Recommendations

Comments of the Radiation and Nuclear Safety Authority of Finland (STUK) to the Draft Recommendations of the International Commission on Radiological Protection STUK welcomes the new draft Recommendations. It shows substantial improvements both in clarity and consistency of the text. More important, the system of radiological protection presented in the current draft is coherent and corresponds to the development in the subject since ICRP 60. We have reviewed the text quite in detail because we believe that the new recommendations should be clear and logical, as they will carry great weight for the next 15 years of radiation protection. In the following, our comments are given organized chapter by chapter, including general comments and more specific comments and suggestions. 1. Introduction The introduction is now very well written. The explicit statement that no changes are needed to regulations based on ICRP 60 and subsequent policy guidance is welcomed. In the first paragraph it is clearly stated that the recommendations deal only with the protection against ionising radiation. Nevertheless, it would be useful to include the definitions of ionising and non-ionising radiation either in the text or in the Glossary. Specific comments (4) There are errors in the names of standards organisations. The correct name of ISO is the International Organization for Standardization. IEC is the International Electrotechnical Commis-sion. (14) For convenience, add the word “dose”, to the first sentence: dose limitation. 2. Aims and scope (25) Add “ionising” before “radiation” on the 3rd line. Although it is explained in the introduction that the Recommendations are confined to ionising radiation, it would be feasible to repeat it once more in the scope. (29) In the penultimate sentence, delete the last words, “over the background dose”. The increase in the incidence of stochastic effects occurs in proportion to any increase in radiation dose. (29) In this paragraph the Commission should refer also to the non-targeted effects and indicate that new knowledge on low level exposures may lead to reassessment of the LNT dose-response relation-ship in the future. The Commission continues to use the term 'practice' in its recommendations although its original meaning as the opposite of intervention is not valid anymore. In paragraph (40) the Commission is discussing about the difference between 'practice' and medical practice and proposes to use the term 'radiological practice in medicine' to distinguish it from 'practice in medicine'. This kind of snobbery may be just confusing, not clarifying. We suggest the Commission to consider the possibility to omit totally the term 'practice' in its recommendations. The section concerning exclusion and exemption, (41) - (47), is sufficiently detailed and seems to be consistent with the concepts as they are currently understood and used. However, the last sentence of (42) is unnecessary semantics and only confuses the reader. We propose to delete it. (43) The concept of detriment should be defined in the Glossary. (47) Foodstuffs/FAO ~ Codex Alimentarius should not be listed here as generic exemption criteria. The use of Codex Alimentarius values as generic exemption levels is taking the values out of their context. The existing Codex values and those in the current draft guideline were only designed to allow international trade after a radiological or nuclear accident or an illegal act. The existing guide-lines deal with a time of one year after a nuclear accident only. The draft guidelines were prepared under certain assumptions on the exposure situation, e.g. that through international trade less than 10 % of an individual’s food would be contaminated during the first year and the fraction would be much lower in later years. These assumptions are not valid to define exemption values from any exposure situation. 3. Biological aspects of radiological protection (49) Error in “…effective doses of up to around 100 mSv (or 100 mGy) …”. Gray is not a unit for effective dose. Either delete the parentheses or modify to read “(or absorbed doses of the order of 100 mGy)”. (68) For clarity, we propose instead of “per Gy” on the second line to write “per absorbed gonadal dose of 1 Gy”. Interpretation of the second sentence is difficult. Proposal: “This risk value relates to continuous low dose-rate exposures and applies to the generations of children and grandchildren.” (71) The terms “the detriment adjusted cancer risk” and ”the detriment-adjusted nominal risk” need more explanation in the main text. (74) In this paragraph ‘The lethality-adjusted cancer risk of Table 2’ is used, but the table itself does not indicate that the cancer risk is related with lethal cancer. (81) The provisory note in ICRP 82, cited in this paragraph in shortened form and out of connection, is misleading. In reality, ICRP 82 states that a situation where the annual effective dose approaches 100 mSv would generally be unacceptable for the population as a whole. The facts of foetal sensitiv-ity have already been presented in the paragraphs above. We propose a new formulation to this para-graph to read: (81) “Finally, for situations of prolonged radiation exposure of the public, continuing for many years, the criteria for protection of the general public should be chosen to ensure an accept-able level of protection for the unborn as well as for small children.” 