Radiological dose reconstruction for birds reconciles outcomes of Fukushima with knowledge of dose-effect relationships

Oxidative stress on the male reproductive organs of wild mice collected from an area contaminated by radioactive materials in Fukushima

The Fukushima Daiichi Nuclear Power Plant accident caused the release of large amounts of radioactive material into the environment. Radiation from radionuclides cause DNA lesions, mainly via oxidation, which adversely affect wild organisms by damaging their germ cells. Here, we investigated the effects of radiation on the reproductive organs of Japanese field mice (Apodemus speciosus) by estimating the dose rate of radiation exposure, the accumulation of DNA lesions, and the expression of DNA repair enzymes. In highly contaminated areas, mouse testes received a radiation dose rate > 0.1 mGy/d. According to the International Commission on Radiological Protection, there is a very low probability of effects in the reference rat species at this exposure level. The results of the current study do not definitively conclude that the expression of 8-oxoguanine DNA glycosylase 1 and superoxide dismutase in mouse testes increase with dose rate and lifetime dose. However, 8-hydroxy-2'-deoxyguanosine accumulation increases in a dose rate- and lifetime dose-dependent manner in mouse testes, but is not observed in the sperm of the cauda epididymis. These results suggest that, although DNA lesions occurred in male germ cells of Fukushima mice, most were successfully repaired by DNA repair enzymes at the observed gene expression level.

Fundamentals of wildlife dosimetry and lessons learned from a decade of measuring external dose rates in the field

Methods for determining the radiation dose received by exposed biota require major improvements to reduce uncertainties and increase precision. We share our experiences in attempting to quantify external dose rates to free-ranging wildlife using GPS-coupled dosimetry methods. The manuscript is a primer on fundamental concepts in wildlife dosimetry in which the complexities of quantifying dose rates are highlighted, and lessons learned are presented based on research with wild boar and snakes at Fukushima, wolves at Chornobyl, and reindeer in Norway. GPS-coupled dosimeters produced empirical data to which numerical simulations of external dose using computer software were compared. Our data did not support a standing paradigm in risk analyses: Using averaged soil contaminant levels to model external dose rates conservatively overestimate the dose to individuals within a population. Following this paradigm will likely lead to misguided recommendations for risk management. The GPS-dosimetry data also demonstrated the critical importance of how modeled external dose rates are impacted by the scale at which contaminants are mapped. When contaminant mapping scales are coarse even detailed knowledge about each animal's home range was inadequate to accurately predict external dose rates. Importantly, modeled external dose rates based on a single measurement at a trap site did not correlate to actual dose rates measured on free ranging animals. These findings provide empirical data to support published concerns about inadequate dosimetry in much of the published Chernobyl and Fukushima dose-effects research. Our data indicate that a huge portion of that literature should be challenged, and that improper dosimetry remains a significant source of controversy in radiation dose-effect research.

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.

Association between gut health and gut microbiota in a polluted environment

Animals host complex bacterial communities in their gastrointestinal tracts, with which they share a mutualistic interaction. The numerous effects these interactions grant to the host include regulation of the immune system, defense against pathogen invasion, digestion of otherwise undigestible foodstuffs, and impacts on host behaviour. Exposure to stressors, such as environmental pollution, parasites, and/or predators, can alter the composition of the gut microbiome, potentially affecting host-microbiome interactions that can be manifest in the host as, for example, metabolic dysfunction or inflammation. However, whether a change in gut microbiota in wild animals associates with a change in host condition is seldom examined. Thus, we quantified whether wild bank voles inhabiting a polluted environment, areas where there are environmental radionuclides, exhibited a change in gut microbiota (using 16S amplicon sequencing) and concomitant change in host health using a combined approach of transcriptomics, histological staining analyses of colon tissue, and quantification of short-chain fatty acids in faeces and blood. Concomitant with a change in gut microbiota in animals inhabiting contaminated areas, we found evidence of poor gut health in the host, such as hypotrophy of goblet cells and likely weakened mucus layer and related changes in Clca1 and Agr2 gene expression, but no visible inflammation in colon tissue. Through this case study we show that inhabiting a polluted environment can have wide reaching effects on the gut health of affected animals, and that gut health and other host health parameters should be examined together with gut microbiota in ecotoxicological studies.

