|Comments to ICRP June 2006 Draft Recommendations by C. Borrás
The current draft has significant improvements over the 2005 version. However, it is still questionable whether there is any need at this point in time for such a detailed new document, when after analyzing in a most comprehensive manner the results of recent scientific studies, the Commission concludes that the uncertainty associated to the findings is such that, in their judgment, changes are not warranted. Examples are the non-cancer radiation effects observed both in the atom bomb survivors and in the Chernobyl workers, and in the averaging and weighting of wR and wT, where the Commission has established “ICRP judged values”, regardless of the fact that it acknowledges that cancer incidence is population, gender and age dependent. We realize that these decisions have been made for simplicity sake, but one wonders why go through the trouble of reviewing all the scientific literature and report on it, if the results are not to be used in a scientific manner.
For medical physicists the problem is that the Foundation document from ICRP Committee 3 is not available for consultation yet and, as consequence, the new ICRP Recommendations will not benefit from the input of the ICRP members who are experts in radiation protection in Medicine.
The other foundation documents have been examined together with this new version of the Recommendations and the dosimetry section is still considered weak, especially regarding the algorithms to combine external and internal exposures, which are not fully developed.
Another disappointment in this new draft is the return to the term “equivalent dose”, which in the 2005 version had been changed to “radiation-weighted dose”, a much clearer concept, which translates well in languages other than English. In Romanic languages both equivalent dose and dose equivalent, the operational dosimetric quantity, have been translated (erroneously) using the same words. Peculiarly, the ICRP 2006 version uses “Committed Radiation-Weighted Dose, HT”. This discrepancy should be eliminated and the term Radiation-Weighted Dose re-adopted.
There remain problems with the concept and application of dose constraints, which in some sections now appear as “action levels”. If this is what the Commission means them to be, why not say so, and eliminate a concept that translates poorly in Romanic languages where it has been translated as dose “restriction”. Because the concept is still contradictory in different areas of the document, there is still a concern that regulators will use constraints as upper boundaries and thus de facto demand they be met as if they were or in lieu of dose limits. This is particularly worrisome in the application of dose constraints to the shielding requirements of medical linear accelerators treatment rooms, an area where many developing countries are spending unjustified amounts of money that curtail the funds available for health care. Let’s hope that the strong statement on Paragraph 43 and the last sentence of Paragraph 223 convinces them otherwise!
The justification of a procedure for an individual patient (Section 6.1.2, Paragraph 250), for “complex diagnostic procedures” (which are not defined) “and radiation therapy” is also of great concern to the medical community. Regulatory authorities demanding justification of each patient undergoing interventional radiology or radiation therapy is an interference with a medical act and it should not be allowed.
There are definitions which need additional clarification; the most important one is “source” in paragraph 34 that states: “The term ‘source’ is used to indicate the cause of an exposure, and not necessarily a physical source of radiation”. Yet its use throughout the document often refers to a discrete entity. It is recommended that the BSS (IAEA 1996) definition be used instead. “Source: Anything that may cause radiation exposure, such as by emitting ionizing radiation or releasing radioactive substances or materials”.
Another problem lies with the use of “operators” and “operating management”. In the nuclear power community, operators are the managers of the facility. In the medical field, operators are the individuals who operate a machine such as an x-ray unit or a linear accelerator. To refer to facility managers, the document uses two terms “operators” and “operating management”. Where it appears, the term “operating management” is clear. On the other hand, “operators” seems to be equivalent to operating management in paragraphs (21), (32), (194), (197) and (232), but it is ambiguous in (371), (378) and (381). It is recommended that the term “operating management” be used throughout the document to avoid confusions.
The other term that should be changed is “radiation worker” in paragraphs (167) and (170), which is not adequate and should be avoided as it could be misleading. "Workers engaged in radiation work" is preferred by the International Labour Organisation (ILO), whose terminology in the occupational health area should be accepted.
The justification of new practices, such as irradiation of humans for security screening or for theft and contraband detection is not considered by the Commission. It should be added to the new Recommendations.
Chapter 10, “Protection of the Environment” is very weak and offers no practical advice to regulators. It may be deleted until the Commission is ready for specific recommendations.
Chapter 11, “Implementation of the Commission Recommendations” does not belong in a document that pretends to be scientifically based. This Chapter should be published as a separate ICRP document or eliminated altogether; the implementation of the ICRP Recommendations has always been the role of international intergovernmental organizations such as the IAEA, ILO, PAHO and WHO through joint publications like the BSS (IAEA 1996).
Specific Comments (By Paragraph)
(59): The word “diagnosis” in “because cancer incidence allows for more accurate diagnosis” is ill-chosen and should be replaced to avoid confusion with cancer diagnosis.
(68) and (71): In (68) the estimate for genetic risk is expressed in Gy; in (71) the estimate for hereditary effects is expressed in Sv. The rational for the different units used should be explained or both quantities should be expressed in the same units.
(78) and (81): The induction of malformations in (78) has a 100 mGy threshold. In (81) the units of utero exposure are in mSv. The rational for the different units used should be explained or the same units should be used in both paragraphs.
(97): The sentence regarding “microdosimetric properties” is confusing and should be reworded.
Table 3: The footnote should read: “All values relate to the radiation incident on the body or, for internal radiation sources, emitted from the source in the body”.
(130): The explanation on the use of the “new computational male and female models” should be expanded and references given.
