity (thermodynamically classified) in the aerosol is associated with particles of thermodynamic diameter (d th ) greater that the AMTD V.2 Lecture 1 - Modes of intakes and ICRP models 18

19. IAEA Definitions Biological half-life, T b The time taken for a biological system, such as a tissue compartment or the whole body, to eliminate, by natural processes other than by radioactive decay, 50% of the amount of a radionuclide that has entered it. Effective half-life, T e The time taken for the amount of a radionuclide deposited in a living organism to be reduced by 50% as a result of the combined action of radioactive decay and biological elimination. V.2 Lecture 1 - Modes of intakes and ICRP models19

20. IAEA Respiratory tract model Extrathoracic (ET) l ET 1, anterior nasal passage, l ET 2, posterior nasal and oral passages, the pharynx and larynx Thoracic l Bronchial (BB: trachea, and main bronchi), l Bronchiolar (bb: bronchioles) l Alveolar-interstitial (AI: the gas exchange region). Lymphatic tissue V.2 Lecture 1 - Modes of intakes and ICRP models 20

21. IAEA Physiological parameters For Reference Man - 176 cm height, 73 kg mass V.2 Lecture 1 - Modes of intakes and ICRP models21

22. IAEA Physiological parameters V.2 Lecture 1 - Modes of intakes and ICRP models22

23. IAEA Physiological parameters V.2 Lecture 1 - Modes of intakes and ICRP models23

24. IAEA What has been changed? l ICRP Pub. 30 treats only average lung dose l ICRP Publication 66: u Calculates doses to specific RT tissues, and u Includes differences in radiosensitivity u RT is represented by five regions n Extrathoracic (ET) airways are divided into ET 1, and ET 2 n Thoracic regions are bronchial (BB), bronchiolar (bb) and alveolar–interstitial (AI), the gas exchange region. n Lymphatic tissue is associated with the extrathoracic and thoracic respectively (LN ET and LN TH ). V.2 Lecture 1 - Modes of intakes and ICRP models24

25. IAEA Respiratory tract model features Deposition of inhaled particulates: l Calculated for each RT region l Both inhalation and exhalation are considered, as a function of: u Particle size, u Breathing parameters and/or u Work load, u Assumed independent of chemical form V.2 Lecture 1 - Modes of intakes and ICRP models25

26. IAEA Respiratory tract model features Default deposition parameters: l Age dependent l Range of particle sizes: u 0.6 nm activity median thermodynamic diameter (AMTD) to u 100  m activity median aerodynamic diameter (AMAD). l For occupationally exposed individuals, based on average daily patterns of activity V.2 Lecture 1 - Modes of intakes and ICRP models26

27. IAEA Respiratory tract model features Inhalation dose coefficients: l AMAD of 5  m - Now considered most likely for the workplace l AMAD of 1  m - Previous workplace default value l AMAD of 1  m - Default for the public V.2 Lecture 1 - Modes of intakes and ICRP models27

28. IAEA Inhalation - Deposition model l Evaluates fractional deposition in each region l Aerosol sizes of practical interest - 0.6 nm to 100 μm l ET regions u Measured deposition efficiencies related to: n Particle size n Airflow u Scaled by anatomical dimensions V.2 Lecture 1 - Modes of intakes and ICRP models28

29. IAEA Inhalation - Deposition model l Thoracic airways - theoretical model for gas transport and particle deposition is used l Calculates particle deposition in BB, bb, and AI regions l Quantifies effects of lung size & breathing rate l Regions treated as a series of filters l Efficiency is evaluated considering: l Aerodynamic processes (gravitational settling, inertial impaction) l Thermodynamic processes (diffusion) V.2 Lecture 1 - Modes of intakes and ICRP models29

30. IAEA Inhalation - Deposition model l Regional deposition fractions calculated for lognormal particle size distributions l Geometric standard deviations (  g ) - a function of the median particle diameter l From 1.0 at 0.6 nm to 2.5 above ~ 1 μm l Deposition parameters are given for three reference levels of exertion for workers u Sitting u Light exercise u Heavy exercise V.2 Lecture 1 - Modes of intakes and ICRP models30

