It is recognized that other international organizations have interests and responsibilities related to environmental radiation protection; notably the United Nations Scientific Committee on Effects of Atomic Radiation and the International Commission on Radiological Protection. The Agency continues to work closely with these organizations with the objective of consolidating a strong international regime for the radiation protection of the environment, comprising legally binding international obligations for controlling discharges into the environment, international standards for limiting discharges, and provisions to ensure their application. The consolidation of the international safety regime will be facilitated by forthcoming conferences being held by the Agency. The International Conference on Issues and Trends in Radioactive Waste Management will take place in Vienna, 9–13 December 2002. Then, in 2003, the Agency will hold a conference dedicated to the issue of protection of the environment from the effects of ionising radiation. This Conference, which will take place in Stockholm, 6–10 October 2003, will provide a timely opportunity to discuss a number of developments in this area, which will take place during 2003, and to consider their implications for guiding future work at national and international levels.

IONISING RADIATION AND BIOTA

Effects of ionising radiation on plants and animals:

The intent of this presentation was to provide a broad review of the status of existing knowledge on the effects of ionizing radiation on plants and animals, in the context of field rather than laboratory settings, and to offer thoughts on what more we need to learn in order to set protection criteria and test for compliance with greater confidence. General findings from historical studies on designed and accidental irradiation of plant communities and animals, including comparative radiosensitivity and modifying factors, were reviewed. Expermintal limitations of most studies and difficulties in response interpretation were discussed in reference to ecological relevance and protection criteria. Recovery of radiation damaged plant communities and animal populations, both during and after radiation exposure, were discussed. The commonly measured responses, mortality and reproduction, were reviewed and questioned as the most radiosensitive, ecologically-relevant endpoints. Our perceptions of major knowledge gaps on effects of ionizing radiation on the environment were reviewed, and the types of specific studies that appear needed were presented. These needs were discussed under the general headings of dosimetry, damage endpoints, and dose/response relationships. In the area of dosimetry for example, more work is needed on critical species identification, dose model refinements to account for temporal and spatial dose distribution, and RBEs for various damage endpoints. It is known that biological effects such as genomic damage occur in organisms at dose rates well-below those required to obviously impair reproduction. The question is, are such effects hamful to populations in the irradiated generation or in succeeding generations, and if so, under what conditions? Many species and ecosystems have not been experimentally irradiated, either with relatively uniform photon exposures from sealed sources, or from radioactive contamination, which produces large dose variations in space and time. Finally, very little, if anything, is known about whether and to what extent chemical and other stresses interact with the stress of chronic irradiation.

A regulatory framework for environmental protection:

Industry, regulatory agencies, and the public have been assessing the environmental impacts of regulated, as well as unregulated activities, for many years now. The basic underlying assumption has generally been that the environment is protected through the protection of humankind. In the United States, the environmental regulatory framework has been improved by having a sound executive policy and national regulatory infrastrcture, increased consultation with other agencies, changes in the process and timetable for rulemaking changes, and improved communications by the Federal regulators. This paper discusses the various mechanisms in the United States for achieving and maintaining protection of the environment; why regulatory openness and stakeholder involvement is an integral piece of a successful program for protection of the environment; and how international organizations can make a valuable contribution in providing international consensus in the global arena of environmental protection.

Chronic radionuclide low dose exposure for non-human biota: challenges in establishing links between speciation in the exposure sources, bioaccumulation and biological effects

In the field of environmental radioprotection, the knowledge gaps concern situations leading to chronic exposure at the lower doses typical of the living conditions of organisms influenced by radioactive releases. For any radionuclide and ecosystem, the specificities of these situations are as followed: (i) various chemical forms occur in the environment as a function of the physico-chemical conditions of the medium; (ii) each transfer from one component to another can lead to a modification of these forms with a “chemical formspecific” mobility and bioavailability; (iii) different categories of non-radioactive toxicants are simultaneously present. In this multipollution context, the biological effects of ionising radiation may be exacerbated or reduced with the potential for action or interaction of all the pollutants present simultaneously. These situations of chronic exposure at low levels are likely to cause toxic responses distinct from those observed after acute exposure at high doses since long-term accumulation mechanisms in cells and tissues may lead to microlocalised accumulation in some target cells or subcellular components. The assessment of these mechanisms is primordial with regard to internal exposure to radionuclides since they increase locally both the radionuclide concentration and the delivered dose, coupling radiological and chemical toxicity. This is the main purpose of the ENVIRHOM research programme, recently launched at IRSN. After a global overview of the experimental strategy and of the first results obtained for phytoplankton and uranium, this paper scans the state of art for uranium within freshwaters and underlines inconsistency encountered when one wants to carry out an Ecological Risk Assessment (ERA) on the chemical or on the radiological standpoint. This example argues for future research needs in order to establish well-defined relationship between chemo-toxicity and radiotoxicity for internal contamination. The operational aim is to bring adequacy between ecological and human health risk assessment for radioactive or “conventionnal” substances.