ICRP Publication 136: Dose Coefficients for Non-human Biota Environmentally Exposed to Radiation

Utilization of metal and radionuclide concentrations to assess the influence of shrimp farming on the geochemical characteristics of sediments

This article assesses the environmental impacts of aquatic biota cultivation, focusing on shrimp farming in Brazil's Northeast, as this practice has proven to be one of the main sources of economic growth in the region. For this purpose, sediment samples were collected from areas impacted and not directly impacted by shrimp farming, and concentrations of key geochemical parameters such as salinity, various elements (K, P, Cu, Mn, Pb, Zn, Al, Ca, Fe, Mg, and Na), and natural radionuclides (K-40, Ra-226 and Ra-228) were compared using statistical tools. Element concentrations were determined using ICP-OES, and naturally occurring radionuclide concentrations were obtained through gamma spectrometry. Statistical tests, such as ANOVA and/or Mann-Whitney, cluster analysis, and principal component analysis, were applied to the results. Additionally, the ERICA Tool software was employed to estimate deleterious effects on both human and non-human biota. Descriptive statistics reveal variability in sediment parameters around shrimp farming. ANOVA and Mann-Whitney tests compare concentrations of shrimp farm sediment and not directly impacted sediment, showing non-significant differences for most elements. pH and salinity, crucial for shrimp health, exhibit higher values in shrimp farm sediment. Alkali and alkaline earth metals, including K and Na, show no significant differences. Factor and cluster analyses suggest that certain elements, mainly radionuclides, are influenced by sediment variability. Hazard indices for naturally occurring radionuclides indicate negligible risk to both human and non-human biota, reinforcing the absence of adverse effects from shrimp farming activities. This study provides a comprehensive analysis of the environmental impacts of shrimp farming, emphasizing the importance of monitoring geochemical parameters for coastal environmental management.

Complexity of responses to ionizing radiation in plants, and the impact on interacting biotic factors

In nature, plants are simultaneously exposed to different abiotic (e.g., heat, drought, and salinity) and biotic (e.g., bacteria, fungi, and insects) stresses. Climate change and anthropogenic pressure are expected to intensify the frequency of stress factors. Although plants are well equipped with unique and common defense systems protecting against stressors, they may compromise their growth and development for survival in such challenging environments. Ionizing radiation is a peculiar stress factor capable of causing clustered damage. Radionuclides are both naturally present on the planet and produced by human activities. Natural and artificial radioactivity affects plants on molecular, biochemical, cellular, physiological, populational, and transgenerational levels. Moreover, the fitness of pests, pathogens, and symbionts is concomitantly challenged in radiologically contaminated areas. Plant responses to artificial acute ionizing radiation exposure and laboratory-simulated or field chronic exposure are often discordant. Acute or chronic ionizing radiation exposure may occasionally prime the defense system of plants to better tolerate the biotic stress or could often exhaust their metabolic reserves, making plants more susceptible to pests and pathogens. Currently, these alternatives are only marginally explored. Our review summarizes the available literature on the responses of host plants, biotic factors, and their interaction to ionizing radiation exposure. Such systematic analysis contributes to improved risk assessment in radiologically contaminated areas.

Internal dose rate due to intake of uranium and thorium by fish from a dam reservoir associated with a uranium mine in Brazil

Uranium mining can cause environmental impacts on non-human biota around mine sites. Because of this, the reduction in non-human biota exposure becomes an important issue. Environmental radioprotection results from the evolution of human radioprotection; it is based on dose rate to non-human biota and uses, as a biological target, and has harmful effects on populations. In the present study, a flooded impoundment created following dam construction in a uranium mine plant undergoing decommissioning was investigated. Internal dose rates due to activity concentration of natural uranium (Unat) and 232Th in omnivorous, phytophagous, and carnivorous fish species were estimated. Radionuclide activity concentrations were obtained by spectrophotometry with arsenazo III in the visible range. The dose rate contribution of 232Th was lower than that of Unat. There were no differences between the internal dose rates to studied fish species due to 232Th, but there were differences for Unat. A dose rate of 2.30·10-2 µGy∙d-1 was found due to the two studied radionuclides. Although this value falls below the benchmark for harmful effects, it is important to acknowledge that the assessment did not account for other critical radionuclides from uranium mining, which also contribute to the internal dose. Moreover, the study did not assess external doses. As a result, the possibility cannot be excluded that dose rates at the study area overcome the established benchmarks for harmful effects.

