The wastewater release from the Fukushima Daiichi nuclear plant is expected to have negligible effects on people and the ocean.

Recent studies apparently finding deleterious effects of radiation exposure on cataract formation in birds and voles living near Chernobyl represent a major challenge to current radiation protection regulations. This study conducted an integrated assessment of radiation exposure on cataractogenesis using the most advanced technologies available to assess the cataract status of lenses extracted from fish caught at both Chernobyl in Ukraine and Fukushima in Japan. It was hypothesised that these novel data would reveal positive correlations between radiation dose and early indicators of cataract formation.The structure, function and optical properties of lenses were analysed from atomic to millimetre length scales. We measured the short-range order of the lens crystallin proteins using Small Angle X-Ray Scattering (SAXS) at both the SPring-8 and DIAMOND synchrotrons, the profile of the graded refractive index generated by these proteins, the epithelial cell density and organisation and finally the focal length of each lens.The results showed no evidence of a difference between the focal length, the epithelial cell densities, the refractive indices, the interference functions and the short-range order of crystallin proteins (X-ray diffraction patterns) in lens from fish exposed to different radiation doses. It could be argued that animals in the natural environment which developed cataract would be more likely, for example, to suffer predation leading to survivor bias. But the cross-length scale study presented here, by evaluating small scale molecular and cellular changes in the lens (pre-cataract formation) significantly mitigates against this issue.

The 2011 Tohoku earthquake-tsunami and the subsequent nuclear accident at the Fukushima Dai-ichi Nuclear Power Station (FDNPS) led to large-scale radionuclide contamination of the marine and freshwater environment. Monitoring studies of marine food products in the Fukushima region have generally demonstrated a declining trend in radiocaesium concentrations. However, the accumulation and elimination of radiocaesium and potential biological effects remain poorly understood for freshwater biota inhabiting highly contaminated areas at Fukushima. Consequently, the present study aimed to assess radiocaesium accumulation and developmental effects on the commercially important catadromous Japanese mitten crab, Eriocheir japonica. E. japonica were collected from four sites along a gradient of radionuclide contamination 4-44 km in distance from the FDNPS in 2017. To determine potential developmental effects, fluctuating asymmetry (FA) was used as a measure of developmental stability. Combined 134Cs and 137Cs values for whole E. japonica from highly contaminated sites 4 and 16 km in distance from the FDNPS were 3040 +/- 521 and 2250 +/- 908 Bq kg-1 wet weight respectively, 30 and 22 times greater than the Japanese standard limit of 100 Bq kg- 1. Estimated total dose rates based on radiocaesium concentrations in whole crabs and sediment ranged from 0.016 to 37.7 mu Gy h-1. No significant relationship between radiocaesium accumulation and FA was recorded, suggesting that chronic radiation exposure at Fukushima is not inducing developmental effects in E. japonica as measured using fluctuating asymmetry. Furthermore, estimated dose rates were below proposed regulatory limits where significant deleterious effects are expected. The present study will aid in the understanding of the long-term consequences of radiation exposure for non-human biota and the management of radioactively contaminated environments.

The Chernobyl Exclusion Zone (CEZ) contains the vast majority of radionuclides released by the accident in nuclear fuel particle form. We present and analyze groundwater measurements collected from the monitoring network in CEZ covering key aquifers over 35 years since the accident. These new data, together with a comprehensive analysis of historical data shows that 90Sr remains mobile in the subsurface environment, while groundwater concentrations of 137Cs, Pu isotopes and 241Am are relatively low, and are not of radiological concern. During the last two decades, 90Sr and 137Cs levels have declined or remained stable over time in the majority of monitoring locations. This is due to natural attenuation driven by gradual exhaustion of the fuel particle source, geochemical evolution of groundwater downstream from waste dumps and radionuclide retention in surface soil due to absorption and bio-cycling. Decommissioning of the cooling pond and construction of the ‘New safe confinement’ over Unit 4 (damaged reactor) also favored better protection of groundwater close to the Chernobyl plant site. Data from confined and unconfined aquifers, as well as rivers, evidence low radiological risks from groundwater contamination both outside the CEZ and to onsite “self-settlers”. Though several groundwater contamination “hot spots” remain in the vicinity of Unit 4, “Red Forest” waste trenches and surface water bodies with contaminated bottom sediments, the findings of this study support a monitored natural attenuation approach to groundwater management in the CEZ.

