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Data on radionuclide transfer to animals from research performed in the former Soviet Union were reviewed to collate transfer coefficient values (Ff) to animal tissues such as liver, kidney and bone, but not muscle which has previously been reported. The derived values were compared with selected data published in the English language literature. The new data are mainly for 90Sr and 137Cs, although some data were also provided for 3H, 54Mn, 59Fe, 60Co, 22Na 65Zn, 131I and U. The Russian language data may provide a basis for better informed evaluation of radiation dose from the consumption of such animal products, which can form important components of the diet in some countries.

Under the International Atomic Energy Agency (IAEA) MODARIA (Modelling and Data for Radiological Impact Assessments) Programme, there has been an initiative to improve the derivation, provenance and transparency of transfer parameter values for radionuclides from feed to animal products that are for human consumption. A description of the revised MODARIA 2016 cow milk dataset is described in this paper. As previously reported for the MODARIA goat milk dataset, quality control has led to the discounting of some references used in IAEA's Technical Report Series (TRS) report 472 (IAEA, 2010). The number of Concentration Ratio (CR) values has been considerably increased by (i) the inclusion of more literature from agricultural studies which particularly enhanced the stable isotope data of both CR and Fm and (ii) by estimating dry matter intake from assumed liveweight. In TRS 472, the data for cow milk were 714 transfer coefficient (Fm) values and 254 CR values describing 31 elements and 26 elements respectively. In the MODARIA 2016 cow milk dataset, Fm and CR values are now reported for 43 elements based upon 825 data values for Fm and 824 for CR. The MODARIA 2016 cow milk dataset Fm values are within an order of magnitude of those reported in TRS 472. Slightly bigger changes are seen in the CR values, but the increase in size of the dataset creates greater confidence in them. Data gaps that still remain are identified for elements with isotopes relevant to radiation protection.

The quality and quantity of data used to derive transfer parameter values for milk are variable and there are many data gaps for elements/radionuclides which may need to be considered for risk assessment of the agricultural foodchain. There has been a recent focus on critically evaluating current methods to fill data gaps and on identifying extrapolation methods to derive suitable values for the elements, and particularly radioisotopes, with no or sparse data. The relationship between fractional absorption of elements in the ruminant gastrointestinal tract and transfer to milk has been explored to determine whether knowledge of the former can be used to predict the latter. A relationship has been derived between fractional absorption of elements and two empirical ratios commonly used to quantify transfer to milk; transfer coefficients (element concentration in milk divided by element daily intake) and concentrations ratios (concentration in milk divided by concentration in feed). We propose that fractional absorption may be used to predict the order of magnitude of the transfer to milk of elements/radionuclides for which no relevant data have yet been identified or collated.

The transfer characteristics of (137)Cs, (85)Sr and (65)Zn to earthworms (Eisenia andrei) in soils with different amounts of the radionuclides have been investigated. The time-dependent whole-body concentration ratios (CR) were derived for worms in artificially contaminated soils with three different activity concentrations. Two parameters of a first order kinetic model, the equilibrium concentration ratio (CR(eq)) and the effective loss rate constant (k), were estimated by a comparison of experimental CR results with model predictions. The estimated CR(eq) (Bq/kg fresh worm per Bq/kg dry soil) ranged from 3.9 × 10(-4) to 4.1 × 10(-3) for (137)Cs, 1.39 × 10(-3) to 2.94 × 10(-2) for (85)Sr, and 1.39 × 10(-3) to 5.0 × 10(-2) for (65)Zn, and consistently decreased with increasing soil activity concentration but the trend was not statistically significant. The CR(eq) for (137)Cs was one to two orders of magnitude lower than previously reported CR(wo-soil) values (based on field data with much less contaminated soil), that for (85)Sr was comparable with other reported values and for (65)Zn was less two to three orders of magnitude lower than CR(wo-soil) values for stable zinc. The estimated k (d(-1)) values ranged from 9 × 10(-2) to 1.4 × 10(-1) for (137)Cs, 7 × 10(-2) to 2 × 10(-1) for (85)Sr, and 6 × 10(-2) to 1.8 × 10(-1) for (65)Zn, and did not show a relationship with soil activity concentration. The effect of CR(eq) on the total dose rate was insignificant for (137)Cs or (65)Zn because external dose rates to the soil dwelling earthworms due to these radionuclides were much greater than the internal dose rate. In contrast, the total dose from (90)Sr was determined by the internal dose rate and therefore proportional to the CR(eq).

A new TRS document on Transfer of radionuclides to Wildlife has compiled equilibrium CR(wo-media) values for a variety of radionuclides and ecosystems. Assessment tools such as the ERICA Tool use equilibrium whole organism concentration ratios (CR(wo-media)) to predict radionuclide activity concentrations in wildlife from those in media (e.g. water). The aim of this paper is to compare and contrast model predictions of doses from (137)Cs to marine organisms using three different approaches: (i) the ERICA Tool utilising the new TRS values to estimate internal and external doses to reference organisms for the Black sea and the Aegean Sea and for the sea close to the Fukushima Dai-ichi plant. (ii) a hydrodynamic site specific model for seawater for parts of the Aegean Sea, Greece which estimates radionuclide concentrations using site specific data and (iii) a biokinetic model for fish applied to the Fukushima releases to the Pacific. The advantages and limitations of these approaches are discussed with respect to determining doses to pelagic fish. The applicability of the three approaches will vary with the objective of an assessment. The site specific model can predict variation in (137)Cs with depth and uses site specific CR values. The application of the biokinetic model to predicted (137)Cs activity concentrations in seawater and fish due to near coastal inputs from Fukushima Dai-ichi showed that the maximum internal dose-rates in fish attributable to (137)Cs would be substantially lower than those determined using equilibrium assumptions in ERICA but the accumulative doses over 100 days were similar.

