The ENVIRHOM programme : Towards the improvment of radiological risk assessment linked to internal contamination.
J. Garnier-Laplace and F. Paquet
Congrès IUR-SETAC, Anvers (Belgique), 4-8 février 2002.
In the framework of environmental chronic exposure to radionuclides, characterized by very low levels of contamination, it still exists a lack of knowledge concerning the resulted consequences for both the biological components of ecosystems and the members of the public. Indeed, in ecotoxicology as well as in radioecology, the available knowledge mainly corresponds to short-term exposure and high “doses” of isolated pollutant. However, these situations of chronic exposure at low levels are likely to cause toxic responses distinct from those observed after acute exposure at high doses, because of the bioaccumulation phenomena. In tissues and cells, these highly localised accumulations of radionuclides, coupling radiological and chemical toxicities, may give rise to particular biological responses of a cell group, capable of causing functional or structural abnormalities. The assessment of these bioaccumulation phenomena is primordial with regard to internal exposure to radionuclides since they increase locally both the radionuclide concentration and the biological effect of the delivered dose. For the environment, taking into account these processes and the resulting biological effects will improve and complete the impact assessment, and should be integrated in models for which the ionising radiation effects on biota are still ignored.
Within this framework, the irsn recently launched a research programme, namely ENVIRHOM. The chosen approach is mainly focused on experiments under controlled conditions. Carried out on a small number of biological models representative of the plant and animal kingdom and man, they would be limited to a restricted number of radionuclides selected for their long half-life and their radiotoxicity with regard to internal contamination.
The full sets of data expected from the present programme should contribute to the development of a complete operational system of radioprotection for whole ecosystems, including man, for situations of chronic exposure.