Assessment of radiation dose to people and wildife inhabiting the Grote Nete catchment in Belgium

We evaluate the impact of the radiological contamination of the Grote Nete catchment in Belgium to people and non-human biota. This region has received effluents from the phosphate and nuclear industries via tributaries of the Grote Nete river in past decades, resulting in the presence of radionuclides such as 241Am, 60Co, 137Cs, 40K, 210Pb, 238Pu, 239,240Pu, 226Ra, 228Ra, 228Th, 232Th, 234U, 235U and 238U. During the period 2016-2021, we measured these radionuclides in the water column, the bed sediment and riverbanks. Additionally, we carried out radon measurements on the riverbanks in 2022. Based on these measurements, the dose rates to people were calculated for different potential exposure scenarios, using the SCK CEN biosphere tool. We also performed an assessment of exposure of ionising radiation to non-human biota (including 222Rn and its daughters) using the ERICA Tool. We observed three types of areas at the Grote Nete riverbank: (a) a lower category exposure with 226Ra concentrations reflecting purely Belgian background values; (b) a middle category with enhanced 226Ra, mainly adsorbed on clay minerals and (c) an upper category extending to maximum values in the order of 103 Bq kg-1. The main component of the dose rate for terrestrial and aquatic organisms is 226Ra followed by 210Pb (terrestrial) or 228Ra, (aquatic). The anthropogenic vector of the contamination (40K, 60Co, 90Sr, 137Cs, 228Th, 232Th, 234,235,238U, 238,239Pu, 241Am) makes a negligible contribution to dose. Overall, the Grote Nete wildlife is not under significant risk from exposure to soil or water-borne radionuclides and radon emanating from the soil, even if the ERICA benchmark of 10 μGy h-1 is occasionally exceeded for 226Ra, 210Pb or 228Ra, because exposures are below the levels at which effects are known to occur. For people, radon inhalation is the main exposure pathway and exposures can reach 1 mSv y-1 for hypothetical residents living at the riverbanks and remaining most of their time in the area, but it can be expected that exposures are much lower at increasing distances from the river. It is concluded that neither people nor the environment are at any significant radiological risk from this situation.

Metrology supporting the European regulation for radiation protection

The European Association of National Metrology Institutes (EURAMET) within its research programme European Metrology Programme for Innovation and Research (EMPIR) funded project EMPIR 19NET03 supportBSS that contributes to the establishment of a European Metrology Network (EMN) for Radiation Protection (RP). The EMN-RP was established in September 2021 with the intent to work as a meeting point for the metrology community and all stakeholders in the field of ionising radiation regulation, thus providing quality assurance for measurements in each of the exposure situations contemplated in the European Legislation. Within project EMPIR 19NET03, work package 3 aims at the preparation of a Strategic Research Agenda (SRA) by identifying the metrology needs to support the European legislation and regulation in Radiation Protection and of two Roadmaps for metrology services, one under the European Council Directive 2013/59/EURATOM and the other under the EURATOM Treaty. Following a Gaps Workshop held in September 2020 and a second internal workshop that took place in April 2022, a questionnaire was prepared for distribution to the stakeholders, e.g. RP platforms and authorities, academia, industry, among other, together with an accompanying paper. In this paper, the authors present the state of the art of European legislation in RP, address the importance of metrology, the practices and activities that need metrology to meet the requirements set in the regulations, emphasise the need for quality assured measurements in all fields, highlight the stakeholders contributions in their specific area and show their vision of the EMN-RP.

