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.

Uptake of the natural radioactive gas radon by an epiphytic plant.

Radon (222Rn) is a natural radioactive gas and the major radioactive contributor to human exposure. The present effective ways to control Rn contamination are ventilation and adsorption with activated carbon. Plants are believed to be negligible in reducing airborne Rn. Here, we found epiphytic Tillandsia brachycaulos (Bromeliaceae) was effective in reducing airborne Rn via the leaves. Rn concentrations in the Rn chamber after Tillandsia plant treatments decreased more than those in the natural situation. The specialized foliar trichomes densely covering Tillandsia leaves play a major role in the uptake of Rn because the amplified rough leaf surface area facilitates deposition of Rn progeny particles and the powdery epicuticular wax layer of foliar trichomes uptakes liposoluble Rn. The results provide us a new ecological strategy for Rn contamination control, and movable epiphytic Tillandsia plants can be applied widely in Rn removal systems.

Internal dosimetry of inhaled iodine-131.

In this paper, the dose assessment for the iodine inhalation exposure in 19 aerosol sizes and three gas/vapor forms at three levels of thyroid uptake, was performed. Two different modes of work (light vs. heavy) and breathing (nose vs. mouth) for aerosol inhalation were investigated. In order to calculate the cumulated activities per unit of inhaled activity, a combined model which included the latest models of both human respiratory and alimentary tract was developed. The S values for 131I were computed based on the ICRP adult male and female reference voxel phantoms by the Monte Carlo method. Then, the committed equivalent and committed effective dose coefficients were obtained (The data are available at http://www.um.ac.ir/∼mirihakim). In general, for the nonzero thyroid uptakes, the maximum cumulated activity was found in the thyroid. When the thyroid is blocked, however, the maximum depends on the work and breathing mode and radioisotope form. Overall, the maximum CED coefficient was evaluated for the inhalation of elemental iodine at thyroid uptake of ∼27% (2.8 × 10-8 Sv/Bq). As for the particle inhalation per se, mouth breathing of 0.6 nm and 0.2 µm AMTD particles showed to have the maximum (2.8 × 10-8 Sv/Bq) and minimum (6.4 × 10-9 Sv/Bq) CED coefficients, respectively. Compared to the reference CED coefficients, the authors found an increase of about 58% for inhalation of the aerosols with AMAD of 1 µm and 70% for 5 µm.

Measurements of radon activity concentration in mouse tissues and organs.

The purpose of this study is to investigate the biokinetics of inhaled radon, radon activity concentrations in mouse tissues and organs were determined after mice had been exposed to about 1 MBq/m3 of radon in air. Radon activity concentrations in mouse blood and in other tissues and organs were measured with a liquid scintillation counter and with a well-type HP Ge detector, respectively. Radon activity concentration in mouse blood was 0.410 ± 0.016 Bq/g when saturated with 1 MBq/m3 of radon activity concentration in air. In addition, average partition coefficients obtained were 0.74 ± 0.19 for liver, 0.46 ± 0.13 for muscle, 9.09 ± 0.49 for adipose tissue, and 0.22 ± 0.04 for other organs. With these results, a value of 0.414 for the blood-to-air partition coefficient was calculated by means of our physiologically based pharmacokinetic model. The time variation of radon activity concentration in mouse blood during exposure to radon was also calculated. All results are compared in detail with those found in the literature.

ICRP dose coefficients: computational development and current status.

Major current efforts within Committee 2 of the International Commission on Radiological Protection (ICRP) involve the development of dose coefficients for inhalation and ingestion of radionuclides, and those for exposure to environmental radiation fields. These efforts build upon changes in radiation and tissue weighting factors (Publication 103), radionuclide decay schemes (Publication 107), computational phantoms of the adult reference male and female (Publication 110), external dose coefficients for adult reference workers for idealised radiation fields (Publication 116), models of radionuclide intake (Publications 66, 100 and 130), and models of radionuclide systemic biokinetics (Publication 130). This paper will review the overall computational framework for both internal and external dose coefficients. For internal exposures, the work entails assessment of organ self-dose and cross-dose from monoenergetic particle emissions (specific absorbed fraction), absorbed dose per nuclear transformation (S value), time-integrated activity of the radionuclide in source tissues (inhalation, ingestion, and systemic biokinetic models), and their numerical combination to yield the organ equivalent dose or effective dose per activity inhaled or ingested. Various challenges are reviewed that were not included in the development of Publication 30 dose coefficients, which were based upon much more simplified biokinetic models and computational phantoms. For external exposures, the computations entail the characterisation of environmental radionuclide distributions, the transport of radiation particles through that environment, and the tracking of energy deposition to the organs of the exposed individual. Progress towards the development of dose coefficients to members of the general public (adolescents, children, infants and fetuses) are also reviewed.

