2005 ICRP Recommendation

Draft document: 2005 ICRP Recommendation
Submitted by Serena Risica, Iatituto Superiore di Sanità (National Insitute of Health)
Commenting as an individual

Comments of Serena Risica to the ICRP 2005 Recommendations In this short document a not exhaustive list of comments is reported, focusing only on main issues. First of all, a fully comprehensive Publication, like the ICRP 1990 Recommendations, would be very helpful. New recommendations making reference to choices and statements contained in different previous publications could not be an effective tool. A list of definitions of concepts or a glossary of terms is considered necessary. In the 2005 Draft Recommendations the use of some terms is sometimes contradictory. Foundation documents were announced as available in the future. To analyse and discuss them is an essential step in order to discuss possible new recommendations. In this sense a new draft of the recommendations and a new consultation stage is highly desirable. One of the novelties of the document is the underlining of the role of constraints. This concept was already contained in ICRP 1990 Recommendations. However, in this draft it seems to be used differently and its connections with dose limit is not so clear as it was previously (how can constraints have the same numerical values as limits?). Justification – which seemed to have been cancelled in previous documents - is welcome back. However, its role in the draft is not clear and its meaning and importance seem to have been highly weakened, in comparison with what was stated in ICRP 1990 Recommendations. In paragraph (18) justification is entrusted only on governments or government agencies and the role of other protagonists, like experts and radiation protectionists, is completely cancelled. In paragraph (19) it is stated that The responsibility for the justification of the use of a particular procedure falls on the relevant medical practitioners. In paragraph (222) a general justification of all medical practices seems to be stated (The medical procedures causing patient exposures are clearly justified and are usually for the direct benefit of the exposed individual). Comment: Justification became in the years one of the three basic principles worldwide accepted in radiation protection. Are still the three principles of justification, optimisation and dose limitation the base of the radiation protection system? If they are, this is not clearly evidenced in the draft. Moreover, the use of ionising radiation in medicine, after natural background, is - as it is well known - the main cause of the exposure to ionising radiation of the population and many exposures are not yet really justified nor optimised. For this reason a general justification of exposures for medical reasons is not considered appropriate. The same can be said of the two statements in (213) First and most important, the limitation of the dose to the individual patient is not recommended because it may, by reducing the effectiveness of the patient’s diagnosis or treatment, do more harm than good and (221) Almost always if a diagnostic radiology examination is medically indicated, the risk of the mother of not doing the procedure is greater than the risk of potential harm to the fetus. They could be appropriate in an ideal society, where all the other steps of justification and optimisation have been already applied. (S3) and (156) It (the Commission) also recognises the 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 situation. Comment: why a so wide change of the system is proposed, while the successive sentence states The use of the optimisation principle, together with the use of constraints and the current dose limits, has led to a general overall reduction in both occupational and public doses over the past decade? Many radiation protectionists and Radiation Protection societies have expressed their perplexity on the idea of changing newly the basic system, a few years after the principles of the ICRP 1990 Recommendations were implemented in many national legislations. Is it not at risk the stability of the system? The change cannot be limited to application of new scientific evidences and improvement of already existing recommendations, where necessary? (111) and table 6. Comment: the nominal probability coefficients for stochastic effects are given without an assessment of the relevant uncertainties. Moreover, is the decrease of coefficients for hereditary effects, due to the choice of considering the effects only on the first two generations, enough conservative? In any case, as regards the total values of the coefficients, the differences are really small: are they significant or within relevant uncertainties? Is it appropriate to introduce so small changes? These probability coefficients were increased in ICRP Recommendations 1990 and now it is proposed to lower them of a small quantity. Is it not at risk for the credibility of the system? The new dosimetry on the effects of atomic bomb survivors – which should substitute the DS86 - was announced to be published within this year: were those conclusions taken into account? (118) The Commission recognises that there are uncertainties on the risk of in-utero-induced solid cancers. However, the Commission suggests that it is reasonable to assume that life-time cancer risk following in utero exposure will be similar to that following irradiation in early childhood… The Commission suggests that in utero exposure should not be a specific protection case in common prolonged exposure situations where the prolonged dose is well below about 100 mSv. Comment: what is well below 100? Is it 80 or 50 or 10? It is not enough clear. Some of the conclusions of ICRP Publication 90 Biological Effects after Prenatal Irradiation (Embryo and Fetus) are the following. (409) Low-LET radiation of 0.1 Gy or less can cause pre-implantation death at certain radiosensitive stages (from experiments with rodent and dogs). Comment: which are the uncertainties in applying these results to women? Moreover, pre-implantation death could not be a problem for the society, but surely it is for the woman involved. (417) Thresholds (specifically for skeletal malformations) become evident within the dose range of 0.05-0.25 Gy. These tend to be lower for induction defects and higher for organ-specific defects. (433) There is pronounced experimental evidence of high radiosensitivity of the developing brain, and of thresholds for the numerous phenomena of damage… The lowest experimentally observed doses causing persistent damage at the anatomical and structural level are in the range of 0.1-0.3 Gy of acute low-LET radiation. Comment: even