Submitted by Anna Friedl, German Commission on Radiation Protection Commenting on behalf of the organisation
Comments of German Commission on Radiological Protection (SSK)
The efforts to clarify the procedures of detriment calculation used by ICRP are highly appreciated. We fully agree with the following statement: "As the methodology of detriment calculation changes, ensuring transparency and traceability is important. A full description of calculation steps is necessary ... . It is also desirable to improve the presentation of the radiation detriment so that non-specialists can have a balanced perspective on the health risks of radiation." We highly welcome increased transparency resulting from these clarifications, which allows discussing individual aspects of the detriment concept and possible needs for adjustment in the future. In particular, we highly appreciate that this increased transparency will allow separating science-based risk assessment and subsequent pragmatic simplification/integration for protection purposes. For the latter, a discussion of the balance between uncertainties associated with the detriment estimates and level of detail of included parameters seems warranted.
In this context it is of some interest that the German SSK has published a number of recommendations and/or position papers on relevant topics such as the linear-no-threshold (LNT) model, the dose and dose rate effectiveness factor (DDREF), the definition of dose limits, sex-specific radiation risks, etc. (see www.ssk.de).
We agree that fundamental knowledge gaps include, among others, risk transfer models and the risks of heritable disease.
We note that future consideration of epidemiological data from non-LSS exposure situations are expected to reduce the importance of the DDREF. In this context it is very important to emphasise that the nominal risk coefficients are calculated at 0.1 Gy and only valid for doses <0.2 Gy (para 64). It seems that this important limitation is often somehow lost in the general understanding, and a major factor contributing to misunderstandings may be the fact that the detriment is given as “per Sv” although the range of its applicability ends at 0.2 Gy or 0.2 Sv, respectively (assuming a linear dose-response curve).
Concerning the detriment calculations for skin cancer, we agree that this issue deserves some fundamental discussions and up-dated risk estimates. We note that the SSK has recently established a Task Group on risk assessment of radiation-induced skin cancer, under the SSK “Radiation Risk” committee.
While we welcome the sensitivity analyses performed in the report, some of them appear to be too trivial to warrant a graphical presentation (e.g. influence of DDREF, Fig. 4.1).
The view expressed concerning the possible inclusion of circulatory diseases into the calculation (i.e., whether the dose-response relationship for this health endpoint is linear down to low doses rather than involving a dose threshold) requires careful and continuous attention. We note that literature on this topic has increased in recent years and UNSCEAR is currently preparing a scientific evaluation.
In paragraph 30 it is not clear how geographic variation is averaged. It is mentioned that an unweighted average of Asian and Euro-American data were used, but it is not clear why then population size data are needed.