Co-exposure to internal and external radiation alters cesium biokinetics and retention in mice.

Exposures in post-accidental situations are complex and include both external exposure and internal contamination with several radionuclides. However, in vivo and in vitro studies generally use simplified exposures, while a recent study suggested that combined external irradiation and internal contamination may induce more severe biological effects compared to single exposures. In an attempt to test the hypothesis of potential non-additive effects of multiple radiological exposures, we used a mouse model of combined external x-ray irradiation at 1 and 5 Gy and internal contamination with injection of 20 KBq 137Cs. The results showed differential kinetics of 137Cs elimination in irradiated animals compared to sham-irradiated, 137Cs injected animals. Moreover, changes in plasma potassium and in relative testis weight were observed 38 days after irradiation and injection in co-exposed animals compared to 137Cs injection alone. These results demonstrate that an external exposure combined with an internal contamination may lead to unexpected changes in biokinetics of radionuclides and biological effects compared to single exposures.

Long term investigation of 137Cs in chicken meat and eggs from northwest Croatia.

This paper presents the results of long-term investigations of 137Cs activity concentrations in chicken meat and eggs from northwest Croatia for the period 1987-2018. The research has been done as a part of monitoring program of radioactive contamination in Croatia. The highest activity concentrations in both of these foodstuffs were measured in 1987 and have been decreasing exponentially ever since. The Fukushima-Daiichi accident in 2011 did not cause any increase of 137Cs activity concentrations. The ecological half-life for 137Cs was estimated to be 8.0 and 8.4 years for chicken meat and eggs respectively. The correlation between 137Cs in fallout and chicken meat as well as between 137Cs in fallout and eggs is very good, the respective correlation coefficients being 0.79 and 0.72, indicating that fallout was the main source of 137Cs contamination in both foodstuffs. The estimated effective doses received by adult members of the Croatian population due to the intake of radiocaesium by chicken meat and egg consumption for the overall observed period are very small, 2.0 and 0.6 µSv respectively. Therefore, chicken meat and chicken egg consumption was not a critical pathway for the transfer of radiocaesium to humans.

Accumulation of 137Cs by Carnivorous Aquatic Macrophytes (Utricularia spp.) on the Savannah River Site.

Plants are an important mode of transfer of contaminants from sediments into food webs. In aquatic ecosystems, contaminant uptake by macrophytes can vary by path of nutrient uptake (roots vs. absorption from water column). Carnivorous plants likely have additional exposure through consumption of small aquatic organisms. This study expanded on previous research suggesting that bladderworts (Genus Utricularia) accumulate radiocesium (137Cs) and examined for (1) a potential association between sediment and plant concentrations and (2) differences in 137Cs accumulation among rooted and free floating Utricularia species. A strong correlation was found between average 137Cs concentrations in all Utricularia species (combined) and sediments (rs = 0.9, p = 0.0374). Among three bladderwort species at common sites, Utricularia floridana, the only rooted species, had higher mean 137Cs concentrations than Utricularia purpurea, and U. purpurea had a greater mean 137Cs concentration than Utricularia inflata.

Complexes of myo-Inositol-Hexakisphosphate (IP6) with Zinc or Lanthanum for the Decorporation of Radiocesium.

Radioactive nuclides leak into the surrounding environment after nuclear power plant disasters, such as the Chernobyl accident and the Fukushima Daiichi Nuclear Power Plant disaster. Cesium-137 (137Cs) (t1/2=30.1 year), a water-soluble radionuclide with a long physical half-life, contaminates aquatic ecosystems and food products. In humans, 137Cs concentrates in muscle tissue and has a long biological half-life, indicating it may be harmful. myo-Inositol-hexakisphosphate (IP6) is a compound found in grain, beans, and oil seeds. IP6 has the ability to form insoluble complexes with metals, including lanthanum (La) and zinc (Zn). We hypothesized that La-IP6 and Zn-IP6 may promote the elimination of 137Cs from the body through the adsorption of La-IP6 and Zn-IP6 to 137Cs in the gastrointestinal tract. Therefore, in this study, we evaluated the adsorptive capacity of La-IP6 and Zn-IP6 complexes with 137Cs in vitro and in vivo. La-IP6 and Zn-IP6 complexes were stable in acidic solution (pH 1.2) at 37°C. In vitro binding assays indicated that La-IP6 and Zn-IP6 complexes adsorbed 137Cs, with the adsorption capacity of Zn-IP6 to 137Cs greater than that of La-IP6. To evaluate the usefulness of La-IP6 and Zn-IP6 in vivo, La-IP6 or Zn-IP6 was administrated to mice after intravenous injection of 137Cs. However, the biodistribution of 137Cs in the La-IP6 treated group and the Zn-IP6 treated group was nearly identical to the non-treated control group, indicating that La-IP6 and Zn-IP6 were not effective at promoting the elimination of 137Cs in vivo.