31. IAEA Respiratory tract - Deposition V.2 Lecture 1 - Modes of intakes and ICRP models31

32. IAEA Respiratory tract - Clearance V.2 Lecture 1 - Modes of intakes and ICRP models32

33. IAEA Clearance from the respiratory tract Clearance from the respiratory tract is treated as two competing processes: l Particle transport by mucociliary clearance or translocation to lymph nodes, and l Absorption to blood V.2 Lecture 1 - Modes of intakes and ICRP models33

34. IAEA Particle transport l Treated as a function of deposition site l Independent of particle size and material l Modeled using several regional compartments with different clearance half-times, e.g. u AI region given 3 compartments, u Clearing to bb with biological half-lives of about 35, 700 and 7000 days. V.2 Lecture 1 - Modes of intakes and ICRP models34

35. IAEA Particle transport V.2 Lecture 1 - Modes of intakes and ICRP models35

36. IAEA Particle transport l Similarly, bb and BB have fast and slow clearance compartments l Clearance from the AI region also involves transfer to lymphatic tissue l For bb, BB and ET; u Compartments to represent material sequestered in tissue and transported to lymphatic tissue V.2 Lecture 1 - Modes of intakes and ICRP models36

37. IAEA Absorption into blood l Depends on the physicochemical form of the radionuclide l Independent of deposition site - Except ET 1 (no absorption is assumed). l Changes in dissolution and absorption with time are allowed V.2 Lecture 1 - Modes of intakes and ICRP models37

38. IAEA Absorption into blood l Material specific dissolution rates preferred l Use default absorption parameters if no specific information is available: F (fast) M (moderate) S (slow). l Broadly correspond to lung classes D (days), W (weeks) and Y (years), but lung classes referred to overall lung clearance rates V.2 Lecture 1 - Modes of intakes and ICRP models38

39. IAEA Absorption rates l Expressed as: u Approximate biological half-lives, and u Corresponding amounts of material deposited in each region that reach body fluids l All the material deposited in ET 1 is removed by extrinsic means, such as nose blows V.2 Lecture 1 - Modes of intakes and ICRP models39

40. IAEA Absorption rates l In other regions, most material not absorbed is cleared to the gastrointestinal tract by particle transport. l Small amounts transferred to lymph nodes are absorbed into body fluids at the same rate as in the respiratory tract. V.2 Lecture 1 - Modes of intakes and ICRP models40

41. IAEA Clearance V.2 Lecture 1 - Modes of intakes and ICRP models41

42. IAEA Absorption rates - Default values V.2 Lecture 1 - Modes of intakes and ICRP models42

43. IAEA Absorption types V.2 Lecture 1 - Modes of intakes and ICRP models43

44. IAEA Deposition of gases and vapours l Respiratory tract deposition is material specific l Inhaled gas molecules contact airway surfaces l Return to the air unless they dissolve in, or react with, the surface lining l Fraction of an inhaled gas or vapor deposited depends on its solubility and reactivity l Regional deposition of a gas or vapor obtained from in-vivo experimental studies V.2 Lecture 1 - Modes of intakes and ICRP models44

45. IAEA Solubility/reactivity classes V.2 Lecture 1 - Modes of intakes and ICRP models45

46. IAEA Deposition of gases and vapours l Guidance on the deposition and clearance of gases and vapours similar to particulates l Default SR classes and absorption types l Type F l Type V, very rapid absorption recommended for elements for which inhalation of gas or vapor form is important l Only low mass concentrations of gases and vapours is considered. V.2 Lecture 1 - Modes of intakes and ICRP models46

47. IAEA Ingestion V.2 Lecture 1 - Modes of intakes and ICRP models47

48. IAEA Ingestion - Gastrointestinal tract model l Current model (ICRP 30) has 4 compartments, u Stomach, u Small intestine, u Upper large intestine and u Lower large intestine l Uptake to blood only from the small intestine - specified by fractional uptake (f 1 ) values V.2 Lecture 1 - Modes of intakes and ICRP models48

