Overall the report is well done and provides a comprehensive presentation of biokinetic and dosimetric modelling approaches, monitoring and retrospective dose assessment. The sections on uncertainty and variability are appreciated. Below please find a few comments and suggestions.
1. Line 226: the subscript “R” should be defined in the definition of absorbed fraction.
2. Line 286: The term “t” (tau), used in the expression hT(t), should be defined – it is unclear if it is intended to be the same as tD (tau sub D), which is used later in the definition (online 287).
3. Line 307: The dose of record is assessed using material-specific parameters in some cases, e.g., absorption Type and/or AMAD/AMTD specific to the material taken in, and using the parameters of the reference worker, e.g., systemic biokinetic model parameters are not changed. The only exception to this is the retrospective assessment of intakes of tritiated water or elemental tritiated gas (see for example, IAEA Safety Report Series No. 37): the linear interpolation method inherently considers the individual-specific biological half-time of tritiated water. It would be beneficial for the text to address the case of doses from intakes of tritiated water.
4. Line 316: The term “z” should be defined. Also, z(t) is defined here as the bioassay function, however, page 21 (line 714) defines m(t) as the bioassay function.
5. Line 345: The term “organ dose” is not defined; however, it is unclear whether the intent was to write “organ absorbed dose” as per line 376. Moreover, line 366 uses the symbol DT for the “Mean absorbed dose in an organ or tissue”. In line 345 the symbol DR(rT) is used but does not appear to be defined in the document. The text should clarify whether the intent is to use the “Mean absorbed dose in an organ or tissue” in line 343.
6. Line 418: “HATM, HATM” should be changed to “HATM, HRTM”.
7. Line 459: The term “radiation dose” is not defined in the document. It is suggested to change the definition of target tissue to “Tissue or organ of the body that is exposed to radiation emitted from all source regions”.
8. Lines 516, 518 and 521: The definitions for SR-0, SR-1 and Sr-2 should specify this classification applies to gases and vapours.
9. Line 643: In the proposed definition of intake, absorption through skin, injection, and intakes through a wound are not considered. It is suggested to define intake as activity that enters the body, either via the respiratory tract, the gastrointestinal tract, a wound, by injection, or by absorption through intact skin.
10. Line 755: For clarity, the text should be change from “… the daily excretion rate (Bq d-1, Bq l-1, or Bq kg-1)” to “… the daily excretion rate (Bq d-1) or concentration (Bq l-1, or Bq kg-1)”.
11. Line 1051: Paragraph 29 states that the committed absorbed dose is calculated, knowing the number of decays occurring in source regions and energy deposition in target regions. This is not consistent with the methodology for dose calculation presented in section 3.7, where the equivalent dose in target tissue rT per nuclear transformation in source region rS is calculated. Committed absorbed dose is not calculated. The first calculation of committed dose is identified in equation 2 of section 3.7, which is the calculation of the committed equivalent dose in the target tissue for the reference male or female.
12. Line 1365: The text should clarify that for purposes of comparison with dose limits and dose recording, the committed effective dose that is assigned to a calendar year is calculated for intakes that have occurred during the calendar year.
13. Line 1458: Paragraph 62 defines the DAC using the sex-averaged breathing rate of 1.1 m3 h-1, resulting in a DAC that is about 10% greater than the DAC as defined in the glossary (see line 282). The discrepancy should be resolved.
14. Line 1971: The text mentions “another study”. The reference to this study should be provided.
15. Line 2664: The “activity in the fast phase of clearance” (from compartment bb1) should be modified to refer to transport rather than clearance.
16. Line 3687: Guidance on the how to define the breathing zone of a worker would be helpful.
17. Line 3890: The reference Stradling 2004 could not be found in the reference section.
18. Line 4395: The recommendation to subtract contributions implies that if the individual’s retention or excretion T1/2 is less than that predicted by the model, then the corrected dose could be negative.
19. Line 4402: The text should clarify how far back in time previous intakes should be considered.