(134): Add how to include them, by what formula.
(135): This section only takes into account exposure from radioactive materials, mainly effluents. It is imperative that under “technical installations”, considerations be given to exposure from radiation generators, such as x-ray units and medical and industrial particle accelerators.
(136 – 138): These sections are OK, but weak. They should be strengthened.
(140): It states the use of “reference values”, which were mentioned before in (18) and (22) but never properly introduced. It is not clear what these “reference values” are. The definition in the Glossary states that they are to be used with biokinetic models. Yet Paragraphs (139- 144) deal with effective dose which includes both external and internal exposures.
(141): The Paragraph is very confusing. Now there are parameter values and reference values. Parameter values are not included in the Glossary but are further discussed. The paragraph should be rewritten for greater clarity.
(150, 152, 152): Is there are difference between accuracy and certainty? If so, explain what is meant by each term.
(154): The statement is weak. Expand.
(177): Change “during the remainder of the pregnancy” to “per annum”, as the remainder of the pregnancy can differ by a large factor.
(180): “It is exceptionally rare that the dose to the offspring can exceed that of the reference adult by a factor of up to about 3”. Where does the factor of 3 come from? Where is the reference?
(187): This statement gives the regulator too much power. It should be re-phrased.
(191): The Paragraph is unclear as it seems to contradict itself. First it requires three levels of justification for medical exposures, which is unacceptable. The generic level of justification may be the responsibility of the regulators, both in the Radiation Safety and in the Health Authorities. For medical exposures it is important to estimate the risk to the patient if a particular procedure is not performed! While the consultation with the medical profession is appropriate, the ICRP should also recognize the role to be played by the Health Authorities in the control of medical exposures, regardless whether the Radiation Safety Authority is within their purview or not. No regulator should be involved in the decision on what is justified and what is not justified on a procedure or an individual basis. Those types of justifications should be the sole concern of the physician responsible for the patient and/or performing the procedure. The last sentence “Justification of medical procedures therefore remains part of the Commission’s Recommendations”, right after the sentence “The responsibility for the justification of the use of a particular procedure falls on the relevant medical practitioners” is confusing. Does this sentence suggest that the second level of justification, the justification of the procedure, is the responsibility of the regulator? Certainly not the individual justification?
(216) and Table 4: The dose constraint for public exposure is supposed to be below 1 mSv. The Commission should place here their caveat of Paragraph (223): “Clearly, it would be a misapplication of radiological principles to select a value for a constraint, compliance with which would involve disproportionate resources”. Unfortunately this is what happens right now in some shielding design constraints, especially around medical linear accelerators in developing countries.
(255): The sentence should read: “Diagnostic reference levels are….”
(269): This Paragraph seems misplaced here. Radiological tests required by insurance companies may or may not be a medico-legal exposure. “Medico-legal” is not discussed nor defined in the text and insurance companies are the only subject matter in (269). It would be very useful if ICRP would include this term, which is not well-defined and is usually associated with medical malpractice or claims resulting from accidental injuries due to negligence, in the glossary. It is recommended that the following wording from the BSS (Appendix II, paragraph 6) under “Justification of Medical Exposures” be adopted. “Any radiological examination for occupational, legal or health insurance purposes undertaken without reference to clinical indications is deemed to be not justified unless it is expected to provide useful information on the health of the individual examined or unless the specific type of examination is justified by those requesting it in consultation with relevant professional bodies.”
(272): Change “limited” to “constrained”.
(276): The recommendations in this Paragraph are weak and should be strengthened.
(278): Change “are called existing exposures” to “are considered existing exposures”, since existing exposures can also arise from past practices which have left residual contamination or elevated radiation levels, not only from natural sources.
(279): Here action levels are constraints. Very confusing, especially the last sentence: “In contrast to action levels below which no action is required, the process of optimisation and constraints do not use any predetermined end point below which no action is warranted to reduce the dose further”. Its meaning should be clarified.
(281): Add “or adsorption through the skin” after “inhalation or ingestion”.
(289): The Recommendation in this Paragraph is confusing and needs to be clarified.
(318): Risk constraint should be defined in the Glossary.
(332): The term “radiotherapy accident” implies that the accident has occurred while delivering radiotherapy. Yet the list of accidents shown as examples mixes accidental medical overexposures of cancer patients (Costa Rica, Poland), with accidents arising from individuals other than patients being exposed to external radiation sources (Vietnam, Thailand). This is confusing. The term should be changed to “accidents with medical sources” and it should clarify that patients under treatment, staff and/or public may be overexposed. Alternatively, the Commission may wish to coin a specific term for accidents in radiotherapy situations. This, however, fails to recognize that overexposures may also occur in the interventional radiology field. The BSS defines “accidental medical exposures” as: (a) any therapeutic treatment delivered to either the wrong patient or the wrong tissue, or using the wrong pharmaceutical, or with a dose or dose fractionation differing substantially from the values prescribed by the medical practitioner or which may lead to undue acute secondary effects; (b) any diagnostic exposure substantially greater than intended or resulting in doses repeatedly and substantially exceeding the established guidance levels; and (c) any equipment failure, accident error, mishap or other unusual occurrence with the potential for causing a patient exposure significantly different from that intended” (IAEA 1996). The ICRP may consider adopting the term.
(339): The intervention levels in ICRP 60 and 63 being now constraints requires further explanation, as it is confusing.