Impact of medical radionuclide discharges on people and the environment

We present a novel methodology to dynamically calculate dose rates to people and wildlife from hospital-released radionuclides reaching the environment through water treatment plants (WTPs), using the biokinetic model D-DAT for aquatic wildlife, applied to 18F, 123I, 131I, 153Sm, 99mTc and 201Tl. We have also developed a method to calculate doses to WTP workers and to farmers from agricultural practices. This proof-of-concept study simulates a generic source term of radionuclide levels in the Belgian Molse Nete River during the year 2018, chosen because the river flow was very low during that year, which constitutes a very conservative, bounding case. The dose rates to wildlife calculated for this hypothetical scenario under conservative assumptions, are well below the ERICA predicted no effects dose rate to wildlife of 10 μGy h-1. Human exposures are also very low, in most cases not exceeding 10 μSv y-1. This work identifies important data gaps and areas of uncertainty in the assessment of radiopharmaceutical effluents. The study, which is part of the EC project SINFONIA, paves the way for a dynamic screening assessment methodology able to perform consistently assessments of the impact of radiopharmaceuticals on people and wildlife. This is particularly relevant since discharges of radiopharmaceuticals in rivers are on the increase and it is necessary to explicitly demonstrate that people and the environment are adequately protected.

Assessment of dose rates to non-human biota from radioactive discharges from Sellafield Ltd. using PC-CREAM

PC-CREAM is a tool for assessing the radiological impact of routine discharges of radionuclides to the environment. It can be used for prospective assessments, to calculate doses to members of the public for authorisation of proposed discharges, or for retrospective assessments of previous discharges where doses are compared with dose limits. These types of assessment are a fundamental requirement of regulations governing the control of radioactive discharges. However, the latest publications of the basic safety standards for radiation protection, EU (Council of the European Union, 2014) and the IAEA (IAEA, 2014), now include the requirement to demonstrate protection of the environment as well as members of the public. To this end, a module has been added to PC-CREAM for calculating dose rates to non-human biota (Anderson et al., 2022). The methodology used for this calculation is based on the recommendations contained in ICRP Publication 108 (ICRP, 2008), which provides a general framework for protection of the environment. The additional module means that PC-CREAM can be used to assess doses to humans and dose rates to biota in an integrated way, for the same set of discharges and using the same dispersion models. This paper describes an assessment of dose rates to biota living in the vicinity of the Sellafield nuclear site, carried out using the new biota module of PC-CREAM. Historical discharges from Sellafield to the sea and atmosphere were considered for the period 1951 to 2017, excluding those from the Windscale fire in 1957. Dose rates calculated for marine biota (flatfish, crabs and brown seaweed) are less than 1 mGy d-1 and are below the lower derived consideration reference level (DCRL) for the ICRP marine reference animals and plants (RAPs). Dose rates for terrestrial biota (bees, deer, earthworms, frogs, wild grass, pine trees and rats) are less than the relevant lower DCRL for terrestrial RAPs, ie 0.1 mGy d-1. Dose rates were also calculated for a user defined organism 'seabird' to represent birds which inhabit both marine and terrestrial environments near Sellafield. For seabird, the lower DCRL of 0.1 mGy d-1 is exceeded throughout the 1950s, 1960s and 1970s, when the discharges were at their highest, due to exposures from the marine environment. Since the mid-1980s, no dose rates were calculated that exceeded the lower DCRLs.

Comparison of methods for the radiological impact assessment of aquatic releases to the waters in the low countries

Accurate assessment of the radiological impact of liquid discharges on the marine environment is challenging despite all developments in recent years. The lack of consensus on this type of assessment manifests itself even stronger when transborder issues are expected, such as in the Low Countries. Belgium and the Netherlands operate nuclear power plants with discharges in the shared estuary of the Western Scheldt, therefore if there are safety concerns, information on both sides of the border must be coherent. This work provides a comparison of two computational methods used for assessment of aquatic releases in the Western Scheldt estuary and the adjacent North Sea.The work demonstrates a fair degree of consistency in modelling the uptake and fate of key anthropogenic radionuclides. Nevertheless, there are also considerable differences found in sediment and sea species with concentrations ranging by over two orders of magnitude in some cases. These explainable differences are methodological in nature, occurring in codes that underwent extensive validation during development. Therefore, the outcomes of this work clearly demonstrate the need to produce explicit guidance that is specifically tailored to the (inter)national water system of concern. This should not be limited to releases from nuclear power plants, but also include other nuclear applications. For all these reasons, more intensive collaboration and model harmonisation across borders is essential, signalling the direction for future investigations.