49. IAEA V.2 Lecture 1 - Modes of intakes and ICRP models49 ICRP 30 Gastrointestinal tract model

50. IAEA New Human Alimentary Tract Model (HATM) ICRP 60 (maintained in ICRP 103) introduced specific risk estimates and w T for radiation-induced cancer of the oesophagus, stomach and colon Dose estimates needed for each region ICRP 30 model u Did not include the oral cavity or the oesophagus u Treated the colon as two regions - upper and lower large intestine. V.2 Lecture 1 - Modes of intakes and ICRP models50

51. IAEA Considerable new data is now available on material transit through the different regions of the gut Data have been obtained using non-invasive techniques New data includes: u Differences between solid and liquid phases u Age and sex related differences u Effect of disease conditions New Human Alimentary Tract Model (HATM) V.2 Lecture 1 - Modes of intakes and ICRP models51

52. IAEA Data are being used: u to determine default transit rates for the defined regions of the alimentary tract u for the 6 age groups given in ICRP 56 New information: u For morphometrical and physiological parameters, and u On the location of target cells and in different regions of the alimentary tract New Human Alimentary Tract Model (HATM) V.2 Lecture 1 - Modes of intakes and ICRP models52

53. IAEA Structure of the new HAT Model V.2 Lecture 1 - Modes of intakes and ICRP models53

54. IAEA  The HATM will be applied to the calculation of doses from ingested radionuclides in future ICRP publications on doses to workers and members of the public. These publications will give values of fractional absorption to blood, f A, for individual elements and their radioisotopes, applicable to different circumstances of occupational and environmental exposure.  Information will also be given, when available, on sites of absorption and retention. The use of alternative assumptions is encouraged in situations where specific information is available. Application of the HATM V.2 Lecture 1 - Modes of intakes and ICRP models54

55. IAEA Entry through Wounds and Skin V.2 Lecture 1 - Modes of intakes and ICRP models55

56. IAEA Entry through wounds and skin l Much of the material may be retained at the wound site, however l Soluble material can be transferred to other parts of the body via blood l Insoluble material is transported slowly to regional lymphatic tissue l Gradually dissolves and eventually enters the blood V.2 Lecture 1 - Modes of intakes and ICRP models56

57. IAEA Entry through wounds and skin l Some insoluble material can be retained at the wound site or in lymphatic tissue for life l If particulate material enters the blood, it deposits in phagocytic cells in u Liver u Spleen u Bone marrow V.2 Lecture 1 - Modes of intakes and ICRP models57

58. IAEA Entry through wounds and skin l Insoluble materials at wound sites and wound site tissues will have most radiation exposure l May need to excise contaminated tissues l Determine the variation of contamination depth at the wound site accurately V.2 Lecture 1 - Modes of intakes and ICRP models58

59. IAEA Entry through wounds and skin Absorbed dose at wound site and in regional lymph nodes can be assessed from l Activity of the deposited material, l Characteristics of the radionuclides l Mass of tissue irradiated and l Time since exposure V.2 Lecture 1 - Modes of intakes and ICRP models59

60. IAEA Entry through wounds and skin l Soluble materials may be transported from the wound site to the blood l Transportation rate depends on solubility l Distribution of the soluble component similar to material entering blood from lungs or GI, however l Some exceptions for radionuclide chemical forms entering blood directly V.2 Lecture 1 - Modes of intakes and ICRP models60

61. IAEA Entry through intact skin l Several materials can penetrate intact skin u Tritium labeled compounds, u Organic carbon compounds and u Compounds of iodine, l A fraction of these activities enter the blood l Specific models need to be developed to assess doses from such intakes, e.g. behaviour of tritiated organic compounds after direct absorption is quite different from that after inhalation or ingestion V.2 Lecture 1 - Modes of intakes and ICRP models61

62. IAEA Entry through intact skin l Both the equivalent dose to the contaminated area and the effective dose need to be considered after of skin contamination. l ICRP biokinetic models can only be used for the calculation of the effective dose arising from the soluble component, once the systemic uptake has been determined. V.2 Lecture 1 - Modes of intakes and ICRP models62