Radiation dose reconstruction for higher aquatic plants and fish in Glyboke Lake during the early phase of the Chernobyl accident

This study deals with an assessment of radiation dose dynamics to fish and higher aquatic plants (helophytes) in Glyboke Lake (10-km exclusion zone) during the early phase of the Chernobyl accident. Models of radioactive contamination of water and sediment and models of radioactive contamination and radiation dose to fish and aquatic plants were developed. It was found that, in 1986, the total dose rate to fish reached 0.25 Gy d^-1. Within 6 months after the accident, the dose rate due to ⁹⁰Sr, ¹³⁴Cs and ¹³⁷Cs had increased. The absorbed dose to prey fish of Glyboke Lake for this period was estimated as being 27-81 Gy of which 4-40 Gy was formed by ¹³¹I exposure. The radiation dose rate due to ⁹⁰Sr, ¹⁰⁶Ru, ^134+137Cs and ¹⁴⁴Ce to aquatic plants reached its quasi-equilibrium values approximately 50 days after the accident and remained virtually unchanged until the end of the 1986 growing season. The highest levels of ⁸⁹Sr, ⁹¹Y, ⁹⁵Zr, ¹⁰³Ru, ¹⁴¹Ce exposure were observed between 30 and 50 days with a decrease by 2-3 times at the end of the growing season. Radiation exposure of the short-lived ¹³¹I, ¹⁴⁰Ba, ¹⁴⁰La, ²³⁹Np reached its maximum within 5-15 days after the accident. The absorbed dose rate to aquatic plants reached 0.69 Gy d^-1, while the contribution of cerium radionuclides to the total dose rate formed 50% in the initial period and reached 90% at the end of the growing season. The magnitude of the radiation dose rate to plant roots was 2.4 times higher than aboveground organs, and that of rhizomes was 1.6 times higher. During the growing season of 1986 the total dose of exposure of plants in Glyboke Lake was about 78 Gy. The results of this study emphasise the necessity to consider the history of exposure of past generation of living organisms as part of the assessment of current radiation effects.

Ecological information and approaches needed for risk communication dialogs for acute or chronic environmental crises

Scientists, social scientists, risk communicators, and many others are often thrust into a crisis situation where they need to interact with a range of stakeholders, including governmental personnel (tribal, U.S. federal, state, local), local residents, and other publics, as well as other scientists and other risk communicators in situations where information is incomplete and evolving. This paper provides: (1) an overall framework for thinking about communication during crises, from acute to chronic, and local to widespread, (2) a template for the types of ecological information needed to address public and environmental concerns, and (3) examples to illustrate how this information will aid risk communicators. The main goal is providing an approach to the knowledge needed by communicators to address the challenges of protecting ecological resources during an environmental crisis, or for an on-going, chronic environmental issue. To understand the risk to these ecological resources, it is important to identify the type of event, whether it is acute or chronic (or some combination of these), what receptors are at risk, and what stressors are involved (natural, biological, chemical, radiological). For ecological resources, the key information a communicator needs for a crisis is whether any of the following are present: threatened or endangered species, species of special concern, species groups of concern (e.g., neotropical bird migrants, breeding frogs in vernal ponds, rare plant assemblages), unique or rare habitats, species of commercial and recreational interest, and species/habitats of especial interest for medicinal, cultural, or religious activities. Communication among stakeholders is complicated with respect to risk to ecological receptors because of differences in trust, credibility, empathy, perceptions, world view valuation of the resources, and in many cases, a history of misinformation, disinformation, or no information. Exposure of salmon spawning in the Columbia River to hexavalent chromium from the Hanford Site is used as an example of communication challenges with different stakeholders, including Native Americans with Tribal Treaty rights to the land.

The Biology of Chernobyl

Environmental disasters offer the unique opportunity for landscape-scale ecological and evolutionary studies that are not possible in the laboratory or small experimental plots. The nuclear accident at Chernobyl (1986) allows for rigorous analyses of radiation effects on individuals and populations at an ecosystem scale. Here, the current state of knowledge related to populations within the Chernobyl region of Ukraine and Belarus following the largest civil nuclear accident in history is reviewed. There is now a significant literature that provides contrasting and occasionally conflicting views of the state of animals and how they are affected by this mutagenic stressor. Studies of genetic and physiological effects have largely suggested significant injuries to individuals inhabiting the more radioactive areas of the Chernobyl region. Most population censuses for most species suggest that abundances are reduced in the more radioactive areas.