Radiology's Ionising Radiation Paradox: Weighing the Indispensable Against the Detrimental in Medical Imaging

Ionising radiation stands as an indispensable protagonist in the narrative of medical imaging, underpinning diagnostic evaluations and therapeutic interventions across an array of medical conditions. However, this protagonist poses a paradox - its inestimable service to medicine coexists with an undercurrent of potential health risks, primarily DNA damage and subsequent oncogenesis. The narrative of this comprehensive review unfurls around this intricate enigma, delicately balancing the indispensable diagnostic utility against the non-negotiable commitment to patient safety. In this critical discourse, the intricacies of ionising radiation are dissected, illuminating not only its sources but also the associated biological and health hazards. The exploration delves into the labyrinth of strategies currently deployed to minimise exposure and safeguard patients. By casting light on the scientific nuances of X-rays, computed tomography (CT), and nuclear medicine, it traverses the complex terrain of radiation use in radiology, to promote safer medical imaging practices, and to facilitate an ongoing dialogue about diagnostic necessity and risk. Through a rigorous examination, the pivotal relationship between radiation dose and dose response is elucidated, unravelling the mechanisms of radiation injury and distinguishing between deterministic and stochastic effects. Moreover, protection strategies are illuminated, demystifying concepts such as justification, optimisation, the As Low As Reasonably Achievable (ALARA) principle, dose and diagnostic reference levels, along with administrative and regulatory approaches. With an eye on the horizon, promising avenues of future research are discussed. These encompass low-radiation imaging techniques, long-term risk assessment in large patient cohorts, and the transformative potential of artificial intelligence in dose optimisation. This exploration of the nuanced complexities of radiation use in radiology aims to foster a collaborative impetus towards safer medical imaging practices. It underscores the need for an ongoing dialogue around diagnostic necessity and risk, thereby advocating for a continual reassessment in the narrative of medical imaging.

The potential impact of marine discharges from Fukushima 10 years after the accident

A previous commentary written on the fifth anniversary of the Fukushima accident described the potential impact of radioactive wastewater on marine organisms, highlighting that the environmental consequences on the marine environment were consequently not as important as feared at the time. In the present article, a new development is considered, namely, the decision to carry out a release of over 10⁶  m³ of Advanced Liquid Processing System-treated wastewater contaminated by radionuclides from the ill-fated Fukushima Daiichi plant into the Pacific Ocean. Although information on the nature of these releases is still rather limited, it is possible to perform a preliminary screening assessment of the potential radiation doses to people and the environment, and this indicates that the radiological impact is very low. Data gaps and the assessment limitations encountered are highlighted, providing direction for future investigations. Integr Environ Assess Manag 2022;18:1530-1538. © 2021 SETAC.

Radiation exposure and risk assessment to earthworms in areas contaminated with naturally occurring radionuclides

The assessment of radiation exposure on biota is one of the main parts of environment protection system. Earthworms have been recognized as an important organism group in the terrestrial ecosystems. According to many researchers the potential risks of naturally occurring radionuclides for soil invertebrates were not significant because the exposure doses to the invertebrate populations were low. Our study aimed to assess the radiation exposure and the radiological risks from naturally occurring radionuclides for earthworm populations at four sites. This research was based on three dosimetric approaches simultaneously: ERICA and RESRAD-BIOTA-the commonly used ones, and also on the original method proposed by Thomas and Liber (Environment International, 27, 341-353, 2001) for aquatic organisms. To calculate radiation dose rates to soil invertebrates inhabiting background and contaminated areas, the specific activities of radionuclides in soil, and, depending on the model, the default, or determined in this study, input mass-geometric parameters had been applied. The weighted absorbed dose rates calculated by different models and site-specific data were 0.3-1.4 μGy/h for the background and from 3.4 to 170 μGy/h for the contaminated sites. Analysis of radiation risks for earthworms indicated that ²²⁶Ra was the key contributor to the external dose rate; ²²⁶Ra and ²¹⁰Po played a dominant role in formation of internal dose rate for radioecological situations in our study. More conservative radiation risk assessments were derived from RESRAD-BIOTA tool. Dose assessments obtained using various models had shown that there are real environmental situations in which the radiological risks to reference organisms are significantly higher than the lowest benchmark protection level proposed for ecosystems.