Consideration on the Long Ecological Half-Life Component of (137)Cs in Demersal Fish Based on Field Observation Results Obtained after the Fukushima Accident.

Radiocesium concentrations in most marine fish collected off the coast of Fukushima and surrounding prefectures have decreased with time, and four years after the Fukushima Daiichi Nuclear Power Plant accident occurred, radiocesium concentrations have generally fallen below the detectable level (ca. < 10 Bq kg(-1)-raw). Only in some demersal fish species have detectable concentration levels still been found, and even these species have showed slow radiocesium decreases. The food web was considered as the major factor causing this phenomenon; however, slow elimination rates of radiocesium from these fish species also could be the cause. The latter effect was examined by considering that the (137)Cs concentration decreasing trend in fish could be fit with a set of three exponentially decreasing components; that is, having short, intermediate, and long biological half-lives. The long ecological half-life component was calculated using a 400-1500 d period of monitoring results for Japanese rockfish (Sebastes cheni) and compared with previous reported laboratory results for biological half-life. The obtained ecological half-lives ranged from 274-365 d, and these values agreed with the biological half-life of this fish species. This result implied that the long biological half-lives of radiocesium in some demersal fish species made their radiocesium contamination periods longer.

Two-Compartment Kinetic Modeling of Radiocesium Accumulation in Marine Bivalves under Hypothetical Exposure Regimes.

Interpreting the variable concentrations of (137)Cs in the field biological samples requires mechanistic understanding of both environmental and biological behavior of (137)Cs. In this study, we used a two-compartment model to estimate and compare the (137)Cs biokinetics in three species of subtropical marine bivalves. Significant interspecific difference of (137)Cs biokinetics was observed among oysters, mussels, and scallops. There was considerable (137)Cs assimilation from phytoplankton in the bivalves, but the calculated trophic transfer factors were generally between 0.04 and 0.4. We demonstrated a major efflux of radiocesium in the scallops (with a rate constant of 0.207 d(-1)), whereas the efflux was comparable between oysters and mussels (0.035-0.038 d(-1)). A two-compartment kinetic model was developed to simulate the (137)Cs accumulation in the three bivalves under four hypothetical exposure regimes. We showed that the bivalves respond differently to the exposure regimes in terms of time to reach equilibrium, equilibrium concentration, and maximum concentration. Bivalves suffering more frequent intermittent exposure may have higher maximum concentrations than those receiving less frequent exposure. The interspecific difference of (137)Cs accumulation in bivalves has important implications for biomonitoring and implementing management techniques. This study represents one of the first attempts to combine both dissolved and dietary pathways to give a realistic simulation of (137)Cs accumulation in marine bivalves under dynamic exposure regimes.

Comparison of Absorbents and Drugs for Internal Decorporation of Radiocesium: Advances of Polyvinyl Alcohol Hydrogel Microsphere Preparations Containing Magnetite and Prussian Blue.

Radiocesium nuclides, used as a gamma ray source in various types of industrial equipments and found in nuclear waste, are strictly controlled to avoid their leakage into the environment. When large amounts of radiocesium are accidentally incorporated into the human body, decorporation therapy should be considered. Although standard decorporation methods have been studied since the 1960s and were established in the 1970s with the drug Radiogardase(®) (a Prussian blue preparation), application of recent advances in pharmacokinetics and ethical standards could improve these methods. Here we designed a modern dosage form of hydrogel containing cesium-absorbents to alleviate intestinal mucosa irritation due to the cesium-binding capacity of the absorbents. The effectiveness of the dosage form on fecal excretion was confirmed by quantitative mouse experiments. The total cesium excretion rate of the crystal form (1.37±0.09) was improved by the hydrogel form (1.52±0.10) at the same dose of Prussian blue, with a longer gastrointestinal tract transit time. Using a mouse model, we compared the effects of several drugs on fecal and urinary excretion of internal cesium, without the use of absorbents. Only phenylephrine hydrochloride significantly enhanced cesium excretion (excretion rate of 1.17±0.08) via the urinary pathway, whereas none of the diuretic drugs tested had this effect. These findings indicate that modifying the dosage form of cesium absorbents is important for the decorporation of internal radiocesium contamination.

