There has been an ongoing process within ICRP to reexamine the basis for estimating risks at low doses and dose rates and to review the detriment calculations. This document testifies a comprehensive treatment of the subject and the outcome has landed in a detailed position paper that not only reviews the currently available information on detriment assessments but, more importantly, identifies improvements that should be considered in future. There has been a large number of parameter variations, sensitivity analyses were done, and several comparisons were made. Some results were obvious from the start, e.g. the dependence from the choice of DDREF or lifetime versus worktime.
The paper clearly illustrates the complexity with the current detriment calculation process where not all steps are easy to follow for non-specialists. The conclusion on better transparency is therefore highly recommended. To take into account a variety of readers in the radiation protection community, the objective or purpose of the document within the frame of science, research, and application of results from these to the practical radiation protection should be more thoroughly clarified in the text. At the moment the clearest clarification is given only on p. 67, where the scope of the work of the Task Group 102 is described. If the items (a) to (d) were explained in the very introduction of the report, many of the questions raising up especially in the audience in the practical radiation protection, would be clarified, such as if there are, and what kind of, direct consequences on practical radiation protection. Without this “setting of the frame”, the text leads the reader to start asking questions that remain unanswered in this report, such as “why the detriment is calculated, or what is correct value”.
The methodology of assessing the detriment is currently divided into two main parts by the ICRP, where the calculation of nominal risks is radiation related and an adjustment is made for lethality, quality of life and years of life lost. This paper as well as some underlying references emphasizes several items that need to be adjusted in future for both parts. New scientific knowledge has evolved since 1990/2000 not only on radiation effects but also in other areas of relevance for cancer radiation risk assessments. ICRP is therefore encouraged to continue the process of updating the methodology and its application, especially taking into account new input data as recommended in the report.
The general opinion that the radiation protection system has to be practical and pragmatic should not be taken as an excuse to discount todays scientific understanding of radiation effects. One of the major challenges is however the extrapolation of biological effects observed at high does to low doses. In particular the application of the DDREF concept in conjunction with LQ dose response curve needs to be reassessed in light of the best scientific evidence. There is variable support for the LNT model by epidemiological studies (Shore et al. 2018 J Radiol Prot 38, 1217) and it is tempting to here quote the British physicist Rees: Absence of evidence is not evidence of absence. For example, UNSCEAR’s studies indicate significant uncertainties relating cancers especially at doses below 100 mGy, and as the doses decrease the uncertainty increases. Therefore the assumption of LNT as well as the justification of DDREF remain important points for further calculations and analyses.
From the point of view of the practical radiation protection, it is of utmost importance that any major changes should not be introduced before the scientific basis supporting them is sufficiently firm and mature. Therefore it would good to have at least a brief discussion included in the report about the way, how ICRP see the process from the basic research to the recommendations in radiation protection, and what is the position of this document in this process. As such it is clear that further work is required, exactly as identified in the document, before the calculation of detriment is sufficiently mature to consider major changes in the current practice of radiation protection.
To conclude, the chapter 5 of the document (and its summary in part 6.3) proposing a number of things which should be done to make the concept more understandable, the data base more defendable etc. is deeply acknowledged.