2005 ICRP Recommendation

Draft document: 2005 ICRP Recommendation
Submitted by Sam Keith, US DHHS
Commenting on behalf of the organisation

GENERAL COMMENTS. Without the background documents (which have yet to be released for comment) it is difficult to thoughtfully review the recommendations. Since we understand that ICRP may release another "draft for consultation", perhaps in the Spring or Summer, we would request to have another opportunity to comment. This would be both warranted and feasible considering that the planned publication has reportedly been pushed back to 2006 or 2007. Much of the radiation biology has already been discussed in other documents. However, the discussion of stochastic and deterministic effects is very good. One premise appears to be consolidation of the information from past documents into this one, and that is a good idea. The executive summary does not completely reflect the document. We are very interested in the portion of the document that discusses RBE from low Energy sources. This has implications for public screening efforts (mammography) and therapy. These sources may have a larger role in the future, and while there is some available data, more is necessary. The use of a writer-editor to make the text read more simply, crisply, and clearly should help the reader understand the document better. The document also includes numerous typographical and spelling errors. The need for this review is consistent with the Commission’s position toward simplicity and clarity, as stated in paragraph S3. A statement should be included concerning exposures for the purpose of security screening. This should fall under the category of public exposures. A section on the justification of such exposures, in general terms (analogous to 9.1 for medical procedures), would also be helpful. Some words in the text show irregular character spacing. An example is the second word in paragraph 154, which appears to be “it” but the letters are superimposed on the version being reviewed. Care-Givers: The draft recommendations provide guidance for exposure of non-patient members of the public and care-givers in medicine that appears to be incomplete and potentially inconsistent with other exposure recommendations. In particular, detriment to non-patients is called secondary and constraints for care givers do not recognize circumstances where children or pregnant females may be present. The ICRP is encouraged to clarify how to provide consistent protection for these individuals. Globally replace “agreed” with “accepted.” As an example, the phrase “no agreed assessment procedures” in paragraph 242 would read better as “no generally accepted assessment procedures.” Medical exposures that carry no benefit to the patient (diagnostic scan for liability purposes) should be addressed as being unjustified. Medical exposures should not be characterized as providing exposure to workers and the public that is considered as secondary or irrelevant. Medical procedures should not unnecessarily expose the unintended group beyond acceptable levels. Medical exposures should be both justified for the procedure and optimized for the patient. The text only addresses justification, but optimization is equally important and should not be overlooked, especially regarding the new wave of digital radiography where increased dose can provide equally good or better images where the improvement does not justify the increased dose. The draft recommendations address higher dose constraints for members of the public who support patients being treated by internal radioactive sources while in the hospital or at home. Training in radiation protection matters should be required for these individuals, otherwise ICRP should recommend that their dose be limited to that of the general public. One can envision an industry dedicated to patient care in which the individuals are treated like the public, their doses are not monitored, but they receive doses exceeding the public and possibly the occupational limit. Care should be taken to avoid endorsing such uses of the general public. The draft states in various places that the goal of radiation protocols is to do less harm to a patient than other methods, or that this is always accomplished. The goal of using radiation is NOT necessarily to be more beneficial for the patient but to not do more harm than other methods. SPECIFIC COMMENTS. S7, last table entry. The text states that constraints should not be reduced by as much as a factor of 10, but that is what is shown in Table S1. The 4th entry (0.01 mSv/yr) appears to have been derived from the 3rd entry (1 mSv/yr) and their ratio is 100, not a value >1 mSv/yr), especially since nuclear medicine procedure rates are increasing. For example, members of the public who need significant medical care at facilities where radioactive patients roam can receive multiples of 5 mSv in any given year. Recommend adding text that addresses this large exposed group and provides constraints to protect them. Para 148. The text states that the focus of medical exposure protection is on justification. The text should be adjusted to address BOTH justification and optimization. First, the procedure should be justified for the diagnosis or therapy, and then optimized for the patient