Interception and transfer of wet-deposited (134)Cs to potato foliage and tubers.

Contamination levels on potato foliage and tubers were investigated by repeated sampling after multiple foliar contaminations of wet-deposited (134)Cs at five different growth stages in a micro-plot field experiment in three successive years. Application of the radionuclide early in the growing season (deposition date 19-27 June, growth stage II = plant establishment) resulted in low (134)Cs activity concentration in potato tubers across sampling occasions (mean 60, 25 and 115 Bq kg(-1) dry weight (D.W.) for years 1, 2 and 3, respectively). Following radionuclide deposition in the middle of the growing season (15-24 July, growth stage III = tuber initiation), (134)Cs activity concentration in tubers across sampling occasions was found to be highest (mean 150, 850 and 660 Bq kg(-1) D.W. for years 1, 2 and 3, respectively). When the radionuclide was sprayed on at later stages (5-7 August, growth stage IV = tuber bulking), (134)Cs activity concentrations in tubers across sampling dates decreased (mean 75, 310 and 395 Bq kg(-1) D.W. for years 1, 2 and 3, respectively). Deposition in the second half of August (15-28 August, late growth stage IV and beginning of growth stage V = tuber maturation) resulted in yet lower (134)Cs activity concentration in tubers. Potato tubers may concentrate as much as up to 2 times more (134)Cs than foliage depending on deposition date of radionuclide.

Bioindicating potential of strontium contamination with Spanish moss Tillandsia usneoides.

Tillandsia species have been recognized as efficient biomonitors of air pollution, but rarely exploited in bioindicating of strontium, an important nuclide. We exposed Tillandsia usneoides, colloquially known as Spanish moss due to its filamentous morphology but is an atypical angiosperm in the family Bromeliaceae, to the solutions with different Sr concentrations (0.1-100 mmol/L). The results showed that plants were able to endure Sr stress for a relatively long period, which suggests that T. usneoides is able to resist this toxic element. T. usneoides had the highest uptake ratio of Sr (82.21 ± 0.12%) when the plants were exposed to 0.1 mmol/L Sr solutions. Sr contents in T. usneoides increased significantly with the increase in applied metal solution concentrations. Low Sr stimulated the formation of chlorophyll, but high Sr decreased the contents of chlorophyll, and no significant effect on the total biomass was found in T. usneoides. In contrast, the permeability of plasma membrane based on the relative electronic conductivity in T. usneoides increased significantly under Sr stress, indicating that Sr probably caused oxidative stress. Moreover, correlation analysis showed that the leaf relative conductivity was significantly positively correlated with Sr contents in the plants after Sr treatments. Therefore, T. usneoides has considerable potential for monitoring Sr polluted environments through measuring Sr contents in the plant directly or exploiting the leaf relative conductivity as an indirect biomarker.

An analysis of the intake of iodine-131 by a dairy herd post-Fukushima and the subsequent excretion in milk.

This study focuses on iodine-131 detected in milk samples from the Dairy Science Unit at Cal Poly, San Luis Obispo, California following events at the Fukushima Dai-ichi Nuclear Power Plant in March of 2011. The milk samples, collected between March 21 and April 11, 2011, were part of the Diablo Canyon Nuclear Power Plant Radiological Environmental Monitoring Program. A correlation is made between the integrated activity of iodine-131 found in milk and the integrated activities of iodine-131 of rainwater, vegetation and air samples that were collected from March 19 to April 18, 2011. A comparison is then made to previous studies conducted on dairy cattle that were administered controlled amounts of iodine-131 through ingestion. The comparison shows good agreement to the model which states that generally 1 percent of the activity of iodine-131 ingested by dairy cattle will be detected in harvested milk. Considering the environmental factors and the uncertainties involved, these data and calculated results derived from a real world situation provide an excellent application and confirmation of studies done under controlled settings.

Dynamic evaluation of environmental impact due to tritium accidental release from the fusion reactor.

As one of the key safety issues of fusion reactors, tritium environmental impact of fusion accidents has attracted great attention. In this work, the dynamic tritium concentrations in the air and human body were evaluated on the time scale based on accidental release scenarios under the extreme environmental conditions. The radiation dose through various exposure pathways was assessed to find out the potential relationships among them. Based on this work, the limits of HT and HTO release amount for arbitrary accidents were proposed for the fusion reactor according to dose limit of ITER. The dynamic results aim to give practical guidance for establishment of fusion emergency standard and design of fusion tritium system.

