Evaluation of cataract formation in fish exposed to environmental radiation at Chernobyl and Fukushima.

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.

Radiocaesium accumulation and fluctuating asymmetry in the Japanese mitten crab, Eriocheir japonica, along a gradient of radionuclide contamination at Fukushima.

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 µGy 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.

Transcriptional Changes in the Ovaries of Perch from Chernobyl.

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.

Subtle effects of radiation on embryo development of the 3-spined stickleback.

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.

Impacts of ionising radiation on sperm quality, DNA integrity and post-fertilisation development in marine and freshwater crustaceans.

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.

Chronic radiation exposure at Chernobyl shows no effect on genetic diversity in the freshwater crustacean, Asellus aquaticus thirty years on.

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.

Impact of Environmental Radiation on the Health and Reproductive Status of Fish from Chernobyl.

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.

Relative comparison of tissue specific bioaccumulation and radiation dose estimation in marine and freshwater bivalve molluscs following exposure to phosphorus-32.

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 32Phosphorus (32P), 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 32P 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 32P 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 µGy 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 32P 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 32P 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.

Reproduction in the freshwater crustacean Asellus aquaticus along a gradient of radionuclide contamination at Chernobyl.

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.

Time trends in radiocaesium in the Japanese diet following nuclear weapons testing and Chernobyl: Implications for long term contamination post-Fukushima.

Estimation of time changes in radiocaesium in foodstuffs is key to predicting the long term impact of the Fukushima accident on the Japanese diet. We have modelled >4000 measurements, spanning 50 years, of 137Cs in foodstuffs and whole diet in Japan after nuclear weapons testing (NWT) and the Chernobyl accident. Broadly consistent long term trends in 137Cs activity concentrations are seen between different agricultural foodstuffs; whole diet follows this general trend with remarkably little variation between averages for different regions of Japan. Model blind tests against post-NWT data for the Fukushima Prefecture showed good predictions for radiocaesium in whole diet, spinach and Japanese radish (for which good long term test data were available). For the post-Fukushima period to 2015, radiocaesium in the average diet followed a declining time trend consistent with that seen after NWT and Chernobyl. Data for different regions post-Fukushima show a high degree of mixing of dietary foodstuffs between regions: significant over-estimates of average dietary 137Cs were made when it was assumed that only regionally-produced food was consumed. Predictions of mean committed effective internal doses from dietary 137Cs (2011 to 2061) in non-evacuated parts of the Fukushima Prefecture show that average internal dose is relatively low. This study focused on average regional ingestion dose rates and does not attempt to make site specific predictions. However, temporal trends identified could form a basis for site specific predictions of long term activity concentrations in agricultural products and diet both outside and (to assess potential re-use) inside currently evacuated areas.

Does Chernobyl-derived radiation impact the developmental stability of Asellus aquaticus 30years on?

Effects of long-term, environmentally relevant doses of radiation on biota remain unclear due to a lack of studies following chronic exposure in contaminated environments. The 1986 Chernobyl accident dispersed vast amounts of radioactivity into the environment which persists to date. Despite three decades of research, impacts of the incident on non-human organisms continues to be contested within the scientific literature. The present study assessed the impact of chronic radiation exposure from Chernobyl on the developmental stability of the model aquatic isopod, Asellus aquaticus using fluctuating asymmetry (FA) as an indicator. Fluctuating asymmetry, defined as random deviations from the expected perfect bilateral symmetry of an organism, has gained prominence as an indicator of developmental stability in ecotoxicology. Organisms were collected from six lakes along a gradient of radionuclide contamination in Belarus and the Ukraine. Calculated total dose rates ranged from 0.06-27.1µGy/h. Fluctuating asymmetry was assessed in four meristic and one metrical trait. Significant differences in levels of pooled asymmetry were recorded between sample sites independent of sex and specific trait measured. However, there was no correlation of asymmetry with radiation doses, suggesting that differences in asymmetry were not attributed to radionuclide contamination and were driven by elevated asymmetry at a single site. No correlation between FA and measured environmental parameters suggested a biotic factor driving observed FA differences. This study appears to be the first to record no evident increase in developmental stability of biota from the Chernobyl region. These findings will aid in understanding the response of organisms to chronic pollutant exposure and the long term effects of large scale nuclear incidents such as Chernobyl and Fukushima.

Development and evaluation of a regression-based model to predict cesium-137 concentration ratios for saltwater fish.

Data from published studies and World Wide Web sources were combined to develop a regression model to predict (137)Cs concentration ratios for saltwater fish. Predictions were developed from 1) numeric trophic levels computed primarily from random resampling of known food items and 2) K concentrations in the saltwater for 65 samplings from 41 different species from both the Atlantic and Pacific Oceans. A number of different models were initially developed and evaluated for accuracy which was assessed as the ratios of independently measured concentration ratios to those predicted by the model. In contrast to freshwater systems, were K concentrations are highly variable and are an important factor in affecting fish concentration ratios, the less variable K concentrations in saltwater were relatively unimportant in affecting concentration ratios. As a result, the simplest model, which used only trophic level as a predictor, had comparable accuracies to more complex models that also included K concentrations. A test of model accuracy involving comparisons of 56 published concentration ratios from 51 species of marine fish to those predicted by the model indicated that 52 of the predicted concentration ratios were within a factor of 2 of the observed concentration ratios.