63. IAEA Systemic Activity V.2 Lecture 1 - Modes of intakes and ICRP models63

64. IAEA Intake l The fraction of an intake entering the systemic circulation is referred to as the uptake l ICRP models for radionuclides in systemic circulation are used to calculate dose coefficients l Following review of data behaviour of radionuclides in the body, a number of elemental models have been revised l Revised models were also used to calculate dose coefficients for workers V.2 Lecture 1 - Modes of intakes and ICRP models64

65. IAEA LUNG ABSORPTION TYPES AND SOURCES OF BIOKINETIC MODELS FOR SYSTEMIC ACTIVITY USED TO CALCULATE INHALATION DOSE COEFFICIENTS FOR WORKERS V.2 Lecture 1 - Modes of intakes and ICRP models65

66. IAEA Revision of systemic models l Models for several elements have been revised, particularly to account for recycling of radionuclides between compartments l Previously, a number of radionuclides (e.g. 239 Pu) were assumed to be retained on bone surfaces - a conservative assumption l Evidence indicates a fraction of plutonium is buried as a result of bone growth and turnover V.2 Lecture 1 - Modes of intakes and ICRP models66

67. IAEA Revision of systemic models l Another fraction is desorbed and re-enters the blood l Some may be re-deposited in the skeleton and liver or be excreted l In contrast, ‘bone volume seeking’ nuclides, such as 90 Sr and 226 Ra, have been assumed to instantaneously distribute in bone volume V.2 Lecture 1 - Modes of intakes and ICRP models67

68. IAEA Revision of systemic models l The process is actually progressive l Generic models for plutonium, other actinides, and for the alkaline earth metals have been developed to: u Allow for the known radionuclide behaviour u Account for knowledge of bone physiology l The model for alkaline earth metals has also been applied, with some modifications, to lead and to uranium. V.2 Lecture 1 - Modes of intakes and ICRP models68

69. IAEA Revision of systemic models V.2 Lecture 1 - Modes of intakes and ICRP models69

70. IAEA Model for Sr, Ra and U V.2 Lecture 1 - Modes of intakes and ICRP models70

71. IAEA Model for Sr, Ra and U l Skeletal activity first deposits on bone surfaces l Return to plasma or migrates to exchangeable bone volume within a few days l Some activity leaves exchangeable bone volume is assumed to return to bone surfaces l Remainder is assigned to non-exchangeable bone volume l Gradually moves to plasma by bone resorption V.2 Lecture 1 - Modes of intakes and ICRP models71

72. IAEA Model for Sr, Ra and U l Soft tissue is represented by 3 compartments, ST0, ST1, and ST2 l For radium and uranium, the liver is kinetically distinct from other soft tissues l Excretion of U through the kidney and exchange of activity between plasma and kidney tissues is also considered V.2 Lecture 1 - Modes of intakes and ICRP models72

73. IAEA Model for Th, Np, Pu, Am and Cm V.2 Lecture 1 - Modes of intakes and ICRP models73

74. IAEA l Th and Pu retention and excretion data are most easily reproduced using a 2 compartment model l Liver 2 represents retention t ½ > 1 year l Liver 1 loses a portion of its activity to the GI tract over a relatively short period (1 year) l Liver 2 shows greater retention of Pu Model for Th, Np, Pu, Am and Cm V.2 Lecture 1 - Modes of intakes and ICRP models74

75. IAEA l Am and Cm  Liver can be treated as a uniformly mixed pool, losing activity to blood and the GI tract with a T b of 1 year l Radioactive material enters Liver 1 l Part of the material is removed to the GI tract via biliary secretion l Rest goes to blood (Am) or Liver 2 (Pu, Np) l Material leaving Liver 2 is assigned to blood Model for Th, Np, Pu, Am and Cm V.2 Lecture 1 - Modes of intakes and ICRP models75

