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The Fukushima Daiichi Nuclear Power Plant accident led to contamination with radioactive cesium in an extensive environment in Japan in 2011. We evaluated the concentration of radioactive cesium in the skeletal muscles of 22 wild boars and the expression of IFN-γ , TLR3 , and CyclinG1 in the small intestine and compared them with those of wild boar samples collected from Hyogo prefecture. The average 137 Cs radioactivity concentration in wild boars in the ex-evacuation zone was 470 Bq/kg. Most of samples still showed radioactivity concentration that exceeded the regulatory limit for foods, but the dose remarkably decreased compared with samples just after the accident. IFN-γ expression was significantly higher in wild boars in the ex-evacuation zone than in samples from Hyogo prefecture. TLR3 expression was also upregulated. CyclinG1 expression also tended to be high. Hence, wild boars might have received some effects of low-dose radiation, and immune cells were activated to some extent. However, pathological examination revealed no inflammatory cell infiltration or pathological damage in the small intestine of wild boars in the ex-evacuation area. Long-term monitoring would be necessary, but we consider that the living body responds appropriately to a stimulus from a contaminated environment.

Purpose To investigate the potential use of Prussian blue-coated magnetic nanoparticles, termed “Prussian blueberry”, to bring about the magnetic elimination of cesium. Methods Prussian blueberry were prepared by a layer-by-layer assembly method. The morphology, structure and physical properties of the Prussian blueberry were investigated as was their ability to magnetically eliminate cesium. Results We confirmed that Prussian blueberry were composed of a magnetite nanoparticle-core and a Prussian blue-shell. Under a magnetic field, Prussian blueberry (5 mg) reduced the cesium concentration of seawater (3 ml) from 150 ppm to about 50 ppm; but regular Prussian blue could not magnetically eliminate cesium. Moreover, Prussian blueberry removed a similar proportion of cesium from a larger volume of seawater, and from fetal bovine serum and cow’s milk. Conclusions Under a magnetic field, Prussian blueberry was able to rapidly eliminate cesium from seawater and from biological matrices such as serum and milk.

Radioactive nuclides cesium (Cs) and strontium (Sr) possess long half-lives, with 135 Cs at approximately 2.3 million years and 87 Sr at about 49 billion years. Their persistent accumulation can result in long-lasting radioactive contamination of soil ecosystems. This study employed geo-accumulation index ( I geo ), pollution load index ( PLI ), potential ecological risk index (PEPI), health risk assessment model (HRA), and Monte Carlo simulation to evaluate the pollution and health risks of Cs and Sr in the surface soil of different functional areas in a typical mining city in China. Positive matrix factorization (PMF) model was used to elucidate the potential sources of Cs and Sr and the respective contribution rates of natural and anthropogenic sources. The findings indicate that soils in the mining area exhibited significantly higher levels of Cs and Sr pollution compared to smelting factory area, agricultural area, and urban residential area. Strontium did not pose a potential ecological risk in any studied functional area. The non-carcinogenic health risk of Sr to the human body in the study area was relatively low. Because of the lack of parameters for Cs, the potential ecological and human health risks of Cs was not calculated. The primary source of Cs in the soil was identified as the parent material from which the soil developed, while Sr mainly originated from associated contamination caused by mining activities. This research provides data for the control of Cs and Sr pollution in the surface soil of mining city. Graphical abstract

In Japan, radiocesium contamination in foods has become of great concern and it is a primary issue to reduce grain radiocesium concentration in rice ( Oryza sativa L.). Here, we report a low-cesium rice mutant 1 ( lcs1 ) with the radiocesium concentration in grain about half that in the wild-type cultivar. Genetic analyses revealed that a mutation in OsSOS2 , which encodes a serine/threonine-protein kinase required for the salt overly sensitive (SOS) pathway in plants, is responsible for the decreased cesium (Cs) concentrations in lcs1 . Physiological analyses showed that Cs + uptake by lcs1 roots was significantly decreased under low-potassium (K + ) conditions in the presence of sodium (Na + ) (low K + /Na + ). The transcript levels of several K + and Na + transporter genes, such as OsHAK1 , OsHAK5 , OsAKT1 , and OsHKT2;1 were significantly down-regulated in lcs1 grown at low K + /Na + . The decreased Cs + uptake in lcs1 might be closely related to the lower expression of these genes due to the K + /Na + imbalance in the lcs1 roots caused by the OsSOS2 mutation. Since the lcs1 plant had no significant negative effects on agronomic traits when grown in radiocesium-contaminated paddy fields, this mutant could be used directly in agriculture for reducing radiocesium in rice grains.

As a result of the 2011 nuclear incident that occurred at the Fukushima Nuclear Power Plant, a large number of abandoned dogs and cats were left within the disaster zone. A small number of these animals were rescued and cared for at shelters. Prior to the dispersal of these animals to their owners or fosterers, we evaluated the degree of internal radiocesium contamination using a specially designed whole-body counter. We conducted 863 non-invasive measurements of gamma rays due to internal radioactive cesium for 68 dogs and 120 cats at one shelter. After plotting graphs of 137Cs density we generated exponential functions of decay from seven dogs and six cats. From the regression formulae, we were able to determine the biological half-lives as 38.2 days for dogs and 30.8 days for cats. We found that in dogs there was a correlation between the biological half-life of radioactive cesium and age. Using our data, we estimated whole-body densities for each cat and dog at the time when they were rescued. We found that there were deviations in the data distributions among the different species, likely due to the timing of rescue, or living habits prior to rescue. A significant correlation was found when extracted feline reproductive organs were analyzed; the coefficients for the estimation of whole-body densities were approximately 7-fold higher than those based on the extracted feline reproductive organs. This may be due to the fact that majority of the radioactive cesium accumulates within muscular tissue with less distribution in other organs. It is possible to plan the appropriate management period in an animal shelter based on the use of the biological half-life of radioactive cesium calculated in this study. We believe that the correlations we uncovered in this work would be of great use for the management of companion animals in the event of a future nuclear accident.

