|PART 5 OF COMMENTS IN 6 PARTS
Comments on Draft for Consultation
2005 RECOMMENDATIONS OF THE INTERNATIONAL
COMMISSION ON RADIOLOGICAL PROTECTION
David C. Kocher
SENES Oak Ridge, Inc.
Center for Risk Analysis
Oak Ridge, Tennessee, U.S.A.
The Commission’s Required Levels of Protection for Individuals
Sections 6.1 and 6.2. The basic idea of including all controllable sources of exposure in the same framework of radiological protection seems like a good one to me. It does address some criticisms of previous recommendations. Furthermore, although the Commission’s approach of defining maximum dose constraints essentially in terms of multiples or fractions of natural background is certain to receive much comment and may take some getting used to, there may not be anything inherently wrong with it. For example, it implicitly takes into account that determinations of acceptable risk are matters of societal judgment, and that these judgments may vary substantially from one country to another.
However, it seems to me that the Commission’s recommendations on maximum dose constraints have a basic problem—namely, that the values do not have a clear basis. They especially do not have a clear basis in the need to limit risks due to radiation. If dose constraints are to be “[t]he most fundamental level of protection” as stated, for example, in Section 5, paragraph (133), they surely should be based on some fundamental protection principle and, furthermore, this principle should be clearly stated. Explanations of the maximum dose constraints in Section 6.1 include such terms as “need for action,” “most that should be allowed,” “increasing need for action,” “require that action be considered,” “legitimate matters for concern,” and “need for action should decrease,” but there usually is no explanation of what those terms mean. For example, on what grounds is there a “need for action”?
In Publication 60, dose constraints were presented as one of the elements of the principle of optimization; they essentially were generic starting points for optimizing exposures from specific sources. Now, however, dose constraints are presented apart from the principle of optimization as if they represent a separate principle, although I suspect that the maximum dose constraints are intended to play essentially the same role as in Publication 60; i.e., they are a ceiling for applying the principle of optimization to specific sources.
Absent a clear statement of their basis, it appears that the maximum dose constraints and the types of sources to which each such constraint should apply were based on little more than practicality and past experience. There may be nothing inherently wrong with this, unless the maximum dose constraints give the appearance of being arbitrary or unreasonably supportive of the status quo, but it seems to me that it is difficult to claim that a set of maximum dose constraints which are based on practicality is somehow “fundamental.” (What is fundamental as well as practical is the principle of optimization, but the difference is that optimization is recognized to be a matter of judgment which cannot be quantified or specified in regulations, whereas dose constraints are starting points which clearly can be defined. Although optimization is a matter of practicality, the fundamental principle behind it is nonetheless clear.)
I also wonder whether the statement in paragraph (157) that natural background does not provide any justification for additional exposures may seem at odds with a scheme of taking natural background into account in developing maximum dose constraints. In other words, will background be seen as providing an excuse for allowing controllable exposures?
Paragraph (161), last sentence. I like the mention of frivolous practices here, but I still believe that the Commission should issue a clear recommendation that frivolous uses of radioactive materials should be banned.
Paragraph (162), last sentence. Here is another statement which seems quite profound, but which I do not understand. What are “corresponding quantified values” (“corresponding” to what)? What “relevant constraint” (the one recommended by the Commission, or a lower value established by regulatory authorities)? Is this statement directed at regulatory authorities or is it a lead-in to the Commission presenting its rationale for the quantified values and the situations to which they apply in the following paragraphs?
Paragraph (163), last sentence. Here again, I find myself wanting to see a discussion on how the Commission thinks that dose constraints lower than the recommended maximum values should be developed. What should be their basis (what considerations should go into establishing them)?
Paragraph (164). In these discussions, it seems that the maximum dose constraints are related to benefits to individuals and requirements for monitoring, training, and information. My only comment is that this rationale does not provide a basis for the maximum dose constraints or the protection scheme in which they are incorporated.
The various rationales are fairly specific about accident and emergency situations for which they are appropriate, but they seem quite vague about routine exposure situations to which they might apply. At a minimum, I think that the Commission should strive to give an extensive listing of the kinds of sources of routine exposure to which the different maximum dose constraints apply. I think that this is especially important in regard to sources involving naturally occurring radionuclides, such as mining and milling wastes and, in regard to exposures of the public, radionuclides in drinking water. I think that it is important to include specific sources of exposure to naturally occurring radionuclides as examples, because doses can vary widely and some of these sources often are not regulated even though doses can be quite high compared with doses from regulated sources of artificial radionuclides. For example, exposures of workers at facilities that process rare-earth materials or other metals can be high in relation to dose limits for occupational exposure, due to the presence of high levels of uranium or thorium, but radiation exposures at such facilities often are not monitored or controlled. The Commission needs to be clear that maximum dose constraints should be applied to any controllable exposure situation, including situations where radiation exposures are incidental to non-nuclear activities.