A number of approaches are now being used to assess the exposure and associated risk to organisms other than humans from ionizing radiation. The assessment of the exposure of wildlife to ionizing radiation requires (i) quantification of the transfer of radionuclides to wildlife and (ii) dose conversion coefficients relating internal and media activity concentrations to estimate absorbed dose rates to wildlife. Most commonly used models estimate dose rates to the whole organism (Beresford et al., 2008 and Vives i Batlle et al., 2010). This approach allows model outputs to be put into context with the available data on the effects of ionizing radiation, which are typically presented as absorbed dose rates to the whole organism so that the risk to wildlife can then be considered (International Commission on Radiation Protection, 2008, Copplestone et al., 2008, Andersson et al., 2009 and Howard et al., 2010). Through model testing and comparison using scenarios, the Biota Working Group (BWG) during the first International Atomic Energy Agency's (IAEA) EMRAS Programme (2003–2007) demonstrated that the dosimetric components of the various available models gave broadly comparable results, but that differences in the transfer components used within the models resulted in large variations in predicted whole organism activity concentrations and resultant internal doses (Beresford et al., 2008, Beresford et al., 2009,Beresford et al., 2010, Yankovich et al., 2010, International Atomic Energy Agency, 2012 and Vives I Batlle et al., 2007). Therefore, the EMRAS BWG recommended that an international handbook on estimating transfer of radionuclides to wildlife be developed. In response, Working Group 5 (WG5) was created within the EMRAS II Programme (2009–2011) to prepare a handbook of readily available quantitative information on the transfer of radionuclides to wildlife (http://www-ns.iaea.org/projects/emras/emras2/). The Wildlife Transfer Technical report Series Handbook (Wildlife TRS) (IAEA, in press) provides transfer parameter values for estimating the transfer of radionuclides from environmental media (soil, and water) to generic wildlife groups, for the purpose of assessing potential internal absorbed dose rates. It is analogous to Technical Report Series No. 472 (IAEA, 2010), which presents transfer parameter values for human foodstuffs. Equilibrium transfer parameter values are provided for wildlife groups in terrestrial, freshwater, marine and brackish (low salinity) environments. The data are intended for use where site-specific data are not available, and to parameterise the initial screening assessment levels of models. The derivation and content of the Wildlife TRS has been briefly described and summarised by Howard et al. (2013a).

Following the Fukushima accident in March 2011, grass samples were collected from 42 sites around Great Britain during April 2011. Iodine-131 was measurable in grass samples across the country with activity concentrations ranging from 10 to 55 Bq kg(-1) dry matter. Concentrations were similar to those reported in other European countries. Rainwater and some foodstuffs were also analysed from a limited number of sites. Of these, (131)I was only detectable in sheep's milk (c. 2 Bq kg(-1)). Caesium-134, which can be attributed to releases from the Fukushima reactors, was detectable in six of the grass samples (4-8 Bq kg(-1) dry matter); (137)Cs was detected in a larger number of grass samples although previous release sources (atmospheric weapons test and the 1986 Chernobyl and 1957 Windscale accidents) are likely to have contributed to this.

Since the Fukushima Dai-ichi accident, monitoring of tissues from hunted game animals ensures compliance with the standard food limits for radionuclides in Japan. We quantified the transfer of (137)Cs from contaminated land to game animals using the Aggregated transfer factor (Tag = activity concentration in meat [Bq kg(-1) fw]/amount in soil [Bq m(-2)]) of (137)Cs for Asian black bear, wild boar, sika deer, green pheasant, copper pheasant and wild duck, collected between 2011 and 2015. Open data sources were used from Fukushima, Miyagi, Ibaraki, Tochigi, and Gunma prefectures. Our initially compiled data showed that the maximum reported (137)Cs activity concentration in wild boar after the Fukushima Dai-ichi accident were lower than those reported after the Chernobyl accident. The geometric mean Tag values (m(2)kg(-1) fw) of (137)Cs in 2015 for Asian black bear, wild boar, sika deer and copper pheasant were similar (1.9-5.1) × 10(-3) while those for green pheasant and wild duck were about 1 order of magnitude lower at (1.0-2.2) × 10(-4). Effective half-lives were 1.2-6.9 y except for sika deer and copper pheasant where no decreases were found. In contrast to the Chernobyl accident, no seasonal change occurred in the meat (137)Cs activity concentrations of the wild animals during the study period.

Information has been complied on the fractional absorption of a range of radionuclides by adult domestic ruminants. Critical analysis of these data has enabled the derivation of recommended values for fractional absorption which will form part of the new handbook of parameter values for the prediction of radionuclide transfer in terrestrial and freshwater environments to be published by the International Atomic Energy Agency. Whilst most data considered were for caesium, strontium and iodine, values for 23 other radionuclides are also given. The recommended fractional absorption values are presented here, together with descriptions of the literature used to derive them. The values for domestic ruminants are compared with those derived by the International Commission for Radiological Protection for adult humans.

Databases have been compiled to derive parameter values relevant to the transfer of radionuclides from feedstuffs to domestic animal products to provide a revision to the IAEA Handbook on transfer parameters TRS 364. Significant new data inputs have been incorporated into the databases from an extensive review of Russian language information and inclusion of data published since the early 1990s. Fractional gastrointestinal absorption in adult ruminants presented in the revised handbook are generally similar to those recommended for adult humans by the ICRP. Transfer coefficient values are presented in the handbook for a range of radionuclides to farm animal products. For most animal products, transfer coefficient values for elements additional to those in TRS 364 are provided although many data gaps remain. Transfer coefficients generally vary between species with larger species having lower values than smaller species. It has been suggested that the difference is partly due to the inclusion of dietary dry matter intake in the estimation of transfer coefficient and that whilst dietary intake increases with size nutrient concentrations do not. An alternative approach to quantifying transfer by using concentration ratios (CR), which do not consider dietary intake, has been evaluated. CR values compiled for the handbook vary considerably less between species than transfer coefficient values. The advantage of the CR approach is that values derived for one species could be applied to species for which there are no data. However, transfer coefficients will continue to be used as few studies currently report CR values or give data from which they can be estimated.

Few data are available to quantify the transfer of both natural and anthropogenic radionuclides to detritivorous invertebrates to facilitate estimation of the internal dose to such biota in models used to assess radiation exposure. To enhance the available data, activity concentrations of (137)Cs, (40)K, (90)Sr, (239 + 240)Pu, (241)Am, (235)U and (238)U were measured in ants (Formicidae) and corresponding undisturbed soil collected from the Zlatibor mountain in Serbia and ant/soil concentration ratios (CR) calculated. The (241)Am concentration ratios for ants were fourfold higher than those calculated for ants in a previous study whereas they are similar to the more numerous data previously reported for a range of detritivorous invertebrates in other studies. CR values for (137)Cs in ants were similar to the few other reported values and slightly lower than those for a range of detritivorous invertebrates. Those for (239 + 240)Pu were slightly higher than those for ants in two other studies but they were close to upper limit of a range of data reported for detritivorous invertebrates. All the CR values will be included in a future revision of the ERICA Tool database and will particularly improve the information available for uranium.

