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The aggregated transfer factor (Tag) is commonly used to represent the actual transfer of radiocesium from soil to wild edible plants, but the values have shown substantial variation since the Fukushima nuclear accident. To elucidate the factors causing this variation, we investigated the effects of spatial scale and vertical 137Cs distribution in the soil on the variation of Tag-137Cs values for one of the most severely contaminated wild edible plants, Eleutherococcus sciadophylloides Franch. et Sav. (Koshiabura). The variation in Tag-137Cs values was not reduced by direct measurement of 137Cs deposition in soil samples from the Koshiabura habitat, as a substitute for using spatially averaged airborne survey data at the administrative district scale. The 137Cs activity concentration in Koshiabura buds showed a significant positive correlation with the 137Cs inventories only in the organic horizon of soil from the Koshiabura habitat. The ratio of 137Cs inventories in the organic horizon to the total 137Cs deposition in soil exhibited substantial variation, especially in broad-leaved deciduous forests that Koshiabura primarily inhabits. This variation may be the cause of the wide range of Tag-137Cs values observed in Koshiabura buds when calculated from the total 137Cs deposition in soil. [ABSTRACT FROM AUTHOR]

Large-scale decontamination work has been carried out in the aftermath of the Fukushima Daiichi nuclear power station accident in Japan in 2011. The soil that was removed and the wastes that were generated during the decontamination will be finally disposed of outside Fukushima Prefecture by 2045. To ensure successful and socially acceptable implementation of this final disposal process, it is essential to have a good understanding of what is considered important by the public. We used a choice-based conjoint analysis in the form of a web-based questionnaire to examine the relative importance of several factors in the choice of the final disposal sites of the removed soil and incinerated ash of the wastes. The questionnaires covered four attributes and 12 levels, namely the distance between the disposal site and a person's residential area, procedural fairness (decision process), distributive fairness (direct mitigation of inequity through multiple siting locations), and the volume and radioactivity of the substances to be disposed. Responses were received from 4000 people nationwide, excluding Fukushima residents. The results showed that the respondents gave high importance to choosing sites that were far from residential areas and to the two types of fairness, especially distributive fairness. The respondents showed no preference for the volume and radioactivity. This indicates that the public cares about the fairness of the siting for the final disposal sites and feels uncomfortable with plans for a final disposal site located close to them. Distributive fairness is necessary to pursue consensus in addition to procedural fairness. [ABSTRACT FROM AUTHOR]

We obtained the aggregated transfer factor (Tag) for 10 common edible wild plant species (four perennial spermatophytes, bamboo shoot, two tree species, and three perennial pteridophytes) in northeastern Japan. Measurement of Tag was carried out in 2012–2019 and we also used publicly available data for 2012–2019: food monitoring data and total deposition data from an airborne survey. The Tag obtained from actual measurements agreed well with Tag values calculated from the publicly available data. The sampling locations were only identified at the municipal level and uncertainty of the deposition for the publicly available data, and thus Tag values showed substantial variation. The Tag of the perennial spermatophytes, including bamboo shoot, and perennial pteridophytes showed single exponential decline with effective half-lives of approximately 2 years, whereas those of tree species did not show distinct temporal change. These results imply that data since 2014 are applicable for Tag estimation for long-term potential ingestion dose in the future to the public because of the slow decline. The calculated Tag values of all species for 2014–2019 ranged from 6.1 × 10−5 to 5.2 × 10−3 m2/kg-fresh mass. The maximum Tag value was observed for the tree koshiabura (Chengiopanax sciadophylloides) and the minimum value was observed for the perennial spermatophyte giant butterbur (Petasites japonica). Tree species showed higher Tag than spermatophyte and pteridophyte perennials. [ABSTRACT FROM AUTHOR]

The spatial distribution of radiation air dose was assessed on the floor of a secondary mixed forest located 35 km northwest of the Fukushima Daiichi Nuclear Power Plant. All trees with diameter at breast height ≥5 cm were measured and mapped within two plots. Radiation air doses were measured on the forest floor at each 1-m grid point and at stem bases and were analyzed in relation to bark texture, tree strata position, and leaf phenology. Radiocesium concentration measured from soils sampled in a similar manner (2-m grid point and at stem bases) in one of the two plots showed significant correlation with the air dose rate. Air dose rate showed a highly heterogeneous spatial distribution and tended to increase toward the stem bases. This trend was distinctive in some tree functional groups, with the rate being higher in some smaller deciduous trees with smooth bark (e.g.Fraxinus lanuginosa, Acer rufinerve). The trends were indistinctive in larger canopy trees with thick, coarse bark (Quercus mongolicasubsp.crispula): in such trees, air dose rate become lower at stem bases than those in the outer range of the concentric zone in some large evergreen conifer trees (Abies firma). However, radiocesium concentration measured near tree stem bases (1 m away from the base) did not vary in relation to tree functional groups. Bark smoothness, which facilitated immediate vertical runoff of contaminated water to lower positions, may have increased air dose rates at the tree bases but would not have enhanced the heterogeneity of radiocesium concentration in the forest floor soils. [ABSTRACT FROM PUBLISHER]

