Seafood dose parameters: Updating 210Po retention factors for cooking, decay loss and mariculture.

210Po has been identified as one of the main contributors to ingestion doses to humans, particularly from the consumption of seafood. The amount of 210Po activity concentration data for various types of seafood has increased greatly in recent times. However, to provide realistic seafood dose assessments, most 210Po data requires correction to account for losses that can occur before the seafood is actually consumed. Here we develop generic correction factors for the main processes associated with reduction of 210Po in seafood - leaching during cooking, radioactive decay between harvest and consumption, and sourcing from mariculture versus wild-caught. When seafood is cooked, the overall mean fraction of 210Po retained is 0.74 for all cooking and seafood types, with the means for various seafood types and cooking categories ranging from 0.56 to 1.03. When considering radioactive decay during the period between harvest and consumption, the overall mean fraction remaining is 0.81 across all seafood preservation/packaging types, with estimates ranging from 0.50 (canned seafood) to 0.98 (fresh seafood). Regarding mariculture influence, the available limited data suggest marine fish and crustaceans raised with processed feed have about one order of magnitude lower (×0.10) 210Po muscle content than wild-caught seafood of the same or similar species, although this ratio varies. Overall, this study concludes that 210Po activity concentrations in seafood at the time of ingestion may be reduced to only about 55% compared to when it was harvested. Therefore, correction factors must be applied to any data derived from environmental monitoring in order to achieve realistic dose estimates. The data also suggest lower 210Po ingestion doses for consumers who routinely favour cooked, long shelf-life and farmed fish/crustaceans. However, more data is needed in some categories, especially for cooking of molluscs and seaweed, and for the 210Po content in all farmed seafood.

Strengths of ecosystem services concept for radiation protection.

The successful ecosystem services concept, defined as the benefits people obtain from ecosystems is still not really reflected in the current approaches for protecting public and environment against radiation promoted by the International Commission on Radiological Protection or other similar approaches. Yet some recent thoughts from international organizations lead us to believe that an eco-based approach could be more promoted in the coming years in environmental radiation protection field. The French Institute for Radiation Protection and Nuclear Safety has identified different fields of application of this concept into radiation protection, in line with its integrated approach of radiological risks management. As the ecosystem services approach makes it possible to highlight biophysical and socio-economic approaches of the impacts of ionizing radiation on ecosystems, it represents a subject of primary importance for future works conducted by IRSN. However, the operationality of the ecosystem services concept is the subject of many debates. In many situations, scientists have not yet fully understood how radioactive contamination could affect ecosystem services, and how to articulate with certainty cause and effect relationships between state of an ecosystem and provision of services. In addition, the concept is also accompanied by contradictory perceptions of the status of humans in ecosystems. To solve these knowledge gaps and uncertainties, it is necessary to acquire robust data on the impacts of radiation on ecosystems both under experimental and realistic conditions, and to integrate all potential consequences (direct and indirect, ecotoxicological but also economic and cultural).

Foliar interception of radionuclides in dry conditions: a meta-analysis using a Bayesian modeling approach.

Uncertainty on the parameters that describe the transfer of radioactive materials into the (terrestrial) environment may be characterized thanks to datasets such as those compiled within International Atomic Energy Agency (IAEA) documents. Nevertheless, the information included in these documents is too poor to derive a relevant and informative uncertainty distribution regarding dry interception of radionuclides by the pasture grass and the leaves of vegetables. In this paper, 145 sets of dry interception measurements by the aboveground biomass of specific plants were collected from published scientific papers. A Bayesian meta-analysis was performed to derive the posterior probability distributions of the parameters that reflect their uncertainty given the collected data. Four competing models were compared in terms of both fitting performances and predictive abilities to reproduce plausible dry interception data. The asymptotic interception factor, applicable whatever the species and radionuclide to the highest aboveground biomass values (e.g. mature leafy vegetables), was estimated with the best model, to be 0.87 with a 95% credible interval (0.85, 0.89).

Assessment of dry and wet atmospheric deposits of radioactive aerosols: application to Fukushima radiocaesium fallout.

The Fukushima Dai-ichi nuclear accident led to massive atmospheric deposition of radioactive substances onto the land surfaces. The spatial distribution of deposits has been estimated by Japanese authorities for gamma-emitting radionuclides through either airborne monitoring surveys (since April 2011) or in situ gamma-ray spectrometry of bare soil areas (since summer 2011). We demonstrate that significant differences exist between the two surveys for radiocaesium isotopes and that these differences can be related to dry deposits through the use of physically based relationships involving aerosol deposition velocities. The methodology, which has been applied to cesium-134 and cesium-137 deposits within 80-km of the nuclear site, provides reasonable spatial estimations of dry and wet deposits that are discussed and compared to atmospheric numerical simulations from the Japanese Atomic Energy Agency and the French Institute of Radioprotection and Nuclear Safety. As a complementary approach to numerical simulations, this field-based analysis has the possibility to contribute information that can be applied to the understanding and assessment of dose impacts to human populations and the environment around Fukushima.