so that the right dose is given for the purpose (not too little and not too much). This combination of justification and optimization is consistent with ICRP recommendations, so optimization should be included equally. Para 152. Since the term “press” can have a limited meaning (newspapers or journalists in general) with a more encompassing term, such as “communications media” may be useful to consider. Para 158. -The text in paragraph 157 states that both the background dose and its variation are relevant in deciding on constraints, however paragraph 158 identifies only the dose (1 mSv/yr) but not the range. It would appear necessary to select both in order to meet the guideline set in paragraph 157 when establishing appropriate constraints. -The Figure 3 diagram should be changed to show the range of background and the annual dose at which no action is needed, so as to be consistent with the messages in Table S1 and Paragraph 157. The value of 0.01 mSv/y is addressed in Table S1 as the minimum value of any constraint, so the 0.01 mSv/yr arrow should be even with the bottom of the rhombus. The term “low” should be changed to “none” since 0.01 mSv/yr is the proposed ICRP level that needs no further action. Also, since ICRP is saying that several tens of mSv require action to be considered (para 160), add an arrow to Figure 3 at approximately this point and label it, “Action must be considered.” Para 161. In the last sentence, change “the need for action should be low” to “there is no need for action” since at doses that are 1/100 background, ICRP is defining the dose as the minimum value of any constraint (Figure S1). Para 163. The paragraph should be revised since the minimum constraint value of 0.01 mSv/yr in Table 7 is not characterized as such in the text of this paragraph. First, there is the need to change “maximum” to “maximum and minimum” in the first sentence since Table 7 provides 3 maximum values of constraints and one minimum value for constraints. In sentence 3, change “They should be” to “The first three should be.” Then add a sentence to the end that identifies 0.01 mSv/yr as the minimum value of any constraint (this keeps the reader from unwittingly dividing 0.01 mSv by a factor of 10). It might read, “The minimum value of any constraint should not need to be lower than 0.01 mSv.” Para 164. In bullet 3, change “corresponds to a low need for action” to “corresponds to no need for action” to be consistent with the message that no further reduction should be considered. Para 170. This paragraph addresses using a higher dose limit for “members of the public supporting patients being treated by internal radioactive sources,” but it should also specify that higher dose limits should require that the individuals be adequately trained in radiation protection matters in order to justify exposures beyond the general public limit. Another aspect of medical exposure should be added to this paragraph, and it involves involuntary exposure of the public by radioactive patients. Recommend adding a sentence that might read, “General individuals who are exposed to radiation emitted by patients without receiving information, training, and individual assessment of their effective dose belong to the public exposure group.” Para 179. In the next to last sentence, editorially remove the comma following “dosimetric.” Para 181. The rationale for establishing an acceptable occupational to public risk ratio of 10:1 is not satisfying. Recommend that it be revisited and rewritten in a manner that ensures the reader can appreciate and accept. If the Commission is using an estimated fatal risk rate associated with the average worker exposure in 1990, then those risks should be revised to current rates based on reduced worker doses (by a factor of >2), reduced risk coefficients (by >10%), and a suggested increase in public dose (due to increased exposures to members of the public from the increasing number of nuclear medicine patients). These might tend to suggest the appropriate ratio of occupational to public risks might be closer to 5 than 10. Para 197. There is disagreement that a goal should be the reduction of the number of exposed individuals, and it is recommended that this sentence be deleted. The actual goal beginning in the late 1980s was to reduce the number of workers receiving high doses and to reduce the collective dose, both of which have been accomplished in the U.S. The caveat was that that employers should not do this by spreading the work and dose over a much larger number of workers such that the individual doses would be lower while the collective dose would remain stable or increase due to training lag. In practice the number of high dose workers has been reduced along with the average worker dose and collective dose. There should be no reason to suggest reducing the number of workers (although this appears to be happening as a result of retirement and death while employment opportunities in some sectors other than medical remain low). With the increasing use of nuclear medicine and radiological procedures on a population that is aging and having more health problems, one can expect the number of medical radiation workers to increase. Pressure in the opposite direction is counterproductive, in opposition to the