We developed a simple and rapid method for detecting dissolved radio-Cs in litter and/or soil seepage water using nonwoven fabrics impregnated with copper-substituted Prussian blue (Cu-NF). In laboratory and field experiments, litter and/or soil seepage water including dissolved radio-Cs were passed through traditional lysimeter systems combined with seven sheets of the Cu-NF. We then examined the recovery ratios of dissolved 137 Cs in the Cu-NF. In the laboratory experiments with faster flow rates (11–2200 mm h −1 ), over 86% of the total dissolved 137 Cs in litter seepage water was detected in the Cu-NF and over 82% of the collected 137 Cs was present in the first three sheets. In the field experiments, 99% of the total dissolved 137 Cs litter seepage water was collected in the Cu-NF and more than 96% of the collected 137 Cs was present in the first three sheets. Furthermore, the recovery ratio of dissolved 137 Cs increased with increasing installation Cu-NF length, probably because the packed soil in the Cu-NF lysimeter become more stable over time. Finally, because only the Cu-NF is measured, it is not necessary to undertake traditional measurement preparations such as filtration to remove particulate radio-Cs materials and evaporative concentration for low concentration of radio-Cs. As a result, we can save time and effort in measurement preparation by using the Cu-NF lysimeter method. [ABSTRACT FROM AUTHOR]

Statistical benchmark data are necessary when considering the basis for radiation protection criteria based on calculated risks. We herein focused on baseline mortality and incidence cancer rates as benchmark data collected from 33 countries. Furthermore, we calculated the lifetime mortality and incidence risks and disability-adjusted life years (DALYs) for all solid cancers, colon cancer, lung cancer, breast cancer, thyroid cancer, and leukemia using the baseline cancer rates and compared them among the countries. The results showed that the lifetime mortality and incidence risks and DALYs for all solid cancers differed among the countries by a factor of 2-4 for males and 2-3 for females; these were low in less-developed countries. Our study proposed that health risk based on baseline cancer rates should be the benchmark for comparing radiation cancer risks., (© 2024 Society for Radiological Protection. Published on behalf of SRP by IOP Publishing Limited. All rights reserved.)

The purpose of this study was to provide benchmark data for discussing the tolerability of cancer risk associated with occupational radiation exposure. It focused on differences in cancer mortality risk by occupation among Japan's working population and examined baseline cancer mortality risks and its variations from 1995 through 2020. Data were collected every five years from national vital statistics sources. By focusing on the same types of cancer among radiation induced effects, cumulative mortality risks were calculated for colorectal, lung, and breast cancer (females only) for those aged 15-74. The average cumulative mortality risk for the working population in Japan has decreased by 30%-60% over the past 25 years. Service workers and male managers were at an average risk, among all workers, while clerical workers and transportation and manufacturing workers had about half the average risk. The risks were higher for professionals and female managers, about 1.5-2 times the average for professionals and up to 5 times the average for female managers. The decrease in the average cancer mortality risk in the working population as a baseline suggests that risk tolerance in society might have changed over time. Since differences in mortality by occupation were confirmed, the usefulness of occupational data as a benchmark needs further investigation, as high-risk/low-risk occupations vary by country and region. The results of this study contribute to put radiation risks into perspective with the background risk of cancer., (© 2024 Society for Radiological Protection. Published on behalf of SRP by IOP Publishing Limited. All rights reserved.)

Environmental decontamination after a nuclear disaster not only contributes to reducing the public's exposure to radiation, it also introduces waste disposal issues arising from the decontamination process. In addition to that issue, the optimisation of decontamination efforts necessitates the consideration of various environmental, economic, and societal factors. Stakeholders' perspectives are important for identifying the multifaceted aspects to be considered. We conducted a semi-structured interview survey in 2019 with ten residents in a rural community in Fukushima, Japan, which experienced a six-year-long evacuation due to the 2011 Fukushima Daiichi Nuclear Power Plant accident. The main survey questions addressed returnees' perceptions of the decontamination of farmlands and forests. The 'Steps for Coding and Theorization' procedure was used for qualitative analysis. The analysis illuminated the positive and negative impacts of the decontamination process on the rebuilding of the returnees' rural lives from various perspectives and identified elements to be considered for the optimisation of future remediation efforts. The removal of radioactive materials had a positive psychological impact on the returnees, fostering a sense of security that their crops were safe and instilling confidence that the high-quality environment of the region had been restored. These aspects were not included among the initial governmental objectives for decontamination, which were aimed solely at reducing radiation exposure. By contrast, the removal of fertile topsoil from farmland had a negative impact on the residents, making them hesitant to resume farming. Our findings suggest that emphasising procedural fairness in decision-making of decontamination options such as reflection of stakeholders' opinions led to residents perceiving their post-decontamination situation more positively. Our results provide valuable insights for optimising remediation strategies for the recovery process following a significant nuclear accident., (Creative Commons Attribution license.)

Amphibians are key components in forest food webs. When examining radioactive contamination in anurans, it is important to understand how radiocesium transfer occurs from lower to higher trophic levels in forest ecosystems. We investigated the activity concentration of radiocesium ((134)Cs and (137)Cs) in Tago's brown frog (Rana tagoi tagoi) captured on the forest floor approximately 2.5 years after the Fukushima Nuclear Power Plant (FNPP) accident. We collected 66 R. tagoi tagoi at different distances from the FNPP. Radiocesium accumulation showed positive correlations with the air radiation dose rate and litter contamination but not with distance from the FNPP. Whole-body radioactivity showed no correlation with body mass or length. Our results suggest that differences in the available food items result in large variability in individual contamination. Contamination level monitoring in terrestrial and aquatic amphibian is necessary for clarifying the processes and mechanisms of radiocesium transfer through forest food webs., (Copyright © 2015 Elsevier Ltd. All rights reserved.)