retained in marine organism tissues were presented, demonstrating the time-dependence and inhomogeneity of radionuclide distributions in tissues.
B.J. Howard (UK) reviewed the available environmental transfer data for terrestrial biota and the different approaches that have been suggested to compensate for the data gaps. The need for transparency regarding the data origin and in the application methodologies was highlighted.
During discussion, it was recognized that equilibrium transfer factors from environmental media to plants and animals are available for some radio-nuclide-organism combinations and generic systems, and that the IAEA’s default values for the marine environment have recently been revised (IAEA TRS-247, to be published). It was suggested that the collation of site and ecosystem specific research data would be valuable, e.g. for non-temperate systems, and that special attention should be paid to technologically enhanced naturally occurring radioactive material in ecosystems.
Rapporteur’s summaries
G. Pröhl (Germany) reported on the contributed papers relating to environmental transfers and dosimetry. The following key findings were identified:
— Transfer parameters presented for arid or tropical conditions were similar to those obtained for temperate environments;
— Information on radionuclide speciation is key to understanding radionu-clide behaviour in soils;
— Allometric relationships are valuable, but more experimentation is needed in order to improve their reliability;
— The weighting factor for alpha radiation is the most sensitive parameter in estimating doses from alpha-emitting radionuclides; agreement on the use of weighting factors for biota is necessary.
S.I. Salomaa (Finland) reported on the contributed papers relating to biological effects and ecosystem studies. A variety of effects on biota were reported in these papers, from which it was clear that humans are not the most sensitive organism for all biological effects considered. The systematic collection of effects data has made it clear that more work is needed in order to understand the effects — including hereditary effects — of radiation at low doses and dose rates on biota. It is generally the case that deterministic end points are ones that principally affect population survival. However, somatic mutations like chromosomal aberrations can be used as indicators of radiation exposure. A systematic review of natural radiation experienced by biota will be
EXECUTIVE SUMMARY
23 necessary in order to interpret environmental effects information and the developing ICRP approach.
Dosimetry
H.-G. Menzel (ICRU) and D.B. Chambers (Canada) reviewed issues related to dosimetric quantities for non-human organisms and radiation weighting factors for biota respectively. The value of absorbed dose as a measure of harm and issues related to averaging doses over time and space, particularly for small short lived organisms, were discussed. The need for weighting factors with which to modify absorbed doses so as to take account of the differences in the effectiveness of different types of radiation in inducing radiation damage was considered. The need for weighting factors that are correctly calculated and relevant for the type of organism and the biological end points of concern was emphasized.
There was a general consensus that absorbed dose and dose rate are the fundamental quantities for biota dosimetry. It was also agreed that radiation weighting factors are an important consideration in assessments under chronic exposure conditions. The available RBE estimates depend upon the reference radiation used and the end points under consideration. For alpha radiation the radiobiological data imply RBE values of around 10, with a possible range of 5–50.
Dosimetric models are available for a number of exposure geometries. It is now possible to develop a robust set of dose conversion factors. Estimates of the dose rate from the natural background are required both as a basis for comparison and also for aggregation with the incremental dose rates from authorized releases.
Biological effects
I. Zinger (UK) explained the known mechanisms of the biological effects of ionizing radiation on individuals, including differences caused by radiation types. Individual level observations have been made on four “umbrella”
biological end points: mortality, morbidity, reproductive capacity and observable DNA damage or mutation. A threshold level for minor effects appears to occur at around 100 mGy/h, while effects are clearly shown at dose rates exceeding 1000 mGy/h. The projection of effects on cells to tissues, organs and the whole body can in principle lead to effects at the population and community level. However, it is generally the case that if individuals are well protected community level effects may also be prevented.
There is a need for more information on chronic effects and for a systematic consideration of RBE. In future it will be important to harmonize research and to focus on the selection of reference organisms. The utilization of biomarkers and the development of standards and environmental criteria are also issues for future consideration.
P.A. Thompson (Canada) described three types of interaction of multiple stressors; additive, synergistic and antagonistic. Additivity is the most frequently used model. However, the current information is insufficient to take account of effects of mixtures of radioactive and non-radioactive stressors.