The biological effects of ionising radiation on Crustaceans: A review.

Historic approaches to radiation protection are founded on the conjecture that measures to safeguard humans are adequate to protect non-human organisms. This view is disparate with other toxicants wherein well-developed frameworks exist to minimise exposure of biota. Significant data gaps for many organisms, coupled with high profile nuclear incidents such as Chernobyl and Fukushima, have prompted the re-evaluation of our approach toward environmental radioprotection. Elucidating the impacts of radiation on biota has been identified as priority area for future research within both scientific and regulatory communities. The crustaceans are ubiquitous in aquatic ecosystems, comprising greater than 66,000 species of ecological and commercial importance. This paper aims to assess the available literature of radiation-induced effects within this subphylum and identify knowledge gaps. A literature search was conducted pertaining to radiation effects on four endpoints as stipulated by a number of regulatory bodies: mortality, morbidity, reproduction and mutation. A major finding of this review was the paucity of data regarding the effects of environmentally relevant radiation doses on crustacean biology. Extremely few studies utilising chronic exposure durations or wild populations were found across all four endpoints. The dose levels at which effects occur was found to vary by orders of magnitude thus presenting difficulties in developing phyla-specific benchmark values and reference levels for radioprotection. Based on the limited data, mutation was found to be the most sensitive endpoint of radiation exposure, with mortality the least sensitive. Current phyla-specific dose levels and limits proposed by major regulatory bodies were found to be inadequate to protect species across a range of endpoints including morbidity, mutation and reproduction and examples are discussed within. These findings serve to prioritise areas for future research that will significantly advance understanding of radiation-induced effects in aquatic invertebrates and consequently enhance ability to predict the impacts of radioactive releases on the environment.

Development and evaluation of a regression-based model to predict cesium concentration ratios for freshwater fish.

Data from published studies and World Wide Web sources were combined to produce and test a regression model to predict Cs concentration ratios for freshwater fish species. The accuracies of predicted concentration ratios, which were computed using 1) species trophic levels obtained from random resampling of known food items and 2) K concentrations in the water for 207 fish from 44 species and 43 locations, were tested against independent observations of ratios for 57 fish from 17 species from 25 locations. Accuracy was assessed as the percent of observed to predicted ratios within factors of 2 or 3. Conservatism, expressed as the lack of under prediction, was assessed as the percent of observed to predicted ratios that were less than 2 or less than 3. The model's median observed to predicted ratio was 1.26, which was not significantly different from 1, and 50% of the ratios were between 0.73 and 1.85. The percentages of ratios within factors of 2 or 3 were 67 and 82%, respectively. The percentages of ratios that were <2 or <3 were 79 and 88%, respectively. An example for Perca fluviatilis demonstrated that increased prediction accuracy could be obtained when more detailed knowledge of diet was available to estimate trophic level.

Worldwide isotope ratios of the Fukushima release and early-phase external dose reconstruction.

Measurements of radionuclides (RNs) in air made worldwide following the Fukushima accident are quantitatively compared with air and soil measurements made in Japan. Isotopic ratios RN:(137)Cs of (131)I, (132)Te, (134,136)Cs, are correlated with distance from release. It is shown, for the first time, that both within Japan and globally, ratios RN:(137)Cs in air were relatively constant for primarily particle associated radionuclides ((134,136)Cs; (132)Te) but that (131)I shows much lower local (<80 km) isotope ratios in soils relative to (137)Cs. Derived isotope ratios are used to reconstruct external dose rate during the early phase post-accident. Model "blind" tests show more than 95% of predictions within a factor of two of measurements from 15 sites to the north, northwest and west of the power station. It is demonstrated that generic isotope ratios provide a sound basis for reconstruction of early-phase external dose rates in these most contaminated areas.

Predicting phosphorus concentrations in British rivers resulting from the introduction of improved phosphorus removal from sewage effluent.

Phosphorus (P) concentration and flow data gathered during the 1990s for a range of British rivers were used to determine the relative contributions of point and diffuse inputs to the total P load, using the Load Apportionment Model (LAM). Heavily urbanised catchments were dominated by sewage inputs, but the majority of the study catchments received most of their annual phosphorus load from diffuse sources. Despite this, almost 80% of the study sites were dominated by point source inputs for the majority of the year, particularly during summer periods when eutrophication risk is greatest. This highlights the need to reduce sewage P inputs to improve the ecological status of British rivers. These modelled source apportionment estimates were validated against land-use data and boron load (a chemical marker for sewage). The LAM was applied to river flow data in subsequent years, to give predicted P concentrations (assuming no change in P source inputs), and these estimates were compared with observed concentration data. This showed that there had been significant reductions in P concentration in the River Thames, Aire and Ouse in the period 1999 to 2002, which were attributable to the introduction of P stripping at sewage treatment works (STW). The model was then used to forecast P concentrations resulting from the introduction of P removal at STW to a 2 or 1mgl(-1) consent limit. For the urbanised rivers in this study, the introduction of phosphorus stripping to a 1mgl(-1) consent level at all STW in the catchment would not reduce P concentrations in the rivers to potentially limiting concentrations. Therefore, further sewage P stripping will be required to comply with the Water Framework Directive. Diffuse P inputs may also need to be reduced before some of the highly nutrient-enriched rivers achieve good ecological status.

