|Comments on 2005 ICRP Recommendation
Jean St. Germain, CHP, DABMP, Radiation Safety Officer
Lawrence Dauer, CHP, Radiation Safety Operations Manager
Matthew Williamson, Lead Physicist
Memorial Sloan-Kettering Cancer Center
Department of Medical Physics
Radiation Safety Service
1. We welcome the opportunity to comment on the recommendations draft.
2. We agree that the new recommendations must represent good science as well as a set of coherent principles that can be universally applied.
3. For consistency in the application of terms, we suggest that a specific “Definition of Terms” be added (e.g., single source, dose constraint, etc.).
Specific Paragraph Comments:
(S3) The Commission explicitly states that there is a need for “stability in regulatory systems at a time when there is no major problem identified with the practical use of the present system of protection in normal situations”. So, why change the system? The explanations given in section 1.2 seem to refer to ‘ease of implementation’ issues, rather than science and coherent principles. In addition, the description of those factors that have resulted in a general overall reduction in doses appears to be chosen to specifically support the draft recommendations alone. Where is the science that dose constraints were part of that reduction? Where does the overall industry focus on ALARA fit into the reductions?
(S4) Dose constraints are suggested as “obligatory, and not maintaining these levels of protection should be regarded as a failure”. We wish to point out that the use of the term ‘obligatory’ will result in these constraints becoming de-facto dose limits without an underlying risk-basis. As risk science continues to develop, the implementation of an unfounded system of constraints will only result in an unjustified reduction in dose limitation, resulting in a large government and institutional fiduciary burden for no scientific gain. In addition, the reference to a ‘failure’ provides just the very negative connotation that will continue the unfortunate popular view that risk-evaluating and recommending bodies are waffling with regard to safety. If the ‘standard of care’ continues to drop, the confidence in the overall system of safety-setting will fall apart. We are concerned that a move in the direction of explicit (dose limits) or implicit (dose constraints) reductions in allowable dose will result in a loss of overall credibility in radiation safety professionals.
(S5) The establishment of the ‘dose constraint’ system appears to be arbitrary with no justification (or benefit) presented for the actual values themselves. Where is the cost justification for these values? In addition, we suggest that the discussion that the dose constraints do not apply to the exposure of patients needs to be expanded in the summary to fully explain how these are not to be applied in any patient setting (both diagnostic and therapeutic).
(S6) We agree that optimization principles need to consider more than ALARA factors.
(S7) The explanation of the 100 mSv maximum constraint is very confusing. It appears that although the ICRP identifies “there is neither individual nor societal benefit from levels of individual exposure above this constraint”, they previously list a number of cases where doses above this level are justified (e.g. emergency situations). Is it the Commission’s intention that doses received above 100 mSv for these exceptions be documented or specially evaluated? Where is the science that supports this value in the first place (especially in light of the comment that the Commission expects that national values may be a factor of 10 less that this! (see paragraph 164)? Is the Commission suggesting that the ultimate maximum dose constraint be a value of merely 10 mSv (1 rem!) at the national level? These levels are consistent with background annual dose values in some areas.
We are concerned that the continued suggestion of 20 mSv as a dose constraint for occupationally exposed individuals is unjustified and, although currently not required under US regulations, would result in work hardships for certain medical staff (e.g. interventional radiologists – a group that is already experiencing staff shortages).
(S8) The Commission needs to specifically define what it means by ‘normal situations’ or expand on the discussion about what it considers ‘abnormal’.
(S12) While we applaud the Commission for developing a set of recommended exclusion values, we suggest that the discussions here and in Section 8 include a description how the Commission specifically defines ‘artificial’ and how the Commission arrived at the values for the ‘artificial’ alpha or beta emitters. We also express our concern that the reference to 0.2 mSv (paragraph 209, Section 8) as a value may result in a de-facto further reduction in the current method of calculating allowable release for unrestricted use in the US that utilizes 0.25 mSv and ALARA considerations (US NRC 10CFR20.1402).
(S14) The Commission correctly refers to the confusion between the terms for weighted tissue dose, dose equivalent, and effective dose. We suggest that the Commission very carefully describes the move to a new name for radiation weighted dose in a tissue or organ. The summary as it is currently written appears to be a work in progress (e.g. ‘the Commission is considering…’) and we are concerned that ICRP should come to a recommendation statement in this regard, taking care that they not take on the responsibility of what is more appropriate to be performed by the ICRU. If the ICRP makes a recommendation that relates to unit definitions and the ICRU is not in concensus, we will certainly have a massively confusing process overall that will result in an inefficient and untenable situation.