Therefore, biological monitoring and individual measurements are important for the consolidation of the information database.
In the discussion which followed, the usefulness of bioassay for biomarkers was pointed out. Hormesis was explained as a phenomenon that is sporadically observed but remains controversial. Some data gaps in the FASSET Radiation Effects Database (FRED) remain.
Population and ecosystem studies
D.S. Woodhead (UK) addressed the question “Can continuous low-level irradiation affect populations?”. He described a study of fish populations in the north-east Irish Sea in which a peak dose of 2 mGy/h can be obtained from the frequency graph of individual exposure of aquatic biota. He used a population model that took account of features of the population such as age at maturity, productive lifespan, and life stages sensitive to radiation. He demonstrated that, since populations show non-linear responses, it is possible, even if individuals are well protected, that community level effects may not always be prevented. As a result, it may be necessary to consider both individual and population responses so as to ensure that protection objectives are achieved.
R.M. Alexakhin (Russian Federation) gave a presentation containing numerous data on effects in contaminated areas around the Techa River and following the Chernobyl accident. Estimated radiation doses to various plants and animals, and their subsequent changes, were presented. High dose rate examples included a pine forest (3.1 Gy/a) and soil invertebrates (7.9 Gy/a) in 1986 soon after the Chernobyl accident. These dose rates had decreased to 0.02 Gy/a and 0.06 Gy/a, respectively, in 1991. Based on this observation, it is possible that the critical ecosystem may change with time.
Application of current and future scientific information
R.J. Pentreath (UK) outlined the concept and use of reference animals and plants, proposed as a device to relate exposure to dose and dose to effects,
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25 in a manner analogous to the use of reference man in the radiation protection of humans. Conditions for the selection of reference animals and plants include:
(1) Typical fauna and flora of a particular environment;
(2) Relevant information already in existence;
(3) Amenability to further research;
(4) Dosimetry easily modelled;
(5) Dose–effect relationships easily seen.
He outlined the sort of information that would be needed to describe a reference duck and benthic fish. He mentioned genetic diversity, emphasizing that plants are more complicated than animals, and indicated that reference animals and plants approach would provide a reasonably complete set of related information for a few types of organism that are typical of the main types of environment.
During the discussions that followed, the use of data obtained after an accident for reference in normal situations was questioned. Individual effects and population effects were discussed in contrast, and more scientific data on population effects were recognized as important for bridging the information gap between individual level and population level effects.
BLANK
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27
Chairperson’s Summary ROUND TABLE 3:
WHAT ARE THE IMPLICATIONS OF
EXISTING KNOWLEDGE ABOUT THE EXPOSURE OF AND EFFECTS OF RADIATION ON
NON-HUMAN SPECIES FOR
THE PROTECTION OF THE ENVIRONMENT, AND WHAT ARE THE MOST SIGNIFICANT GAPS?
K. Higley, USA*
Panellists’ introductions
K.A. Higley (USA) noted that we need to carefully examine our own inherent prejudices when selecting our starting point for determinations. It is important to review data needs objectively. Also, while we should foster a healthy debate on knowledge gaps, we should not give the public the impression that the environment is in imminent danger.
J. Garnier-Laplace (France) pointed out that there are many knowledge gaps — bioavailability is key, as are the chronic nature of exposure and the geochemical behaviour of radionuclides. The different scales for biological effects (e.g. early to delayed and subcellular to population) also need to be considered.
J.M. Godoy (Brazil) asked what price we will have to pay in order to implement the proposed ICRP approach. If the costs are overly burdensome — and especially if there is no obvious benefit — the proposed methods will not be accepted. Thus, we will need to consider how to streamline these methods. It would be useful to look at existing areas with high background exposure for insight.
R. Avila (Sweden) agreed that the more we learn, the less we seem to know. It is important to identify which data gaps are the more important, but this may be context specific. He questioned the use of equilibrium transfer factors and suggested that parameters that were more amenable to research, and had a more direct physical meaning, might be more appropriate. He also
* On behalf of Y. Zhu (China) with contributions from C.A. Robinson (IAEA).
suggested that standards and assessment methodologies that allow for uncer-tainties should be developed.
