Issues and practices in the use of effects data from FREDERICA in the ERICA Integrated Approach

The ERICA Integrated Approach requires that a risk assessment screening dose rate is defined for the risk characterisation within Tiers 1 and 2. At Tier 3, no numerical screening dose rate is used, and the risk characterisation is driven by methods that can evaluate the possible effects of ionising radiation on reproduction, mortality and morbidity. Species sensitivity distribution has been used to derive the ERICA risk assessment predicted no-effect dose rate (PNEDR). The method used was based on the mathematical processing of data from FRED (FASSET radiation effects database merged with the EPIC database to form FREDERICA) and resulted in a PNEDR of 10 microGy/h. This rate was assumed to ascribe sufficient protection of all ecosystems from detrimental effects on structure and function under chronic exposure. The value was weighed against a number of points of comparison: (i) PNEDR values obtained by application of the safety factor method, (ii) background levels, (iii) dose rates triggering effects on radioactively contaminated sites and (iv) former guidelines from literature reviews. In Tier 3, the effects analysis must be driven by the problem formulation and is thus highly case specific. Instead of specific recommendations on numeric values, guidance on the sorts of methods that may be applied for refined effect analysis is provided and illustrated.     

An overview of the ERICA Integrated Approach to the assessment and management of environmental risks from ionising contaminants

The ERICA project (environmental risks from ionising contaminants: assessment and management, EC contract no. FI6R-CT-2004-508847) concluded with the publication of two main outputs: the ERICA Integrated Approach to the assessment and management of environmental risks from ionising radiation, of which also introduces the user to the second main output, the ERICA Tool, which is a software programme with supporting databases, that together with its associated help will guide users through the assessment process. More than 60 European scientists contributed to the ERICA Integrated Approach. In addition, a large number of experts, policy makers, and decision-makers in different areas have contributed views on the ERICA Integrated Approach and its associated Tool from the user's perspective, through participation in the End-Users Group set up under the ERICA project. Databases on transfer, dose conversion coefficients and radiation effects on biota have been developed specifically for the purpose of the Integrated Approach, and incorporated into, or interacting with, the Tool. Species sensitivity distributions of biological effects data have been performed and did not reveal, for chronic exposure, any statistical grounds for separation between terrestrial, marine and freshwater ecosystems in terms of species sensitivity to radiation; on the basis of such analysis a universal screening dose rate criterion of 10 microGy h(-1) incremental dose rate is suggested for exiting the assessment procedure while being confident that environmental risks are negligible. This criterion is used for the two first tiers (conservative assessment with limited data requirement and various possibilities of incorporating user-defined parameter values, including the screening dose rate criterion) of the assessment methodology. Exposure situations of concern are carried through a third tier, making use of all relevant databases and with a number of issues and options listed to support and guide decision-making. This article provides an overview to the ERICA Integrated Approach, whereas further articles of this special issue describe in-depth different vital aspects of the Integrated Approach.     

Transfer of radionuclides in aquatic ecosystems--default concentration ratios for aquatic biota in the Erica Tool

The process of assessing risk to the environment following a given release of radioactivity requires the quantification of activity concentrations in environmental media and reference organisms. The methodology adopted by the ERICA Integrated Approach involves the application of concentration ratios (CR values) and distribution coefficients (K(d) values) for aquatic systems. Within this paper the methodologies applied to derive default transfer parameters, collated within the ERICA Tool databases, are described to provide transparency and traceability in the documentation process. Detailed information is provided for the CR values used for marine and freshwater systems. Of the total 372 CR values derived for the marine ecosystem, 195 were identified by literature review. For the freshwater system, the number of values based on review was less, but still constituted 129 from a total of 372 values. In both types of aquatic systems, 70-80% of the data gaps have been filled by employing "preferable" approaches such as those based on substituting values from taxonomically similar organisms or biogeochemically similar elements.     

Application of the ERICA Assessment Tool to freshwater biota in Finland

In recent years there has been growing international interest in the assessment of doses and risks from ionising contaminants to biota. In this study the ERICA Tool, developed within the EC 6th Framework Programme, was applied to estimate incremental dose rates to biota in freshwater ecosystems in Finland mainly resulting from exposure to the Chernobyl-derived radionuclides ¹³⁷Cs, ¹³⁴Cs and ⁹⁰Sr. Data sets consisting of measured activity concentrations in fish, aquatic plants, lake water and sediment for three selected lakes located in a region with high ¹³⁷Cs deposition were applied in the assessment. The dose rates to most species studied were clearly below the screening level of 10 μGy h⁻¹, indicating no significant impact of the Chernobyl fallout on these species. However, the possibility of higher dose rates to certain species living on or in the bottom sediment cannot be excluded based on this assessment.     

Derivation of transfer parameters for use within the ERICA Tool and the default concentration ratios for terrestrial biota

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.     