Multifaceted effects of chronic radiation exposure in Japanese red pines from Fukushima prefecture

Despite many studies carried out to date, the long-term effects of chronic exposure on plants and animals inhabiting the territories affected by the Fukushima Dai-Ichi NPP accident remain the subject of scientific discussions. Our investigations were performed on Japanese red pine, the native tree species that is widely spread in the radioactive contaminated areas. Earlier observations revealed the radiation-induced cancellation of the apical dominance in young trees of this species. To understand the mechanism of such transformation, we evaluated the morphometric parameters of needles, the frequency of cytogenetic abnormalities, and the concentrations of the major classes of phytohormones in several natural populations of young red pine trees growing under different exposure conditions in Fukushima prefecture. No significant relationships between the morphometric parameters of needles and dose rates at the experimental sites were revealed. The frequencies of aberrant cells in the needle's intercalary meristem and the frequencies of cancellation of the apical dominance in the young pine populations in the radioactive contaminated areas were significantly higher than in the reference population. However, only cytogenetic abnormalities increased with the dose rate. We have not found the relation between the frequency of cytogenetic abnormalities in needles and cancellation of the apical dominance in the individual trees. In this paper, for the first time, it is shown that chronic radiation exposure changes the concentration ratio of the major classes of phytohormones in the needles of Japanese red pine. Given the complete lack of information about the most important regulatory system of plants in chronically irradiated populations, this study fills a substantial gap in our knowledge. Finally, our findings indicated that the most probable causes of the cancellation of apical dominance observed in chronically exposed Japanese red pines are radiation damage to the apical meristems of the trees and changes in their phytohormonal balance.

Radiocesium concentration ratios and radiation dose to wild rodents in Fukushima Prefecture

Radiocesium was dispersed from the Fukushima Dai-ichi disaster in March 2011, causing comparatively high radioactive contamination in nearby environments. Radionuclide concentrations in wild rodents (Apodemus argenteus, and Apodemus speciosus) within these areas were monitored from 2012 to 2016. However, whole-organism to soil transfer parameters (i.e., concentration ratio, CR_wo-soil) for wild rodents at Fukushima were not determined and hence were lacking from the international transfer databases. We augmented the 2012-2016 data by collecting soil activity concentrations (Bq kg^-1, dry mass) from five rodent sampling sites in Fukushima Prefecture, and developed corresponding CR_wo-soil values for radiocesium (¹³⁴Cs and ¹³⁷Cs) based on rodent radioactivity concentrations (Bq kg^-1, fresh mass). The CR_wo-soil were added to the Wildlife Transfer Database (WTD; http://www.wildlifetransferdatabase.org/), supporting the development of the International Commission on Radiological Protection's (ICRP) environmental protection framework, and increasing the WTD from 84 to 477 entries for cesium and Muridae ('Reference Rat'). Significant variation occurred in CR_wo-soil values between study sites within Fukushima Prefecture. The geometric mean CR_wo-soil, in this paper, was higher than that reported for Muridae species for Chernobyl. Radiocaesium absorbed dose rates were also estimated for wild rodents inhabiting the five Fukushima study sites and ranged from 1.3 to 33 μGy h^-1. Absorbed dose rates decreased by a factor of two from 2012 to 2016. Dose rates in highly contaminated areas were within the ICRP derived consideration reference level for Reference Rat (0.1-1 mGy d^-1), suggesting the possible occurrence of deleterious effects and need for radiological effect studies in the Fukushima area.

Dose-dependent genomic DNA hypermethylation and mitochondrial DNA damage in Japanese tree frogs sampled in the Fukushima Daiichi area

The long-term consequences of the nuclear disaster at the Fukushima Daiichi Nuclear Power Plant (FDNPP) that occurred on March 2011, have been scarcely studied on wildlife. We sampled Japanese tree frogs (Dryophytes japonicus), in a 50 -km area around the FDNPP to test for an increase of DNA damages and variation of DNA methylation level. The ambient dose rate ranged between 0.4 and 2.8 μGy h^-1 and the total estimated dose rate absorbed by frogs ranged between 0.3 and 7.7 μGy h^-1. Frogs from contaminated sites exhibited a dose-dependent increase of global genomic DNA methylation level (5-mdC and 5-hmdC) and of mitochondrial DNA damages. Such DNA damages may indicate a genomic instability, which may induce physiological adaptations governed by DNA methylation changes. This study stresses the need for biological data combining targeted molecular methods and classic ecotoxicology, in order to better understand the impacts on wildlife of long term exposure to low ionizing radiation levels.

Dose reconstruction supports the interpretation of decreased abundance of mammals in the Chernobyl Exclusion Zone

We re-analyzed field data concerning potential effects of ionizing radiation on the abundance of mammals collected in the Chernobyl Exclusion Zone (CEZ) to interpret these findings from current knowledge of radiological dose–response relationships, here mammal response in terms of abundance. In line with recent work at Fukushima, and exploiting a census conducted in February 2009 in the CEZ, we reconstructed the radiological dose for 12 species of mammals observed at 161 sites. We used this new information rather than the measured ambient dose rate (from 0.0146 to 225 µGy h⁻¹) to statistically analyze the variation in abundance for all observed species as established from tracks in the snow in previous field studies. All available knowledge related to relevant confounding factors was considered in this re-analysis. This more realistic approach led us to establish a correlation between changes in mammal abundance with both the time elapsed since the last snowfall and the dose rate to which they were exposed. This relationship was also observed when distinguishing prey from predators. The dose rates resulting from our re-analysis are in agreement with exposure levels reported in the literature as likely to induce physiological disorders in mammals that could explain the decrease in their abundance in the CEZ. Our results contribute to informing the Weight of Evidence approach to demonstrate effects on wildlife resulting from its field exposure to ionizing radiation.