Comments from floor (overview)
The need for more information in order to establish the way in which radiation effects observed at the individual level may be manifested in populations or species was highlighted as a key issue. There is a need to develop a system of protection that allows the uncertainties in the scientific information to be expressed, while being communicable to a wide range of stakeholders. Consistency in the approaches used to regulate radioactive and non-radioactive pollutants was discussed at some length; it was concluded that the present developments in environmental radiation protection would benefit from experience gained from the environmental management of non-radioactive pollutants.
In view of an absence of obvious evidence of harm, the need for basic research was questioned and discussed. It was suggested that there exists a wealth of data from more than 50 years of releases from the nuclear industry (into both the biotic and the abiotic part of the environment). This should be used to develop assessment methods for non-human species further. For example, we are lacking in information on exposures and effects at the level of populations. Quantitative assessments exist, especially for areas around nuclear power facilities, but better analysis is needed.
The detailed application of ICRP’s proposed set of reference animals and plants in the light of area specific conditions was discussed. The need for the approach to be communicable to a wide range of stakeholders was again illustrated during the discussions.
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29
Chairperson’s Summary TOPICAL SESSION 5:
IMPLICATIONS OF ICRP PROPOSALS FOR INTERNATIONAL SAFETY STANDARDS
Z. Pan, China*
L.-E. Holm (ICRP) described the current ICRP position with regard to establishing a framework for assessing the impact of ionizing radiation on non-human species. ICRP Publication 91 sets out the recommendations of the ICRP Task Group to the Main Commission, with the Main Commission’s response set out in the Foreword.
The new ICRP recommendations expected in 2005 will include a framework for the protection of non-human species derived from ICRP Publication 91. In the meantime, a new Task Group has been formed to refine the framework, and especially to further develop the reference animal and plant approach. The new Task Group is currently considering a list of 11 animals and plants and aims to report to the Main Commission late in 2005.
An important point of focus will be consistency of approach to the protection of humans and of non-human species. With regard to the protection of humans, the 2005 recommendations are likely to include “Levels of Concern” that are related to background dose rates (excluding radon). For animals and plants, ICRP intend to define “Derived Consideration Levels” to represent doses and effects relative to their background dose rates. Mr. S.
Mundigl (OECD/NEA) described the role of the OECD Nuclear Energy Agency and its Committee on Radiation Protection and Public Health, which have been involved in a process of stakeholder consultation about the new ICRP recommendations, including the environmental protection framework.
In particular, OECD/NEA sponsored a meeting in February 2002 on environ-mental issues and recently one on the draft ICRP recommendations as a whole.
These meetings included participants representing operators, regulators and NGOs.
One of the views that emerged from the meetings was that the reference animal and plant approach is potentially complicated and may be difficult to implement. The approach needs to be consistent with the broad principles of
* Assisted by J. Loy (Australia).
sustainable development and to be simple and cost effective for operators to implement. The relationship of the environmental framework to the human protection system of justification, optimization and limitation needs further elaboration — particularly since there may be times when optimization of human protection affects protection of the environment. C.A. Robinson (IAEA) described current thinking within the IAEA about the development of safety standards for the radiation protection of non-human species. The IAEA has done work on the ethical principles that lie behind environmental radiation protection, concluding that, while there are differing ethical approaches, there is broad agreement on the basic protection principles. The IAEA’s role will be to develop guidance for implementation of the higher level advice flowing from ICRP.
