|PART 6 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.
Optimization of Protection
Most discussions in this section seem reasonable and unobjectionable. I particularly liked the “dose matrix” idea, because it preserves information.
However, as indicated in a previous comment, I believe that this section needs to include more discussion on the issue of whether optimization of protection is to be applied strictly on a source-specific basis (each source should be optimized independently of all others), or whether there should be some consideration of optimizing aggregates of different sources or effects of optimizing one source on other sources.
Paragraph (196). I would repeat a previous comment that stakeholder involvement is most beneficial if full disclosure of information on doses and risks is provided. Right-to-know and informed consent are important concerns here.
Paragraph (202), second sentence. On what basis should the importance of each matrix element listed below be established? Will this be discussed in the “foundation document” noted in paragraph (203)?
Exclusion of Sources from Scope of the Recommendations
Section 8.1. In a previous comment on Section 2.3, I noted that the Commission’s distinction between “exclusion” and “exemption” may not be clear, may seem artificial, and may contravene national legislation in some countries. This section muddies the waters even more, because the section title refers to “exclusion” but the precedents cited refer specifically to “exemption.” Again, I think that the Commission needs to be more careful in dealing with these two concepts, particularly in regard to recommendations on exclusion of artificial sources.
Paragraph (205), first two sentences. As indicated in a previous comment, I agree that 0.01 mSv per year is a reasonable exemption (if not exclusion) level for artificial radionuclides.
Paragraph (206) and Table 10. I believe that it is essential that this paragraph and the presentation in Table 10 include statements that the recommended levels (exemption levels, preferably) apply only to artificial radionuclides in solid materials or in small volumes of contained liquids. This limitation is suggested by precedents discussed in paragraph (205), but it is not included in the Commission’s recommendations. Allowing concentrations in air or drinking water at the recommended levels could result in doses that clearly would be much too high to justify exclusion or exemption. The Commission must place appropriate limitations on application of recommended exclusion (or exemption) levels to avoid misinterpretations.
Paragraph (208), second sentence. Strikingly absent from this list of protective actions is treatment of drinking water by operators of municipal water supplies, which can be done at a reasonable cost at fairly low activity concentrations of naturally occurring radionuclides.
Paragraph (209) and Table 10. As in the case of artificial radionuclides discussed in Section 8.1, it is essential that this paragraph and the presentation in Table 10 include statements that the recommended exclusion levels apply only to naturally occurring radionuclides in solid materials; use of the term “materials” by itself is insufficient. The assertion in the last sentence of this paragraph that the proposed exclusion level for natural alpha emitters would correspond to annual effective doses from consumption of food and water of no more than 0.2 mSv is absurd. For example, a concentration of 228Ra in drinking water of 1.0 Bq per gram corresponds to an annual effective dose of about 500 mSv, assuming a daily consumption of drinking water of 2 L and the dose coefficient for ingestion of 228Ra by adults in Publication 72. When consideration is given to costs of water treatment and the large number of people who obtain drinking water from municipal supplies (i.e., application of ALARA to this exposure situation), reasonable exclusion levels for naturally occurring radionuclides in drinking water probably should be substantially more than a factor of 1,000 lower than the value in Table 10. It also is obvious that these levels cannot be applied to radionuclides in air.
General comments. I agree with the Commission’s desire to eliminate trivial exposure situations from concern in radiological protection. However, this is a delicate political issue in some countries. Therefore, if the Commission’s recommendations are to be taken seriously, it is necessary, in my view, to do two things: reconsider the matter of “exclusion” vs. “exemption,” with greater emphasis placed on exemption, especially for artificial radionuclides, and make it clear that recommended exclusion (or exemption) levels apply only to solid materials or to contained liquids containing artificial radionuclides.
It also is important, in my view, that the Commission’s recommendations emphasize that exemptions from regulation normally should apply only to receipt, possession, use, transfer, and disposal of exempted materials, but that exemptions do not apply to production of exempted materials. For example, it is completely reasonable to exempt smoke detectors containing 241Am, small sources used to calibrate radiation detection equipment, and thorium in lamps, but the manufacture of such items clearly should not be exempted from regulatory control.
I have already commented on my belief that a serious shortcoming of the draft 2005 Recommendations is that the recommendations on medical exposure do not acknowledge a patient’s right to full disclosure of information on doses and risks due to medical procedures. My other important concern is the neglect of a significant increase in biological effectiveness of x rays used in many medical procedures. These concerns apply, for example, to the statement in paragraph (218), last sentence.