Estimating radiological exposure of wildlife in the field

The assessment of the ecological impact due to radionuclides at contaminated sites requires estimation of the exposure of wildlife, in order to correlate radiation dose with known radiological effects. The robust interpretation of field data requires consideration of possible confounding effects (e.g., from the tsunami at Fukushima) and an accurate and relevant quantification of radiation doses to biota. Generally, in field studies the exposure of fauna and flora has often been characterised as measurements of the ambient dose rate or activity concentrations in some components of the environment. The use of such data does not allow the establishment of a robust dose-effect relationship for wildlife exposed to ionising radiation in the field. Effects of exposure to radioactivity depend on the total amount of energy deposited into exposed organisms, which is estimated by adding doses (or dose rates) for all radionuclides and exposure pathways. Realistic dose estimation needs to reflect the entire story of the organisms of interest during their whole exposure period. The process of identifying and collecting all the related information should allow the "W" questions (Which organisms are exposed, Where, When and hoW) to be answered. Some parameters are well known to influence dose (rate): the organism life stage, its ecological characteristics (e.g. habitat, behaviour), the source term properties (e.g. discharging facility, nature of radiation), etc. The closer the collated data are to the ideal data set, the more accurate and realistic the dose (rate) assessment will be. This means characterising each exposure pathway (internal and external), the activity concentration in each exposure source, the time each organism spends in a given place, as well as the associated dose. In this paper the process of data collation in view of dose reconstruction is illustrated for Japanese birds exposed to radioactive deposition following the Fukushima accident. With respect to the Chernobyl Exclusion Zone we will also consider variability under field conditions, availability of relevant datasets and options for better estimating internal and external doses received by wildlife.

Plants in the Light of Ionizing Radiation: What Have We Learned From Chernobyl, Fukushima, and Other "Hot" Places?

Perhaps the main factor determining success of space travel will be the ability to control effects of ionizing radiation for humans, but also for other living organisms. Manned space travel will require the cultivation of food plants under conditions of prolonged exposure to ionizing radiation. Although there is a significant literature concerning the effects of acute high dose rate exposures on plant genetics, growth, and development, much less is known concerning the effects of chronic low dose irradiation especially those related to the impacts of the high energy protons and heavy ions that are encountered in the space environment. Here, we make the argument that in situ studies of the effects of radionuclides at nuclear accident sites (e.g., Chernobyl and Fukushima), atomic bomb test sites, and areas of naturally high radiation levels, could provide insights concerning the mechanisms of radiation effects on living systems that cannot be assessed short of conducting research in space, which is not yet feasible for large scale, long term, multigenerational experiments. In this article we review the literature concerning the effects of chronic low-dose rate radiation exposure from studies conducted in Chernobyl, Fukushima, and other regions of the world with high ambient radiation levels (parts of India in particular). In general, mutation rates and other measures of genetic damage are considerably elevated, pollen and seed viability are reduced, growth rates are slower, and the frequency of developmental abnormalities is increased, although there is considerable variation among taxa for these effects. In addition, there are interactions between radiation and other environmental stressors (e.g., temperature, drought, heavy metals) that may play important roles in determining susceptibility to radiation induced stress.

Is non-human species radiosensitivity in the lab a good indicator of that in the field? Making the comparison more robust

Ecological risk assessment has globally become the basis for environmental decision-making within government and industry for chemical substances. Regarding radioactive substances, recently revised International and European Basic Safety Standards are pushing the development of member state policy on environmental regulation in the field of radiological protection. Within this framework, existing derived effect benchmarks for ionising radiation and non-human species need to be more robust to reinforce their credibility when used as levels of exposure considered to be safe for the environment. Actually, the derivation of such benchmarks has mainly relied on laboratory studies from a limited number of species. Moreover lab species would be apparently less radiosensitive than for example terrestrial wildlife chronically exposed to ionising radiation in the Chernobyl Exclusion Zone. Additionally to the results of such comparison that still need to be confirmed, another way to challenge benchmarks is to improve the quality/quantity of radiotoxicity data constituting the basis for a statistically-based comparison. This is the major focus of this paper where we demonstrate through various examples how to make the comparison more robust (i) by analysing the discrepancy between lab and field at the taxonomic level rather than at the ecosystem level, (ii) by extending the knowledge base making use of acute radiotoxicity data, (iii) by identifying environmental factors modifying radiological dose-effect relationship in the field.