In the first bullet, end of the second sentence, does the inclusion of “highly contaminated ground” refer only to accidents; that is, does it go with “i.e.” (the syntax here is not clear)? Does the Commission intend that a maximum constraint of 100 mSv per year would be appropriate for “highly contaminated ground” which resulted from past routine practices or deliberate actions (old mill tailings piles, for example)? I think that this needs to be clarified.
In the second bullet, end of second sentence, what are examples of situations where exposures are difficult to control, and how do they differ from “existing controllable exposures” in the last sentence? In regard to the latter, there are lots of existing controllable exposures for which the appropriate dose constraint should be far lower than 20 mSv per year, and even well below the next level at 1 mSv per year. Regulation of exposures to naturally occurring radionuclides in drinking water is a good example.
Of all the aspects of the draft 2005 Recommendations that are new, the one I support most enthusiastically is the inclusion of an effective dose of 0.01 mSv per year as a minimum constraint to be applied to any situation (a floor to optimization and ALARA, if you will). One of the great failings of radiological protection, at least in the U.S., is a lack of generally applicable exemption principles. We have implemented such a principle in an indirect way by means of many case-specific exemptions from regulation, but it would be better if we could establish a de minimis (trivial) dose as a matter of principle, in part because existing exemptions correspond to doses that are highly variable from one case to another.
Paragraph (165). I still don’t see a basis for the recommended maximum dose constraints in these statements. The third sentence seems like an important statement which could benefit from discussion of the Commission’s views on how situations where one individual is exposed to several significant sources could be identified and what kinds of additional restrictions should be applied, especially when exposures of the public are of concern. The Commission has previously argued, e.g., in Section 5, paragraph (134), that it is difficult to assess total doses to members of the public from all controllable sources, so some attempt to reconcile these apparently contradictory statements seems in order.
Table 7. As in the case of Table S1 in the Summary, on which I commented previously, when this table is viewed by itself (and it often will be divorced from explanations which accompany it), the point that maximum dose constraints do not apply to medical exposures or directly to potential exposures is lost. I think that this needs to be mentioned in the table itself, perhaps in a footnote, because “all types of exposure situations that can be controlled” in the title certainly include medical and potential exposures. I also mentioned previously that “normal situation” and “controllable existing exposures” need to be defined carefully somewhere, and I believe that definitions should be given with this table.
Paragraph (166). I think that the Commission needs to emphasize that regulatory constraints to be set below a maximum value can be highly source- or practice-specific, and that there are good reasons why this is so. Especially in the U.S., the radiological protection community has been hammered mercilessly on grounds that explicit or implicit limits on dose or risk in standards for different sources and practices are highly variable, thus showing a lack of consistency (harmonization) of radiation standards. The clear implication of such criticisms is that some standards are not adequately protective. I think that this issue needs to be addressed, because important and damaging misconceptions about the variability of various radiation standards for different sources and practices abound.
The next-to-last sentence of this paragraph again indicates that dose constraints are separate from the principle of optimization. But isn’t it true that some of the dose constraints recommended by the Commission are based essentially on generic considerations of doses that are reasonably achievable for specific sources in all cases? So, once more, there is a need to understand the basis for the maximum dose constraints.
Paragraph (168). It seems clear from these statements that the Commission believes that there generally is no need to inform the public about their radiation exposures. To me, this position is objectionable and should be reconsidered. There is no distinction in these discussions between accidents and routine exposures, but surely the public has a right to information about possible consequences of accidents when they occur. Even in routine exposure situations, the Commission is now endorsing the importance of stakeholder involvement as input to the process of optimization, e.g., in Section 7, paragraph (196), but there can be no meaningful input if stakeholders (the public) are not informed about their doses and risks. This is especially the case in dealing with cleanup of contaminated sites. I also don’t see a good reason why the public shouldn’t be informed about doses and risks from routine releases from nuclear facilities in their area. Site operators are required to report estimated doses to regulators, so why not report them to the public (e.g., by means of yearly statements in newspapers)? A good analogy here is that in the U.S., every operator of a public drinking water supply is required to inform every user once a year about levels of contaminants in their drinking water.
Paragraph (169), last sentence. I commented on this before, but it is objectionable to me that administrative and support staff who could receive radiation exposure in the workplace would not be informed about their exposures. They may not require training and they may not need to be monitored individually if area dosimeters are used, but a right to information seems basic to me and should not be compromised.
Paragraph (172). I think that this is a valuable discussion, in part because a somewhat different concept of a maximally exposed individual (MEI) is often used in risk assessments for hazardous chemicals in the U.S.
