|1. General Comment on the Whole Foundation Document
This foundation document does not reflect many comments to the draft version of a new ICRP recommendation that was released last year. ICRP should issue answers in a concrete manner to many common comments.
2. Comment on the Adoption of LNT Hypothesis
Concerning the adoption of LNT hypothesis indicated in the lines 188-190, the assertion to be "scientific" should be changed to "realistic from the viewpoint of radiation protection."
The cancer risk by radiation described in this foundation document is the estimation based on the effect of the cluster damage at the cell level, and it should be noted that the cancer risk due to the cluster damage is not proved at all. The lines 1281-1284 state that epidemiological methods used for the estimation of cancer risk do not have the power to directly reveal cancer risks in the dose range of up to some ten mSv.
Thus, at the low dose under some ten mSv, the cancer risk at individual level is not proved epidemiologically nor biologically. Therefore, it is not "a scientific hypothesis" to apply a proportional relation between the dose and the risk, and it should be expressed as "a realistic hypothesis from the viewpoint of radiation protection."
3. Comment on the epidemiological data
The research on health effects of those living in high natural background radiation area@is an excellent information source because it includes both males and females and every age group, and it does not suffer any special stress. Thanks to the accumulation of data, a detection sensitivity equal to that of occupational exposure has been realized. It is the data to be considered in order to estimate the risk of low dose / low dose rate.
4. Comment on Cell Survival Curve
The lines 916-923 state that "a special feature for some cell types is hypersensitivity to doses less than 0.5 Gy, typically at 0.2-0.3 Gy". However, this phenomenon is observed only on certain cells, and the mechanism is not made clear. Therefore, it should not be generalized at the present stage.