Ni in PM10 can contribute to health problems such as cardiovascular mortality at low ambient concentrations, and in the UK is measured through the Heavy Metals Network. Localised concentrations of nickel in PM10 have resulted in a Sheffield air quality monitoring station exceeding the EU target value of 20 ng/m3. Two localised sources of nickel have been identified; one relating to point source emissions, and one relating to fugitive dust emissions. Fugitive dust emissions from a Sheffield steelworks have therefore been assessed using a novel approach, with six months of sticky pad and PM10 dust monitoring, and subsequent elemental characterisation of dust and control samples using ICP-OES and ICP-MS used to inform dust dispersion modelling. Three new fugitive dust source areas on-site were identified from the dust monitoring and characterisation results. Emission rates of Ni were estimated from each source, with adjustments made based on the dust monitoring and characterisation results. Dispersion modelling was undertaken using the new and existing Ni dust sources and results compared favourably to previous studies. Source apportionment of measured concentrations was investigated with regard to the modelling and characterisation results and showed that on-site fugitive dust sources were not significantly different to a fugitive nickel source identified in previous research. However, both source apportionment results and dust monitoring results show that Ni concentrations at the local monitoring station were not increased when fugitive emissions from the study site were highest, or when the winds from the direction of the site were most frequent, indicating that fugitive dust emissions that caused increased concentrations throughout this study period were derived from sources in the area other than the study site.

The Chornobyl accident in 1986 led to radioactive contamination of surface water bodies (SWB) in the Chornobyl Exclusion Zone (ChEZ), including lakes (Azbuchyn, Glyboke, Yanov crawl etc) and the Cooling Pond (CP). An abundance in fallout the dispersed fuel particles (FPs) was a specific feature of the accident, comprising the debris of irradiated nuclear fuel in different states of uranium oxidation mixed with construction materials. Contamination of SWB by 90Sr and transuranic isotopes was mainly because of FPs. Experimental studies on the behaviour of FPs in soils and aquatic systems have shown that main factors controlling release of radionuclides outside FPs are: composition of the matrix, state of initial oxidation and oxidation properties of the environment. FPs behavior in SWB has not been sufficiently studied, though limited data suggest contrasting differences to terrestrial environments. Mainly is because of the different oxidation properties of soil and bottom sediment, creating better conservation conditions for FPs in sediment. In case when in SWB bed become dry and exposed, as is the case in the CP after decommissioning, an intensive processes of primary soil formation begin on exposed areas. This later forced dissolution of FPs, and hence radionuclides transition into more mobile forms followed by release to groundwater and surface runoff. We have developed convenient method for identifying Chornobyl FPs based on radiography, which comprises the exposure of X-ray film by spreading over a thin-layered dry solid sample. Processing X-ray films and image analysis makes it possible to estimate the size of FPs, as well as dispersion and distribution of radionuclide activity within the FPs of different size fractions. This also facilitates picking up single FPs to carry out extended individual analysis by EDXRF, SEMs etc. The radiography method was used to estimate the chemical resistance of FPs after sequential leaching to predict the behaviour of radionuclides in natural field conditions. Overall, more than 120 samples were collected from bottom sediments cores taken from different SWB in ChEZ and analyzed by radiography. The results obtained show that from 70 to 90% of activity of radionuclides in sediments are associated with FPs. One gram of sediment contains several 10s to several 100s of individual FPs, while there is significant spatial heterogeneity of FPs density over the territory of ChEZ. The majority of FPs are less than 3 microns and their contribution to total activity was estimated as minor. The main contribution to activity (>70%) comes from particles with a diameter of more than 10 microns and, accordingly, mobility of radionuclides will be determined by processes of destruction and leaching of radionuclides from particles of these size. Chemically resistant FPs are of 3-5 microns, and the highest concentration of fuel particles is typical for SWB located in close proximity to the ChNPP. Up to 7% of the activity remains associated with FPs after being treated with strong 8M nitric acid indicating that 90Sr, transuranic and, partly, 137Cs are confined in chemically very stable particles and may not be mobilized under natural conditions for many decades.

