General comments

It is appreciated that the ICRP evaluated properly the new knowledge for example BEIR VII (2006), a recent report from the French Academies (2005), and CERRIE (2004; especially in 4.4.5). Moreover it is welcomed that the ICRP has not adopted the data which have large variations such as the value of 1.5 as DDREF in BEIR VII and an epidemiological report of Cardis et al. from the view point of uncertainty as noted in section 4.4.1.2. However, there still remain unchanged some opaque parts especially in the field of the estimation of numerical values. We request the Committee will continue to remove black boxes more.

Specific comments

• 1. The LNT hypothesis (p.5, Lines.192-193 / pp.64-68, Chapter4, 4.4.5)
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  • The statement of the LNT in Principal Conclusions (p.5, ll. 192-193) should be modified to the same explanation as the last paragraph at pp. 68, Chapter 4, Section 4.4.5; i.e. the phrase "a scientifically plausible assumption; uncertainties on this judgement are recognised" should be replaced to "a prudent basis for the practical purposes of radiological protection".
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  • Reason: It should be appreciated that the Committee clearly states that the LNT hypothesis is for the purposes of radiological protection, due to the uncertainty associated with the estimation of the risk from low dose/dose-rate irradiation. A fear or unreasonable concern about low level radiation/radioactivity of general public is based on the LNT hypothesis; the statement of ICRP that the LNT hypothesis is only for the purpose of radiological protection and does not necessarily reflect the actual effect of very low dose would reduce the anxiety of the public. However, in this regard, the statement that the use of LNT hypothesis is a "scientifically plausible assumption" (p.5, ll.192-193) may be misleading, because of the word "scientifically".
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• 2. Source of Epidemiological Data for estimating the human risk (pp. 41-, Chapter 4, section 4.4)
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  • It is appreciated that the Committee considered epidemiological data on medical exposure, occupational exposure, and environmental exposure as well as A-bomb survivors. However, we have another set of data which should be taken into consideration from research on health effects of those living in high natural background radiation area. The strength of these data are as follows; (1) they cover both males and females, (2) they cover all ages, (3) the exposure is protracted one at low dose rate, (4) the exposure was under non-stressful situation compared to medical exposures and A-bomb survivors. These data have accumulated and a number of qualified papers have been published to demonstrate that there was no increase in cancer mortality in that area where the natural background radiation is 3 times as high as the average (J. Radiat. Res., 41 Suppl., 31-41, 2000).

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• 3. Estimation of nominal risk coefficients for cancer and hereditary effects (Chapter 4, Section 4.4)
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  • Each step in the estimation of nominal risk coefficients should be more transparent.
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    • (1) Black boxes in Box 1
    • For example, the reason must be explained well why the Committee has chosen these seven populations used for the estimation of nominal risk coefficients which were changed from the populations used in Pub 60 (pp. 46). Moreover, numerical data for each population should be shown, as used to be shown in Pub 60.
    • (2) Basis on unpublished data
    • Only published data should be used for the ICRP recommendations. The latest data on LSS of A-bomb survivors would be used in this draft documents, even though not published. The Committee should have another consultation after the data would be published and reviewed by public.
  • Reason: There were frequent changes of numerical values of nominal risk coefficients even after previous Committee 1 Foundation Document had been published. It is desirable the process of the estimation in the ICRP recommendation should be able to be followed, checked and reproduced by others.

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• 4. Editorial comment
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  • The critical error of equation (2) at pp. 87, ll. 2715 has not fixed yet. The two sides of any equation must be commensurable or have the same dimensions. The denominator "induced mutation rate" should be modified to "induced mutation rate per dose".