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To provide detailed concentration ratios (CR) of iodine (I) and plutonium (Pu) from water to marine biota in Japan, we calculated the values using open available data sources. All the available CR data obtained in this study and previously reported in Japanese literature, we summarized the edible part CR data of I and Pu for algae, cephalopods, crustaceans, molluscus (except cephalopods), and fish groups. Newly summarized geometric mean value of these biota groups provided similar value that recommended by the IAEA TRS 422 (2004) but it was clear that algae data much smaller than in Japanese data compared to those in TRS 422.

Background: This study was carried out to provide environmental transfer parameter values to estimate activity concentrations of these radionuclides in agricultural crops when direct contamination occurred. Materials and Methods: Mass interception fractions (FBs) and weathering half-lives (Tws) of 131I and radiocaesium were calculated using openly available monitoring data obtained after the Fukushima Daiichi Nuclear Power Plant accident. FB is the ratio between the initial radioactivity concentration of a radionuclide retained by the edible part of the plant (Bq kg–1 fresh weight [FW]) and the amounts of deposited radionuclide in that area (Bq m–2). Tw values can be calculated using activity concentrations of crops decreased with time after the initial contamination. Results and discussion: Calculated FB and Tw values for 131I and radiocaesium were mostly obtained for leafy vegetables. The analytical results showed that there was no difference of FBs between 131I and radiocaesium by t-test; geometric mean values for leafy vegetables cultivated under outdoor conditions were 0.058 and 0.12 m2 kg–1 FW, respectively. Geometric mean Tw value of 131I in leafy vegetables grown under outdoor conditions was 8.6 d, and that of radiocaesium was 6.6 d; there was no significant difference between Tw values of these radionuclides by Wilcoxon rank sum test. Conclusion: There was no difference between 131I and radiocaesium for FBs and Tws. By using these factors, we would be able to carry out a rough estimation of the activity concentrations of 131I and radiocaesium in the edible part of leafy crops when a nuclear accident occurred.

Internal dose from the ingestion of contaminated agricultural products is an important part of the biospheric radiation dose assessment for nuclear waste management. Cow's milk is consumed by infants, and they are relatively more sensitive to radiation than adults; thus we focused on the radionuclide transfer coefficient from feed to milk (Cft_milk). Many countries use Cft_milk values compiled in the IAEA Technical Report Series in mathematical models. Most of the original data sources for the values were from literature published in the 1950’s to 1970’s and they are getting difficult to access nowadays, or they were reported after the Chernobyl accident in Russian and Ukrainian languages and they are not accessible to a wide audience. It is necessary to confirm the original data for transparency of the dose assessment results and also to update the data sets by adding newly observed data. In this paper, therefore, we carried out a literature survey by tracing back references listed in the IAEA reports especially for Cs, I and Pu, and we compared those data with recently published data obtained by research institutes in many countries. Our comparison results showed that Cft_milk values of I and Cs were similar among the data sources; however, Pu values differed by four orders of magnitude among the sources, which could cause large uncertainties in assessment results.

The fate of strontium-90 (90Sr) from water to aquatic biota is of concern since the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, because of continuing small 90Sr releases to the seawater from the FDNPP site. The Japanese diet includes many edible marine and freshwater species, and the environmental parameter, that is, the concentration ratio (CR) from water to biota is useful to estimate the potential 90Sr intake, especially from frequently consumed seafoods. However, widely used CR data for radiation dose assessment only have provided values for biota types such as fish, crustaceans, macroalgae etc. and thus it is difficult to identify specific data for each species. In this study, therefore, we collated CR data of Sr for aquatic biota by surveying available open data sources from the 1950’s to 2019, not only for edible parts but also whole and inedible parts. In total, we obtained 3800 CR data: 3013 data for marine biota, 28 data for brackish water biota, and 759 data for freshwater biota. The results showed that species-specific CRs may decrease the uncertainties compared to those published in IAEA documents; however, different diets and living areas by species may lead to different uncertainties for different species.