The collection efficiency of the DustScan DS100 directional sticky pad dust gauge has been analysed in order to estimate airborne dust concentrations for use in atmospheric dispersion models. A DS100 directional sticky pad dust monitor was tested for 10 months at a quarry boundary with respect to a Wilson and Cook (WAC) sampler, with comparisons primarily made with regard to directional wind speeds over the relevant monitoring periods, as recorded by an on-site meteorological station. The mass of dust collected using the DS100 monitor fluctuated between 3.1% and 21.3% of that caught by the WAC sampler over each period. Variations in collection efficiency were modelled using the count of wind speeds per half hour period and two distinct periods were observed. The main trend showed that higher wind speeds decreased relative DS100 efficiency, with low wind speed (3 m/s) and high wind speed (5 m/s) periods showing modelled efficiency above 10% and below 5% respectively in comparison to the WAC sampler. However, a central period of 9 weeks during the monitoring study showed a reverse of this pattern, with significant wind speeds over 5 m/s correlating with higher DS100 efficiency. Although dust catch on each sampler varied significantly over the study period, an average DS100 efficiency of approximately 7% in comparison to the WAC is suggested for use in estimating airborne dust concentrations for use in atmospheric dispersion models.

The Chernobyl and Fukushima nuclear power plant (NPP) accidents that occurred in 1986 and 2011 respectively have led to many years of chronic radiation exposure of wildlife. However, controversies remain on the dose threshold above which an impact on animal health occurs. Fish have been highly exposed immediately after both accidents in freshwater systems around Chernobyl and in freshwater and marine systems around Fukushima. The dose levels decreased during the years after the accidents, however, little is known about the effects of environmental low doses of radiation on fish health. The present laboratory study assesses the effects of an environmentally relevant dose range of radiation (0.1, 1 and 10 mGy/day) on early life stages of the 3-spined stickleback, Gasterosteus aculeatus. The cardiac physiology and developmental features (head width, diameter, area) of high exposed embryos (10 mGy/day) showed no significant change when compared to controls. Embryos exposed to the medium and high dose were slower to hatch than the controls (between 166 and 195 h post-fertilization). After 10 days of exposure (at 240 h post-fertilization), larvae exposed to the high dose displayed comparable growth to controls. High-throughput sequence analysis of transcriptional changes at this time point revealed no significant changes in gene regulation compared to controls regardless of exposure conditions. Our results suggest that exposure of fish embryos to environmental radiation elicits subtle delays in hatching times, but does not impair the overall growth and physiology, nor the gene expression patterns in the recently hatched larvae.

Fish have been highly exposed to radiation in freshwater systems after the Chernobyl Nuclear Power Plant (NPP) accident in 1986 and in freshwater and marine systems after the more recent Fukushima NPP accident in 2011. In the years after the accident, the radioactivity levels rapidly declined due to radioactive decay and environmental processes, but chronic lower dose exposures persisted. To gain insights into the long-term effects of environmental low dose radiation on fish ovaries development, a high-throughput transcriptomic approach including a de novo assembly was applied to different gonad phenotypes of female perch: developed gonads from reference lakes, developed/irradiated from medium contaminated lake, and both developed/irradiated and undeveloped from more highly contaminated lakes. This is the most comprehensive analysis to date of the gene responses in wildlife reproductive system to radiation. Some gene responses that were modulated in irradiated gonads were found to be involved in biological processes including cell differentiation and proliferation (ggnb2, mod5, rergl), cytoskeleton organization (k1C18, mtpn), gonad development (nell2, tcp4), lipid metabolism (ldah, at11b, nltp), reproduction (cyb5, cyp17A, ovos), DNA damage repair (wdhd1, rad51, hus1), and epigenetic mechanisms (dmap1). Identification of these genes provides a better understanding of the underlying molecular mechanisms underpinning the development of the gonad phenotypes of wild perch and how fish may respond to chronic exposure to radiation in their natural environment, though causal attribution of gene responses remains unclear in the undeveloped gonads.

