|We welcome the opportunity to comment on the very considerable amount of work carried out to compile and collate the large amount of research data relating to the early and late effects of radiation on normal tissues and organs.|
The considerable diversity in the nature of these research studies leads to our major observation, which is that we would have expected more discussion on the strenghts and weaknesses of each study and how such diverse offerings were compared and contrasted. Indeed, without this level of detail, commenting on the document appears to require substantial repetition of the work by the reviewer. Because of this, we have focussed on areas where changes have been recommended rather than on the entire document. This is principally on the threshold doses for the eye, although most of the comments below also apply to consideration of cardio-vascular effects.
We agree that where the eye is concerned, there is evidence to suggest that the threshold should be reviewed. However, we cannot understand the rationale behind the selection of 500mSv. We think more transparency is needed and suspect that, since the underlying data seems more qualitative than quantitative, this has resulted in a somewhat subjective choice of threshold.
Most of the research studies relate to acute exposures and it is difficult to see how this information has been extrapolated to low level chronic exposure. The thought processes, weighted significance of each study and the extent to which other possible confounding factors which could have contributed to cataracts were considered, require more detailed explanation. For example Blakely et al, 2010 is quoted as a recent study, but the report does not seem to state what was found or how this was used in the study itself. In summary, more transparency is needed.
It is appreciated that a document of this type must have a very considerable and detailed scientific content. However, as its stated purpose is to consider "the radiation protection context", the document would be more helpful for those involved in operational rather than research work by a slightly changed format. Most colleagues found their understanding of the document was increased by reading about the response of a particular organ then referring to the relevant section of the chapter on thresholds, rather than by reading the document from front to back as currently drafted. For example, the understanding of the eye may benefit from the threshold tables (page 275-280) being linked more closely with the main eye section of the document.
The overall conclusion is that the reasoning that has led to the findings, recommendations and suggestions in the document is not clear and that without such clarity it seems precipitate to consider what impact this publication may have on the setting of dose limits. Fully informed comment requires further consultation of an amended document or the consultation needs to be for a considerably longer period.