The following matters were raised during the discussion:
— The need to expand the process of optimization, with consideration given to the protection both of humans and of non-human species and to the need to take account of the views of stakeholders in this process;
— The need for an IAEA action plan, it being noted that a role of the Conference was to advise the IAEA on areas for future cooperative activities;
— The place of environmental justice and respect for human dignity in the assessment process, it being agreed that this issue was most important at the stage when risk management decisions were being taken;
— The possible need for changes in the membership and approach of ICRP, including the Main Commission, to most effectively advance environ-mental protection issues;
— Whether domestic animals and agricultural plants need to be considered;
— The relationship between the reference animal and plant approach and existing national approaches;
— The value of continuing stakeholder involvement, including involvement through OECD/NEA;
— Whether there should be consideration of protection of the abiotic environment (ICRP is of the view that ionizing radiation does not cause damage directly to the non-living environment, while accepting that there are strong societal commitments to an overall clean environment).
EXECUTIVE SUMMARY
TO THE DEVELOPMENT OF AN APPROACH TO THE PROTECTION OF NON-HUMAN SPECIES?
J. Loy, Australia
R.L. Andersen (World Nuclear Association) agreed that the ICRP proposals provided an appropriate way forward. He emphasized that practices within the current framework are protective of the environment, but that the conceptual gap called for a practical and flexible solution. International leadership is required, and it would be valuable to have a “roadmap” of the directions to be taken, the outcomes sought and the roles of the different inter-national organizations.
S. Carroll (Greenpeace) welcomed the fact that the issues dealt with by the Conference were now being addressed. From a Greenpeace point of view, it was important to take a “top down” approach that reflected societal views about environmental protection, rather than a “bottom up” approach driven by scientific numbers. He saw the reference organism approach as useful, but not necessarily sufficient for management decisions, especially decisions by society about the values of different environments that go beyond the protection of biota. The approach could be improved by taking account of approaches to environmental protection against the effects of non-radioactive pollutants — it should at least reflect current best practice.
H. Forsström (EC) spoke from the viewpoint of an organization that funds research. His view was that the ICRP proposals were positive but incomplete as regards a number of matters, and it was not clear how these matters would be addressed. The objectives of the proposed system needed clarification and the whole approach needed to be able to be simply explained.
There was a need to cooperate with organizations working with non-radioactive pollutants and to define research priorities.
N. Gentner (UNSCEAR) said that despite data gaps we already knew enough to start setting up a system for the protection of non-human species.
The ICRP proposals were very sound. All relevant organizations needed to play a part in ensuring consistency between approaches used to control non-radioactive pollutants and the system for the protection of humans. The issues
to be resolved included the use of dose rates (consistent with concentrations of chemicals) and the value of RBEs. Conservatism should be built into the system, but at one clear point, not everywhere.
The following matters were raised during the discussion:
— The meaning of the “top down’’ approach advocated by S. Carroll (Greenpeace);
— The need for regulators to have specific numbers as a basis for decisions on licences (the ICRP approach will establish an assessment process which will need to be incorporated into national regulatory assessment processes);
— Whether the approach will engender public confidence, and the role of the precautionary principle (it was acknowledged that there was a need to make clear what the proposed system could do and what it could not do, and that even with incomplete information it would engender public confidence if it was clear that an effective start was being made);
— The timescale over which dose rates should be used;
— The tension between having a general framework for assessment on one hand and clear presentation on the other, and the need for public under-standing and acceptance;
— The fact that society will take decisions about the degree of protection to be accorded to different environments — some may be kept as near to
“pristine” as possible (the ICRP guidance based on reference animals and plants can serve as a tool but cannot be definitive);
— Evidence based decision making in wildlife legislation and the need for further R&D and for the definition of research priorities.
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33
Chairperson’s Summary ROUND TABLE 5:
COMMUNICATION WITH THE PUBLIC AND THE ROLE OF THE MEDIA
P. Rickwood, IAEA*
This round table addressed three main issues: the role of the media (what do journalists do?); what the media communicate (what is a good story?) and risk perception (why is radiation so scary?). Each of these points is considered in turn.
(1) The role of the media: What do journalists do?
The role of journalists is different from that of scientists. Indeed, journalists and scientists can be said to have rather different cultures.
Journalists tend to be rather individualistic and to be interested in breaking stories rather than in educating the public — a role that scientists often expect
Journalists tend to be rather individualistic and to be interested in breaking stories rather than in educating the public — a role that scientists often expect