Field effects studies in the Chernobyl Exclusion Zone: Lessons to be learnt

In the initial aftermath of the 1986 Chernobyl accident there were detrimental effects recorded on wildlife, including, mass mortality of pine trees close to the reactor, reduced pine seed production, reductions in soil invertebrate abundance and diversity and likely death of small mammals. More than 30 years after the Chernobyl accident there is no consensus on the longer-term impact of the chronic exposure to radiation on wildlife in what is now referred to as the Chernobyl Exclusion Zone. Reconciling this lack of consensus is one of the main challenges for radioecology. With the inclusion of environmental protection in, for instance, the recommendations of the International Commission on Radiological Protection (ICRP), we need to be able to incorporate knowledge of the potential effects of radiation on wildlife within the regulatory process (e.g. as a basis on which to define benchmark dose rates). In this paper, we use examples of reported effects on different wildlife groups inhabiting the Chernobyl Exclusion Zone (CEZ) as a framework to discuss potential reasons for the lack of consensus, consider important factors influencing dose rates organisms receive and make some recommendations on good practice.

The importance of deriving adequate wildlife benchmark values to optimize radiological protection in various environmental exposure situations

The actions to be taken to demonstrate that the environment is adequately protected against the detrimental effects of ionising radiation, and if needed to protect it, must be commensurate with the overall level of risk to non-human biota. To judge the level of risk, the estimated dose rates absorbed by animals and plants need to be compared with dose criteria, a benchmark or reference value. A variety of aspects will influence the final value of the derived benchmark, including: the aim of the application of the benchmark, the protection goals of the assessment, the data on radiation-induced biological effects considered, and the methodology used. Benchmark values have been proposed by several international organizations (UNSCEAR, ICRP, IAEA), countries (USA, Canada) and research projects (ERICA, PROTECT), for different application purposes and protection goals and using a variety of methodologies. This paper describes the aspects that need to be considered in the derivation of numerical benchmarks, the approaches used by different organizations and the benchmark values they have proposed for the radiation protection of the environment. The benchmark values proposed are compared with the dose-rates at which radiation-induced biological effects have been described in animals and plants.

Effect of gamma radiation on the production of bystander signals from three earthworm species irradiated in vivo

The effect of gamma radiation delivered over 24 h on the induction of bystander signals of three earthworm species exposed in vivo was investigated: A. chlorotica, A. caliginosa, and E. tetraedra. Worms were exposed to external gamma irradiation (Co-60 source) for 24 h and samples of head, body, and clitellum were dissected from exposed and control worms and placed in culture medium for 24 h at 19 C. The harvested medium was filtered and assayed for expression of bystander signals using both clonogenic and mitochondrial reporter assays. Different responses were observed in the different species and in the different tissues. A. chlorotica worm-treated reporters show insignificant mitochondrial response for all sections, yet a significant clonogenic reduction in survival for body sections. A. caliginosa worm-treated reporters show a significant mitochondrial response for some sections and insignificant mitochondrial response and insignificant reduction in clonogenic survival for the rest. E. tetraedra worms from a control site show significant evidence of bystander signalling, measured by mitochondrial response in reporter cells, for all sections while those harvested from a contaminated site show insignificant changes in baseline signalling when exposed to the challenge dose. In vivo exposure of earthworm species shows evidence of bystander signalling using two different reporter assays. This effect varied between the different species and tissues. There is also evidence of attenuated bystander signalling in worms harvested from a site contaminated with radiation.

Haematological analysis of Japanese macaques (Macaca fuscata) in the area affected by the Fukushima Daiichi Nuclear Power Plant accident

Several populations of wild Japanese macaques (Macaca fuscata) inhabit the area around Fukushima Daiichi Nuclear Power Plant (FNPP). To measure and control the size of these populations, macaques are captured annually. Between May 2013 and December 2014, we performed a haematological analysis of Japanese macaques captured within a 40-km radius of FNPP, the location of a nuclear disaster two years post-accident. The dose-rate of radiocaesium was estimated using the ERICA Tool. The median internal dose-rate was 7.6 μGy/day (ranging from 1.8 to 219 μGy/day) and the external dose-rate was 13.9 μGy/day (ranging from 6.7 to 35.1 μGy/day). We performed multiple regression analyses to estimate the dose-rate effects on haematological values in peripheral blood and bone marrow. The white blood cell and platelet counts showed an inverse correlation with the internal dose-rate in mature macaques. Furthermore, the myeloid cell, megakaryocyte, and haematopoietic cell counts were inversely correlated and the occupancy of adipose tissue was positively correlated with internal dose-rate in femoral bone marrow of mature macaques. These relationships suggest that persistent whole body exposure to low-dose-rate radiation affects haematopoiesis in Japanese macaques.