Over 150 publications reporting studies conducted in the former USSR were reviewed to provide transfer coefficients (F(f)) to the muscle of domestic animals from experiments using chronic administration, often for long timescales in large scale experiments. Only a few of these studies were made available in the English language literature or taken into account in international reviews. The values derived have been compared with expected values reported by the IAEA's Handbook of parameter values for the prediction of radionuclide transfer in temperate environments (TRS 364) where possible. The information presented here has been used in the current updating of parameters recommended for environmental assessments by the IAEA. Many of the reported values are for Sr due to the Mayak accident and Cs due to the Chernobyl accident. Nevertheless, the reported data for a wide range of radionuclides, in particular for Ru, Sb, and Zn markedly improve the extent of available data.

An essential step in the development of any modelling tool is the validation of its predictions. This paper describes a study conducted within the Chernobyl exclusion zone to acquire data to conduct an independent test of the predictions of the ERICA Tool which is designed for use in assessments of radiological risk to the environment. Small mammals were repeatedly trapped at three woodland sites between early July and mid-August 2005. Thermoluminescent dosimeters mounted on collars were fitted to Apodemus flavicollis, Clethrionomys glareolus and Microtus spp. to provide measurements of external dose rate. A total of 85 TLDs were recovered. All animals from which TLDs were recovered were live-monitored to determine (90)Sr and (137)Cs whole-body activity concentrations. A limited number of animals were also analysed to determine (239,240)Pu activity concentrations. Measurements of whole-body activity concentrations and dose rates recorded by the TLDs were compared to predictions of the ERICA-Tool. The predicted (90)Sr and (137)Cs mean activity concentrations were within an order of magnitude of the observed data means. Whilst there was some variation between sites in the agreement between measurements and predictions this was consistent with what would be expected from the differences in soil types at the sites. Given the uncertainties of conducting a study such as this, the agreement observed between the TLD results and the predicted external dose rates gives confidence to the predictions of the ERICA Tool.

A number of models have recently been, or are currently being, developed to enable the assessment of radiation doses from ionising radiation to non-human species. A key component of these models is the ability to predict whole-organism activity concentrations in a wide range of wildlife. In this paper, we compare the whole-organism activity concentrations predicted by eight models participating within the IAEA Environmental Modelling for Radiation Safety programme for a range of radionuclides to terrestrial and freshwater organisms. In many instances, there was considerable variation, ranging over orders of magnitude, between the predictions of the different models. Reasons for this variability (including methodology, data source and data availability) are identified and discussed. The active participation of groups responsible for the development of key models within this exercise is a useful step forward in providing the transparency in methodology and data provenance required for models which are either currently being used for regulatory purposes or which may be used in the future. The work reported in this paper, and supported by other findings, demonstrates that the largest contribution to variability between model predictions is the parameterisation of their transfer components. There is a clear need to focus efforts and provide authoritative compilations of those data which are available.

Following the Chernobyl accident in 1986, restrictions were placed on the movement and slaughter of sheep within upland areas of the UK because radiocaesium activity concentrations in their meat exceeded 1000 Bq kg(-1) fresh weight. Some farms remain under restriction in 2007. From 1991 to 1993 detailed studies were conducted on three sheep farms within the restricted area of west Cumbria to systematically assess the various parameters which may contribute to the observed variability in radiocaesium activity concentrations within sheep flocks. This paper reports the spatial variation in soil and vegetation activity concentrations across the grazed areas at these farms and determines the influence of grazing behaviour on variability in (137)Cs activity concentrations between individual sheep within the flocks. Together with previously reported results, these new data are used to draw conclusions on the factors determining variability within the three flocks. However, the factors are too site specific to be able to generalise the findings to other farms within the restricted areas of the UK.

Sulphur-35 is released during the routine operation of UK gas-cooled reactors. An experiment to determine the rates of transfer of different forms of (35)S to goat milk is described. Lactating goats received (35)S orally as single administrations of sulphate, L-methionine, or grass contaminated either through root uptake of (35)S as sulphate or through aerial deposition of (35)S as carbonyl sulphide onto the grass. Transfer was higher for (35)S administered as methionine compared with (35)S administered as sulphate. Changes in activity concentrations in milk for all sources of (35)S demonstrated two components of loss. The first component had a half-life of circa 1 d for all sources, the second was longer in goats administered carbonyl sulphide (44 d) than in all of the other treatments (circa 10 d). The rate of transfer of (35)S to milk of a further group of goats receiving (35)S-sulphate daily appeared to reach equilibrium within 30 d. Extrapolation of transfer parameters derived to other dairy ruminants is discussed.

Radionuclides released into the Irish Sea by the Sellafield reprocessing plant are deposited onto tide-washed pastures along the western coast of the United Kingdom. Many of these pastures are grazed by sheep or cattle. This paper describes a controlled feeding study, in which saltmarsh vegetation harvested from close to the Sellafield plant, was fed to lambs and adult female sheep for a period of 8 weeks. Activity concentrations of (60)Co, (95)Nb, (106)Ru, (134)Cs, (137)Cs, (238)Pu, (239,240)Pu and (241)Am were determined in edible tissues and transfer parameters estimated. The activity concentrations of some of the radionuclides will not have been in equilibrium with those in the diet. Nevertheless, the study was reasonably realistic in terms of agricultural management as the period of the study was similar to that for which lambs graze on the saltmarshes. A field study to determine the activity concentrations of (137)Cs and (239,240)Pu in the milk of ewes grazing a saltmarsh close to Sellafield is also described.

A study to measure the transfer of radiocaesium to adult female sheep through a breeding cycle is described. The transfer of radiocaesium from the diet to muscle (estimated as the equilibrium transfer coefficient) was significantly lower to pregnant, and especially lactating, animals compared to non-lactating and barren animals. High dry matter intake rates were also associated with significantly lower transfer coefficients. Known relationships between dry matter intake rates and protein turnover could credibly explain some of these differences. However, when described as the concentration ratio, radiocaesium transfer to meat was apparently highest during lactation. The apparent difference in results obtained by the two approaches of determining transfer is the consequence of daily dry matter intake being a denominator within the estimation of transfer coefficient. A wider discussion of transfer coefficients and concentration ratios leads us to suggest that the concentration ratio is the more robust and potentially generic parameter.