Paragraph (221), first sentence. This statement is agreeable, but there is no good reason why the same right should not be extended to any medical procedure involving radiation exposure of a patient.
Paragraph (225), first and last sentences. These statements also are agreeable, but, again, there is no good reason why the same right should not apply more generally.
The recommendations on potential exposures somehow seem disconnected from the recommendations for other types of exposure, even though the Commission’s efforts to relate the two by essentially equating dose and risk constraints is obvious. I say this because the focus is on risk in the recommendations on potential exposures, even though the use of risk in the rest of the system of radiological protection is minimized and the maximum dose constraints do not evidently have a basis in limitation of risk. Thus, it seems to me that a risk constraint is not really based on limitation of risk but, rather, is basically a constraint on probability-weighted dose, which I don’t regard as quite the same as risk.
Paragraph (228), last sentence. What is meant by “dispersal” of waste? Does this mean discharge to the environment without containment, or is it synonymous with “disposal”? Depending on what “dispersal” means, it is not obvious to me that dispersal will increase potential exposures compared with normal exposures. This sentence also suggests once again that “normal exposure” needs to be defined carefully.
Paragraph (229), first sentence. It is not obvious to me that dose constraints should not be applied directly to potential exposures, at least in some situations. Indeed, this statement appears to be at odds with the reference to Publication 77 in the last sentence of the third bullet item in paragraph (164), because that publication notes that an effective dose of 0.3 mSv per year is an appropriate dose constraint for disposal of radioactive waste. In assessing the acceptability of waste disposal facilities, it is reasonable to assume a normal release scenario, assign a probability of one to it, and estimate potential doses in the future for comparison with a dose constraint. Waste disposal is often regulated in this way, and it would be unfortunate if the Commission recommended against a common and accepted, as well as sensible, approach.
Use of risk constraints for potential exposures, while seemingly reasonable, can cause problems. As noted in paragraph (233), there is the issue of estimating probabilities of scenarios, which is a dicey proposition for waste disposal. Also, when the probability of a scenario for release from a disposal facility is low, the associated dose constraint, if the scenario occurs, can be quite high, and this could affect public acceptability of a facility.
Paragraph (230), second sentence. There is no reason why attributable incidence of health effects, rather than death, could not be used as a measure of risk. This would conform to the usual approach in regulating other carcinogens. I would also comment that if the Commission’s recommended nominal probability coefficient for lethality adjusted cancer risk in Table 6 is used for this purpose, the quantity calculated is not risk of fatal cancers.
Paragraph (230), last sentence. Is it true that Publication 81 applied a risk constraint to geologic disposal (only)? I read that document as being applicable to solid waste disposal in general, including disposal in near-surface facilities. The term “geologic disposal” often is reserved for disposal far below the ground surface.
Paragraph (234). Two nits here. Shouldn’t “2 10−4” in the first sentence be written with a multiplication sign (“2 × 10−4”), and similarly for the other numbers in scientific notation? Also, I think that it is important to state explicitly that risk constraints are annual risks.
More generally, I have never understood the Commission’s preference for annual risk, rather than lifetime risk. At least in my value system, you only die once, so lifetime risk is all that matters. Using annual dose in regulations for situations other than potential exposures makes sense, because regulators need a way to check on the acceptability of practices on a regular basis. However, there is not really anything for the regulators to check in attempting to control potential exposures, so I don’t see that using annual risk makes much sense. Does the Commission use annual risk because the corresponding lifetime risks are uncomfortably high? Regardless of the Commission’s reasoning, using annual risk serves to hide actual risks, and I do not believe that this is a good thing.
Paragraph (240), end of first sentence. As noted in a previous comment, probability of incidence of a stochastic effect could be used, and probably is preferred if comparisons with estimated risks from other carcinogens are called for. Indeed, it seems a bit inconsistent for the Commission to focus on fatal stochastic effects when the basic data used as a starting point for estimating detriment are data on incidence. That is, there seems to be somewhat of an inconsistency in addressing potential exposures compared with other situations.