Paragraph (173). This discussion is encouraging because it gets at an issue with the recommendations in Publication 60 which I have been concerned about for a long time. At the time Publication 60 was published, the Commission was developing age-specific dose coefficients for intakes of radionuclides. However, Publication 60 was silent on the question of whether the public dose limit and dose constraints, which applied to routine exposure and were expressed in terms of an annual effective dose, were to be applied to the highest dose in a year, taking into account dependencies of annual doses on age, or to an annual dose averaged over a lifetime (i.e., a population of all ages). By not addressing this point, the presumption was that annual dose limits and constraints for routine exposure of the public applied to the highest dose in any year when exposures of a population of all ages are considered.
To me, an important implication of this approach is that an annual dose limit or constraint for the public corresponds poorly with lifetime risk (or average annual dose), because the highest estimated dose in any year often occurs in infants or children but the lifetime risk from continuous exposure is determined mainly by exposures during adult years. Furthermore, in cases of continuous exposure, the lifetime risk which is obtained when a limit on annual dose is applied to any age can vary greatly depending on the radionuclides of concern; i.e., exposures at a given maximum annual dose can correspond to greatly different lifetime risks.
So, even though the Commission appears to be less concerned about limitation of risk than was the case in developing Publication 60, I still think that it is important to state explicitly that compliance with dose constraints for the public which apply to routine exposure situations should be assessed on the basis of annual effective doses averaged over a lifetime, rather than the highest effective dose in any year (at any age). The discussion in this paragraph hints that the Commission may be leaning in this direction. However, I believe that a direct and unambiguous statement is needed to remove any doubt.
Whether it would be a good idea for the Commission to develop age-averaged effective dose coefficients and age-averaged habit data for application to routine exposure situations is less clear to me. Development of age-averaged habit data for ingestion can get complicated, because the age-dependence of ingestion intakes by different pathways (drinking water and various kinds of food) is not the same and can vary from one country to another. The Commission also would need to consider whether age-specific habit data would be incorporated in dose coefficients or kept separate. That is, would dose coefficients be normalized to a unit activity intake or to a unit activity concentration in the environment? The latter option, which was used by the U.S. Environmental Protection Agency in developing risk coefficients in Federal Guidance Report No. 13, might make more sense.
Paragraph (178), first sentence. The reference to paragraph (146) can’t be correct, because that paragraph addresses medical exposure.
The statement itself, which is quite agreeable, reminds me that the Commission might consider a more specific definition of a “controllable source” of exposure to naturally occurring radionuclides. In my view, exposures to naturally occurring radionuclides are controllable if they are increased as a result of human activities (the term used in the U.S. is “technologically enhanced naturally occurring radioactive material”). However, even this can be somewhat complicated because levels of naturally occurring radioactivity in drinking water can be controlled when drinking water is provided by a municipal water supply, but not when drinking water is supplied by a domestic well, and levels of naturally occurring radionuclides in foodstuffs probably should not be considered controllable unless they are enhanced by processing of food or result from human activities.
Paragraph (179), first sentence. Here again, on what basis is action certain to be warranted? Is it because associated risks of lung cancer clearly are intolerable, is it because lower levels should always be reasonably achievable, or what?
Paragraph (180), third sentence. I don’t understand the intent of this sentence. Does the constraint established by national authorities represent a mandatory action level (i.e., reductions in radon levels above the constraints are required), with the lower “most applicable level at which to act” (whatever that means!) representing a level where action to reduce levels is encouraged but not required? I am having trouble understanding the difference between a constraint established by national authorities and a “level at which to act,” which apparently must be below the constraint.
I also think that the Commission needs to be careful about recommending that national authorities impose mandatory requirements on homeowners to reduce levels of indoor radon below some value. Guidance and encouragement seem appropriate, but I’m not so sure that imposing requirements is a good idea when a right to privacy in one’s home is basic.
Paragraph (183), first sentence. Beginning this sentence with “Because of these deficiencies” is a puzzle to me, because I fail to see how the Commission’s development of detriment had anything to do with deciding on acceptable (barely tolerable) levels of risk due to radiation, which is the subject of discussion in the previous two paragraphs. It seems to me that detriment was designed to deal with deficiencies in using fatal health effects as a measure of harm from radiation exposure, but that is a totally separate issue from the issue of deciding what levels of risk are acceptable (or unacceptable).
Paragraph (185), second sentence. In claiming that constraints on single sources would be more restrictive that dose limits in normal situations, I think that the Commission has failed to appreciate that this may not be the case in regard to some sources of public exposure. For example, if exposures to mining and milling wastes fall under “normal situations,” which seems reasonable to me, at least during mining or milling operations, then achieving an annual effective dose much below 1 mSv may be difficult.
Paragraph (187), first sentence. What “risk constraints”? Recommendations on, and uses of, risk constraints, in contrast to dose constraints, have not been discussed up to this point.