Cl-36 is an important component of nuclear waste. The concentrations of stable chlorine (Cl) in pig and cow tissues were measured to provide information which can be used to parameterize models of (36)Cl transfer into agricultural animals. The concentration of stable Cl in cows' milk was 1.0 +/- 0.2 g L(-1), in cow muscle it was 0.7 +/- 0.2 g kg(-1) wet mass (wm) and in pig muscle 0.4 +/- 0.1 g kg(-1) wm. The concentration of stable Cl in cow and pig liver was 0.9 +/- 0.3 g kg(-1) wm, which was about two-fold higher than that in the kidney and lung. Due to homeostatic control, stable Cl concentrations in animal tissues are not related to the amount ingested daily in herbage at intake rates in the normal physiological range of up to 188 g day(-1) for cows and up to 40 g day(-1) for pigs. Therefore, the commonly used transfer coefficient is not suitable for use in quantifying the transfer of (36)Cl to milk and meat. Since the metabolism of stable Cl and (36)Cl in an animal's body is identical, the average equilibrium ratios of (36)Cl to stable Cl in the daily ration ((36)Cl (g kg(-1))/Cl (g kg(-1))) and animal tissues will be the same. We therefore conclude that the average equilibrium Cl isotopic ratio in the dietary daily intake should be used to predict the contamination of meat and milk with (36)Cl.

A number of assessment frameworks have been proposed to provide a mechanism to demonstrate protection of the environment from ionising radiation. Whilst some of these are being used for assessment purposes they have largely not been validated against field measurements. In this paper we compare the predictions of transfer parameters recommended by one of these frameworks (FASSET) with observed whole-body 90Sr and radiocaesium activity concentrations in a range of mammal and invertebrate species sampled within the Chernobyl exclusion zone. Predicted activity concentrations were generally within the observed ranges and mean predictions for reference organisms were similar to, or circa one order of magnitude higher than, the observed means. However, some predictions were more than one order of magnitude lower than observed values. No data were available to test predictions for the other radionuclides released by the Chernobyl accident. In a separate paper the outputs of this assessment will be used to estimate doses to reference organisms and compare these to observed radiation induced effects reported within the Chernobyl zone.

Assessment of the transfer of radionuclides to wild species is an important component in the estimation of predicted doses to biota. Reviews of available data for the many potential radionuclide-biota combinations which may be required for environmental assessments highlight many data gaps for terrestrial species. Here, we discuss different approaches which have been suggested to compensate for these data gaps. All of the reviewed approaches have merit; however, there is a requirement for transparency in methodology and data provenance which in some instances is currently missing. Furthermore, there is a need to validate the various methodologies to enable their use with confidence. The requirements of improving our ability to predict radionuclide transfer to wild species are discussed and recommendations made.

Experience after the Chernobyl accident has shown that restoration strategies need to consider a wide range of different issues to ensure the long-term sustainability of large and varied contaminated areas. Thus, the criteria by which we evaluate countermeasures need to be extended from simple cost-benefit effectiveness and radiological protection standards to a more integrated, holistic approach, including social and ethical aspects. Within the STRATEGY project, the applicability of many countermeasures is being critically assessed using a wide range of criteria. Attention is being given to issues such as practicability, feasibility, capacity and environmental side-effects, as well as social factors such as public perceptions of risk, communication of information and the need for dialogue and consultation with affected communities, and ethical aspects such as informed consent and the fair distribution of costs and doses. Although such socio-ethical factors are now the subject of a substantial field of research, there has been little attempt to integrate them in a practical context for decision makers. Within this paper, we specifically consider the ethical aspects of restoration strategies and suggest practical means by which these can be taken into account in the decision making process, introducing a value matrix. The paper covers two critical areas: evaluation of individual countermeasures, and use of the matrix to ensure transparent and systematic consideration of values in selection of a restoration strategy.

In this paper a compartment model of the highly vulnerable Arctic terrestrial food chain "lichen-reindeer-man" is outlined. Based upon an analysis of measured (137)Cs and (90)Sr contents in lichen and reindeer meat from 1961 up to 2001, site specific model parameters for two regions in north-western Arctic Russia and for Kautokeino municipality in Arctic Norway have been determined. The dynamics of radionuclide activity concentrations in the "lichen-reindeer-man" food chain for all areas was satisfactorily described by a double exponential function with short-term and long-term effective ecological half-lives between 1-2 and 10-12 years, respectively, for both (137)Cs and (90)Sr. Using parameter values derived from the model, life-time internal effective doses due to consumption of reindeer meat by reindeer-breeders after an assumed single pulse deposit of 1 kBq m(-2) of (137)Cs were estimated to be 11.4 mSv (Kola Peninsula), 5 mSv (Nenets Autonomous Area), and 2 mSv (Kautokeino, Norway). Differences in vulnerability to radiocaesium deposition were due to differences in transfer between lichen and reindeer and in diet between the three regions.

Previous discharges of radioactivity from the Mayak Production Association plant in the Urals have resulted in considerable radionuclide contamination of the Techa River, and consequent high radiation doses during the late 1940s and 1950s to residents of villages along the Techa river. The most contaminated villages close to the site were evacuated in the period 1954-1962. The objective of this recent study was to conduct a preliminary assessment of the current radioactive contamination of soil, vegetation and foodstuffs in the two remaining villages closest to the Mayak site, Muslyumovo and Brodokalmak. The highest contamination levels in soil were found in the floodplain at 5.5 MBq m(-2) for 137Cs and 1.0 MBq m(-2) for 90Sr. Radionuclide contamination in soil of the villages was much lower, but exceeded that expected from global fallout. Data from 1207 measurements of 137Cs in milk and 1180 for 90Sr in milk for the period 1992-1999 were collated. There was no change with time in the 90Sr or 137Cs activity concentration in milk over the measured period. There were significantly higher 137Cs activity concentrations in milk sampled during the housed winter period in Muslyumovo compared with the grazing summer period, but compared to that for Brodokalmak or for either settlement for 90Sr. The highest measured activity concentrations in food products of 137Cs and 90Sr were found in river fish, waterfowl, poultry and milk. The measured activity concentrations of 137Cs and 90Sr in some animal products were higher than that expected from soil and vegetation from fields and pasture in the villages (not including the floodplain) confirming that the highly contaminated floodplains are contributing to contamination of some animal products.

