From human to environmental radioprotection: Some crucial issues worth considering

The need to establish a system capable of ensuring adequate protection of the environment from the harmful effects of ionising radiation is at present particularly challenged. This comes both from a restrictive consideration of the environment in the so far existing system for human radioprotection, and the planetary-wide growing concerns about man's technogenic influence on his environment which have yielded 'sustainability' and 'precaution' as guiding principles for environmental protection. For the sake of protection, the environment is traditionally addressed through its biota since these are the sensitive components of ecosystems. Similarities between man and biotas root from the ubiquitous mechanistic effects of radiation on life which disrupt molecules. However, important differences also arise in a number of perspectives, from the vast biodiversity of species with a large spectrum of radio-sensitivities to their hierarchical self-organisation as interacting populations within ecosystems. Altogether, these aspects are prone to promote complex arrays of different responses to stress which lie beyond the scope of human radioprotection which only considers individuals of one single species. The focus on individuals in a bottom-up approach, due to its easier amenability to quantification, has prompted the development of current ecotoxicological methods as a scientific foundation to regulating environmental protection. Exclusive basement of Ecological Risk Assessment on this reductionist approach, however, is currently questioned by the most recent ecological theories which call for additional consideration of more holistic, top-down, approaches. In moving from man to environment radioprotection, these current challenges are discussed by highlighting some crucial issues linked to setting up dose limits in chronic exposure, weighting them according to radiation types (RBE), identifying appropriate effect endpoints (stochastic/deterministic, individual/population- or ecosystem-relevant), and taking due account of other concomitant contaminants (synergies/antagonisms) which call for filling critical gaps in knowledge. (author)