Foundation docs Optimisation; Dose to Individual

Draft document: Foundation docs Optimisation; Dose to Individual
Submitted by Judith Johnsrud, The Sierra Club, Radiation Committee
Commenting on behalf of the organisation

Comments submitted on behalf of the U.S. Sierra Club, Radiation Committee, on: ASSESSING DOSE OF THE REPRESENTATIVE INDIVIDUAL FOR THE PURPOSE OF RADIATION PROTECTION OF THE PUBLIC July 8, 2005 The Sierra Club is appreciative of the ICRP’s soliciting comments from stakeholders -- the overwhelming majority of whom are members of the public -- on ICRP’s foundation documents for the Commission’s 2005 draft Recommendations. It is our understanding that the ICRP has withdrawn its draft Recommendations for full revision, in response to the extensive criticisms filed in late 2004, a commendable decision. For the purpose of determining permissible radiation exposure limits for the public, the use of the concepts of both a “critical group” and, based on that selected sub-population, a “hypothetical representative individual” within the critical group is not an acceptable approach for assuring adequate radiation protection for real individual members of the public. Acceptable radiation protection cannot be based on unverified assumptions, averages, estimates, uncertainties, hypotheticals, theoreticals, reasonableness, unsubstantiated inferences, ”relatively conservative assessments,” or “avoidance of excessive conservatism,” to name only a few such terms used in this document. Nor is comparing the assumed and calculated factors applied to the “representative individual,” as described in this document, with the “dose constraint” previously established in the Commission’s 2005 Recommendations an approach that will assure adequate real protection for real individuals. It is noteworthy that the document excludes occupational and medical exposures and is addressing only doses for members of the public. It is therefore unclear how ICRP is considering the additive exposures received by workers from sources they encounter as members of the public, or the additive doses from medical practices that are received by members of the public and by workers – in other words, the total radiation exposures experienced by individuals from all sources. Those sources and doses may be properly described as multiple, additive, cumulative and synergistic. With respect to the totality of doses actually received, this issue is of particular significance at the present time, when regulatory agencies are proposing to release large amounts of radioactively contaminated materials and wastes from regulatory control and permit them to be recycled and reused, potentially in consumer products. They may also be allowed to be disposed of in ordinary municipal solid waste landfills not designed to maintain appropriate control, or they may be allowed to be incinerated in increasing quantities. The prospective analysis that predicts larger future sources of exposure is of particular importance in today’s radiation protection. The task of devising sufficiently accurate and complete criteria for standards is unquestionably difficult, but the ranges, the uncertainties, and unstated assumptions here render this foundation document disturbingly inadequate. At base is an unstated assumption that there are doses of ionizing radiation, in addition to naturally occurring exposures, that are “safe” for members of the public who will receive no benefit, nor any benefit that is greater than or commensurate with the additive risk of damage incurred. Yet the U.S. National Academies of Science Committee on the Biological Effects of Ionizing Radiation BEIR VII Report, released on June 29, clearly states that the linear no-threshold dose-response hypothesis continues to be accepted. The thrust of this long-awaited report is a reconfirmation of the BEIR V Committee’s 1990 conclusion that, so far as they could determine, there is no “safe” level of radiation exposure. Consonant with this finding is a mounting body of research in the allied field of radiation microbiology that is identifying some previously unrecognized mechanisms of radiation damage at very low doses. Some of this recent research is well described in the ICRP Committee 1 Task Group 2005 draft Report, titled “Low-dose Extrapolation of Radiation-Related Cancer Risk. These current research findings on delayed mutational effects, genomic instability, double strand breaks, chromosomal aberrations, imperfect repair, and bystander effect have led some of those scientists to the conclusion that a single radiation track through a cell is sufficient to initiate any of a number of injuries that may prove carcinogenic or result in other forms of biologic damage. In Table 3 of the text under the probabilistic calculation method, it is stated that the representative individual “is identified such that the probability is less than about 5% that a person drawn at random from the hypothetical population will receive an annual effective dose exceeding the dose constraint. This seems a rather deceptive way of stating that some 5% of the population could be allowed to receive an annual effective dose that is higher than the dose received by the so-called representative individual – apparently a dose higher than permissible. If this is not the case, a revised wording to clarify would be helpful. Perhaps the most disturbing aspect of this foundation document is its continuing failure to differentiate sufficiently among the variabilities of individuals in our species. Particularly distressing is the ICRP’s decision, in the name of simplification (3.4), to reduce the number of age categories to merely three, concluding that “an appropriate level of protection can be achieved by comparing the assessed dose to the foetus or breast-fed infant with the dose limit for members of the public.” A member of the public a new-born baby indeed is, but it is also more sensitive than an adult, or than a ten year old child. It is long overdue for the ICRP to give proper recognition to differential sensitivities and vulnerabilities among the differing segments of exposed populations. The use of “representative individual” doesn’t do it. This foundation document does discuss the importance of characterization of environmental factors related to both external and internal exposures. However, reliance is on dose assessments within the framework of the “critical group” that is presumably homogeneous in part due to the spatial homogeneity of the geographic locus of the group – similar geologic, atmospheric, temperature, and hydrologic conditions, similar foodstuffs, shelter, etc. In the real world, as is admitted, conditions and situations of individuals are highly variable. The goal of protecting populations from radiation injury should not be based on a static and unrepresentative “representative individual” – any more than radiation standards in the U.S. should continue to be based on “standard” or “reference” man, who, as he is defined, may be in the least sensitive sector of the exposed population. Radiation protection worldwide would be enhanced by abandoning the dose constraint approach that in turn relies on the representative individual within the critical group. ICRP states at the outset that its recommendations are intended to give more emphasis to the individual, rather than to society as a whole. The goal is commendable; the means of achieving it as described in this document do not succeed. The paradigm shift now occurring in the field of low-level radiation biology suggests that adoption of the precautionary principle – setting dose standards far more restrictive than current ones – would be the prudent course of action for ICRP