Adverse outcome pathways (AOPs) for radiation-induced reproductive effects in environmental species: state of science and identification of a consensus AOP network

BACKGROUND

Reproductive effects of ionizing radiation in organisms have been observed under laboratory and field conditions. Such assessments often rely on associations between exposure and effects, and thus lacking a detailed mechanistic understanding of causality between effects occurring at different levels of biological organization. The Adverse Outcome Pathway (AOP), a conceptual knowledge framework to capture, organize, evaluate and visualize the scientific knowledge of relevant toxicological effects, has the potential to evaluate the causal relationships between molecular, cellular, individual, and population effects. This paper presents the first development of a set of consensus AOPs for reproductive effects of ionizing radiation in wildlife. This work was performed by a group of experts formed during a workshop organized jointly by the Multidisciplinary European Low Dose Initiative (MELODI) and the European Radioecology Alliance (ALLIANCE) associations to present the AOP approach and tools. The work presents a series of taxon-specific case studies that were used to identify relevant empirical evidence, identify common AOP components and propose a set of consensus AOPs that could be organized into an AOP network with broader taxonomic applicability.

CONCLUSION

Expert consultation led to the identification of key biological events and description of causal linkages between ionizing radiation, reproductive impairment and reduction in population fitness. The study characterized the knowledge domain of taxon-specific AOPs, identified knowledge gaps pertinent to reproductive-relevant AOP development and reflected on how AOPs could assist applications in radiation (radioecological) research, environmental health assessment, and radiological protection. Future advancement and consolidation of the AOPs is planned to include structured weight of evidence considerations, formalized review and critical assessment of the empirical evidence prior to formal submission and review by the OECD sponsored AOP development program.

Dose Rate Assessment Exercises with Stylized Phantom of Neon Flying Squid from Northwest Pacific

Radiation protection for non-human marine organisms still faces many challenges. To establish a more realistic radiation dosimetry model of cephalopods, this study developed a stylized phantom of neon flying squid (Ommastrephesbartramii) containing ten organs and tissues based on magnetic resonance imaging (MRI) technology. The internal and external dose conversion coefficients for eight radionuclides (134Cs, 137Cs, 131I, 110mAg, 60Co, 54Mn, 65Zn, 95Zr) of each organ/tissue were determined with Monte Carlo simulation using the Geant4 toolkit. Furthermore, with the reported coastal seawater radioactivity levels at the coastal area of Fukushima Daiichi Nuclear Power Plant after the accident in 2011 as the source term, the radiological dose rate for O. bartramii was evaluated with the stylized phantom developed in this study and with the conventional whole-organism ellipsoidal model in the ERICA Assessment Tool. Both results showed that the dose rate for O. bartramii derived from the FDNPP accident releases exceeded the generic no-effects screening benchmark level (10 μGy h−1).

Ensuring robust radiological risk assessment for wildlife: insights from the International Atomic Energy Agency EMRAS and MODARIA programmes

In response to changing international recommendations and national requirements, a number of assessment approaches, and associated tools and models, have been developed over the last circa 20 years to assess radiological risk to wildlife. In this paper, we summarise international intercomparison exercises and scenario applications of available radiological assessment models for wildlife to aid future model users and those such as regulators who interpret assessments. Through our studies, we have assessed the fitness for purpose of various models and tools, identified the major sources of uncertainty and made recommendations on how the models and tools can best be applied to suit the purposes of an assessment. We conclude that the commonly used tiered or graded assessment tools are generally fit for purpose for conducting screening-level assessments of radiological impacts to wildlife. Radiological protection of the environment (or wildlife) is still a relatively new development within the overall system of radiation protection and environmental assessment approaches are continuing to develop. Given that some new/developing approaches differ considerably from the more established models/tools and there is an increasing international interest in developing approaches that support the effective regulation of multiple stressors (including radiation), we recommend the continuation of coordinated international programmes for model development, intercomparison and scenario testing.