The fate of 137 Cs derived from the Fukushima nuclear accident fallout and associated radiological hazards are largely dependent on its mobility in the surface soils of forest ecosystems. Thus, we quantified microbial and adsorptive retentions of 137 Cs in forest surface (0–3 cm) soils. The K 2 SO 4 extraction process liberated 2.1%–12.8% of the total 137 Cs from the soils. Two soils with a higher content of clay- and silt-sized particles, organic carbon content and cation exchange capacity showed higher 137 Cs extractability. Microbial biomass was observed in all of the soils. However, the 137 Cs extractability did not increase after destruction of the microbial biomass by chloroform fumigation, providing no evidence for microbial retention of the Fukushima-fallout 137 Cs. The results indicate that uptake of 137 Cs by soil microorganisms is less important for retention of potentially mobile 137 Cs in the forest surface soils compared to ion-exchange adsorption on non-specific sites provided by abiotic components.

The Fukushima nuclear accident released radioactive materials into the environment over the entire Northern Hemisphere in March 2011 and the Japanese government is spending large amounts of money to clean up the contaminated residential areas and agricultural fields. However, we still do not know the exact physical and chemical properties of the radioactive materials. This study directly observed spherical Cs-bearing particles emitted during a relatively early stage (March 14–15) of the accident. In contrast to the Cs-bearing radioactive materials that are currently assumed, these particles are larger, contain Fe, Zn and Cs and are water insoluble. Our simulation indicates that the spherical Cs-bearing particles mainly fell onto the ground by dry deposition. The finding of the spherical Cs particles will be a key to understand the processes of the accident and to accurately evaluate the health impacts and the residence time in the environment.

After the accident of the Fukushima 1 Nuclear Power Plant in March 2011, radioactive cesium was released and paddy fields in a wide area including Fukushima Prefecture were contaminated. To estimate the levels of radioactive Cs accumulation in rice produced in Fukushima, it is crucial to obtain the actual data of Cs accumulation levels in rice plants grown in the actual paddy field in Fukushima City. We herein conducted a two-year survey in 2011 and 2012 of radioactive and non-radioactive Cs accumulation in rice using a number of rice cultivars grown in the paddy field in Fukushima City. Our study demonstrated a substantial variation in Cs accumulation levels among the cultivars of rice.

The treatment of radioactive wastewater has attracted extensive attention. Here, an adsorbent was designed to achieve efficient, stable, and recyclable removal of cesium ion contamination, and its adsorption properties were studied in detail. Prussian blue, a promising adsorbent for radioactive wastewater purification, has been often hindered in application due to its small size and easy agglomeration. To address this issue, the luffa fiber with a large specific surface area was employed to form networks loading Prussian blue particles and enhance adsorption capacity. In this paper, the recyclable Prussian blue/luffa was prepared by an in situ synthesis approach. Means such as XRD, SEM, EDS, FTIR, and XPS were applied to characterize its morphology and physicochemical properties. It exhibited outstanding selective removal efficiency for Cs + ions and the ability to be rapidly separated from wastewater. The equilibrium and adsorption kinetics followed the Langmuir isotherm and pseudo-second-order model with a maximum adsorption capacity of 102.01 mg/g. Both pH and temperature had effects on the adsorption performance. The removal efficiency of Cs + by Prussian blue/luffa still retained 71.2% after the 3-cycle test, and the possible mechanism was ion caging and ion exchange. In addition, the presence of co-existing ions only reduced the removal rate by less than 10.0%. Importantly, phytotoxicity assessment is urgently needed to address the adverse effects of applied nanoparticle composites on environmental and human safety. The phytotoxicity assessment was investigated, and the results indicated that the composite had no obvious biotoxicity. It is expected to be a highly potential material for disposing of radioactive wastewater. Future applications may extend to the treatment of various types of radioactive waste, providing a sustainable and effective solution to the field of nuclear waste management.

Objective This study aims to estimate the ecological exposure of adult residents of Fukushima Prefecture to 134 cesium (Cs) and 137 Cs through ingestion and inhalation between July 2 and July 8, 2011. Methods Fifty-five sets of meals with tap water, each representing one person’s daily intake, were purchased in local towns in Fukushima Prefecture. Locally produced cow’s milk (21 samples) and vegetables (43 samples) were also purchased. In parallel, air sampling was conducted at 12 different sites using a high-volume sampler. Nineteen sets of control meals were collected in Kyoto in July 2011. 134 Cs and 137 Cs levels in the samples were measured using a germanium detector. Results Radioactivity was detected in 36 of the 55 sample meals from Fukushima, compared with one of 19 controls from Kyoto. The median estimated dose level (μSv/year) was 3.0, ranging from not detectable to 83.1. None of the cow’s milk (21) or vegetable (49) samples showed levels of contamination above the current recommended limits (Bq/kg) of 200 for milk and 500 for vegetables. The total effective dose levels by inhalation were estimated to be <3 μSv/year at nine locations, but samples at three other locations close to the edge of the 20-km radius from the crippled nuclear power plant showed higher levels of contamination (μSv/year): 14.7 at Iitate, 76.9 at Namie, and 27.7 at Katsurao. Conclusions Levels of exposure to 134 Cs and 137 Cs in Fukushima by ingestion and inhalation are discernible, but generally within recommended limits.