Considerations on the ICRP model predictions of the transfer of (137)Cs from food to the milk and urine of lactating mothers.

A recent work has shown that the current ICRP biokinetic model for the transfer of caesium radionuclides from food to human breast milk was able to describe with satisfactory accuracy (137)Cs activity concentrations in human breast samples collected a few weeks after the Chernobyl accident as well as in samples collected some years later. However, systematic discrepancies were observed for the predictions of the activity concentrations in urine samples. In the present work, modifications to the model were investigated with the aim of improving the agreement between model predictions and data. It turned out that the disagreement for the urine data was ascribable to the mathematical simplifications used by the ICRP to describe urinary excretion in the first few days after delivery. However, the predictive performances of the model remained unchanged even when differences in the bioavailability of caesium from the ingested food types were considered or metabolic interactions between caesium and potassium were introduced into the model formulation.

Evidence for an increase in trisomy 21 (Down syndrome) in Europe after the Chernobyl reactor accident.

The objective of this study is to investigate the prevalence of Down syndrome (DS) associated with Chernobyl fallout. Maternal age-adjusted DS data and corresponding live birth data from the following seven European countries or regions were analyzed: Bavaria and West Berlin in Germany, Belarus, Hungary, the Lothian Region of Scotland, North West England, and Sweden from 1981 to 1992. To assess the underlying time trends in the DS occurrence, and to investigate whether there have been significant changes in the trend functions after Chernobyl, we applied logistic regression allowing for peaks and jumps from January 1987 onward. The majority of the trisomy 21 cases of the previously reported, highly significant January 1987 clusters in Belarus and West Berlin were conceived when the radioactive clouds with significant amounts of radionuclides with short physical half-lives, especially (131)iodine, passed over these regions. Apart from this, we also observed a significant longer lasting effect in both areas. Moreover, evidence for long-term changes in the DS prevalence in several other European regions is presented and explained by exposure, especially to (137)Cs. In many areas, (137)Cs uptake reached its maximum one year after the Chernobyl accident. Thus, the highest increase in trisomy 21 should be observed in 1987/1988, which is indeed the case. Based on the fact that maternal meiosis is an error prone process, the assumption of a causal relationship between low-dose irradiation and nondisjunction is the most likely explanation for the observed increase in DS after the Chernobyl reactor accident.

Radiocesium distribution in the tissues of Japanese Black beef heifers fed fallout-contaminated roughage due to the Fukushima Daiichi Nuclear Power Station accident.

This study examined the accumulation and tissue distribution of radioactive cesium nuclides in Japanese Black beef heifers raised on roughage contaminated with radioactive fallout due to the accident at the Fukushima Daiichi Nuclear Power Station on March 2011. Radiocesium feeding increased both (134)Cs and (137)Cs levels in all tissues tested. The kidney had the highest level and subcutaneous adipose had the lowest of radioactive cesium in the tissues. Different radioactive cesium levels were not found among parts of the muscles. These results indicate that radiocesium accumulated highly in the kidney and homogenously in the skeletal muscles in the heifers.

[Dependences of 137Cs and 90Sr concentration ratios in fish on the potassium and calcium concentrations in the freshwater reservoirs].

Activities of 137Cs and 90Sr, concentrations of the potassium and calcium ions in water and accumulation of the radionuclides in the organisms of various freshwater fish have been measured in the stagnant and semistagnant water reservoirs of Ukraine contaminated as a result of the Chernobyl accident. On the basis of the numerous experimental data for different regions the statistical parameters were derived describing the dependencies of the 137Cs and 90Sr concentration ratios in the muscle tissue of various fish species on the potassium and calcium concentrations in water, respectively.

Quantum chemical calculation studies toward microscopic understanding of retention mechanism of Cs radioisotopes and other alkali metals in lichens.

We evaluate stability of cesium (Cs) and other alkali-metal cation complexes of lichen metabolites in both gas and aqueous phases to discuss why lichens can retain radioactive Cs in the thalli over several years. We focus on oxalic acid, (+)-usnic acid, atranorin, lecanoric acid, and protocetraric acid, which are common metabolite substances in various lichens including, e.g., Flavoparmelia caperata and Parmotrema tinctorum retaining Cs in Fukushima, Japan. By performing quantum chemical calculations, their gas-phase complexation energies and aqueous-solution complexation free energies with alkali-metal cations are computed for their neutral and deprotonated cases. Consequently, all the molecules are found to energetically favor cation complexations and the preference order is Li[Formula: see text]Na[Formula: see text]K[Formula: see text]Rb[Formula: see text]Cs[Formula: see text] for all conditions, indicating no specific Cs selectivity but strong binding with all alkali cations. Comparing complexation stabilities among these metabolites, lecanoric and protocetraric acids seen in medullary layer are found to keep higher affinity in their neutral case, while (+)-usnic acid and atranorin in upper cortex exhibit rather strong affinity only in deprotonated cases through forming stable six atoms' ring containing alkali cation chelated by two oxygens. These results suggest that the medullary layer can catch all alkali cations in a wide pH range around the physiological one, while the upper cortex can effectively block penetration of metal ions when the metal stress grows. Such insights highlight a physiological role of metabolites like blocking of metal-cation migrations into intracellular tissues, and explain long-term retention of alkali cations including Cs in lichens containing enough such metabolites to bind them.