Impacts of (14)C discharges from a nuclear fuel reprocessing plant on surrounding vegetation: Comparison between grass field measurements and TOCATTA-χ and SSPAM(14)C model computations.

This article compares and discusses the ability of two different models to reproduce the observed temporal variability in grass (14)C activity in the vicinity of AREVA-NC La Hague nuclear fuel reprocessing plant in France. These two models are the TOCATTA-χ model, which is specifically designed for modelling transfer of (14)C (and tritium) in the terrestrial environment over short to medium timescales (days to years), and SSPAM(14)C, which has been developed to model the transfer of (14)C in the soil-plant-atmosphere with consideration over both short and long timescales (days to thousands of years). The main goal of this article is to discuss the strengths and weaknesses of the models studied, and to investigate if modelling could be improved through consideration of a much higher level of detail of plant physiology and/or higher number of plant compartments. These models have been applied here to the La Hague field data as it represents a medium term data set with both short term variation and a sizeable time series of measurements against which to compare the models. The two models have different objectives in terms of the timescales they are intended to be applied over, and thus incorporate biological processes, such as photosynthesis and plant growth, at different levels of complexity. It was found that the inclusion of seasonal dynamics in the models improved predictions of the specific activity in grass for such a source term of atmospheric (14)C.

Foliar interception of radionuclides in dry conditions: a meta-analysis using a Bayesian modeling approach.

Uncertainty on the parameters that describe the transfer of radioactive materials into the (terrestrial) environment may be characterized thanks to datasets such as those compiled within International Atomic Energy Agency (IAEA) documents. Nevertheless, the information included in these documents is too poor to derive a relevant and informative uncertainty distribution regarding dry interception of radionuclides by the pasture grass and the leaves of vegetables. In this paper, 145 sets of dry interception measurements by the aboveground biomass of specific plants were collected from published scientific papers. A Bayesian meta-analysis was performed to derive the posterior probability distributions of the parameters that reflect their uncertainty given the collected data. Four competing models were compared in terms of both fitting performances and predictive abilities to reproduce plausible dry interception data. The asymptotic interception factor, applicable whatever the species and radionuclide to the highest aboveground biomass values (e.g. mature leafy vegetables), was estimated with the best model, to be 0.87 with a 95% credible interval (0.85, 0.89).

¹³7Cs concentrations in foliose lichens within Tsukuba-city as a reflection of radioactive fallout from the Fukushima Dai-ichi Nuclear Power Plant accident.

(137)Cs concentrations in ten species of foliose lichens collected within Tsukuba-city in August 2013 ranged from 1.7 to 35 kBq/kg. The relationships between (137)Cs in two dominant species, Dirinaria applanata and Physcia orientalis, and the air dose rate (µSv/h) at the sampling sites were investigated. (137)Cs in P. orientalis measured about 1 year after the Fukushima nuclear accident was correlated (r(2) = 0.80) more closely with the air dose rate than those measured after about 2 years (r(2) = 0.65), possibly demonstrating its continued value as a biomonitor to reflect ambient fall-out levels. In contrast, those of Dirinaria applanata were not correlated with the air dose rate in either year.

Effective half-lives of ¹³7Cs from persimmon tree tissue parts in Japan after Fukushima Dai-ichi Nuclear Power Plant accident.

To estimate the radiocesium decreasing rates from persimmon trees during a period of about 3 y following the accident at Tokyo Electric Power Company's Fukushima Dai-ichi Nuclear Power Plant (FDNPP), we conducted measurements of tree tissue parts collected in 2011-2013. The sampling was carried out in Chiba, 220 km south of FDNPP; radioactive fallouts discharged from FDNPP had mainly been observed in March-April 2011 on the sampling site. We measured (137)Cs concentrations in the tree tissue parts, i.e., fruits (flesh, skin and seeds), leaves and newly emerged branches, and then the effective half-lives (T(eff)) of (137)Cs were calculated. Leaf samples were classified into two types by sampling months according to the growing stages, that is, immature (April-May) and mature (June-November) leaves. All these parts showed exponential declines in (137)Cs concentration with good adjusted contribution ratios of higher than ca. 0.7. The calculated T(eff) values from all tissue parts were similar with the average of 229 d (range: 216-243 d). From these results, we concluded that each tree tissue was representative for the calculation of Teff. For comparison to these observation results, open source food monitoring data from 2011 to 2013 including (137)Cs data for persimmon fruits collected in Fukushima Prefecture were used to calculate T(eff) for persimmon trees. Values of Teff were obtained for persimmon fruits grown in each local government area in Fukushima Prefecture and they ranged from 303 to 475 d.