needs of public health, unwise, and therefore without basis. Para 208. K-40 in building materials as a major gamma source should be relatively rare, other than K compounds in purple K fire extinguishers in those buildings. Fortunately that gamma ray intensity is low for K-40. Perhaps K-40 could be eliminated from this paragraph. Para 212. ICRP recommends that high dose air crews, staff, and couriers be considered occupational workers. U.S. law does not currently allow such regulation at the national level, and it would be up to individual states to implement such standards, but since flights cross state boundaries, regional or national compacts among states are the only conceivable means of accomplishing this. Para 213. - The text addresses not limiting patient exposure and emphasizing only justification as a protective measure. This is not consistent with previous ICRP recommendations that justification and optimization provide the protection framework. Recommend that optimization be clearly added and developed in this paragraph and in all other relevant sections. -Reference is made to restricting worker and public doses from patients to those given in Chapter 6.4 (radon in dwellings and workplaces). One must presume that the intent was to limit such doses to the constraints found in Chapter 6.5 (individual dose limits). If this is not the case, it is recommended that the Commission change their position. -The text states first that dose limitation does not apply to patients and second that the recommendations apply to medical service workers and the public. One interpretation is that medical workers and members of the public can be exposed to unlimited radiation dose from patients; another is that their doses are constrained to the Chapter 6.5 limits. It is recommended that ICRP consider these individuals to be workers and public, and to constrain their doses to those provided in Chapter 6.5. As in all cases, these workers need training and they also need dosimetry if expected to receive more than 2 mSv/y (10% of the occupational constraint). Treating them as individuals not needing protection is not appropriate or justifiable. -Recommend the Commission address a group of public individuals currently omitted from the medical section (unaware and untrained public individuals exposed as bystanders to radiation emitted by patients) and include an appropriate dose constraint (1 mSv/yr). The current text addresses only public members caring for the patient at home. Dose limits for the unaware public in the U.S. is currently 5 mSv/patient, such that multiples of this dose could be received in a single year, without any benefit to either the patient or the public individual exposed. It is unclear how one justifies such exposure, considering that some of it is to pregnant women and their fetuses. Para 214. -After stating that “hospitals and radiology installations have to be reasonably accessible to the public,” recommend adding “and the public should expect to be reasonably protected from the radiation released from those installations and their patients.” -The text noted that exposures may be more difficult to control than those in an industrial premise, so the recommendation is that those installations may need to be actively involved in their control practices. -In the next to last sentence, it is addressed that therapeutic exposures may produce “some risk of stochastic effects in adjacent non-target tissue ….” The words “some risk” should be replaced with “significant risk” since, based in LNT and doses of perhaps 10 Gy, one can calculate a cancer risk of 50% (5%/Gy). This is significant, and the text should not downplay that potential risk. -The last sentence states that hospital “exposure is thus more difficult to control than it is in industrial premises” may not have experienced the challenges to exposure control that exist in some of those premises. Recommend deleting the text starting with “whose exposure” to the end of the paragraph, or else change “exposure is thus more difficult” to “exposure in some cases might be more difficult.” Para 215. -In sentence 1, after “radiological protection” add “and risk assessment.” The practical application of radiological protection involves limiting the dose but not necessarily assessing the risk (according to paragraph 82), and physicians are exempt from the need to follow the paragraph 82 guidelines (according to paragraph 213). Since the medical community espouses and the public expects physician to help patients balance risks and benefits associated with a given procedure, physicians should be trained to evaluate both sides of the equation. -The next to last sentence needs more teeth to protect the patient. It states that the physician “should be aware of the risks and benefits of the procedures involved.” Not only should the physician be aware of the risks and benefits, ICRP should recommend that they proactively help patients to understand both. Experience indicates that physicians generally do not know the doses delivered, and if they don’t, they are not aware of the risks. Para 216. The first and last sentences do not appear to be accurately written, and should be adjusted to state that radiation protocols are intended to not do any more harm than alternative methods. Although