|The commission’s work on developing a framework for protection of the environment is needed. The concept of RAPs, being used as points of reference when assessing impacts on many different representative organisms, could well become a valuable help for those making site specific assessments.
Points of reference
In order to become such points of reference, there is a need of knowledge about the RAPs life characteristics, transfer of radionuclides in their environment and to themselves, relevant dose models and probable effects coupled to relevant doses. The current report deals with the transfer part, whereas the other parts have been covered in earlier ICRP reports.
The very fundamental aspect of a point of reference is that it is well defined, so that you know where you are when standing at this point. Compilations of transfer data e.g. in the ERICAtool has shown that transfer is very variable for a given combination of organism and radionuclide. This is also the case for this compilation of CR-values. This report is a first step to provide some transfer data for RAPs, and work is continuing to improve the knowledge about transfer to RAPs, but I believe the report needs to further discuss the applicability of points of references when, at this stage, the location of these points are not always well defined. How could the presented values be used, and what is the recommended (by ICRP) use of the values.
IAEA and ICRP
As mentioned in this ICRP report there is an ongoing work to compile CR-data in a living database www.wildlifetransferdatabase.org from which CR-values could be extracted and used as relevant.
Currently two separate international organizations have made their extractions of data and plan to publish their results (IAEA handbook on wildlife transfer, and ICRP transfer to RAPS). The work is in part done by the same persons, and in effects parts of the text in the two reports would be identical. This might be a bit confusing for those persons not directly involved in the work and needs to be explained. A suggestion is that this ICRP report refer to the IAEA handbook as a compilation of available CR-values at the level of broad organism groups, and that this ICRP report follows the same general methodology (which still could be described in the report), but with the difference in aim clearly pointed out, i.e. to compile data as specific as possible for the RAPs and providing derived values if no values are available in the database (again following methodologies presented/ suggested in the IAEA handbook).
When discussing the resulting CR-values, it would be valuable to point out any differences compared to what was found for the IAEA-handbook and to discuss the reasons for these differences and justify that the ICRP RAP value in deed is more appropriate for the RAP than the value given in the IAEA-handbook for a broader group.
(Another source of CR data to which the derived values possibly could be compared and discussed, would be CR-values derived with allometric methods e.g. as given in Resrad biota. As the RAPs are well defined in terms life characteristics (size, what they eat etc) this might well be possible to achieve).
CR-values in the report
In general the report would benefit from more guidance on how to use the values given for the RAP, given that a variation over 2 orders of magnitude for a CR is not uncommon.
It is for example questionable if it is useful to give only the best estimate value, without any information on e.g. variation, in the tables in the main report. If values are used deterministically in a screening assessment, one might not want to use the best estimate, but rather something more conservative (e.g. 95th percentile), and if you perform a probabilistic realistic assessment you would need information on the known variation in the CR. In both cases the reader would need to consult the tables in annexes rather than main report tables.
Chapter 4 is an important chapter where the values for each RAP should be discussed. In the draft version of the report, the depth and content of this discussion varies between the different RAPs. It includes whether CRs are at all applicable, the number and robustness of CRs directly available in the database and the robustness of those derived, environmental factors known to be affecting the site specific CRs. But not all aspects are covered for all RAPs. In some cases the discussion ends with question marks rather than guidance.
The idea of reference sites in order to increase the knowledge about transfer to RAPs in a systematic way, covering a range of environmentally different sites, seems appropriate.
Comments to specific paragraphs
(4) is missing
(6) The report states that it intends to fill the gap in reference data that could be used to relate exposure to different release rate scenarios. It is rather giving data to relate exposure to media concentration.
(82) The paragraph starts discussing the use of stable elements and justifies its use in marine environment. The latter part states that the situation is different in freshwater (does not say in what respect) and continues discussing differences between substances under homeostatic control and others. The logic of the argumentation could be improved.
Table 4.1 -4.4: It could be questioned whether these tables only giving best estimate value would ever be used, in most cases one would need information on the variation too, so that tables in appendix would be the ones that is actually used.
(89, 1212) The statement “it is not therefore immediately apparent which environmental media activity concentration, if any, should constitute the starting point in the derivation of CR values” does not help the reader. Especially as there is no further discussion considering duck CR for freshwater. I think ICRP also need to present their conclusions on similar issues, not only pointing out the apparent questions.
(93) This paragraph gives a discussion on important environmental factors giving rise to some of the variation in CR seen at different sites. It also points out how the CRs are affected. It would be valuable if similar paragraphs could be added for other ecosystems, radionuclides and RAPs.
(94) Would not the first sentence be applicable to all RAPs?
(97) The data coverage is given as a percentage for seaweed, but as number of radionuclides for the other RAPs. Suggest changing “50%” to “20 out of the 40”
(100) Make the word flatfish bold
(102) For comparison, it is known that moose calves in Sweden have a higher content of Cs-137 than adults (40% according to Palo et al., 20% according to SSM monitoring results).