Arctic residents, whose diets comprise a large proportion of traditional terrestrial and freshwater foodstuffs, have received the highest radiation exposures to artificial radionuclides in the Arctic. Doses to members of both the average population and selected indigenous population groups in the Arctic depend on the rates of consumption of locally-derived terrestrial and freshwater foodstuffs, including reindeer/caribou meat, freshwater fish, goat cheese, berries, mushrooms and lamb. The vulnerability of arctic populations, especially indigenous peoples, to radiocaesium deposition is much greater than for temperate populations due to the importance of terrestrial, semi-natural exposure pathways where there is high radiocaesium transfer and a long ecological half-life for this radionuclide. In contrast, arctic residents with diets largely comprising marine foodstuffs have received comparatively low radiation exposures because of the lower levels of contamination of marine organisms. Using arctic-specific information, the predicted collective dose is five times higher than that estimated by UNSCEAR for temperate areas. The greatest threats to human health and the environment posed by human and industrial activities in the Arctic are associated with the potential for accidents in the civilian and military nuclear sectors. Of most concern are the consequences of potential accidents in nuclear power plant reactors, during the handling and storage of nuclear weapons, in the decommissioning of nuclear submarines and in the disposal of spent nuclear fuel from vessels. It is important to foster a close association between risk assessment and practical programmes for the purposes of improving monitoring, formulating response strategies and implementing action plans.

Over the last decade, there has been considerable progress in the development of countermeasures for preventing or reducing contamination of animal products by radioisotopes of iodine, caesium and strontium. In this paper, recent significant technical improvements are summarised and the current availability of countermeasures and their usefulness in the event of a nuclear accident reviewed. An improved understanding of factors controlling the metabolism of radioiodine and radiostrontium has enabled previously suggested countermeasures to be either optimised or dismissed. For radiocaesium in particular, experience since the Chernobyl accident has enabled effective and feasible countermeasures to be identified and successfully implemented in different situations. It has also been more widely understood that countermeasure effectiveness, although important, is not the only criterion which needs to be determined. In addition, cost and practical considerations such as availability, technical feasibility, acceptability and side-effects need to be taken into account. Evaluation of these factors has shown that some previously recommended countermeasures are unlikely to be feasible.

Concentration ratios (CRwo-media) are used in most radioecological models to predict\ud whole-body radionuclide activity concentrations in wildlife from those in environmental media. This\ud simplistic approach amalgamates the various factors influencing transfer within a single generic value\ud and, as a result, comparisons of model predictions with site-specific measurements can vary by orders\ud of magnitude. To improve model predictions, the development of 'condition-specific' CRwo-media\ud values has been proposed (e.g. for a specific habitat). However, the underlying datasets for most\ud CRwo-media value databases, such as the wildlife transfer database (WTD) developed within the IAEA\ud EMRAS II programme, include summarised data. This presents challenges for the calculation and\ud subsequent statistical evaluation of condition-specific CRwo-media values. A further complication is\ud the common use of arithmetic summary statistics to summarise data in source references, even though\ud CRwo-media values generally tend towards a lognormal distribution and should, therefore, be\ud summarised using geometric statistics. In this paper, we propose a statistically-defensible and robust\ud method for reconstructing underlying datasets to calculate condition-specific CRwo-media values from\ud summarised data and deriving geometric summary statistics. This method is applied to terrestrial\ud datasets from the WTD. Statistically significant differences in sub-category CRwo-media values (e.g.\ud mammals categorised by feeding strategy) were identified, which may justify the use of these CRwomedia\ud values for specific assessment contexts. However, biases and limitations within the underlying\ud datasets of the WTD explain some of these differences. Given the uncertainty in the summarised\ud CRwo-media values, we suggest that the CRwo-media approach to estimating transfer is used with\ud caution above screening-level assessments.

Hexacyanoferrates have been identified as highly effective radiocaesium binders which effectively reduce radiocaesium uptake and transfer to milk and meat. In Russia a hexacyanoferrate called ferrocyn has been produced for use as a countermeasure. In 1989-1992, experiments were undertaken in Russia to study the effectiveness of four different ferrocyn materials as 137Cs binders, their potential toxicity, effect on production rates of cow milk, effect on animal health and ease of implementation in routine agricultural practice. Four different ferrocyn delivery forms have been used: 98% pure powder, sustained release rumen boli (15% ferrocyn), salt licks (10% ferrocyn) and sawdust with 10% ferrocyn adsorbed (bifege). In initial experiments with different cows, sheep and pigs these four ferrocyn materials were effective in reducing radiocaesium transfer to animal products. Daily administration of ferrocyn powder at a rate of 3-5 g per cow reduced 137Cs transfer by up to 90% in milk. One single administration of three boli per cow (containing 30 g ferrocyn per boli) reduced 137Cs transfer by 50-75% for a period of 2 months. Salt licks containing 10% ferrocyn (0.22 kg ferrocyn per 2.2 kg briquette provided once) reduced transfer of 137Cs up to twofold for up to 10 days whilst bifege, given at a rate of 30-60 g day-1 (3-6 g day-1 ferrocyn), reduced 137Cs transfer by 90-95%. However, large-scale application of these ferrocyn materials on collective and private farms in agricultural trials in 1994 resulted in a lower effectiveness. Therefore, in 1996 a comparative assessment of the application of the four ferrocyn forms was made under carefully controlled conditions. The results fully validated the previous experimental data, and showed the importance of meeting recommended procedures for treatment, particularly when hexacyanoferrates are administered on a day-to-day basis.

The results of a study in which groups of sheep were given single oral administrations of 14C, 3H and 35S and then slaughtered over a period of 1 year are reported. The experimental data were used to investigate the potential of metabolically based models for describing the transfer of the three radionuclides to sheep tissues. The structure of these models is based upon a simplified understanding of the transfer of the macro-elements C, H and S by processes such as respiration and protein synthesis/degradation. A consequence of this approach is that the three models have many common parameters. The models reproduced the general trends of the observations, accounting for 74%, 66%, and 58% of the observed variation in the 14C, 3H and 35S data, respectively, suggesting that they may provide a useful alternative approach to modelling the transfer of these radionuclides. The models presented are limited to the particular experimental situation for which they were developed, and further experimental work would be required to extend them. However, such metabolically based models have great potential: for example, they should be able to account for the influence of dietary intake, physiological status or the form of the radionuclide in the animals diet (e.g. tritiated water or organically bound tritium).