76. IAEA Model for Th, Np, Pu, Am and Cm l Kidneys are assigned two compartments, u One loses activity to urine u Another that returns activity to blood l “Urinary bladder contents” is treated as a separate pool that receives all material destined for urinary excretion V.2 Lecture 1 - Modes of intakes and ICRP models76

77. IAEA Radioactive progeny l A number of radionuclides decay to nuclides that are themselves radioactive l It has been assumed that the decay products would follow the biokinetics of their parents l A few exceptions made for decay products which are isotopes of noble gases or iodine l The revised biokinetic models apply separate systemic biokinetics to the parent and its decay products for intakes of radioisotopes of lead, radium, thorium and uranium. V.2 Lecture 1 - Modes of intakes and ICRP models77

78. IAEA Excretion V.2 Lecture 1 - Modes of intakes and ICRP models78

79. IAEA Excretion l Urinary bladder and colon have w T values l Specific information is given on excretion pathways in the urine and faeces in revised biokinetic models for workers l GI tract model is used to assess doses from systemic activity lost into the faeces l Secretion of radionuclides from the blood into the upper large intestine is assumed l A urinary bladder model has been adapted for calculating doses to the bladder wall V.2 Lecture 1 - Modes of intakes and ICRP models79

80. IAEA Dose coefficients l Dose coefficients - committed effective doses per unit intake - for ingestion and inhalation l The values of committed effective dose are: u For specific routes of intake u Cannot be used directly to assess doses from; n Injection into the blood or n Transfer to the blood from wounds or skin absorption V.2 Lecture 1 - Modes of intakes and ICRP models80

81. IAEA Dose coefficients l For many radionuclides, dose coefficients are given for different lung absorption types and/or for different f 1 values l Best choice of dose coefficient should be based on physical and chemical properties of the materials in the workplace l If there is little information on intake characteristics use the f 1 value that gives the highest dose V.2 Lecture 1 - Modes of intakes and ICRP models81

82. IAEA Workplace specific assessments l After accidental exposures, use individual and situation specific parameters to calculate equivalent doses and effective dose l In routine situations specific circumstances of exposure rather than using default parameters. l Respiratory tract model uses an AMAD of 5  m as a default particle size V.2 Lecture 1 - Modes of intakes and ICRP models82

83. IAEA Workplace specific assessments l Deposition of airborne particles is subject to: u Sedimentation u Impaction u Diffusion l Deposition and inhalation dose coefficients depend on aerosol parameters, e.g. AMAD l Ingestion dose coefficients depends on an appropriate f 1 value V.2 Lecture 1 - Modes of intakes and ICRP models83

84. IAEA Effect of particle size on aerosol deposition l Aerosol deposition of occupational concern is highest in the AI region of the thorax l AI deposition decreases with increasing particle size l Extent of deposition in each region, as well as the chemical form inhaled, has an appreciable influence on the effective dose V.2 Lecture 1 - Modes of intakes and ICRP models84

85. IAEA Influence of particle size on deposition in various regions of the respiratory tract V.2 Lecture 1 - Modes of intakes and ICRP models85

86. IAEA Effect of particle size on aerosol deposition l Committed effective dose for Type M and S 239 Pu compounds decreases with increasing AMAD l Reflects decreasing deposition in the AI region and BB and bb with increasing AMAD l In this case, the assumption of Type M characteristics is more restrictive than Type S for the calculation of effective dose l Other aerosol characteristics have slight influence on the committed effective dose V.2 Lecture 1 - Modes of intakes and ICRP models86

87. IAEA Influence of AMAD on the committed effective dose V.2 Lecture 1 - Modes of intakes and ICRP models87

88. IAEA References GSR INTERNATIONAL ATOMIC ENERGY AGENCY, Occupational Radiation Protection, Safety Guide No. RS-G-1.1, ISBN 92- 0-102299-9 (1999). INTERNATIONAL ATOMIC ENERGY AGENCY, Assessment of Occupational Exposure Due to Intakes of Radionuclides, Safety Guide No. RS-G-1.2, ISBN 92-0-101999-8 (1999). INTERNATIONAL ATOMIC ENERGY AGENCY, Indirect Methods for Assessing Intakes of Radionuclides Causing Occupational Exposure, Safety Guide, Safety Reports Series No. 18, ISBN 92-0-100600-4 (2002). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Basic Anatomical and Physiological Data for Use in Radiological Protection Reference Values. ICRP Publication 89. (2002) An. ICRP 32 (3-4). V.2 Lecture 1 - Modes of intakes and ICRP models88