Environmental consequences of uranium atmospheric releases from fuel cycle facility: II. The atmospheric deposition of uranium and thorium on plants.

Uranium and thorium isotopes were measured in cypress leaves, wheat grains and lettuce taken in the surroundings of the uranium conversion facility of Malvési (South of France). The comparison of activity levels and activity ratios (namely (238)U/(232)Th and (230)Th/(232)Th) in plants with those in aerosols taken at this site and plants taken far from it shows that aerosols emitted by the nuclear site (uranium releases in the atmosphere by stacks and (230)Th-rich particles emitted from artificial ponds collecting radioactive waste mud) accounts for the high activities recorded in the plant samples close to the site. The atmospheric deposition process onto the plants appears to be the dominant process in plant contamination. Dry deposition velocities of airborne uranium and thorium were measured as 4.6 × 10(-3) and 5.0 × 10(-3) m s(-1), respectively.

Epiphytic fruticose lichens as biomonitors for retrospective evaluation of the (134)Cs/(137)Cs ratio in Fukushima fallout.

In 2011-2013, sampling of epiphytic fruticose lichens of the genera Usnea, Bryoria and Alectoria was carried out on Sakhalin and Kuril Islands (the Sakhalin region, Russia) to investigate contamination of these organisms with the Fukushima-derived (134)Cs and (137)Cs. Activities of the radionuclides were determined in all 56 samples of lichens taken for the analysis. After correction for radioactive decay (on 15 March 2011), the activity concentrations ranged from 2.1 Bq kg(-1) (d.w.) to 52 Bq kg(-1) for (134)Cs and from 2.3 Bq kg(-1) to 52 Bq kg(-1) for (137)Cs. Cesium-134 and (137)Cs activities for the whole set of lichens (n = 56) were strongly positively correlated; Spearman's rank correlation coefficient was calculated as 0.991 (P < 0.01). The activity concentrations of (134)Cs and (137)Cs in Usnea lichens from the Sakhalin and Kunashir islands declined with a factor of three in the period from 2011 to 2013. The average biological half-time for both cesium radionuclides in lichens of the genus Usnea is estimated as 1.3 y. The mean of 0.99 ± 0.10 and median of 0.99 were calculated for the decay corrected (134)Cs/(137)Cs activities ratios in the lichens (n = 56). The radionuclides ratio in the lichens did not depend on location of sampling site, species and the time that had passed after the Fukushima accident. The regression analysis has shown the background pre-Fukushima level of (137)Cs of 0.4 ± 0.3 Bq kg(-1), whereas the ratio between the Fukushima-borne (134)Cs and (137)Cs in the lichens was estimated as 1.04. The (134)Cs/(137)Cs activities ratio in lichens from the Sakhalin region is consistent with the ratios reported by others for the heavy contaminated areas on Honshu Island in Japan following the Fukushima accident. The activity concentrations of natural (7)Be in lichens from the Sakhalin region varied between 100 Bq kg(-1) and 600 Bq kg(-1); the activity concentrations did not exhibit temporal variations during a 2y-period of observations. The applicability of epiphytic fruticose lichens as retrospective bio-monitors for the air-borne radiocesium contamination of the environment is discussed.

Radioactive contamination of pine (Pinus sylvestris) in Krasnoyarsk (Russia) following fallout from the Fukushima accident.

Following the Fukushima accident in March 2011, samples of pine trees (Pinus sylvestris) were collected from three sites near the city of Krasnoyarsk (Siberia, Russia) during 2011-2012 and analyzed for artificial radionuclides. Concentrations of Fukushima-derived radionuclides in the samples of pine needles in April 2011 reached 5.51 ± 0.52 Bq kg(-1)(131)I, 0.92 ± 0.04 Bq kg(-1)(134)Cs, and 1.51 ± 0.07 Bq kg(-1)(137)Cs. An important finding was the detection of (134)Cs from the Fukushima accident not only in the pine needles and branches but also in the new shoots in 2012, which suggested a transfer of Fukushima cesium isotopes from branches to shoots. In 2011 and 2012, the (137)Cs/(134)Cs ratio for pine needles and branches collected in sampling areas Krasnoyarsk-1 and Krasnoyarsk-2 was greater than 1 (varying within a range of 1.2-2.6), suggesting the presence of "older", pre-Fukushima accident (137)Cs. Calculations showed that for pine samples growing in areas of the Krasnoyarskii Krai unaffected by contamination from the nuclear facility, the activity of the Fukushima-derived cesium isotopes was two-three times higher than the activity of the pre-accident (137)Cs.