Bounding uncertainties around the conceptual representation of species in radiological assessment in the context of routine atmospheric release

Wildlife protection has become of regulatory interest since the International Commission on Radiological Protection (ICRP) developed an approach to assess the level of radiological protection specifically for animals and plants. For the purpose of demonstrating compliance with regulation to protect the environment against routine authorised discharges from nuclear facilities, the wide variety of biota inhabiting an ecosystem needs to be condensed to a limited set of representative organisms, as proposed by the ICRP with a set of 'reference animals and plants' which can be considered representative of many other species. It is now recommended in the International Atomic Energy Agency Safety Standards, and internationally accepted, that the use of such a limited number of organisms to represent a pool of species is adequate for radiation protection purposes, particularly in planned exposure situations. Adding site-specific species to that set of surrogate species can respond to various interests, such as ensuring a site-specific context to the assessment that addresses stakeholder interests and can aid in stakeholder consultation and risk communication. Moreover, there is a need to question whether the use of the set of surrogate organisms is conservative enough to cover a wider range of biodiversity. Previous studies partially answered this question and this paper adds a range of test cases. A selection of hypothetical representations of possible site-specific species are assessed on the basis of possible variations in size (mass) and occupancy habits. Dose rates are evaluated to determine the greatest difference between hypothetical organisms and those for reference organisms (ROs), considering radionuclides (RNs) potentially discharged in atmospheric routine release from different nuclear facilities. Differences observed in the results between hypothetical organisms and ROs were less than one order of magnitude in all cases, the difference being dependent on the RNs considered. These findings do not preclude the inclusion of site-specific species in environmental radiological assessments if it is considered necessary, but they provide reassurance that using ROs for radiological impact assessments in the case of routine atmospheric discharges is sufficient.

Areas of research to support the system of radiological protection

This document presents the ICRP's updated vision on "Areas of Research to Support the System of Radiological Protection", which have been previously published in 2017. It aims to complement the research priorities promoted by other relevant international organisations, with the specificity of placing them in the perspective of the evolution of the System of Radiological Protection. This document contributes to the process launched by ICRP to review and revise the System of Radiological Protection that will update the 2007 General Recommendations in ICRP Publication 103.

First transcriptome profiling of D. melanogaster after development in a deep underground low radiation background laboratory

Natural background radiation is a permanent multicomponent factor. It has an influence on biological organisms, but effects of its deprivation still remain unclear. The aim of our work was to study for the first time responses of D. melanogaster to conditions of the Deep Underground Low-Background Laboratory DULB-4900 (BNO, INR, RAS, Russia) at the transcriptome level by RNA-seq profiling. Overall 77 transcripts demonstrated differential abundance between flies exposed to low and natural background radiation. Enriched biological process functional categories were established for all genes with differential expression. The results showed down-regulation of primary metabolic processes and up-regulation of both the immune system process and the response to stimuli. The comparative analysis of our data and publicly available transcriptome data on D. melanogaster exposed to low and high doses of ionizing radiation did not reveal common DEGs in them. We hypothesize that the observed changes in gene expression can be explained by the influence of the underground conditions in DULB-4900, in particular, by the lack of stimuli. Thus, our study challenges the validity of the LNT model for the region of background radiation doses below a certain level (~16.4 nGy h-1) and the presence of a dose threshold for D. melanogaster.

Bomb 137Cs in modern honey reveals a regional soil control on pollutant cycling by plants

¹³⁷Cs is a long-lived (30-year radioactive half-life) fission product dispersed globally by mid-20th century atmospheric nuclear weapons testing. Here we show that vegetation thousands of kilometers from testing sites continues to cycle ¹³⁷Cs because it mimics potassium, and consequently, bees magnify this radionuclide in honey. There were no atmospheric weapons tests in the eastern United States, but most honey here has detectable ¹³⁷Cs at >0.03 Bq kg⁻¹, and in the southeastern U.S., activities can be >500 times higher. By measuring honey, we show regional patterns in the biogeochemical cycling of ¹³⁷Cs and conclude that plants and animals receive disproportionally high exposure to ionizing radiation from ¹³⁷Cs in low potassium soils. In several cases, the presence of ¹³⁷Cs more than doubled the ionizing radiation from gamma and x-rays in the honey, indicating that despite its radioactive half-life, the environmental legacy of regional ¹³⁷Cs pollution can persist for more than six decades.

Radioactive ¹³⁷Cs is a fission product remaining in the environment from mid-20th century nuclear testing. Here the authors show that vegetation thousands of kilometers from testing sites continues to cycle ¹³⁷Cs, and consequently, bees magnify this contaminant in honey in regions with low soil potassium.