if the risk may be lower for prolonged exposures, is “well below 100 mSv” enough conservative? (456) Analyses of the atomic bomb data suggest that the magnitude of cancer risk in adulthood from in-utero exposure may be similar to that from radiation exposure in early childhood. Comment: the high radiosensitivity of small children compared to adults is very well known. Is the proposed maximum dose enough conservative, too? Moreover, at the end of the document a list of open questions and needs for future research shows the still great and numerous uncertainties on these estimates. For example (463) The risk of defects in brain development is still not clear in the low dose range at low dose rate… (464)…It cannot be excluded that individuals who received slight developmental defects of the brain from prenatal irradiation may suffer more strongly from mental deficiencies in old age than unexposed individuals. This is a completely open field that should be studied. (466) … It is clearly important to study the lifetime risk after prenatal irradiation instead of considering to age 15 years. Long-term follow-up of the in-utero irradiated atomic bomb survivors is therefore a high priority. Conclusions: are the cited statements of ICRP 2005 Recommendations enough prudent? Do they respect the precautionary principle? (157) The Commission considers that the annual effective dose from natural radiation sources, and its variation from place to place, is of relevance in deciding the levels of maximum constraints that it now recommends. (159) The need for action is likely to be high if an effective dose from a single source is more than about a hundred times the global average background dose. Fig.3, (161) The need for action should decrease for doses additional to those due to the background of natural sources, if they are well below the annual background dose. etc. Comment: There are several other toxic substances (see e.g. arsenic), which are present naturally in the environment in variable quantities. The possibility of using background levels of these substances as reference values was discussed and excluded many years ago, stating that what is natural cannot be a parameter for acceptable levels of exposure. This statement is accepted by the international scientific community and was re-mantained in the studies on the polar environment . Conclusion: is it wise to base radiation protection on a choice already rejected by the international scientific community, even if in another field of environmental science? In any case, in (157) in comparison to what presented in the documents previously circulated, the new choice to use the background dose without the radon contribution is appreciable. However, it is surprising that the resulting scheme of fig.3 does not change considering the need for action likely to be high if an effective dose from a single source is more than about a hundred times the global average dose. This means that instead of multiplying the global average dose for a factor of 10 it is multiplied by a factor of 100. This means that actually natural background is not the basis for the choice. (164) The value of an effective dose of 0.01 mSv/year is the minimum constraint that should be considered for application in any situation. This value corresponds to a low need for action… giving rise to trivial risk to the exposed individuals. Comment: if 0.01 mSv is considered a trivial risk, how can 0.2 mSv (even if it had been correctly assessed, see (209) and relevant comments in annex 1) be considered an acceptable dose to define an exclusion level? An exclusion level should not be relevant to a trivial risk? If the reason is that such levels of exposures to natural radioactivity are unavoidable, it should be more clearly explained. However, on this issue see also comment to paragraph (209). (201) about dose matrix. Comment: a clearer explanation would help the comprehension and, if possible, some examples would be very useful. On this point a foundation document is also announced (203). Can the discussion on this point be delayed after the publication and analysis of the foundation document? Chapter 8. Exclusion was clearly defined in ICRP 1990 Recommendations (see its paragraph 291) Sources that are essentially uncontrollable, such as cosmic radiation at ground and potassium-40 in the body can be best dealt with the process of exclusion from the scope of the regulatory instruments,…Comment: in this draft a different use of the concept of exclusion seems to be made, without a clear definition somewhere. As regards artificial radioactivity, exclusions levels are not necessary and may be not appropriate, because artificial radioactivity is always controllable and amenable to control. As regards natural radioactivity, it was not chosen to exclude some single exposures (as in ICRP 1990 Recommendations), but to fix some levels of unit activity concentration. Two comments can be made to this choice: first of all, not all the exposures to activity concentrations below the stated values are uncontrollable. Moreover, natural radionuclides have much different radiotoxicity per unit activity concentration, in themselves and depending also on the scenarios of exposure (indoor or outdoor, external or internal, inhalation or ingestion, etc.). Therefore, the choice of only one value for all the radionuclides in the natural chains, except radon and its decay products in air (see (209)), and all scenarios could exclude high exposures from regulations. This point is explained with some examples in a short document, enclosed as annex 1. (The calculations contained in this document were already presented at the November meeting of the EU art.31 group of experts). (220) Prenatal doses from most properly done diagnostic procedures present no measurably increased risk of prenatal death,… Comment: with the uncertainties underlined above, can this be stated without any doubt? Or prenatal deaths can happen but we cannot detect them? (226) Exposures to ionising radiation for insurance companies are considered justified? On which basis? (A34) … exposure at young ages confers much greater breast risk than exposure at older ages. Comment: is not time ripe to begin to differentiate tissue-weighting factors for gender and age? The risk factors for some gender-related-cancers, like breast cancers, are really too different to be calculated by means of average values. This effort, of considering risk factors differentiated for gender, is already undertaken in other scientific fields. Lastly, a couple of editorial notes. (89) At the end: the cited Publication 89 is missing in the References (B23) row 8: the cited publication [6] is missing in the References