|Response from the Health Protection Agency staff to the 5 June 2006 Draft ICRP recommendations.
The staff of the Radiation Protection Division of the Health Protection Agency (HPA-RPD, formerly the National Radiological Protection Board) welcome the opportunity to comment on the revised draft ICRP recommendations dated 5 June 2006. Having commented in detail on the previous draft recommendations in December 2004, we are pleased to see that many of these comments have been taken into account. We feel that the revised draft represents a significant improvement and in particular feel that the basic principles of radiological protection are now stated clearly and coherently. We also welcome the view that the recommendations do not suggest any need for changes to protection standards based on the previous recommendations in ICRP Publication 60 (paragraph 12). The following general and specific comments have been collated from many staff of HPA-RPD, particularly those who were not involved in the development of the draft recommendations.
„h The draft recommendations now clearly set out the basic principles of radiological protection with generally clear definitions of the terms used. The document sets out which previous ICRP publications and advice still apply and often, but not always, any changes are explicit and clear.
„h The first five chapters of the recommendations are stronger than the remaining chapters. Much of the material in Chapters 6 to 11 is in the nature of a discussion of the issues rather than specific advice and could potentially be shortened or moved to the supporting documents.
„h There have been relatively few changes to the section on medical exposures since the previous draft and it still lacks clarity in places. There is little attention given to medical exposures in the first five sections of these draft recommendations despite their importance as one of the major sources of controllable public doses. It is also hard to comment on sections relating to medical exposures as the impending ICRP Committee 3 report on medical exposures is not yet available.
Section 1 ¡V Introduction
Paragraph 11 - The second feature of the revised recommendations (dose limits) certainly does not apply to medical exposures and the third (dose constraints) only applies, if at all, in a very limited way. It is consequently confusing to say that the second feature applies to ¡¥all regulated sources¡¦ and the third to ¡¥all exposure situations¡¦.
Paragraph 17 ¡V the last sentence regarding ¡¥estimates of probability coefficients¡¦ is not clear and this terminology does not seem to be used elsewhere in the draft or to be included in the glossary.
Section 2 ¡V The aims and scope of the recommendations
Particular question raised by ICRP
The treatment of scope, exclusion and exemption is a significant improvement on the previous draft and is considered adequate.
Paragraphs 28-33 - Section 2.2, the structure of the system of protection -a number of aspects of the system of protection described in this section do not apply to medical exposure of patients. It would be helpful if a general statement to this effect was made at the beginning of the section and specific comments made in the text whenever the aspect under discussion was not appropriate for medical exposures, e.g:- in Paragraph 30 the 2nd bullet point: optimisation of medical exposures of patients does not involve dose constraints for the purpose of reducing ¡¥inequities¡¦ in individual doses and benefits. The benefit from a medical exposure and hence the ¡¥optimum¡¦ dose is individual to each patient. There is nothing to be gained from trying to make all patients and their exposures equal. In the 3rd bullet point: Insert ¡§apart from those used for medical exposures¡¨ after ¡§all regulated sources¡¨.
Paragraph 33 ¡V the first 3 sentences do not apply to medical exposures. This paragraph is not totally clear. In particular, the third sentence could be interpreted as saying that the dose constraint should not limit the selection of any potential options that may be used to limit the dose.
Paragraph 40 - is the use of the term ¡¥radiological practice in medicine¡¦ just a suggestion (to whom?) or is it going to be used by ICRP in these new recommendations? The fact that it is not used in section 6 suggests that it is the former, but if you don¡¦t use it why suggest it?
Section 3 ¡V Biological Aspects of Radiological Protection
In this section the incorporation of and reference to Annex A makes the section clear and concise. We support the use of cancer incidence data for the basis of risk estimates. HPA-RPD also endorses the judgement made on DDREF, as fractional values give an unrealistic impression of accuracy. The explanation of changes to nominal risk coefficients and how these might impact on safety standards is much improved from the previous draft recommendations.
Paragraph 49 - line 2 should be result not results.
Paragraph 57 ¡V The points made regarding the uncertainty of the effects at low doses are certainly valid but this paragraph does then raise the question of when can you calculate numbers of radiation induced health effects? Also line 3 should read ¡¥Unambiguously¡¦.
Table 2 ¡V most of the numbers in this table are presented to one decimal place except for the present total where only 1 significant figure is used. This is inconsistent with the numbers given in paragraph 71 and Annex A.
Paragraph 72 and Table 2 - Is the age range of the ¡¥Adult¡¦ population in this Table different from the age range of the ¡¥Adult Workers¡¦ population in the corresponding Table in the previous ICRP draft recommendations and in ICRP 60? If it is and includes older ages, this could be another reason why the risks are lower than in ICRP 60.
Paragraph 73 - line 4 should read ¡¥¡Kan overestimate of mortality risks in the future¡K.¡¦
Paragraph 75 ¡V this paragraph is not totally clear. Is ICRP advocating that people should still use 5% per Sv or that the change from about 5% to about 4% does not affect regulation? It is also strange that 5% per Sv in paragraph 73 becomes 0.00005 per mSv in paragraph 75 and a consistent terminology would be better.
Paragraph 80 ¡V in the last sentence is it necessary to say that there is insufficient information to derive wTs for in utero irradiation? There is no suggestion that separate values are required for infants so why consider separate values for in utero exposure? This seems to be inconsistent with the intended use of wTs for calculation of effective dose for regulatory purposes. Also, this refers specifically to radionuclide exposures for which a proportion of the dose may be delivered postnatally, depending on the radionuclide.
Paragraph 81 ¡V is this paragraph advocating that dose to the fetus does not need to be considered if doses are below about 100 mSv, for example in considering routine discharges of radionuclides to the environment? This does not seem acceptable for those few radioisotopes where the dose to the fetus can be an order of magnitude greater than that to the mother from the same intake.