89. IAEA References INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Limits for Intakes of Radionuclides by Workers, ICRP Publication 30, Part 1, Annals of the ICRP 2(3/4), Pergamon Press, Oxford (1979). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Limits for Intakes of Radionuclides by Workers, ICRP Publication 30, Part 2, Annals of the ICRP 4(3/4), Pergamon Press, Oxford (1980). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Limits for Intakes of Radionuclides by Workers, ICRP Publication 30, Part 3 (including addendum to Parts 1 and 2), Annals of the ICRP 6(2/3), Pergamon Press, Oxford (1981). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Individual Monitoring for Intakes of Radionuclides by Workers: Design and Interpretation, ICRP Publication 54, Annals of the ICRP 19(1-3), Pergamon Press, Oxford (1988). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Age-dependent Doses to Members of the Public from Intake of Radionuclides: Part 1, ICRP Publication 56, Annals of the ICRP, 20(2), Pergamon Press, Oxford (1989). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Human Respiratory Tract Model for Radiological Protection, ICRP Publication 66, Annals of the ICRP 24(1-3), Elsevier Science Ltd., Oxford (1994). V.2 Lecture 1 - Modes of intakes and ICRP models89

90. IAEA References INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Age-dependent Doses to Members of the Public from Intake of Radionuclides: Part 2, Ingestion Dose Coefficients, ICRP Publication 67, Annals of the ICRP 23(3/4), Elsevier Science Ltd., Oxford (1993). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Dose Coefficients for Intakes of Radionuclides by Workers, ICRP Publication 68. Annals of the ICRP 24(4), Elsevier Science Ltd., Oxford (1994). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Age-dependent Doses to Members of the Public from Intake of Radionuclides: Part 3, Ingestion Dose Coefficients, ICRP Publication 69, Annals of the ICRP 25(1), Elsevier Science Ltd., Oxford (1995). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Age-dependent Doses to Members of the Public from Intake of Radionuclides: Part 4, Inhalation Dose Coefficients, ICRP Publication 71, Annals of the ICRP 25(34), Elsevier Science Ltd., Oxford (1995). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Age-dependent Doses to Members of the Public from Intake of Radionuclides: Part 5, Compilation of Ingestion and Inhalation Dose Coefficients, ICRP Publication 72, Annals of the ICRP 26 (1), Pergammon Press, Oxford (1996). INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Individual Monitoring for Internal Exposure of Workers: Replacement of ICRP Publication 54, ICRP Publication 78, Annals of the ICRP 27(3-4), Pergamon Press, Oxford (1997). V.2 Lecture 1 - Modes of intakes and ICRP models90

91. IAEA References INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION, Guide for the Practical Application of the ICRP Human Respiratory Tract Model. ICRP Supporting Guidance 3. Ann. ICRP 32 (1-2). (2002) NATIONAL COUNCIL ON RADIATION PROTECTION AND MEASUREMENTS, Deposition, Retention and Dosimetry of Inhaled Radioactive Substances, NCRP Report No.125, NCRP, Bethesda (1997). NATIONAL COUNCIL ON RADIATION PROTECTION AND MEASUREMENTS, Evaluating the Reliability of Biokinetic and Dosimetric Models and Parameters Used to Assess Individual Doses for Risk Assessment Purposes, NCRP Commentary No.15, NCRP, Bethesda (1998). NATIONAL COUNCIL ON RADIATION PROTECTION AND MEASUREMENTS, Development of a Biokinetic Model for Radionuclide-Contaminated Wounds and Procedures for Their Assessment, Dosimetry and Treatment, NCRP report 156 (2006) V.2 Lecture 1 - Modes of intakes and ICRP models91