Epithelial cell shape change of Drosophila as a biomonitoring model for the dose assessment of environmental radiation

Inevitable exposure to ionizing radiation from natural and human-made sources has been increasing over time. After nuclear disasters, such as the Fukushima accident, the public concerns on health risk of radiation exposure because of radioactive contamination of the environment have increased. However, it is very difficult to assess the biological effects of exposure caused by environmental radiation. A reliable and rapid bioassay to monitor the physiological effects of radiation exposure is therefore needed. Here, we quantitatively analyzed the changes in cell shape in Drosophila epidermis after irradiation as a model for biomonitoring of radiation. Interestingly, the number of irregularly shaped epithelial cells was increased by irradiation in a dose-dependent manner. A dose-response curve constructed with the obtained data suggests that the measurement of the number of irregular shaped cell in the epidermis is useful for the assessment of radiation dose. In addition, a comparison of the variation in the different samples and the data scored by different observers showed that our evaluation for cellular morphology was highly reliable and accurate and would, therefore, have immense practical application. Overall, our study suggests that detection of morphological changes in the epithelial cells is one of the efficient ways to quantify the levels of exposure to radioactive radiation from the environment.

Ionizing radiation and taxonomic, functional and evolutionary diversity of bird communities

Ionizing radiation from nuclear accidents at Chernobyl, Fukushima and elsewhere has reduced the abundance, species richness and diversity of ecosystems. Here we analyzed the taxonomic, functional and evolutionary diversity of bird communities in forested areas around Chernobyl. Species richness decreased with increasing radiation, mainly in 2007. Functional richness, but not functional evenness and divergence, decreased with increasing level of ionizing radiation. Evolutionary distinctiveness of bird communities was higher in areas with higher levels of ionizing radiation. Regression tree models revealed that species richness was higher in bird communities in areas with radiation levels lower than 0.7 μSv/h. In contrast, when radiation levels were higher than 16.67 μSv/h, bird species richness reached a minimum. Functional richness was affected by two variables: Forest cover and radiation level. Higher functional richness was found in bird communities in areas with forest cover lower than 50%. In the areas with forest cover higher than 50%, the functional richness was lower when radiation level was higher than 0.91 μSv/h. Finally, the average evolutionary distinctiveness of bird communities was higher in areas with forest cover exceeding 50%. These findings imply that level of ionizing radiation interacted with forest cover to affect species richness and its component parts, i.e. taxonomic, functional, and evolutionary diversity.

Long-term effects of ionizing radiation after the Chernobyl accident: Possible contribution of historic dose

The impact of the Chernobyl NPP accident on the environment is documented to be greater than expected, with higher mutation rates than expected at the current, chronic low dose rate. In this paper we suggest that the historic acute exposure and resulting non-targeted effects (NTE) such as delayed mutations and genomic instability could account at least in part for currently measured mutation rates and provide an initial test of this concept. Data from Møller and Mousseau on the phenotypic mutation rates of Chernobyl birds 9-11 generations post the Chernobyl accident were used and the reconstructed dose response for mutations was compared with delayed reproductive death dose responses (as a measure of genomic instability) in cell cultures exposed to a similar range of doses. The dose to birds present during the Chernobyl NPP accident was reconstructed through the external pathway due to Cs-137 with an estimate of the uncertainty associated with such reconstruction. The percentage of Chernobyl birds several generations after the accident without mutations followed the general shape of the clonogenic survival percentage of the progeny of irradiated cells, and it plateaued at low doses. This is the expected result if NTE of radiation are involved. We suggest therefore, that NTE induced by the historic dose may play a role in generating mutations in progeny many generations following the initial disaster.