A review is presented of data on solid-liquid distribution coefficients (Kd-s) of the main radiologically important radionuclides of the Chernobyl release within geological deposits at the Chernobyl Nuclear Power Plant (ChNPP) Site. The Kd values for Sr, Cs and Pu for Quaternary sandy deposits that form sedimentary cover at Chernobyl fall within the range of parameters reported in international sorption databases. In agreement with general knowledge on radionuclide geochemical behavior and affinity to soils, Kd-s increase in the sequence: Sr < Cs < Pu. Alluvial and fluvioglacial sandy deposits are characterized by larger Kd values then deposits of eolian genesis due to higher content of clay minerals in fine fractions. For Sr, laboratory batch tests have given Kd values that are in a reasonable agreement with in situ measurements. At the same time, the Sr-90 Kd-s obtained from groundwater transport model calibrations were noticeably lower than experimentally determined values, thus showing potential limitations of the Kd-approach. Monitoring data on mobility of Sr-90, Cs-137 and Pu-239,Pu-240 in groundwater in the Chernobyl zone on a whole are consistent with the radionuclide Kd-s summarized in this article. The highest concentrations in groundwater (based on data for 2012-2014) were observed for Sr-90, while orders of magnitude lower concentrations were observed for Cs-137 and Pu-239,Pu-240. At the same time, detection of Cs-137 and Pu-239,Pu-240 in groundwater at sites with a relatively deep groundwater table suggests the possibility of facilitated transport of small amounts of these radionuclides in the form of non-retarded colloids or complexes. (C) 2019 Elsevier Ltd. All rights reserved.

Strontium-90 (90Sr) is the major long-lived radionuclide derived from the Chernobyl accident, and is still being detected in the heavily contaminated catchments of the Chernobyl Exclusion Zone. This study examines the long-term decrease in the dissolved-phase 90Sr concentration and the concentration–discharge (90Sr-Q) relationship in stream water since the accident. We show that the slow decline in 90Sr follows a double-exponential function, and that there is a clear relationship between 90Sr and Q. This study is the first to reveal that the log(90Sr)-log(Q) slope has been gradually decreasing since the accident. This trend persists after decay correction. Thus, it is not caused by the physical decay of 90Sr and environmental diffusion, but implies that the concentration formation processes in stream water have been changing over a long period. We propose a hydrochemical model to explain the time-dependency of the 90Sr-Q relationship. This paper presents a mathematical implementation of the new concept and describes the model assumptions. Our model accurately represents both the long-term 90Sr trend in stream water and the time-dependency of the 90Sr-Q relationship. Although this paper considers a small catchment in Chernobyl, the conceptual model is shown to be applicable to other accidental releases of radionuclides.

My review, based on nearly thirty years of research on Chernobyl and dozens of visits to the contaminated areas of Belarus, Ukraine and Russia, argues that Manual for Survival ignores the thousands of scientific studies on Chernobyl which are available in the international scientific literature. In doing so, it presents a biased and misleading account of the health and environmental effects of the accident. I believe that this book only perpetuates the many myths about the accident effects and has very little basis in sound science.

Abstract Analysis of genetic diversity represents a fundamental component of ecological risk assessments in contaminated environments. Many studies have assessed the genetic implications of chronic radiation exposure at Chernobyl, generally recording an elevated genetic diversity and mutation rate in rodents, plants, and birds inhabiting contaminated areas. Only limited studies have considered genetic diversity in aquatic biota at Chernobyl, despite the large number of freshwater systems where elevated dose rates will persist for many years. Consequently, the present study aimed to assess the effects of chronic radiation exposure on genetic diversity in the freshwater crustacean, Asellus aquaticus, using a genome‐wide SNP approach (Genotyping‐by‐sequencing). It was hypothesized that genetic diversity in A. aquaticus would be positively correlated with dose rate. A. aquaticus was collected from six lakes in Belarus and the Ukraine ranging in dose rate from 0.064 to 27.1 µGy/hr. Genotyping‐by‐sequencing analysis was performed on 74 individuals. A significant relationship between geographical distance and genetic differentiation confirmed the Isolation‐by‐Distance model. Conversely, no significant relationship between dose rate and genetic differentiation suggested no effect of the contamination gradient on genetic differentiation between populations. No significant relationship between five measures of genetic diversity and dose rate was recorded, suggesting that radiation exposure has not significantly influenced genetic diversity in A. aquaticus at Chernobyl. This is the first study to adopt a genome‐wide SNP approach to assess the impacts of environmental radiation exposure on biota. These findings are fundamental to understanding the long‐term success of aquatic populations in contaminated environments at Chernobyl and Fukushima.

