2023 Volume 22 Issue 3 Pages 109-131
Knowledge of the concentrations of radioactive materials in edible wild species is important to reduce the health risks associated with radiation exposure. Between 2015 and 2019, we collected 2094 parts of 380 edible wild photosynthetic species (plants, terrestrial cyanobacteria, and epilithic lichens), 72 parts of 27 non-edible wild photosynthetic species, and 22 parts of 15 edible cultivated plant species, for a total of 2187 parts of 422 species growing in areas affected by the 2011 Fukushima Daiichi Nuclear Power Station accident. Aggregated transfer factor (Tag) values of radioactive cesium-137 (137Cs) transferred to organisms from the habitat O-horizon and soil were investigated. Geometric mean values of 137Cs Tag of edible parts of wild species differed greatly among species in both vegetative organs and sexual reproductive organs (maximum/minimum ratio of species Tag of ~2000 in vegetative organs and ~920 in sexual reproductive organs). Multiple regression analysis was performed to determine the factors that were associated with species geometric mean Tag values in representative edible parts of vegetative organs and sexual reproductive organs of edible wild species. Forest species tended to have higher Tag values than open-land-habitat species (P < 0.023). Although data were obtained only for vegetative organs, Tag values were higher for adherent species, such as those that adhere to tree trunks or stones (e.g., by adhering roots) (P < 0.010). Species’ ecological traits were significantly influenced species-level 137Cs Tag. Because 137Cs Tag values differ greatly depending on the species, it is important to use species as a unit in food-safety assessments of radioactivity in edible photosynthetic organisms.