4. Dosimetric quantities: (93) We suggest that “In such situations” should be replaced by “For such purposes” in the last sen-tence. (110) The second sentence is not complete. Some words are missing here. (114) This paragraph advises to calculate the arithmetic mean dose of 14 organs. However, two of them are either male or female (prostate and uterus/cervix). If averaging is mentioned here, it should be noted that the arithmetic mean dose in 13 organs is calculated for both genders, as is explained in 120. (118) It would be helpful if there were an explicit statement on how to proceed with male breasts. In the calculation of effective dose, should they be given the dose value of zero or the dose value of the male breast tissue? Annex B does not give a definitive answer to this either. (120) Both of the equations in (4.6) should include the factor 1/13 in front of the summation, as they are related to the arithmetic means. (121) We propose to add the word “often” to the penultimate line to read: “…operational quantities are often used…” (122) fourth sentence. We propose to add the word “operational” in the beginning: “Operational dose equivalent quantities are …”. The last sentence could benefit from some editing (the operational quantities at 0.07 mm depth and 10 mm depth have not been mentioned: it is not clear what the word “respectively” refers to). (132) We propose to add the word “usually” to the second sentence to read: “This measured value is usually taken as an assessment…” (135) There is a misprint in the parentheses of the last sentence: …(pathway analysis of environ-mental transport…) (136) The last sentence should be clarified. The paragraph discusses both diagnostic and therapeutic procedures, and it is probably impossible to state all necessary advice in one sentence. The planning of radiation therapy is not based on equivalent doses but on absorbed dose. When stochastic effects at lower doses are of interest, risk-benefit assessments could be based on equivalent doses together with age-dependent risk models. (137) Using the concept of “equivalent dose to local tissues” in this paragraph – and in applications mentioned here in general – may cause serious mistakes in practice, because the actual dose quantity is not always mentioned (one may speak of just “dose” or “patient dose”) and the name sievert is given for the unit of both equivalent dose and effective dose. This paragraph is also in conflict with paragraph (93) where it was said that doses should be evaluated in terms of absorbed dose for such purposes, instead of using equivalent dose. (147) We agree that it is not usually reasonable to use effective dose or collective dose in epidemiol-ogical studies. However, we think that collective dose is useful in many situations involving deci-sions of the consequences of low doses and a large number of people. An addition would make the statement in the penultimate sentence acceptable: “The computation of cancer deaths based on col-lective doses involving trivial exposures to large populations in the remote future should be avoided”. (148) (and 229-231): The concept of S(E1, E2, ∆T) will be useful for many purposes, if it is being used to describe the distribution of collective dose with respect to the dose range and time span. However, the traditional concept of collective dose (integrating all dose levels) should not be dis-carded: the formal integration limits from zero to infinity are more reasonable than some arbitrary minimum and maximum. As already noted in ICRP 60, the time period and population over which the collective dose is summed should be specified, and when discussing collective equivalent dose ICRP 60 suggests that the collective dose can be subdivided into compartments of specified dose ranges. We agree with the text in the document that it is difficult and uncertain to try to estimate doses and their effects for exposures that will be realized over long time periods (paragraph 57). However, the arguments for not including low doses are not convincing. On the contrary, leaving low doses without consideration in the collective dose is in serious conflict with the text elsewhere in this document and other ICRP documents. For example, the building block document ICRP Publication 99 concludes that, in spite of the uncertainties involved, “the LNT theory remains the most prudent risk model for the practical purposes of radiological protection”. This is also accepted in the present document (e.g. paragraphs 29 and 30). 