Limitations of existing methods to describe the bioavailability of dietary radionuclides to ruminants (the transfer coefficient and apparent absorption coefficient) have led to the alternative suggestion of using the true absorption coefficient (A(t)). Various approaches to estimating A(t) for radiocaesium, involving the intravenous administration of a second isotope, are presented and discussed with reference to results from studies in which a range of radiocaesium sources were examined in sheep. Although estimates of A(t) differed between the sources, they were reasonably consistent between measurement techniques. Those methods which involved the estimation of endogenous faecal excretion of radiocaesium could be used with previously contaminated animals and did not require continuous administrations of radiocaesium isotopes, but gave unreliable results for sources of low bioavailability. Methods based on estimating the turnover rate of dietary radiocaesium through blood plasma were sufficiently sensitive to measure A(t) for the range of sources studied. However, they require previously uncontaminated animals and continuous administration of both isotopes for approximately 7 days. Bioavailability is more effectively measured as A(t) than as the transfer or apparent absorption coefficients since A(t) does not incorporate factors relating to the metabolism of radiocaesium in the tissues of the animal. The results of these studies show that differences in transfer coefficients between sheep and cattle and between sheep of differing ages are not due to variation in absorption across the gut. The potential for applying these approaches to other radioactive elements is discussed.

The model of radiocaesium transfer to sheep presented by Galer et al. [1] provides reliable predictions only for sheep of a similar body weight to those used in the development of the model (approximately 30 kg). To extend the applicability of the model, it was necessary to re-parameterise it in terms of activity concentrations in tissues rather than total activities within them (although for gut compartments the use of activity has been retained). The rate coefficients for the new model have been estimated by fitting the model to the data used by Galer et al. [1] which was derived from a single “calibration” experiment. The new model was found to account for 94% of the observed variation in the data (n=42), a result similar to that obtained by Galer et al. [1]. The model has also been tested against data not used in its development but obtained from four separate experiments undertaken by three different laboratories. Good agreement between the predictions of the new model and observations was found for most circumstances and for several breeds of sheep with different body weights. It is concluded that the new model provides a useful dynamic description of radiocaesium transfers to the tissues of sheep of different breeds and under different contamination scenarios.

The validity of an in vitro extraction technique to predict the availability for absorption of radiocaesium in the sheep gut has been assessed. The technique (a 2-h extraction with caesium chloride) was found to be valid for sources with a low availability for transfer across the gut, but inappropriate for ionic radiocaesium or radiocaesium incorporated internally within herbage. For such radiocaesium sources, which have a high in vitro availability, no correlation was found between in vitro extraction and true absorption measurements. A true absorption value of 0.80 is recommended for these sources, although values for individual sheep in the range 0.60 to 1.00 should be expected.

An IAEA handbook presenting transfer parameter values for wildlife has recently been produced. Concentration ratios (CRwo-media) between the whole organism (fresh weight) and either soil (dry weight) or water were collated for a range of wildlife groups (classified taxonomically and by feeding strategy) in terrestrial, freshwater, marine and brackish generic ecosystems. The data have been compiled in an on line database, which will continue to be updated in the future providing the basis for subsequent revision of the Wildlife TRS values. An overview of the compilation and analysis, and discussion of the extent and limitations of the data is presented. Example comparisons of the CRwo-media values are given for polonium across all wildlife groups and ecosystems and for molluscs for all radionuclides. The CRwo-media values have also been compared with those currently used in the ERICA Tool which represented the most complete published database for wildlife transfer values prior to this work. The use of CRwo-media values is a pragmatic approach to predicting radionuclide activity concentrations in wildlife and is similar to that used for screening assessments for the human food chain. The CRwo-media values are most suitable for a screening application where there are several conservative assumptions built into the models which will, to varying extents, compensate for the variable data quality and quantity, and associated uncertainty. © 2012 Elsevier Ltd.

The transfer coefficient of 110mAg to a range of sheep tissues and its biological half-life in these tissues has been determined. Liver was shown to be the major site of 110mAg deposition and retention, with a transfer coefficient of Ff 7.1 d kg-1 and a biological half-life of 79 d. These results also suggest that previous estimates of the transfer of silver to muscle were too high, although further work would be required to confirm this. There is a need for accurate data which can be used to predict the transfer of 110mAg to food-producing animals.

Radiological doses to terrestrial wildlife were examined in this model inter-comparison study that emphasised factors causing variability in dose estimation. The study participants used varying modelling approaches and information sources to estimate dose rates and tissue concentrations for a range of biota types exposed to soil contamination at a shallow radionuclide waste burial site in Australia. Results indicated that the dominant factor causing variation in dose rate estimates (up to three orders of magnitude on mean total dose rates) was the soil-to-organism transfer of radionuclides that included variation in transfer parameter values as well as transfer calculation methods. Additional variation was associated with other modelling factors including: how participants conceptualised and modelled the exposure configurations (two orders of magnitude); which progeny to include with the parent radionuclide (typically less than one order of magnitude); and dose calculation parameters, including radiation weighting factors and dose conversion coefficients (typically less than one order of magnitude). Probabilistic approaches to model parameterisation were used to encompass and describe variable model parameters and outcomes. The study confirms the need for continued evaluation of the underlying mechanisms governing soil-to-organism transfer of radionuclides to improve estimation of dose rates to terrestrial wildlife. The exposure pathways and configurations available in most current codes are limited when considering instances where organisms access subsurface contamination through rooting, burrowing, or using different localised waste areas as part of their habitual routines.

Initial information since the releases of radioactive materials from the Fukushima Daiichi nuclear power plant, in Japan, shows that some animal food products are contaminated with 131I (mostly milk) and, to a lesser extent with 134Cs and 137Cs. Current knowledge on the transfer of these radioisotopes to animal products and available relevant countermeasures and management options to reduce radiation doses to humans are summarized. Much of this knowledge was obtained during the years of global fallout from atmospheric nuclear weapons tests and the response to the Chernobyl accident, in Ukraine in 1986.

Under the International Atomic Energy Agency (IAEA)'s EMRAS (Environmental Modelling for Radiation Safety) programme, activity concentrations of (60)Co, (90)Sr, (137)Cs and (3)H in Perch Lake at Atomic Energy of Canada Limited's Chalk River Laboratories site were predicted, in freshwater primary producers, invertebrates, fishes, herpetofauna and mammals using eleven modelling approaches. Comparison of predicted radionuclide concentrations in the different species types with measured values highlighted a number of areas where additional work and understanding is required to improve the predictions of radionuclide transfer. For some species, the differences could be explained by ecological factors such as trophic level or the influence of stable analogues. Model predictions were relatively poor for mammalian species and herpetofauna compared with measured values, partly due to a lack of relevant data. In addition, concentration ratios are sometimes under-predicted when derived from experiments performed under controlled laboratory conditions representative of conditions in other water bodies.