Carotenoid distribution in wild Japanese tree frogs (Hyla japonica) exposed to ionizing radiation in Fukushima

The nuclear accident in the Fukushima prefecture released a large amount of artificial radionuclides that might have short- and long-term biological effects on wildlife. Ionizing radiation can be a harmful source of reactive oxygen species, and previous studies have already shown reduced fitness effects in exposed animals in Chernobyl. Due to their potential health benefits, carotenoid pigments might be used by animals to limit detrimental effects of ionizing radiation exposure. Here, we examined concentrations of carotenoids in blood (i.e. a snapshot of levels in circulation), liver (endogenous carotenoid reserves), and the vocal sac skin (sexual signal) in relation to the total radiation dose rates absorbed by individual (TDR from 0.2 to 34 µGy/h) Japanese tree frogs (Hyla japonica). We found high within-site variability of TDRs, but no significant effects of the TDR on tissue carotenoid levels, suggesting that carotenoid distribution in amphibians might be less sensitive to ionizing radiation exposure than in other organisms or that the potential deleterious effects of radiation exposure might be less significant or more difficult to detect in Fukushima than in Chernobyl due to, among other things, differences in the abundance and mixture of each radionuclide.

When a duck is not a duck; a new interdisciplinary synthesis for environmental radiation protection

This consensus paper presents the results of a workshop held in Essen, Germany in September 2017, called to examine critically the current approach to radiological environmental protection. The meeting brought together participants from the field of low dose radiobiology and those working in radioecology. Both groups have a common aim of identifying radiation exposures and protecting populations and individuals from harmful effects of ionising radiation exposure, but rarely work closely together. A key question in radiobiology is to understand mechanisms triggered by low doses or dose rates, leading to adverse outcomes of individuals while in radioecology a key objective is to recognise when harm is occurring at the level of the ecosystem. The discussion provided a total of six strategic recommendations which would help to address these questions.

Current Status of the Blue Butterfly in Fukushima Research

Adverse biological impacts of the Fukushima nuclear accident have been revealed using the pale grass blue butterfly, Zizeeria maha, since 2012, which were often considered incompatible with the conventional understanding of radiation biology. This discrepancy likely originates from different system conditions and methodologies. In this article, we first respond to comments from the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) regarding our study; "technical errors" in unit usage and mathematical models noted by UNSCEAR are not errors but reflect our research philosophy not to introduce theoretical assumptions associated with unit conversion and mathematical fit. Second, we review our recent studies to support the original 2012 conclusions. Because the high morphological abnormality rate and small body size detected in Fukushima in 2011 have already ceased, likely through adaptive evolution, their present geographical distributions were investigated throughout Japan. Local populations showing relatively high abnormality rates and small body sizes were rare and basically restricted to Miyagi and its northern populations excluding the Fukushima populations, supporting the causal involvement of the accident. Lastly, we stress the importance of understanding the whole picture of the biological impacts of the Fukushima accident. In addition to the direct radiation impacts, indirect impacts through unknown radiation-associated mechanisms, such as immunological responses to insoluble particulate matter and nutritional deficiencies in plants and animals, would be in effect. Further environmental studies beyond conventional radiation biology and physics are necessary to understand the complex responses of organisms, including humans, to the Fukushima nuclear accident.

On the divergences in assessment of environmental impacts from ionising radiation following the Fukushima accident

The accident at the Fukushima-Daiichi Nuclear Power Station on March 11, 2011, led to significant contamination of the surrounding terrestrial and marine environments. Whilst impacts on human health remain the primary concern in the aftermath of such an accident, recent years have seen a significant body of work conducted on the assessment of the accident's impacts on both the terrestrial and marine environment. Such assessments have been undertaken at various levels of biological organisation, for different species, using different methodologies and coming, in many cases, to divergent conclusions as to the effects of the accident on the environment. This article provides an overview of the work conducted in relation to the environmental impacts of the Fukushima accident, critically comparing and contrasting methodologies and results with a view towards finding reasons for discrepancies, should they indeed exist. Based on the outcomes of studies conducted to date, it would appear that in order to avoid the fractured and disparate conclusions drawn in the aftermath of previous accidents, radioactive contaminants and their effects can no longer simply be viewed in isolation with respect to the ecosystems these effects may impact. A combination of laboratory based and field studies with a focus on ecosystem functioning and effects could offer the best opportunities for coherence in the interpretation of the results of studies into the environmental impacts of ionising radiation.

Ecological effects of exposure to enhanced levels of ionizing radiation

Irradiation of plants and animals can result in disruption of ecological relationships between the components of ecosystems. Such effects may act as triggers of perturbation and lead to consequences that may differ essentially from expected ones based on effects observed at the organismal level. Considerable differences in ecology and niches occupied by different species lead to substantial differences in doses of ionizing radiation absorbed by species, even when they all are present in the same environment at the same time. This is especially evident for contamination with α-emitting radionuclides. Radioactive contamination can be considered an ecological factor that is able to modify the resistance in natural populations. However, there are radioecological situations when elevated radioresistance does not evolve or persist. The complexity and non-linearity of the structure and functioning of ecosystems can lead to unexpected consequences of stress effects, which would appear harmless if they were assessed within the narrower context of organism-based traditional radioecology. Therefore, the use of ecological knowledge is essential for understanding responses of populations and ecosystems to radiation exposure. Integration of basic ecological principles in the design and implementation of radioecological research is essential for predicting radiation effects under rapidly changing environmental conditions.