5. The system of radiological protection of humans General comments: We find that for the most part of the draft recommendations the principles of justification and opti-mization are treated well. We support using the concept of dose constraint from a single source for planned, emergency and existing exposures (192) with the requirement stated in (184): “Compliance with the relevant dose constraint is not in itself a sufficient condition to satisfy Commission’s rec-ommendations; radiological protection must also be optimized …” and in (198): “The intention of the optimization process is to result in exposures that are below the relevant constraints.” Discussions of optimization and dose constraints are in line with these statements for example in (30), (33), (182), (183), (193), (209) and (221). However, as regards public exposure in emergency situations (218) or in existing situations (219) the application of source related constraints and performing optimization seem to be described in a different way which is not consistent with the stated intention of optimiza-tion. We would prefer similar application of the dose constraints and optimization for prospective management of planned, emergency and existing exposures even if the selected constraints may dif-fer, as mentioned in (223). Specific comments and suggestions: (162) Third bullet, Existing exposure situations: The present wording “…including natural back-ground radiation…” should be modified by deleting the word “background”. Radon is the main ex-ample of controllable natural radiation and should not be included in the concept of `background ra-diation` (167) Exposure of the foetus of a pregnant patient (in contrast to a pregnant worker) should not be considered as being public exposure. The foetus may well benefit from the examination or treatment of the mother, and the limit for public exposure is not applicable, although exposure of the foetus always needs special consideration. (177) This paragraph deals with pregnant workers. However, the last sentence: “Additional guidance is given in Section 6.3.” is misleading because section 6.3 concerns pregnant patients. (179) The first and second sentences of this paragraph discuss entirely different situations. Therefore, the paragraph is confusing: it may give the impression that no emphasis needs to be put on the dose to the foetus in medical examinations. We suggest that the first sentence should either be deleted or separated in a paragraph of its own (with further elaboration), or relocated to section 6.3. (186) For clarity, the same terms as in (162) should be used, i.e. ”existing exposure situations” (187) “those situations which are determined by the regulator” is very vague. What is behind it? Ex-posure for NORMs in certain industries? (202) The sentence ”Epidemiological studies have shown a statistically significant excess of cancer deaths in populations exposed to doses in excess of around 100 mSv”, although often encountered, is misleading and should be deleted. There are several examples of a significant cancer excess for doses below 100 mSv. For instance, cancer incidence in the A-bomb survivors shows a significant dose-response for the dose interval 0 - 100 mSv (Pierce and Preston 2000). (218, 219) These paragraphs are very unclear and should be reformulated, as pointed out in our gen-eral comments above. (229) Proposal: “…is not always a useful tool…” (We think that it often is, although we agree that collective dose may not be useful if very long time periods are involved.) (230) Collective dose is not a useful tool for preliminary judgements of the feasibility of an epidemi-ological study - both the magnitude of individual doses and the number of exposed people are much more important issues in this case. We suggest deleting this paragraph. (231) We agree that the uncertainties concerning doses in the remote future are greater than for doses in the near future. However, as far as the LNT hypothesis is kept as the basis of radiation protection, similar reasoning is not applicable to low doses. It is not clear that radiation safety is improved by “diluting doses” to a larger population. Therefore, we propose that the second and third sentence of the paragraph should be replaced by the following text: "In the decision-making process, because of the increasing uncertainty of the relevance of very low doses received in the remote future, less weight could be given to such doses.” Nevertheless the uncertainty concerning dose, effects and population size in the future should not be taken as a cause for disregarding exposure to future generations, caused by activities of the present time. This should be clearly stated. 6. Medical exposure of patients The general impression is that there is not much new information as compared to earlier ICRP rec-ommendations, and some points would even mean impairment. More text would have been expected in some points. There is a need for editorial improvements: there are some very difficult sentences which require several times of reading in order to be understood. In addition, the subordination of the sections “Volunteers for research” and “Medico-legal exposures” under the section related to patient comforters and carers is not logical. Good points, possibly improvements as compared to earlier recommendations, are the following: • The emphasis that protection of the staff should be designed to minimise any sense of isola-tion experienced by the patient (particularly relevant in nuclear medicine and brachytherapy) • The guidance on the meaning of Diagnostic Reference Levels, which points out that patient doses can also be too low (to achieve a sufficient image quality) • The guidance on radiation protection for patient comforters and carers, and for members of the public meeting with patients after therapy with unsealed radionuclides Specific comments (244) Because limitation of the dose to the individual patient is not recommended, the emphasis should be on justification and optimization of the procedures. Optimization in this context is as im-portant