The outcome of the PROTECT project (Protection of the Environment from Ionising Radiation in a Regulatory Context) is summarised, focusing on the protection goal and derivation of dose rates which may detrimentally affect wildlife populations. To carry out an impact assessment for radioactive substances, the estimated dose rates produced by assessment tools need to be compared with some form of criteria to judge the level of risk. To do this, appropriate protection goals need to be defined and associated predefined dose rate values, or benchmarks, derived and agreed upon. Previous approaches used to estimate dose rates at which there may be observable changes in populations or individuals are described and discussed, as are more recent derivations of screening benchmarks for use in regulatory frameworks. We have adopted guidance and procedures used for assessment and regulation of other chemical stressors to derive benchmarks. On the basis of consultation with many relevant experts, PROTECT has derived a benchmark screening dose rate, using data on largely reproductive effects to derive species sensitivity distributions, of 10μGyh-1 which can be used to identify situations which are below regulatory concern with a high degree of confidence. © 2010 IOP Publishing Ltd.

Dose rate benchmarks are required in the tiered approaches used to screen out benign exposure scenarios in radiological ecological risk assessment. Such screening benchmarks, namely the predicted no-effect dose rates (PNEDR), have been derived by applying, as far as possible, the European guidance developed for chemicals. To derive the ecosystem level (or generic) PNEDR, radiotoxicity EDR10 data (dose rates giving a 10% effect in comparison with the control) were used to fit a species sensitivity distribution (SSD) and estimate the HDR5 (the hazardous dose rate affecting 5% of species with a 10% effect). Then, a multi-criteria approach was developed to justify using an assessment factor (AF) to apply to the HDR5 for estimating a PNEDR value. Several different statistical data treatments were considered which all gave reasonably similar results. The suggested generic screening value of 10 μGyh-1 (incremental dose rate) was derived using the lowest available EDR10 value per species, an unweighted SSD, and an AF of 2 applied to the estimated HDR5. Consideration was also given to deriving screening benchmark values for organism groups but this was not thought to be currently appropriate due to few relevant data being currently available. © 2010 IOP Publishing Ltd.

Environmental monitoring programs often measure contaminant concentrations in animal tissues consumed by humans (e.g., muscle). By comparison, demonstration of the protection of biota from the potential effects of radionuclides involves a comparison of whole-body doses to radiological dose benchmarks. Consequently, methods for deriving whole-body concentration ratios based on tissue-specific data are required to make best use of the available information. This paper provides a series of look-up tables with whole-body:tissue-specific concentration ratios for non-human biota. Focus was placed on relatively broad animal categories (including molluscs, crustaceans, freshwater fishes, marine fishes, amphibians, reptiles, birds and mammals) and commonly measured tissues (specifically, bone, muscle, liver and kidney). Depending upon organism, whole-body to tissue concentration ratios were derived for between 12 and 47 elements. The whole-body to tissue concentration ratios can be used to estimate whole-body concentrations from tissue-specific measurements. However, we recommend that any given whole-body to tissue concentration ratio should not be used if the value falls between 0.75 and 1.5. Instead, a value of one should be assumed.

A review of studies conducted before and after the Chernobyl accident is presented, showing that both the duration and the extent of radiocesium contamination of ruminants will be more severe in unimproved ecosystems compared with agricultural areas. Although such unimproved ecosystems provide comparatively small quantities of food for human consumption, the integrated dose from these areas to the human population can be large. Ecological characteristics that make unimproved ecosystems particularly vulnerable to this form of pollution include the presence of (1) soils that do not immobilize radiocesium and therefore allow its uptake into vegetation; (2) vegetation species with high uptake rates of radiocesium; (3) the predominant utilization by small ruminants which attain higher muscle radiocesium levels than cattle. Unimproved ecosystems, which often are located at high altitudes, are predisposed to receiving higher fallout because of high precipitation rates which enhance the likelihood of deposition. Countermeasures have been developed and used successfully to reduce radiocesium levels in ruminants grazing in unimproved ecosystems. Apart from decontamination by altering farming practices and providing uncontaminated feeds, sustained reductions of 50% to 80% in the radiocesium concentrations of both milk and meat have been achieved in many ruminant species when AFCF is given via a sodium chloride lick or as a sustained-release bolus. Food production in unimproved ecosystems must be evaluated separately from that of ordinary agricultural systems. In addition to detailed studies on the behavior of radiocesium, consideration should be given to the collection of aggregated transfer coefficients from various ecosystems which were affected by Chernobyl fallout. By combining bioavailability estimates and aggregated transfer coefficients, based on Chernobyl and nuclear weapons test fallout data, it may in the future be possible to make a rapid assessment of both the immediate and the long-term impact of a future nuclear accident on food production in unimproved ecosystems.

Soil ingestion has been identified as a potentially important source of radionuclides to grazing animals. Seasonal patterns of soil adherence to vegetation and its implications for the radionuclide intake of grazing animals were measured at two west Cumbrian sites. Soil adhesion to vegetation was highly seasonal, being highest in autumn and winter. At Site 1 (a lowland pasture close to the British Nuclear Fuels plc Sellafield Reprocessing Plant, Cumbria, UK), vegetation samples were found to consist of up to 46% soil (by dry weight). Therefore, the importance of soil as a potential source of radionuclides to grazing animals was also seasonal; soil comprised up to 92% of the 137Cs and potentially all of the 239/240Pu of vegetation samples at Site 1 and up to 62% of the 137Cs at Site 2 (an upland farm contaminated following the Chernobyl accident). Analyses of sheep faecal samples confirmed the seasonal importance of soil as a potential source of radionuclides. The importance of soil adhering to vegetation, as a source of contaminant 137Cs, increased with time after the Chernobyl accident. Calculations of soil ingestion must be made when the intake of radionuclides by grazing animals is being studied. In some circumstances, present radioecological models may considerably underestimate the importance of soil ingestion.