Assessing radiation impact at a protected coastal sand dune site: an intercomparison of models for estimating the radiological exposure of non-human biota

This paper presents the application of three publicly available biota dose assessment models (the ERICA Tool, R&D128/SP1a and RESRAD-BIOTA) to an assessment of the Drigg coastal sand dunes. Using measured ⁹⁰Sr, ⁹⁹Tc, ¹³⁷Cs, ²³⁸Pu, ^239+240Pu and ²⁴¹Am activity concentrations in sand dune soil, activity concentration and dose rate predictions are made for a range of organisms including amphibians, birds, invertebrates, mammals, reptiles, plants and fungi. Predicted biota activity concentrations are compared to measured data where available. The main source of variability in the model predictions is the transfer parameters used and it is concluded that developing the available transfer databases should be a focus of future research effort. The value of taking an informed user approach to investigate the way in which models may be expected to be applied in practice is highlighted and a strategy for the future development of intercomparison exercises is presented.     

Application of the ERICA Integrated Approach to the Drigg coastal sand dunes

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.     

Methods for calculating dose conversion coefficients for terrestrial and aquatic biota

Plants and animals may be exposed to ionizing radiation from radionuclides in the environment. This paper describes the underlying data and assumptions to assess doses to biota due to internal and external exposure for a wide range of masses and shapes living in various habitats. A dosimetric module is implemented which is a user-friendly and flexible possibility to assess dose conversion coefficients for aquatic and terrestrial biota. The dose conversion coefficients have been derived for internal and various external exposure scenarios. The dosimetric model is linked to radionuclide decay and emission database, compatible with the ICRP Publication 38, thus providing a capability to compute dose conversion coefficients for any nuclide from the database and its daughter nuclides. The dosimetric module has been integrated into the ERICA Tool, but it can also be used as a stand-alone version.     

Decision-making in environmental radiation protection: using the ERICA Integrated Approach

The ERICA Integrated Approach and its associated tool and databases provide a method by which the likely impact of radioactive discharges on the environment can be evaluated, see Fig. 1. The various factors, which should be taken into account when making decisions both during and after an assessment has been made, are discussed for each stage in the assessment process for a hypothetical case study. The assessment will demonstrate the issues associated with the decision-making process at Tiers 1 and 2 within the ERICA Tool and how they may vary. The case study, set in England, evaluates the environmental impact of radioactive substances released under authorisation in response primarily to conservation legislation, because of the need to demonstrate that no adverse impacts will occur on Natura 2000 sites as a result of the release of an authorised substance.     

Background exposure rates of terrestrial wildlife in England and Wales

It has been suggested that, when assessing radiation impacts on non-human biota, estimated dose rates due to anthropogenically released radionuclides should be put in context by comparison to dose rates from natural background radiation. In order to make these comparisons, we need data on the activity concentrations of naturally occurring radionuclides in environmental media and organisms of interest. This paper presents the results of a study to determine the exposure of terrestrial organisms in England and Wales to naturally occurring radionuclides, specifically (40)K, (238)U series and (232)Th series radionuclides. Whole-body activity concentrations for the reference animals and plants (RAPs) as proposed by the ICRP have been collated from literature review, data archives and a targeted sampling campaign. Data specifically for the proposed RAP are sparse. Soil activity concentrations have been derived from an extensive geochemical survey of the UK. Unweighted and weighted absorbed dose rates were estimated using the ERICA Tool. Mean total weighted whole-body absorbed dose rates estimated for the selected terrestrial organisms was in the range 6.9 x 10(-2) to 6.1 x 10(-1) microGy h(-1).     

Estimating the exposure of small mammals at three sites within the Chernobyl exclusion zone--a test application of the ERICA Tool

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.     

Addressing uncertainties in the ERICA Integrated Approach

Like any complex environmental problem, ecological risk assessment of the impacts of ionising radiation is confounded by uncertainty. At all stages, from problem formulation through to risk characterisation, the assessment is dependent on models, scenarios, assumptions and extrapolations. These include technical uncertainties related to the data used, conceptual uncertainties associated with models and scenarios, as well as social uncertainties such as economic impacts, the interpretation of legislation, and the acceptability of the assessment results to stakeholders. The ERICA Integrated Approach has been developed to allow an assessment of the risks of ionising radiation, and includes a number of methods that are intended to make the uncertainties and assumptions inherent in the assessment more transparent to users and stakeholders. Throughout its development, ERICA has recommended that assessors deal openly with the deeper dimensions of uncertainty and acknowledge that uncertainty is intrinsic to complex systems. Since the tool is based on a tiered approach, the approaches to dealing with uncertainty vary between the tiers, ranging from a simple, but highly conservative screening to a full probabilistic risk assessment including sensitivity analysis. This paper gives on overview of types of uncertainty that are manifest in ecological risk assessment and the ERICA Integrated Approach to dealing with some of these uncertainties.     

A model for radiological consequences of nuclear power plant operational atmospheric releases

A dynamic dose and risk assessment model is developed to estimate radiological consequences of atmospheric emissions from nuclear power plants. Internal exposure via inhalation and ingestion, external exposure from clouds and radioactivity deposited on the ground are included in the model. The model allows to simulate interregional moves of people and multi-location food supply in the computational domain. Any long-range atmospheric dispersion model which yields radionuclide concentrations in air and on the ground at predetermined time intervals can easily be integrated into the model. The software developed is validated against radionuclide concentrations measured in different environmental media and dose values estimated after the Chernobyl accident. Results obtained using the model compare well with dose estimates and activities measured in foodstuffs and feedstuffs.     