Crustaceans have been designated as internationally important model organisms in the development of environmental radioprotection measures. Despite the known sensitivity of sperm to ionizing radiation, the impacts of chronic radiation exposure on male fertility in crustaceans have not been studied. For the first time, the present study aimed to assess the impacts of chronic radiation exposure on male fertility, sperm DNA damage and concomitant impacts on breeding in two amphipod crustaceans. Echinogammarus marinus and Gammarus pulex (male fertility only) were exposed to phosphorus-32 at dose rates of 0, 0.1, 1 and 10 mGy/d and sperm parameters, DNA damage and knock-on impacts on breeding were assessed. Sperm quality parameters and DNA damage were assessed using a fluorescent staining method and single cell gel electrophoresis respectively. Concomitant effects of male exposure to radiation on fecundity were determined by pairing phosphorus-32 exposed males to unexposed sexually mature females. In E. marinus, a statistically significant reduction of 9 and 11% in the quality of sperm was recorded at dose rates of 1 and 10 mGy/d respectively, with no significant effects recorded on sperm counts. Conversely in the freshwater G. pulex, no significant impact of radiation on sperm quantity or quality was recorded. For E. marinus, a statistically significant increase in DNA damage was recorded at doses of 10 mGy/d. Reduced fecundity and an increase in the frequency of abnormal embryos was recorded in female E. marinus breeding with males exposed to radiation. These findings suggest sperm quality may be a sensitive indicator of radiation exposure in invertebrates with potential impacts on the unexposed embryo, though unclear dose-response and differences between two closely related species necessitate further study before robust conclusions can be drawn.

The 1957 ‘Kyshtym accident’ at the Mayak Plutonium production site in the Southern Urals of Russia was the World’s first major nuclear accident, leading to evacuation of 1000 km of land and causing significant environmental damage. Sergey Fesenko, an internationally recognised authority on the Kyshtym and Chernobyl accidents, presents a very valuable summary of the fascinating ecosystem research conducted after the accident (Fesenko 2019). In the years after the explosion, most of the released radioactivity decayed away, but the remaining (approximately 5% of the total release) relatively long-lived Sr-90 (half-life 28.8 years) caused chronic long-term exposure of wildlife. As documented by Fesenko (2019), this research represents some of the first real field studies of the effects of radiation on the natural environment. Doses to pine needles during the ‘acute’ phase of the accident reached 800 Gy and doses to mammals and birds exceeded 10 Gy in the most contaminated areas. Soviet researchers documented the lethal and sub-lethal effects of these huge doses on trees and small and large mammals in the affected areas. In a process repeated in the Chernobyl ‘Red Forest’ nearly 30 years later, they observed that extremely high beta-radiation doses to the leaves and buds of trees had lethal effects. Domestic animals exposed to external doses of 1.4–3.0 Gy and 4–54 Gy to the gastrointestinal tract (GIT) showed symptoms of acute radiation sickness and most died. The studies of the effects of much lower chronic dose rates (from the early 1960s onwards) made a major contribution to interesting new concepts in radioecological and radiobiological research, including ‘radioadaptation’ of animals and plants to living in contaminated areas. They also included findings of long-term ecosystem effects. Apparent effects on soil invertebrate populations were seen at dose rates (5–12 mGy d) which, though by normal standards are very high, are nevertheless significantly lower than might be expected from laboratory experiments on these organisms. Similarly, as late as the 1990s, major reproductive effects on birds were observed; though not given in Fesenko (2019), the Sr contamination level is reported in (Sazykina and Kryshev 2006) as being extremely high (55 MBq m). Some of the findings summarised in the review are relevant to research apparently showing effects on organisms at Chernobyl at dose rates much lower than would be expected from laboratory radiobiological studies (Garnier-Laplace et al 2013), though the strength of evidence in these studies has been questioned (Smith 2019). We have to acknowledge (as Fesenko does (2019)) the inevitable limitations of field research into the effects of radiation on wildlife. Studies of long-term (often subtle at low chronic dose rates) effects after Kyshtym, Chernobyl and, to a much lesser extent, Fukushima may be confounded by early ecosystem damage from extremely high dose rates due to shortlived radionuclides. At both Kyshtym and Chernobyl, initial damage of forest ecosystems was severe in the (most usually studied) hot-spots. Further confounding can occur from the difficulty in separating radiation effects from natural environmental variation. Simple contrasts between high dose rate areas and ‘controls’ are rarely sufficient to demonstrate effects as (unless there are very many true replicates) they can rarely capture this variation. It is all too easy for authors (and reviewers) to assume, uncritically, that observed correlations between some biological effect and dose rate is causal. But models apparently accounting for radiation effects together with potential confounders such as habitat quality and food | Society for Radiological Protection Journal of Radiological Protection