Protection of the Environment
Paragraph (242), second sentence. I think that the term “harmonized” in discussions on protection of non-human species could be misinterpreted when protection of humans is based mainly on control of stochastic effects, for which no threshold is assumed, in individuals, whereas protection of plants and animals most likely will be based for the most part on prevention of non-stochastic effects, which have a threshold, in populations. Thus, the basic approaches to protection are quite different, and “harmonization” probably has a rather restricted meaning. Also, “harmonization” has been used most often in discussions on reconciling standards for protection of human health from exposure to radionuclides compared with hazardous chemicals. I think that this term should be used more carefully, or its intended meaning in this discussion should be explained more fully.
Paragraph (248). This entire paragraph is confusing to me. Does the Commission think that the focus of a system of radiological protection for plants and animals should be on protection of species or individual organisms? The second bullet item in paragraph (247) seems to indicate that the focus will be on protection of species, but the statement that “it therefore seems appropriate to focus on the individual for the purpose of developing an assessment framework” casts some doubt on this. The last two sentences mainly serve to confuse the issue in my mind, and the last sentence looks like a cop-out by the Commission.
Paragraph (A1), second sentence. Here again, estimated morbidity (incidence) would seem to be a perfectly reasonable metric to express detriment.
Paragraph (A12), last two sentences. Would it be better for purposes of a set of recommendations that presumably will be in place for a number of years to use revised estimates of cancer incidence based on the new dosimetry data (DS02)? It may look peculiar if the Commission recommends detriment coefficients on the basis of data which will be outdated by the time that the 2005 Recommendations are issued in final form.
Paragraph (A16), next-to-last sentence. The meaning of this sentence would be clearer if a comma were inserted after “(CLL)” to avoid a possible misinterpretation that “multiple myeloma” belongs with “excluding.”
Paragraph (A17), last bullet item. I think that it would be helpful to mention by how much the genetic risk coefficient is reduced by neglecting estimated risks beyond the first two generations. What portion of the reduction in risk by a factor of 5 noted in the following sentence results from this change?
Section A.3.1 and Section A.3.2, paragraph (A24). These discussions are puzzling to me. Although they consider issues of uncertainty (but only in general terms and without quantification), no analysis of uncertainty is presented, the title of Section A.3.1 notwithstanding, and there is no discussion about whether these sources of uncertainty were taken into account in the Commission’s analysis of stochastic risks. Are these discussions mainly intended to be cautionary, or what?
Paragraph (A22). In the first sentence, change “kev” to “keV.” Also, an important omission from this sentence is the point that photons of energy less than 30 keV, including mammography x rays, probably are substantially more effective than 30-250 keV photons.
The second sentence fails to mention the crucial point that central values of radiation effectiveness factors (REFs) presented in NCI/CDC (2003) differ substantially from the corresponding radiation weighting factors recommended by the Commission for photons of energy less than 250 keV and electrons of energy less than 15 keV. The reader might get the wrong impression about this from these words.
Section A.3.5. Compared with the approach used in Publication 60, I would agree that the new recommendation on calculating detriment is an improvement. However, there still is some degree of arbitrariness, and it still is not obvious how detriment should be compared with measures of health risk used for other carcinogens (usually incidence).
Paragraph (A31), last sentence. The decision not to use the q sub min adjustment for skin cancer may be reasonable on the basis of the different factors that go into it, but there are monetary costs of treatment which are a kind of detriment to persons with basal cell carcinoma or their insurers, and I wonder if this should be taken into account. The approach to estimating detriment for skin cancer also does not take into account that rarer melanomas of the skin, which can be caused by radiation, are a serious medical problem for afflicted individuals.
Paragraph (A39), first bullet item. Does this approach make sense when gonadal cancer and heritable effects are not experienced in the same individual?
Paragraph (A41), next-to-last sentence. This statement may be a bit confusing when compared with the statement in the first bullet item of paragraph (A39). Perhaps there should be a footnote in Table A2 to the effect that the tissue weighting factor for gonads includes cancer in the ovary and testes and heritable effects.
Paragraph (B14), last sentence. I would reiterate a previous point that another important issue is the need to harmonize (achieve consistency) in approaches to protection of human health from exposure to radionuclides and other carcinogens. Although this point is not directly relevant to discussions in this paragraph, the Commission needs to recognize that this is an important issue which adversely affects how many people view radiological protection.
Paragraph (B21), second sentence. How will scorable DNA damage be taken into account in a system of radiological protection for plants and animals? In particular, how is this endpoint relevant to protection of species?
Paragraph (B22), next-to-last sentence. I wonder how easily background dose rates can be applied to protection of biota when radiosensitivity varies greatly among species and some species may not be able to tolerate unusually high background dose rates.