radiation may be less harmful than the alternatives, this end is not guaranteed in every case (look at cardiac cath patients with gross tissue necrosis due to procedural complications or inexperienced physicians). The goal is for the radiation methodology do no more harm than the alternatives, and ICRP should ensure that this is the message included throughout the draft. Para 217. -In line 2, recommend changing “In diagnosis, this means reducing unnecessary exposures” to “In diagnosis, this means eliminating unnecessary procedures and exposures.” If a procedure is given for the purpose of litigation protection, paying for equipment, or reducing the diagnostic burden, both the procedure and the patient dose may be unnecessary. It has been said that when a young woman reports to a medical facility with abdominal pain (which could mean the flu), the first order of business is to administer an abdominal CT scan to start the diagnostic process, leading to potentially unnecessary exposure of their ovaries. Para 220. -In sentence 1, recommend changing “no measurably increased risk” to “no significantly increased risk” since one can measure (or calculate) a potential risk based on LNT for any dose increase. -In the last sentence, change “can result in developmental harm” to “can result in any of these health effects.” Therapeutic exposures will not be limited only to producing developmental effects; they can produce any of the effects given in sentence 1. Para 222. -One should not state in a blanket manner that all medical procedures using radiation are justified, and there are examples to the contrary. A less definitive statement would be more prudent. -For sentence 3, the advent of digital radiography makes it useful to restate the text as, “It is difficult to make a quantitative balance between loss of diagnostic information by reducing the dose to the patient and gain of diagnostic information by increasing the dose, such as with digital radiography.” Para 226. -Recommend adding categories of public individuals (e.g., coworkers) for which adventitious exposures can readily exceed the 0.01 mSv/yr minimum constraint, and place them under the 1 mSv/yr public constraint umbrella. Coworkers can receive higher doses than individuals in waiting rooms or using public transportation. A new Tl-201 stress test patient delivers a dose of 0.01 mSv to a nearby coworker in perhaps as little as 15 minutes, which is shorter than a typical meeting. Consider that patients are not always told they will be radioactive for extended periods (typically for days to months) or are advised that the diagnostically useful radiation will be gone in quickly. With the rate of nuclear medicine procedures increasing, greater attention to such exposures may be prudent. -The last sentence should specify both that the individuals be properly informed of the risks and of the protective measures.” Para 234. Recommend adding the units of measure “y-1” following the occupational and public risk constraint values (as these were calculated using the annual dose constraints for these groups. Also recommend including the public risk coefficient that was applied to the 0.1 mSv/yr dose to achieve a 5E-6 yr-1 risk constraint. It appears to calculate back to 5E-3 Sv-1. Para 237. The text states that the ICRP approach applies only to situations where a small number of persons are exposed. This does not seem to be a practical approach since a large nuclear power plant accident could expose many individuals (as was addressed in the text). Assessing the radiological impact is important, even if other factors such as land exclusion contribute to the impact. The recommendations should provide a plan for dealing with multiple insults. Para 242. The text on protecting the environment from chemicals should be revised to clarify 1) that chemical releases do not utilize ALARA and this places environmental controls of chemicals and radiation on uneven footing, and 2) that with the large number of chemicals being introduced every year, that chemical releases are NOT “often” based on potential human and wildlife impact. The text reads, “releases of chemicals from other industries are OFTEN based upon their potential impact upon both humans and wildlife.” The ICRP statement does not seem to be consistent with practice. Para 244. -Pluralize “Reference Animal” since there are plans to have more than one. -If ICRP intends to develop reference animals and plants, it should also develop reference radiation and tissue weighting factors and example health effects that would be expected to be relevant to non-human exposures, or provide guidelines for identifying what effects might be relevant to protection. Without such guidance, providing reference animal and plant data in this document is considered premature as it could leave the user with too many new questions without a reasonable approach to solving them. Para 247. This paragraph is overly speculative. It identifies 2 possible objectives, but it should identify at least 2 firm objectives and be written to provide guidelines on selecting other objectives. The text could begin with, “Some basic objectives … should be to ….” The first bullet on safeguarding human health and limiting stochastic effects in individuals should be eliminated since