(Equation S1) Be consistent in the equation graphics, note the extra set of parentheses.
(S18) Is there a justification for a set of recommendations for non-human species? Without a direct link to human exposures, this whole approach appears absurd at best and a waste of very limited resources at worst. The approach certainly does not appear to meet the overall aim of the recommendations in the first place (see S2) that ‘the primary aim of radiological protection is to provide an appropriate standard of protection for MAN…’ We suggest that the discussion of environmental non-human dose limits is certainly not appropriate for this document and represents a level of dose limit bureaucracy without any human-oriented justification. The Commission seems to have lost its overall focus with this issue.
( 6) The rationale given for the reasons for a new set of recommendations is weak. Other than the ICRP documents that have been developed since 1990, there is no supporting evidence in the discussion that the philosophical shift from ‘the greatest good for the greatest number’ to the ‘individual’ is real or even justified. What is the impetus for change, given that many have only just implemented the 1990 recommendations? In fact, some nations (e.g. USA) are still struggling to justify implementation of those. It appears that this set of recommendations may simply be change for change’s sake and not based on sound scientific evidence or on overwhelming societal response. In addition, the recommendations in the draft appear to be a work in progress rather than a clearly defined set of well-founded, simplified recommendations.
( 9) The reference to additional sources and ‘increased doses from existing sources’ appear to be inconsistent with the Commission’s summary statements that the overall dose to persons has been reduced over the past 10 years. Are the doses going down or up? If down, then the need for additional recommendations is very much reduced. In either case, a documentary basis should be offered for such a significant statement.
( 10) We emphasize that the implementation of the de-facto dose limitation system (aka – dose constraints) may engender ‘fear’ and may result in a public that is unable to keep risks in perspective as limits keep falling.
(11) This argument is based on a vague description of public ‘interest’. A corollary argument could be made that interest in the potentially hormetic uses of radiation has greatly increased. Why not provide a policy statement on that subject? We again suggest that the discussion of environmental non-human dose limits is certainly not appropriate for this document and represents a level of dose limit bureaucracy without any human-oriented justification.
(18) This paragraph is extremely confusing when one considers the justification for medical exposures. In this case the judgment on justifiability is certainly NOT the responsibility of governments, but on physicians (as is discussed in #19).
(19) There is no supporting documentation or basis described for why for medical exposures “a more detailed form of justification has to be applied to the procedures within the practice”. In addition, this wording seems to imply that medical exposures may hold a different inherent risk than other exposures, an implication that could lead to a confusing set of protection principles and could result in a dual approach to regulation.
(20) It is not clear what this paragraph is referring to. Clarity is needed.
(26-28) ‘Excluded completely from the scope of Recommendations’ would suggest that exemptions are not necessary below this level. The use of the terms ‘exclusion’ and ‘exemption’ appear to be inconsistent.
(31) What does this paragraph have to do with the format of recommendations? A discussion of incremental risk as an ultimate measure should appear elsewhere in the documents.
(38) The Commission should expand the discussion of what is meant by “above the natural background”. Are they advocating the use of a single value or a range of values and how does one decide if linear effects have begun. Does this imply that “natural background” levels do not harbor any risks at all?
(40) Why is the Commission implementing a new term: ‘tissue reactions’, when the former term ‘deterministic effects’ has been widely accepted in practice?
(51) Again, this document appears to be a ‘work in progress’ rather than a specific set of draft recommendations based on science. “The Commission is considering a new name…” Is the Commission considering a new name, same units of J/kg? This will leave us with Gray, Considered-new-name, and Sievert. This action may result in more confusion. Does this discussion have any relevance here? Is it required in this venue? We suggest that the ICRP defer to the ICRU on this point.
(54) Although the ICRP is emphasizing that the ‘effective dose’ is not to be used to assess risks of stochastic effects in retrospective situations or in epidemiological evaluations and notes that the main use is to enable external and internal irradiation to be added to demonstrate compliance with quantitative restrictions, the ICRP should also add a statement that it is appropriate to use ‘effective dose’ when comparing various irradiations (e.g. nuclear medicine, industrial, x-ray diagnostic tests, etc.).
(56) The sentence beginning with “It is in order to improve…” is a clumsy sentence and should be reworded for clarity.
(61) The use of the clumsy wording “less well correlated” when referring to RBE values obtained from in-vitro investigations on cells suggests that in-vivo investigations on animals are ‘more’ well correlated with carcinogenesis in humans. What is the reference for such statements? Can the ICRP define what is meant by less or more correlated. Also the wording “partially also for neutrons” does not specify how the data were used.