Biodistribution of (137)Cs in a mouse model of chronic contamination by ingestion and effects on the hematopoietic system.

The aim of this work was to define the possible occurrence of hematological changes during the course of a chronic ingestion of (137)Cs. A mouse model was used, with ingestion through drinking water with a cesium concentration of 20 kBq l(-1). Ingestion started in parent animals before mating, and (137)Cs intake and its effect on the hematopoietic system was studied in offspring at various ages between birth and 20 weeks. (137)Cs content was measured in various organs, indicating that (137)Cs was distributed throughout the organism including lympho-hematopoietic organs, i.e., femurs, spleen and thymus. However, we did not observe any effect on the hematopoietic system, whatever the parameter used. In fact, blood cell counts, mononuclear cell counts and progenitor frequency in bone marrow and spleen, and Flt3-ligand, Erythropoietin, G-CSF and SDF-1 concentration in plasma remained unchanged when compared to control animals. Moreover, phenotypic analysis did not show any change in the proportions of bone marrow cell populations. These results indicate that, although (137)Cs was found in all organs implicated in the hematopoietic system, this did not induce any changes in bone marrow function.

Comparison of 137Cs uptake, depuration and continuous uptake, originating from feed, in five salmonid fish species.

The origin of 137Cs contamination, contamination levels, and its effective ecological half-life can differ among fish species, but until recently it was unknown whether interspecific differences in radiocaesium metabolism existed. We compare the trophic transfer of 137Cs in five salmonid species under controlled conditions. Fish were fed a diet containing 200 Bq kg-1 wet wt concentration of 137Cs for a fixed period of time. While there were almost no differences in contamination levels among individual fish within a species during fixed periods, the rate of 137Cs uptake was statistically different among the species examined, for which the effective half-life of 137Cs ranged 49-84 days. No significant difference in rate of decline in the quantity of 137Cs was apparent among species in two experiments after correcting for differences in growth. The effective half-life was shortest in Oncorhynchus mykiss and O. masou-two species exhibiting the best growth rate in both experiments-indicating an influence of the dilution effect associated with growth. When continuously fed 200 Bq kg-1 wet wt concentration of 137Cs for a period of 209-294 days, contamination levels in the five species ranged 216-240 Bq kg-1 wet wt, and reached a steady state value. Our results indicate metabolic rate, although accompanying a change of body size, did not affect 137Cs contamination levels in fish, which implies that contamination levels in the diet strongly determined contamination levels in fish.

The transfer of 239+240Pu, 241Am, 137Cs and 90Sr to the tissues of horses.

Horses are important food sources in several countries however, data on their radionuclide uptake is less available than for many other farm animals. Information on the transfer of artificial radioisotopes from the environment to the food supply is necessary for internal dose assessment and assuring the safety of the population relying on this food source. This study provides data for a less studied farm animal and, in the case of 241Am and 239+240Pu, relatively poorly studied radionuclides with respect to transfer to animal products. The transfer parameters for 239+240Pu, 241Am, 137Cs and 90Sr to the organs of 1-year old fillies, 10-year old mares and through the placental barrier into foetuses were quantified after 60-days feeding with contaminated soil or diet contaminated by a leachate solution. The transfer of radionuclides from ingested soil to tissues was generally lower, by up to three orders of magnitude, than from a diet contaminated by a leachate solution. The ingestion of soil is a particularly important source of radionuclide intake to grazing animals in the Semipalatinsk Test Site. For 241Am there is a lack of available data, the two singular entries for mutton and beef in the IAEA handbook are higher than all values observed in the current study. The maximum observed transfer factor for 241Am was 72 ± 22*10-5 d kg-1 FW in the liver of the mare fed with leachate contaminated feed. For 239+240Pu the maximum transfer factor was 31.8 ± 8*10-5 d kg-1 FW observed also in the liver of the mare fed with leachate contaminated feed. The filly fed with leachate contaminated feed had the highest transfer parameter value for 137Cs, 35.3*10-3 d kg-1 FW. The highest 90Sr transfer factor was found in the ribs of the filly fed leachate contaminated feed, 720 ± 144 *10-3 d kg-1 FW. The results presented in this paper can be used to improve the current internal dose estimates from the ingestion of horse meat produced in the area, however they are based on a low sample size; future studies need to use a larger number of animals.