as justification and should not be neglected. The second sentence should read: ”The emphasis is then on the justification and optimization of the medical procedures”. (246) In practice, radiation exposure in medicine is not solely controlled by the physician. The role of other personnel is also important for the radiological protection of patients. We propose the last sen-tence to read: ”exposures...are controlled by the physician with the help of other health care profes-sionals (radiographers, physicists etc)...” (247) For generic justification, it is important to consider also the possibility of using other modali-ties which do not expose the patient to ionizing radiation. This principle should be incorporated in the text. (250) The paragraph gives an impression that individual justification is needed only in complex di-agnostic procedures and in radiotherapy. This is against the current firm understanding that all medi-cal radiological procedures must have an individual justification by the responsible physician (the practitioner), even if the consideration needs more details for high dose procedures. (251) This paragraph can be misinterpreted to indicate that optimization would be of secondary im-portance in medical exposure of patients, which is a very dangerous misunderstanding. The text has to be modified so that the importance of optimization in medical exposures is highlighted as a crucial element in order to achieve good results of diagnosis or treatment. (252) The text in this paragraph is particularly difficult to understand. The following sentence in connection with medical exposure is almost non-understandable: ”This level of dose, or constraint, is aimed at not selecting from the process of optimization any protection options that would involve individual doses above the appropriate constraint.” The message of this sentence as applied to medi-cal exposure should be explained in a more understandable way. (255) The first sentence should read: ”Diagnostic reference levels are used...” (256) The text of this paragraph is obscure. • ”The levels are not intended to be used in a precise manner and the multiplicity of levels will reduce their usefulness” ; What is meant by “precise manner” in this context and what is the meaning of “multiplicity of levels”? • ”…must be large enough to be effective”; This could be better worded, e.g., ”should be optimized to eradicate the tumour with acceptable risk of health tissue complications” More detailed consideration would be needed for optimization in radiotherapy. In the present ver-sion, optimization is discussed primarily for diagnostic radiology. Optimization in radiotherapy is mentioned very briefly in (256) and (258), within the discussion on Diagnostic Reference Levels and below this heading. This is very confusing because the concept of DRL does not relate to radiother-apy at all. Instead, the optimization in radiotherapy should be discussed more thoroughly and in a separate sub-section with appropriate title. (259) The last sentence is slightly misleading. Observed doses should consistently be well below the diagnostic reference level - it is not a dose level target. Other words than “well below” would depict the situation where the quality might become a problem, e.g. “far below”. In section 6.3, Exposure of pregnant patients, cancer risk for the foetus has not been mentioned at all. A sentence from p. (80) should be added to p (260): “Life time cancer risk following in utero expo-sure is assumed to be similar to that following irradiation in early childhood. “ (261) There are also other situations than nuclear medicine that may involve notable foetal doses. Computed tomography, interventional procedures and extensive diagnostic procedures of the lower abdominal area are examples of such procedures and should be mentioned here. (262) The third sentence should be modified. Radiotherapy always needs careful planning (not only in pregnant patients). In addition to radiotherapy, it would be useful to add a separate paragraph for procedures that should be adopted in diagnostic radiology of pregnant and potentially pregnant patients. A mere referral to ICRP 84 is not quite satisfactory. It is important to ascertain whether a female patient is pregnant prior to any radiological procedure involving abdominal or pelvic exposure - not only prior to radio-therapy. (265) This should be deleted. There is unnecessary repetition in (265) and (266). (266, 269 and 274): The word “episode” in these paragraphs should be elaborated more, its meaning is not clear. (267) Biomedical (or actually any) research does not usually provide any benefit to the volunteers directly. Therefore, it is inappropriate to treat exposure from such research as if it were medical ex-posure. Dose constraints and careful consideration of the acceptability of such studies are necessary. (269) There are also other medico-legal exposures than examinations required by insurance compa-nies. These can be for example age determinations of refugees and examinations of possible smug-glers on frontiers or airports. Justification and optimization procedures for these exposures need bet-ter consideration. (270) A proposal to correct the first sentence: “Unsealed radionuclides are used in the diagnosis or treatment of various diseases in the form of radiopharmaceuticals that are given to the patient by in-jection, ingestion or inhalation.” 