(68) The ICRP is promulgating a switch from the step function to a revised continuous function for Wr values for neutrons. The science behind the reasoning for changing the continuous function is not referenced or discussed. Where are the references that changed the approach from ICRP-60?
(82) This paragraph appears to offer a very limited view of radiation protection. Why is it necessary to define radiation protection in this manner? Section 2 has already addressed this topic in more detail. What does the ICRP mean when it refers to ‘controlling exposures’? Does this include ALARA and preventing exposures?
(88) This is confusing. Is the ICRP implying that where any person approaches or exceeds a dose constraint, that individual-specific calculations are required to be performed? Also, why allow the use of committed effective dose coefficients for prospective studies here but not allow its use in retrospective studies earlier? Why is there such a distinction being made?
(90) This paragraph appears to refer to additional work in progress. Have the new models already been used to develop new conversion coefficients? If this work is not completed yet, why is this paragraph relevant in a recommendations document?
(91) Rather than not give ALI values, the ICRP should continue to use and give these values along with a note that they are not to be used alone to show compliance with constraints. By not giving them and then stating that they can be very useful, the ICRP is sending a confusing mixed message. This continues with paragraph (92) that discusses a further useful defined quantity (DAC).
(93) Once again, the ICRP is referring to incomplete work in a recommendation-setting document. This paragraph refers to a very significant change for those industries that deal with internal exposures as well as emergency response organizations. Recommendations should be set on known science and not on hopeful wishful ideas of completed work.
(94) and (95) Why does the ICRP change to ‘tissue reactions’. We suggest that you keep the wording ‘deterministic’. Also, it is unclear what the recommendation from ICRP on deterministic ‘tissue reactions’ is? In paragraph 94 the complexity of the problem is discussed very generally and in paragraph 95 it is stated that controlling for stochastic will avoid the occurrence of most tissue reactions. What about those of us that deal with both medical and emergency situations? These paragraphs read to us as “tough problem to solve” and “we don’t have a recommendation”. Is this what was intended?
(96) Keep ‘deterministic effects’ rather than ‘tissue reactions’.
Section 4.2 title limits the discussion below, it should refer to ‘other effects’ as well (e.g. fetus, non-cancer, etc.)
(100) Is this paragraph referring to net irradiations above background levels or to gross overall irradiations?
(105) “…the Commission finds no good reasons to change its 1990 recommendations of a DDREF of 2”. This statement should be expanded and a more full explanation given on the decision-making process.
(106) Although the Commission refers to post-1990 human data, the Commission should emphasize that to date no hereditary effects have been seen for humans. The current wording appears to refer to some studies that have shown real effects.
(110) This paragraph should include a discussion about the fact that the ICRP is using cancer incidence, not cancer survival as a measure of detriment risk. What about those cancers that no have increased survivability because of medical advances? Was this considered in the recommendations? If so, how and what were the conclusions? Describe the decision-making process in more detail.
(111) It should be emphasized that these values were derived using statistical means and policy-setting decisions and that they should not be used for individual risk assessment.
(112) The new ‘nominal probability coefficient’ is given as 4.4% per Sv as compared with the 5% per Sv from ICRP-60. Why is there a change in the precision of the number? Has the underlying data precision increased since 1990?
(118) Based on this data, the ICRP should make a recommendation or a strong statement that termination of pregnancy at fetal doses of less than 100 mSv is NOT justified based upon radiation risk. This statement is much needed in the medical field where physicians may be called upon to make such a judgment recommendation.
(130) “This should include all the sources causing substantial exposures to the individual.” How does the ICRP intend on defining ‘substantial exposure’? Should a reference to Table S1 be given 0.01 mSv per year. Would this suggest that all exposures greater than 0.01 mSv (1 mrem) should be considered a ‘substantial exposure’?
Section 5.2 – The principle of Justification should also be discussed here. We also feel that this principle should continue to be generally discussed and not limited to medical exposures only.
(132) “…should be regarded as a failure.” The ICRP should clarify here what it means by failure and should refer to both optimization AND justification.
(133) The dual nature of constraints and limits is confusing and should be further clarified or dropped in favor of the dose limit approach in ICRP-60.
(143) the further clarification of occupational exposure given in (169) should be referenced here.
(164) What does the Commission define as a ‘dominant source’ and when exactly does the Commission recommend a figure of 0.3 mSv/year be an appropriate dose constraint?
This section is very unclear.