The environmental geochemistry of trace elements and naturally radionuclides in a coal gangue brick-making plant.

An investigation focused on the transformation and distribution behaviors of trace elements and natural radionuclides around a coal gangue brick plant was conducted. Simultaneous sampling of coal gangue, brick, fly ash and flue gas were implemented. Soil, soybean and earthworm samples around the brick plant were also collected for comprehensive ecological assessment. During the firing process, trace elements were released and redistributed in the brick, fly ash and the flue gas. Elements can be divided into two groups according to their releasing characteristics, high volatile elements (release ratio higher than 30%) are represented by Cd, Cu, Hg, Pb, Se and Sn, which emitted mainly in flue gas that would travel and deposit at the northeast and southwest direction around the brick plant. Cadmium, Ni and Pb are bio-accumulated in the soybean grown on the study area, which indicates potential health impacts in case of human consumption. The high activity of natural radionuclides in the atmosphere around the plant as well as in the made-up bricks will increase the health risk of respiratory system.

TOCATTA: a dynamic transfer model of (3)H from the atmosphere to soil-plant systems.

This paper describes a dynamic compartment model (TOCATTA) that simulates tritium transfer in agricultural plants of several categories including vegetables, pasture and annual crops, exposed to time-varying HTO concentrations of water vapour in the air and possibly in irrigation and rainwater. Consideration is also given to the transfer pathways of HTO in soil. Though the transfer of tritium is quite complex, from its release into the environment to its absorption and its incorporation within the organic material of living organisms, the TOCATTA model is relatively simple, with a limited number of compartments and input parameters appropriate to its use in an operational mode. In this paper, we took the opportunity to have data obtained on an ornamental plant - an indoor palm tree - within an industrial building where tritium was released accidentally over several weeks (or months). More specifically, the model's ability to provide hindsight on the chronology of the release scenario is discussed by comparing model predictions of TFWT and OBT activity concentrations in the plant leaves with measurements performed on three different leaves characterized by different developmental stages. The data-model comparison shows some limitations, mainly because of a lack of knowledge about the initial conditions of the accident and when it actually started and about the processes involved in the transfer of tritium. Efforts are needed in both experimental and modelling areas for future evaluation of tritium behaviour in agricultural soil and plants exposed to gaseous HTO releases and/or to irrigation with contaminated water.

A review of lung-to-blood absorption rates for radon progeny.

The International Commission on Radiological Protection (ICRP) Publication 66 Human Respiratory Tract Model (HRTM) treats clearance of materials from the respiratory tract as a competitive process between absorption into blood and particle transport to the alimentary tract and lymphatics. The ICRP recommended default absorption rates for lead and polonium (Type M) in ICRP Publication 71 but stated that the values were not appropriate for short-lived radon progeny. This paper reviews and evaluates published data from volunteer and laboratory animal experiments to estimate the HRTM absorption parameter values for short-lived radon progeny. Animal studies showed that lead ions have two phases of absorption: ∼10 % absorbed with a half-time of ∼15 min, the rest with a half-time of ∼10 h. The studies also indicated that some of the lead ions were bound to respiratory tract components. Bound fractions, f(b), for lead were estimated from volunteer and animal studies and ranged from 0.2 to 0.8. Based on the evaluations of published data, the following HRTM absorption parameter values were derived for lead as a decay product of radon: f(r) = 0.1, s(r) = 100 d(-1), s(s) = 1.7 d(-1), f(b) = 0.5 and s(b) = 1.7 d(-1). Effective doses calculated assuming these absorption parameter values instead of a single absorption half-time of 10 h with no binding (as has generally been assumed) are only a few per cent higher. However, as there is some conflicting evidence on the absorption kinetics for radon progeny, dose calculations have been carried out for different sets of absorption parameter values derived from different studies. The results of these calculations are discussed.

A study on determination of potentially hazardous plutonium isotopes in environmental samples.

Due to the lack of stable plutonium isotopes, and the high mobility as well as long half-life, plutonium is considered one of the most important radioelement in safety assessment of environmental radioactivity and nuclear waste management. A number of analytical methods have been developed over the past decades for determination of plutonium in environmental samples. The article discusses different analytical techniques and presents the results of plutonium isotopes determination by alpha spectrometry and accelerator mass spectrometry in environmental samples. The concentrations of plutonium isotopes in analyzed samples indicates its measurement is of great importance for environmental and safety assessment, especially in contaminated areas.