Criteria are needed to be able to judge the level of risk associated with dose rates estimated for non-human biota. In this paper, European guidance on the derivation of predicted no-effect chemical concentrations has been applied to appropriate radiation sensitivity data. A species sensitivity distribution fitted to the data for all species resulted in a generic predicted no-effect dose rate of 10 μGy h−1. Currently, data are inadequate to derive screening values for separate organism groups. A second, higher, benchmark could aid in decision making by putting results into context on the scale of no effect to a risk of ‘serious’ effect. The need for, meaning and use of such a value needs to be debated by the wider community. This paper explores potential approaches of deriving scientific input to this debate. The concepts proposed in this paper are broadly consistent with the framework for human protection.

An ability to predict radionuclide activity concentrations in biota is a requirement of any method assessing the exposure of biota to ionising radiation. Within the ERICA Tool fresh weight whole-body activity concentrations in organisms are estimated using concentration ratios (the ratio of the activity concentration in the organism to the activity concentration in an environmental media). This paper describes the methodology used to derive the default terrestrial ecosystem concentration ratio database available within the ERICA Tool and provides details of the provenance of each value for terrestrial reference organisms. As the ERICA Tool considers 13 terrestrial reference organisms and the radioisotopes of 31 elements, a total of 403 concentration ratios were required for terrestrial reference organisms. Of these, 129 could be derived from literature review. The approaches taken for selecting the remaining values are described. These included, for example, assuming values for similar reference organisms and/or biogeochemically similar elements, and various simple modelling approaches.

The EC-funded project 'Environmental Risks from Ionising Contaminants: Assessment and Management' (ERICA) developed an 'Integrated Approach' for assessing the impact of ionising radiation on ecosystems. This paper presents the application of the ERICA Integrated Approach, supported by a software programme (the ERICA Tool) and guidance documentation, to an assessment of the Drigg coastal sand dunes (Cumbria, UK). Targeted sampling provided site-specific data for sand dune biota, including amphibians and reptiles. Radionuclides reported included (90)Sr, (99)Tc, (137)Cs, (238)Pu, (239+240)Pu and (241)Am. Site-specific data were compared to predictions derived using the ERICA Tool. Some under- and over-predictions of biota activity concentrations were identified but can be explained by the specific ecological characteristics and contamination mechanism of the dunes. Overall, the results indicated no significant impact of ionising radiation on the sand dune biota and the Integrated Approach was found to be a flexible and effective means of conducting a radiation impact assessment.

A compilation has been undertaken of data which can be used to derive animal product transfer coefficients for radionuclides, including an extensive review of Russian language information. The resultant database has been used to provide recommended transfer coefficient values for a range of radionuclides to (i) cow, sheep and goat milk, (ii) meat (muscle) of cattle, sheep, goats, pigs and poultry and (iii) eggs. The values are used in a new IAEA handbook on transfer parameters which replaces that referred to as 'TRS 364'. The paper outlines the approaches and procedures used to identify and collate data, and assumptions used. There are notable differences between the TRS 364 'expected' values and the recommended values in the revised Handbook from the new database. Of the recommended values, three milk values are at least an order of magnitude higher than the TRS 364 values (Cr, Pu (cow) Pu (sheep)) and one milk value is lower (Ni (cow)). For meat, four values (Am, Cd, Sb (beef) I (pork)) are at least an order of magnitude higher than the TRS 364 values and eight values are at least an order of magnitude lower (Ru, Pu (beef), Ru, Sr, Zn (sheep), Ru, Sr (pork), Mn (poultry)). Many data gaps remain.

A number of approaches have been proposed to estimate the exposure of non-human biota to ionizing radiation. This paper reports an inter-comparison of the unweighted absorbed dose rates for the whole organism (compared as dose conversion coefficients, or DCCs) for both internal and external exposure, estimated by 11 of these approaches for selected organisms from the Reference Animals and Plants geometries as proposed by the International Commission on Radiological Protection. Inter-comparison results indicate that DCCs for internal exposure compare well between the different approaches, whereas variation is greater for external exposure DCCs. Where variation among internal DCCs is greatest, it is generally due to different daughter products being included in the DCC of the parent. In the case of external exposures, particularly to low-energy β-emitters, variations are most likely to be due to different media densities being assumed. On a radionuclide-by-radionuclide basis, the different approaches tend to compare least favourably for 3H, 14C and the α-emitters. This is consistent with models with different source/target geometry assumptions showing maximum variability in output for the types of radiation having the lowest range across matter. The intercomparison demonstrated that all participating approaches to biota dose calculation are reasonably comparable, despite a range of different assumptions being made. © 2007 Springer-Verlag.

The hypothesis is tested that there is a generic relationship between the calcium intake and the transfer of radiostrontium to milk which can be used for all dairy ruminants. In addition to the daily calcium intake, the relationship also requires values for the strontium to calcium observed ratio, which describes the discrimination in transfer of the two elements to milk (a value of 0.11 is used), and the calcium concentration in milk. The relationship had previously only been validated for dairy cattle as there were insufficient data for other ruminant species. Here, we present recently available data for dairy goats, and also a limited amount of data for sheep derived from the literature. From the comparison between these data and predicted values, we conclude that it is possible to derive a generic model of the transfer of radiostrontium to the milk of dairy ruminants.

An extensive programme of experiments was conducted in the former USSR on transfer of radionuclides to a wide range of different agricultural animals. Only a few of these studies were made available in the English language literature or taken into account in international reviews of gastrointestinal uptake. The paper gives extended information on Russian research on radionuclide absorption in the gut of farm animals performed in controlled field and laboratory experiments from the 1960s to the current time. The data presented in the paper, together with English language values, will be used to provide recommended values of absorption specifically for farm animals within the revision of the IAEA Handbook of Parameter Values IAEA [International Atomic Energy Agency, 1994. Handbook of Parameter Values for the Prediction of Radionuclide Transfer in Temperate Environments, IAEA technical reports series No. 364. International Atomic Energy Agency, Vienna].

In summer 1993 we measured the transfer of (239/240)Pu to milk from herbage from a pasture located 5 km from the Chernobyl nuclear power plant. In one treatment cows were allowed to graze freely on the pasture. In a second treatment, cows were fed herbage collected from the pasture in stalls. The milk transfer coefficient; F(m) did not vary significantly between treatments and the mean value of 7.5x10(-6)d l(-1) was higher than previously reported values. Despite many values of F(m) for Pu in the literature we identified few relevant original data sets. Transfer coefficient values for Pu are only appropriate when used in conjunction with a specified time period or an appropriate model which allows for the biological half-life. We recommend for screening purposes an F(m) value of 1x10(-5)d l(-1) for Pu, with an order of magnitude lower value being appropriate for cows which are only exposed for one grazing season.