(169) Why not refer to the potential for exposures in the definition. (e.g. if a worker is likely to exceed 2 mSv/year (10% of the dose constraint) then they should be considered an occupational worker that will require additional training and knowledge)?
(173) This paragraph is referring to future work that the ICRP is considering and should not be part of the recommendations, until the science is concluded.
(175) The dose constraint of 1 mSv during the remainder of the pregnancy for declared pregnant women needs to be discussed in much more detail, with a basis for this decision given. Where is the justification for such a low value, a fraction of background? Note that this value is a factor of 5 lower than current US NRC regulations on declared pregnant women! Implementation of this constraint will have an absolutely negative impact on medical workers who have declared their pregnancy and may preclude these women from working with radiation in a medical environment. Such an unreasonably low value also is inconsistent with the risk discussions in Section 4.
(178) The reference to paragraph 146 does not seem to be correct.
(180) In the previous definitions of dose constraint the Commission appears to state that below the constraint, optimization is necessary. If this is so, then the discussion in paragraph 180 is confusing as it sets a maximum dose constraint at 10 mSv from radon (is this inconsistent with Table S1?) and then declares that below this constraint, no optimization is necessary.
(185) How are we to interpret the dose constraint concept in light of the recommendation that the dose limit continue to be 20 mSv per year (a value equal to the dose constraint)? The concept of dose constraints is difficult to grasp.
Table 9 – why does the annual dose limits for radiation weighted dose to the skin continue to be averaged over 1 cm squared? The US NRC has revised this upwards to 10 cm squared based on recent work by the NCRP (http://www.hsrd.ornl.gov/nrc/frdocs/66FR36502.pdf) and other recent journal articles (Baum, 2001, Analysis of Potential Radiobiological Effects related to a Unified Skin Dose Limit, Health Physics, p. 537-543). The ICRP should consider revising the approach to 500 mSv averaged over 10 cm squared.
(189) The Commission should explain why this definition of optimization is considered ‘broader’. Broader than what? Perhaps the earlier view was limited to cost /benefit considerations?
(203) “The Commission intends to publish…” We encourage the Commission to develop those methods first and make recommendations second.
(215) The Commission should also recommend that other health professionals may require training on radiation protection. (in addition to physicians).
(216 and 219) While the discussion on the justification of medical procedures is warranted, the recommendation that the physician must provide justification for each individual complex diagnostic procedure or therapy is unacceptable. This could have significant impact on medical institutions, especially those specializing in cancer care. The Commission appears to recognize this as a potential problem in the last sentence of paragraph 219, however, the development of criteria and patient categories in advance will not effectively resolve this situation. It appears that the ICRP may be walking a fine line between recommendations on justifying medical exposures and setting the standards on the practice of medicine on an individual basis.
(225) Following the dose constraint methodology presented earlier in the document, how are we to interpret the statement “dose in the region of a few millisieverts per episode is likely to be reasonable”? Can we apply the 20 mSv dose constraint as noted in Table S1? Also, the statement “This constraint is not to be used rigidly.” Is not consistent with the harsh wording about dose constraints in both the summary (S4) and paragraph (132) wherein exceeding a dose constraint is considered a ‘failure’. Perhaps, if the maximum dose constraint can be higher, then the value should be specified as the maximum amount and not implied as an ill-defined lower value (“a few millisieverts”) that can be flexibly applied.
(227) Is the Commission implying that only radioiodine treatments for thyroid cancer require restrictions on patients? What about other therapeutic procedures, such as permanent brachytherapy (e.g. prostate seed implants) procedures, radioiodinated monoclonal antibodies for lymphoma treatments, and others?
(239-240) The recommendations on hot particles are confusing and unclear as written. Is this only referring to potential post-accident exposures? What are the specific recommendations? How are they quantitified?
Section 11 – this section appears to be an ongoing ‘justification’ for the Commission’s actions on non-human protection, rather than a set of policy recommendations. We also emphasize that this shift in Commission’s focus is unwarranted and we encourage the Commission to continue to espouse the ICRP-60 view that “the standards of environmental control needed to protect man … will ensure that other species are not put at risk…at the present time, the Commission concerns itself with mankind’s environment only with regard to the transfer of radionuclides through the environment, since this directly effects the radiological protection of MAN.”
The approach certainly does not appear to meet the overall aim of the recommendations in the first place (see S2) that ‘the primary aim of radiological protection is to provide an appropriate standard of protection for MAN…’ We suggest that the discussion of environmental non-human dose limits is certainly not appropriate for this document. Therefore, we suggest that Appendix B represents unnecessary detail and promulgates a level of dose limit bureaucracy without any human-oriented justification.