Addressing ecological effects of radiation on populations and ecosystems to improve protection of the environment against radiation: Agreed statements from a Consensus Symposium

This paper reports the output of a consensus symposium organized by the International Union of Radioecology in November 2015. The symposium gathered an academically diverse group of 30 scientists to consider the still debated ecological impact of radiation on populations and ecosystems. Stimulated by the Chernobyl and Fukushima disasters' accidental contamination of the environment, there is increasing interest in developing environmental radiation protection frameworks. Scientific research conducted in a variety of laboratory and field settings has improved our knowledge of the effects of ionizing radiation on the environment. However, the results from such studies sometimes appear contradictory and there is disagreement about the implications for risk assessment. The Symposium discussions therefore focused on issues that might lead to different interpretations of the results, such as laboratory versus field approaches, organism versus population and ecosystemic inference strategies, dose estimation approaches and their significance under chronic exposure conditions. The participating scientists, from across the spectrum of disciplines and research areas, extending also beyond the traditional radioecology community, successfully developed a constructive spirit directed at understanding discrepancies. From the discussions, the group has derived seven consensus statements related to environmental protection against radiation, which are supplemented with some recommendations. Each of these statements is contextualized and discussed in view of contributing to the orientation and integration of future research, the results of which should yield better consensus on the ecological impact of radiation and consolidate suitable approaches for efficient radiological protection of the environment.

Ethical foundations of environmental radiological protection

Assessing the potential ecological impact of ionising radiation raises a number of ethical questions. These include fundamental questions such as what exactly constitutes harming the environment, and how the environment should be valued, as well as links to political protection principles such as sustainability and biodiversity. Starting from developments within ecological risk assessment, this paper summarises some of the ethical issues concerning the protection of the environment from radiation. Chapter 2 gives a brief overview of different philosophical and cultural world views on valuing the environment in a context of radiation risk. Chapter 3 addresses some recent challenges to proposed environmental protection frameworks, including practical applications following the Chernobyl and Fukushima accidents, and some scientific developments such as the ecosystem approach. Finally, Chapter 4 offers some recommendations on how ethical evaluation can help produce a more robust and transparent approach to the protection of the environment. In conclusion, there is a need for a holistic evaluation of the environmental impacts of ionising radiation that not only considers the direct consequences on the health of humans and non-human species, but also the more complex social, ethical, and economic consequences of both human and non-human exposures.

Overview of ICRP Committee 5: protection of the environment

Protection of the environment is integral to the system of radiological protection, as outlined in the 2007 Recommendations of the International Commission on Radiological Protection (ICRP, Publication 103). The Commission's activities in this area are mainly pursued by Committee 5 and its associated Task Groups. Publication 91 broadly outlines the approach to radiological protection of the environment, and its alignment with approaches to environmental protection from hazardous substances in general. Publications 108 and 114 provide the cornerstones of the environmental protection system and relevant databases. Publication 124 considers its application in planned, existing, and emergency exposure situations. The system centres on 12 Reference Animals and Plants (RAPs) with broad relevance for environmental protection based on their ubiquity and significance as well as other criteria, as described in Publication 108 The databases comprise general biology of the RAPs, transfer parameters, dose conversion coefficients, and effects data. Derived Consideration Reference Levels (DCRLs) were established for each RAP; a DCRL represents a band of dose rates that might result in some deleterious effects in individuals of that type of RAP. Newly established Task Group 99 will compile the RAP-specific reference information into monographs, with the view of updating information and improving the applicability of the system in different exposure situations. For certain scenarios, more precise and ecosystem-specific protection benchmarks may be justified, which would have to be informed by consideration of representative organisms (i.e. representative of a particular ecosystem and relevant to the specific scenario; Publication 124). Committee 5 will explore this further, making use of a limited number of case studies.

Are Organisms Adapting to Ionizing Radiation at Chernobyl?

Numerous organisms have shown an ability to survive and reproduce under low-dose ionizing radiation arising from natural background radiation or from nuclear accidents. In a literature review, we found a total of 17 supposed cases of adaptation, mostly based on common garden experiments with organisms only deriving from typically two or three sampling locations. We only found one experimental study showing evidence of improved resistance to radiation. Finally, we examined studies for the presence of hormesis (i.e., superior fitness at low levels of radiation compared with controls and high levels of radiation), but found no evidence to support its existence. We conclude that rigorous experiments based on extensive sampling from multiple sites are required.