existing guidance and regulations are already in place for this purpose, and it detracts from the focus of the paragraph (to protect the non-human portions of the environment). Consider eliminating the word “status” from the last sentence since the introduction of any radioactive material into an environment, no matter how small, would represent a change in status. If something more specific is intended, then a more specific term should be used or the text qualified. Para 248. The double negative in the next to last sentence should be converted for clarity. It might read, “it would be appropriate to provide advice that could be used in such legal contexts.” Since ICRP is entering the legal arena at this point, there is great need for the organization to publish its background documents for review and comments before issuing its recommendations for public comment. The 3rd sentence addresses the appropriateness of focusing on the individual, but it conflicts with the last sentence that addresses that the question of individual versus population protection is “not … of … concern to the Commission.” Para 249. ICRP is speculating that increasing the dose to an animal by 2 orders of magnitude (perhaps from 2 to 200 mGy) produces “known adverse effects on individual organisms.” It isn’t clear that ICRP has the data to support the text, so the background documents are needed for review before a public or agency comment period begins. Para 250. Remove the last sentence and add its message to the first one to keep from hiding the total message. The text would read, “The Commission wishes to point out that the recommended system does not prescribe the setting of regulatory standards, but it does provide a basis for such derivation where that is considered appropriate.” It should be noted that the present text is considered insufficient to accomplish this goal. ANNEX B. Para B6. In addition to developing a common scientific basis and approach for relating exposure, dose, and effect, such a basis must be developed for identifying what the relevant effects should include. For humans, it’s generally cancer, so we’ll need cancer risk coefficients for animals and comparable biomarkers of effect for plants. ICRP should state whether or not they plan to develop such factors Para B18. The “frequency of radiation effects” can be applied to populations, but it cannot be applied to “individual animals or plants.” Para B19. The statement that “information on dose responses is usually obtained at the individual level” is not considered correct. Results for a single individual are often discounted as being scientifically indefensible, and more credibility is applied to studies involving a reasonably large number of individuals. The text goes on the state that “radiation effects at the population level … are mediated via effects on individuals.” But this statement is also skewed inappropriately. Although individuals can be affected, an effect that is observed in an individual cannot necessarily be ascribed to the dose. Cancer, for example, is a disease for which one must compare the study rate with the normal rate, and it cannot be known with absolute certainty whether a particular cancer was the result of exposure to the radiation of interest, to natural background radiation, to chemicals, or as a result of a genetic predisposition. -Recommend rewriting the next to last sentence without the negatives (“… it would be appropriate to provide advice that could be used in such legal contexts”). -The last sentence mentions that the Commission is not directly concerned with whether individuals or populations are protected. Figure B1. -Since the text in the document mentions treating human and animal/plant protection in the same manner, it is unclear why there should be any difference between Figure B1 and Figure 3. -Figure B1 also disagrees with the text in paragraphs 249 and B20. Figure B1 shows “raised concern” at “>several times background” while paragraphs 249 and B20 address “increasingly serious concern” at doses that are “orders of magnitude greater than background.” This type of inconsistency in terminology and magnitude indicate a need for editorial and scientific review. Para B23. Recommend removing “molecular, cellular” since we have such limited understanding of how an in vitro molecular or cellular event might translate into an in vivo tissue or organ effect in humans, animals, or plants. Para B27. The Commission expressed a desire to develop an assessment framework for radiation and pointed out that “many international agreements and statutes call for protection against pollution.” One piece that is missing from this entire document is a discussion on the system or systems that are currently used to protect individuals from chemicals. If ICRP wishes to have a consistent approach, they should identify how their 2005 recommendations can be structured to be applicable to chemical protection measures for individual animals and plants, and the rational for differences should be provided. For those radioactive substances where the chemical effects may be more significant than the radiation effects (e.g., uranium), providing an approach for assessing the total risk to plants and animals on a common scale would be useful and consistent with the text.