Non-invasive imaging of radiocesium dynamics in a living animal using a positron-emitting 127Cs tracer.

Visualizing the dynamics of cesium (Cs) is desirable to understand the impact of radiocesium when accidentally ingested or inhaled by humans. However, visualization of radiocesium in vivo is currently limited to plants. Herein, we describe a method for the production and purification of 127Cs and its use in visualizing Cs dynamics in a living animal. The positron-emitting nuclide 127Cs was produced using the 127I (α, 4n) 127Cs reaction, which was induced by irradiation of sodium iodide with a 4He2+ beam from a cyclotron. We excluded sodium ions by using a material that specifically adsorbs Cs as a purification column and successfully eluted 127Cs by flowing a solution of ammonium sulfate into the column. We injected the purified 127Cs tracer solution into living rats and the dynamics of Cs were visualized using positron emission tomography; the distributional images showed the same tendency as the results of previous studies using disruptive methods. Thus, this method is useful for the non-invasive investigation of radiocesium in a living animal.

Concentrations of 137Cs radiocaesium in the organs and tissues of low-dose-exposed wild Japanese monkeys.

OBJECTIVES: Following the massive earthquake that struck eastern Japan on March 11, 2011, a large amount of radioactive material was released into the environment from the damaged reactor of the Fukushima Daiichi Nuclear Power Plant (FDNPP). After the FDNPP accident, radiocaesium was first detected in muscle samples from wild Japanese monkeys exposed to radioactive materials, and haematologic effects, changes in head size, and delayed body weight gain were also reported, but little is known about the distribution of 137Cs in the organs and tissues of wild Japanese monkeys. RESULTS: We detected the 137Cs in various organ and tissue samples of 10 wild Japanese monkeys inhabiting the forested areas of Fukushima City that were captured between July and August 2012. Among muscle, brain, heart, kidney, liver, lung, and spleen, muscle exhibited the highest and the brain the lowest 137Cs concentration. The concentration (mean ± SD) of 137Cs in muscle, brain, heart, kidney, liver, lung, and spleen was 77 ± 66, 26 ± 22, 41 ± 35, 49 ± 41, 41 ± 38, 53 ± 41, and 53 ± 51 Bq/kg, respectively. These results can help us understand the biological effects of long-term internal radiation exposure in non-human primates.

Effective and ecological half-lives of 137Cs in cow's milk in alpine agriculture.

In the mountainous "Hohe Tauern" region of Salzburg (Austria), milk samples have been collected in a long-term montitoring programme since 1988, at eight alpine sites used for extensive, seasonal stock farming. For this alpine environment with its acidic soils developed on silicate bedrock, high soil-to-plant transfer factors and long-lasting (137)Cs contamination levels in milk--the main product of seasonal agriculture at elevated altitudes--are characteristic features. The decrease in (137)Cs concentration in milk measured since 1988 turned out to be best described by one or two effective half-lives. For the period from 1993 to 2007, which can be modelled with one effective half-life for all sites, effective half-lives between 3.7 and 15.0 years (ecological half-lives: 4.3-29.9 years) were obtained. The effective half-life increases with mean altitude of the investigated graze pastures, probably due to reduced migration velocities of (137)Cs and low (137)Cs half-value depths of a few centimetres in the soil.

[Decreasing of 137Cs specific activities in hydrobionts inhabiting water-bodies of different type].

The rate of decrease of 137Cs content in hydrobionts from water-bodies of Ukraine that contaminated as result of Chernobyl accident has been calculated. The retrospective analysis of 137Cs content in fish of water-bodies has been transmitted.

[The role of different species of hunt game animals in formation of irradiation dose of population in territories polluted by 137Cs].

This article includes the data on 137Cs accumulation in different species of game animals studied in two regions of Bryansk area. Based on Hunting Commission data on numbers of bagging by hunters in these regions, a count of total hunting production polluted with 137Cs was obtained. It was shown that wild ungulates are the main dose-forming factor in risk group. A calculation of volume of 137Cs transferred from forest biocenosi into towns and villages of the regions in question was also performed.