Aquatic organisms at Chernobyl have now been chronically exposed to environmental radiation for three decades. The biological effects of acute exposure to radiation are relatively well documented, but much less is known about the long-term effects of chronic exposure of organisms in their natural environment. Highly exposed fish in freshwater systems at Chernobyl showed morphological changes in their reproductive system in the years after the accident. However, the relatively limited scope of past studies did not allow robust conclusions to be drawn. Moreover, the level of the radiation dose at which significant effects on wildlife occur is still under debate. In the most comprehensive evaluation of the effects of chronic radiation on wild fish populations to date, the present study measures specific activities of 137Cs, 90Sr, and transuranium elements (238Pu, 239,240Pu, and 241Am), index conditions, distribution and size of oocytes, as well as environmental and biological confounding factors in two fish species perch ( Perca fluviatilis) and roach ( Rutilus rutilus) from seven lakes. In addition, relative species abundance was examined. The results showed that both fish species are, perhaps surprisingly, in good general physiological and reproductive health. Perch, however, appeared to be more sensitive to radiation than roach: in the most contaminated lakes, a delay of the maturation of the gonads and the presence of several undeveloped phenotypes were evident only for perch and not for roach.

With respect to environmental protection, understanding radionuclide bioconcentration is necessary to relate exposure to radiation dose and hence to biological responses. Few studies are available on tissue specific accumulation of short-lived radionuclides in aquatic invertebrates. Short-lived radionuclides such as (32)Phosphorus (P-32), although occurring in small quantities in the environment, are capable of concentrating in the biota, especially if they are chronically exposed. In this study, we firstly compared tissue specific bioaccumulation and release (depuration) of P-32 in adult marine (Mytilus galloprovincialis, MG) and freshwater bivalve molluscs (Dreissena polymorpha, DP). Secondly, using the Environmental Risk from Ionising Contaminants Assessment and Management (ERICA) tool, we calculated tissue specific doses following determination of radionuclide concentration. Marine and freshwater bivalves were exposed for 10 days to varying P-32 concentrations to acquire desired whole body average dose rates of 0.10, 1.0 and 10 mGy d(-1). Dose rates encompass a screening dose rate value of 10 mu Gy h(-1) (0.24 mGy d(-1)), in accordance with the ERICA tool. This study is the first to relate tissue specific uptake and release (via excretion) of P-32 from two anatomically similar bivalve species. Results showed highly tissue specific accumulation of this radionuclide and similarity of accumulation pattern between the two species. Our data, which highlights preferential P-32 accumulation in specific tissues such as digestive gland, demonstrates that in some cases, tissue-specific dose rates may be required to fully evaluate the potential effects of radiation exposure on non-human biota. Differential sensitivity between biological tissues could result in detrimental biological responses at levels presumed to be acceptable when adopting a 'whole-body' approach.

Nuclear accidents such as Chernobyl and Fukushima have led to contamination of the environment that will persist for many years. The consequences of chronic low-dose radiation exposure for non-human organisms inhabiting contaminated environments remain unclear. In radioecology, crustaceans are important model organisms for the development of environmental radioprotection. Previous laboratory studies have demonstrated deleterious effects of radiation exposure on crustacean reproduction. However, no studies have documented the effects of chronic radiation exposure on the reproduction of natural crustacean populations. Based on data from laboratory exposures, we hypothesised that populations of the freshwater isopod Asellus aquaticus exposed to radiation for thirty years at Chernobyl would display reduced reproductive output and altered timing of reproduction. To test this hypothesis, A. aquaticus was collected from six lakes at Chernobyl over two years with total dose rates ranging from 0.06–27.1μGy/h. No significant differences in the fecundity, mass of broods or proportion of reproducing female A. aquaticus were recorded. Significant differences in the body mass of gravid females were recorded suggesting different timings of reproduction, however this was not related to radiation contamination. No significant effect of a range of environmental parameters on A. aquaticus reproduction was recorded. Our data suggests current dose rates at Chernobyl are not causing discernible effects on the reproductive output of A. aquaticus. This study is the first to assess the effects of chronic low-dose radiation exposure on the reproductive output of an aquatic invertebrate at Chernobyl. These findings are consistent with proposed radiological protection benchmarks for the maintenance of wildlife populations and will assist in management of environments impacted by radiation.