7. Exposure to natural sources It is appreciated that the exposure to natural sources is dealt with in the Recommendations for the first time as a separate chapter. The lengthy introductory part with references to UNSCEAR is there-fore adequate even in the Recommendations. We also noted with satisfaction the new approach of the Commission to recommend estimation of risks posed by domestic radon to be carried out by apply-ing the results of the European pooling study. Specific comments and suggestions: (282) The paragraph could be clarified. Second sentence: Replace “water from mineral sources” by “drinking water (tap and bottled water)”. Suggestion for third sentence: “Modern construction prac-tices have caused increased indoor radon concentrations, giving rise to widespread exposure in many dwellings, where radon is often the predominant source of prolonged exposure”. (285) Uniform units should be used. The last sentence should be replaced with something like: “These elevated indoor exposures could generally be avoided by proper measures and choice of ma-terial during the construction. Also reduction afterwards is possible but more expensive”. (286) penultimate sentence, the last word (variable?) is missing. (287) We propose to add a new sentence before the last one of this paragraph: “Direct flow of radon bearing soil air into living spaces is the main reason for elevated indoor radon concentrations.“ (294) The numerical values of any exclusion levels for natural sources should be deleted from this chapter (and the numerical values presented are absolutely too high!). They have been excluded from section 2.4 and should not appear here either. This paragraph should end with full stop after “human body” in the second sentence. (295) Delete this paragraph, or at least the second sentence of it. It is out of the scope of Ch. 7. (299) The historical units of WL and WLM should not be used any more. It is better to use only SI units and special dose units (300) We propose to edit the end of the last sentence to read: “…for new buildings, where radon pre-vention measures are far more cost effective than remedial measures for existing buildings”. (303) For clarity it is proposed to replace in the second line the words “radon exposure can be merged with other exposures” simply by “workers are exposed to both radon and other types of ion-ising radiation” (304) The last sentence could be deleted, as ICRP 65 deals only with radon-222. (305) In this paragraph the word “constraints” should be replaced with “national action levels” 8. Potential exposures (309) “It should be recognised that the potential for exposures may lead to actions to reduce the probability…” instead of “...exposures, if they occur, may lead to actions to reduce the probability… (322) The first sentence is not complete. (329) “The management of corpses containing significant amount of radioactive substances…” This seems to be an exaggerated fear, reminding of post-Chernobyl legends concerning the early victims. We suggest deleting this. (332) The list of accidents is erroneous. The accident in Vietnam 1992 had nothing to do with radio-therapy, and the accident in Thailand 2000 was not a radiotherapy accident, regardless of the origin of the source. In Panama, however, 28 patients got twice the planned dose of treatment because of an erroneous use of a computerized treatment planning system, and at least 5 died as a consequence. This was reported by IAEA in 2001 and could rather be included, if the intention really is to list ra-diotherapy accidents specifically. 9. Emergency situations and existing situations (Chapters 9.4 and 9.5) Involvement of various stakeholders in decision making of protective actions and countermeasures should be emphasized in these chapters, because the actions would directly relate to the public and various societal and political interests would be involved 10. Protection of the environment A short chapter on protection of the environment is appreciated, although it cannot be regarded as recommendation. The informative and modest nature of the chapter could be emphasized by leaving the subheadings out. 11. Implementation of the Commission´s recommendations Stakeholder involvement: The draft recommendation does not fully consider the carefully prepared view on stakeholder in-volvement as part of optimization and decision making, described in the Supporting Document on Optimization. We propose that paragraph (41) of the Optimization document would be inserted as such e.g. to be paragraph (369bis): “The involvement of stakeholders does not imply that operating management and/or authorities relinquish their responsibility to make the final decision, or their ac-countability for that decision. The question of final responsibility for decisions must not be obscured during the shared steps of decision framing and the implementation of the optimization process. The responsibility for the “final decision” with respect to the adequacy of protection solutions finally lies with the operating management and/or the authority. “ (386) This is an important and welcomed paragraph. The meaning of the last sentence should be clarified, however. What is meant by `administrative conditions of service´ of those occupationally exposed?