Tin-113 and Selenium-75 radiotracer adsorption and desorption kinetics in contrasting estuarine salinity and turbidity conditions

Batch experiments were performed to study adsorption and desorption of ⁷⁵Se and ¹¹³Sn radiotracers at environmentally representative concentrations of ~0.3 ng L^-1 and ~3 ng L^-1, respectively. The radiotracers were incubated with wet bulk sediments from the Gironde Estuary and the Rhône River, combining freshwater and coastal seawater salinity (S = 0, S = 32) and three different Suspended Particulate Matter (SPM) concentrations (10 mg L^-1, 100 mg L^-1, 1000 mg L^-1) to simulate six hydrologically contrasting situations for each particle type. Results showed no measurable adsorption for ⁷⁵Se under the experimental conditions, whereas >90% of ¹¹³Sn rapidly adsorbed onto the particles during the first hours of exposure. Adsorption efficiency increased with increasing SPM concentration and seemed to be slightly greater for the Rhône River sediments, potentially related to the intrinsic mineral composition. Desorption of spiked sediments exposed to filtered, unspiked freshwater and seawater only occurred for ¹¹³Sn (<15% of the previously adsorbed ¹¹³Sn) in the Garonne River sediments. This study provides insights to the potential environmental behaviour of hypothetical radionuclide releases of Se and Sn into highly dynamic and contrasting aquatic systems. Multiple accidental scenarios for the case of the Gironde Estuary and the Rhône River are discussed. These scenarios suggest that the environmental fate of soluble radionuclides like Se will be associated to water hydrodynamics and potentially more bioavailable whereas highly particle-active radionuclides like Sn will follow natural river/estuarine sedimentary regimes. Information on reactivity of radionuclides is important for improving the precision of current approaches aiming at modelling environmental radionuclide dispersion in continent-ocean transition systems.

137Cs and 40K in gray seals Halichoerus grypus in the southern Baltic Sea

This study presents levels of ¹³⁷Cs and ⁴⁰K concentrations in the placentas of seals gathered in the period 2007-2015. The mean activity of ¹³⁷Cs and ⁴⁰K was 5.49 Bq kg^-1w.w. and 136.6 Bq kg^-1 ww respectively. Statistically significant correlation was observed between the ¹³⁷Cs activities in placenta and in herring-the staple food for seals. The concentrations of ¹³⁷Cs and ⁴⁰K were also determined in other tissues (muscle, liver, lung, and brain) of wild seals. The concentrations of ¹³⁷Cs were from 2.59 Bq^-1 ww (lungs) to 24.3 Bq kg^-1 ww (muscles). The transfer factor values for ¹³⁷Cs (seal tissue/fish) ranged from 0.89 to 2.42 in the case of the placentas and from 1.35 to 8.17 in the case of the muscle. For adults seal, the effective dose from ¹³⁷Cs was 2.98 nGy h^-1. The mean external radiation dose to pup was 0.77 nGy h^-1 from ¹³⁷Cs and 6.69 nGy h^-1 from ⁴⁰K.

Effects of historic radiation dose on the frequency of sex-linked recessive lethals in Drosophila populations following the Chernobyl nuclear accident

Contrary to the effects of high doses of radiation, the effects of low doses of radiation are still being investigated. Low doses and their non-targeted effects in particular are of special interest for researchers. The accident that occurred at the Chernobyl Nuclear Power Plant (NPP) gives researchers the opportunity to view these effects outside of a laboratory environment. For this paper, the relationship between low historic radiation doses and the persistent genetic damage observed in populations of fruit flies (Drosophila melanogaster) around the Chernobyl NPP over 3 years will be investigated. Data from Zainullin et al. (1992) on the frequency of sex-linked recessive lethals (SLRLs) in D. melanogaster around the Chernobyl NPP. To calculate the absorbed historic external dose, a method based on the Gaussian plume model was used to find the external dose from both plume shine and ground shine. The dose attributed to the ground shine dose made a greater contribution to the overall absorbed external historic radiation dose than the plume shine dose. For earlier generations of Drosophila living in the radioactive contaminated sites, the SLRL frequencies appeared to correlate with the dose in a linear no-threshold relationship. The later descendent generations appeared to have developed a radio-adaptive-like response. This work contributes to the understanding of historic dose effects on wildlife health following the accidental release of high mount of radioactive materials into the environment.