Changes in point and diffuse source phosphorus inputs to the River Frome (Dorset, UK) from 1966 to 2006.

Changes in the relationship between soluble reactive phosphorus (SRP) concentration and river flow between 1966 and 2006 were assessed for the River Frome, UK using the recently developed Load Apportionment Model. The resulting source load estimates gave good agreement with known changes within the catchment. The model indicated an increase in point source contribution to the total river load from 46% to 62% between 1970 and 1985. This corresponded with the population increase within the catchment during that time. The predicted mean SRP load was highest between 1996 and 2000 (30 t y(-1)), with 49% coming from point sources. Despite no lowering in population or major changes in agricultural practice, the model predicted a reduced load of 18.1 t y(-1) for the period 2001 to 2005, due mainly to a decrease in point source inputs from 14.6 t y(-1) to 6.1 t y(-1) (equivalent to 34% of the total load). This prediction matches the major improvements in sewage treatment that occurred within the catchment in 2002. This study thus provides a major validation of the Load Apportionment Model. The model provides an effective and rapid method of determining past changes in phosphorus sources, based entirely on the P concentration - flow relationship: critically, it does not require any historical information on land use, fertiliser application rates, topography, soil types and sewage inputs. Further decreases in SRP concentration in the River Frome during the algal growing season would be best achieved by further reductions of STW inputs.

The role of physical processes controlling the behaviour of radionuclide contaminants in the aquatic environment: a review of state-of-the-art modelling approaches.

This paper is aimed at presenting and discussing the methodologies implemented in state-of-the-art models for predicting the physical processes of radionuclide migration through the aquatic environment, including transport due to water currents, diffusion, settling and re-suspension. Models are briefly described, model parameter values reviewed and values recommended. The different modelling approaches are briefly classified and the advantages and disadvantages of the various model approaches and methodologies are assessed.

Modelling of phosphorus inputs to rivers from diffuse and point sources.

The difference in timing of point and diffuse phosphorus (P) delivery to a river produces clear differences in the P concentration-flow relationship. Point inputs decrease in concentration with increasing river flow, due to dilution of a relatively constant input, whereas diffuse (non-point) load usually increases with river flow. This study developed a simple model, based on this fundamental difference, which allowed point and diffuse inputs to be quantified by modelling their contribution to river P concentration as a power-law function of flow. The relationships between total phosphorus (TP) concentration and river flow were investigated for three contrasting UK river catchments; the Swale (Yorkshire), the Frome (Dorset) and the Avon (Warwickshire). A load apportionment model was fitted to this empirical data to give estimates of point and diffuse load inputs at each monitoring site, at high temporal resolution. The model produced TP source apportionments that were similar to those derived from an export coefficient approach. For many diffuse-dominated sites within this study (with up to 75% of the annual TP load derived from diffuse sources), the model showed that reductions of point inputs would be most effective in order to reduce eutrophication risk, due to point source dominance during the plant and algae growing period. This modelling approach should provide simple, robust and rapid TP source apportionment from most concentration-flow datasets. It does not require GIS, information on land use, catchment size, population or livestock density, and could provide a valuable and versatile tool to catchment managers for determining suitable river mitigation options.

Are passive smoking, air pollution and obesity a greater mortality risk than major radiation incidents?

BACKGROUND: Following a nuclear incident, the communication and perception of radiation risk becomes a (perhaps the) major public health issue. In response to such incidents it is therefore crucial to communicate radiation health risks in the context of other more common environmental and lifestyle risk factors. This study compares the risk of mortality from past radiation exposures (to people who survived the Hiroshima and Nagasaki atomic bombs and those exposed after the Chernobyl accident) with risks arising from air pollution, obesity and passive and active smoking. METHODS: A comparative assessment of mortality risks from ionising radiation was carried out by estimating radiation risks for realistic exposure scenarios and assessing those risks in comparison with risks from air pollution, obesity and passive and active smoking. RESULTS: The mortality risk to populations exposed to radiation from the Chernobyl accident may be no higher than that for other more common risk factors such as air pollution or passive smoking. Radiation exposures experienced by the most exposed group of survivors of Hiroshima and Nagasaki led to an average loss of life expectancy significantly lower than that caused by severe obesity or active smoking. CONCLUSION: Population-averaged risks from exposures following major radiation incidents are clearly significant, but may be no greater than those from other much more common environmental and lifestyle factors. This comparative analysis, whilst highlighting inevitable uncertainties in risk quantification and comparison, helps place the potential consequences of radiation exposures in the context of other public health risks.