Stakeholder interaction within the ERICA Integrated Approach

Within the ERICA project, stakeholder involvement has been addressed within three main areas: generic interactions throughout the project, specific consultation by means of attendance to events and considerations as part of the ERICA Integrated Approach and Assessment Tool. The word stakeholders meant namely any individual or group who may be affected by or have an interest in an issue, and to include experts, lay-people and the public. An End-Users-Group (EUG) was set up to facilitate the two-way dialogue between the ERICA Consortium and stakeholders. The ERICA EUG consisted of representatives of 60 organisations ranging from regulatory bodies, national advisory bodies, academia, non-governmental organisations, industry, consultants and inter-governmental organisations. Stakeholder interaction was included from the very start of the project. Inputs from the EUG were recorded and in most instances incorporated within the development of the project and thus influenced and helped to shape some of the ERICA deliverables.     

Dose assessment for marine biota and humans from discharge of (131)I to the marine environment and uptake by algae in Sydney, Australia

Iodine-131 reaches the marine environment through its excretion to the sewer by nuclear medicine patients followed by discharge through coastal and deepwater outfalls. ¹³¹I has been detected in macroalgae, which bio-accumulate iodine, growing near the coastal outfall of Cronulla sewage treatment plant (STP) since 1995. During this study, ¹³¹I levels in liquid effluent and sludge from three Sydney STPs as well as in macroalgae (Ulva sp. and Ecklonia radiata) growing near their shoreline outfalls were measured. Concentration factors of 176 for Ulva sp. and 526 for E. radiata were derived. Radiation dose rates to marine biota from ¹³¹I discharged to coastal waters calculated using the ERICA dose assessment tool were below the ERICA screening level of 10 μGy/hr. Radiation dose rates to humans from immersion in seawater or consumption of Ulva sp. containing ¹³¹I were three and two orders of magnitude below the IAEA screening level of 10 μSv/year, respectively.     

Features of Prooxidant and Antioxidant Systems of Greater Plantain <Emphasis Type="Italic">Plantago major</Emphasis> Growing for a Long Time under Conditions of Radioactive Contamination

The viability and state of the prooxidant and antioxidant systems of Plantago major seed progeny from cenopopulations growing for a long time at the East-Ural Radioactive Trace (EURT) has been estimated. Radiation doses of maternal plants have been calculated using our empirical data in ERICA Tool. The absorbed dose rates for plantain in the EURT zone varied from 19 to 157 μGy/h, which is 178–1455 times higher than the background values. These relatively low levels of chronic irradiation did not cause a significant decrease in the survival rate of P. major seed progeny; the rate of root and leaf growth decreased only in seedlings from the most polluted cenopopulation. A prooxidant shift was revealed in seedlings from the EURT zone. Given the same regime of enzyme protection (SOD, CAT, and POX) against active oxygen forms, the average rate of accumulation of secondary products of lipid peroxidation (MDA) was 3.3 times higher in impact samples than in background samples. The level of prooxidant shift in impact samples is not linearly related to dose rates that are classified as low doses.     

Extension of sensitivity and uncertainty analysis for long term dose assessment of high level nuclear waste disposal sites to uncertainties in the human behaviour

Biosphere dose conversion factors are computed for the French high-level geological waste disposal concept and to illustrate the combined probabilistic and deterministic approach. Both ¹³⁵Cs and ⁷⁹Se are used as examples. Probabilistic analyses of the system considering all parameters, as well as physical and societal parameters independently, allow quantification of their mutual impact on overall uncertainty. As physical parameter uncertainties decreased, for example with the availability of further experimental and field data, the societal uncertainties, which are less easily constrained, particularly for the long term, become more and more significant. One also has to distinguish uncertainties impacting the low dose portion of a distribution from those impacting the high dose range, the latter having logically a greater impact in an assessment situation. The use of cumulative probability curves allows us to quantify probability variations as a function of the dose estimate, with the ratio of the probability variation (slope of the curve) indicative of uncertainties of different radionuclides. In the case of ¹³⁵Cs with better constrained physical parameters, the uncertainty in human behaviour is more significant, even in the high dose range, where they increase the probability of higher doses. For both radionuclides, uncertainties impact more strongly in the intermediate than in the high dose range. In an assessment context, the focus will be on probabilities of higher dose values. The probabilistic approach can furthermore be used to construct critical groups based on a predefined probability level and to ensure that critical groups cover the expected range of uncertainty.     

Background and anthropogenic radionuclide derived dose rates to freshwater ecosystem: nuclear power plant cooling pond: reference organisms

The radiological assessment of non-human biota to demonstrate protection is now accepted by a number of international and national bodies. Therefore, it is necessary to develop a scientific basis to assess and evaluate exposure of biota to ionizing radiation. Radionuclides from the Ignalina Nuclear Power Plant (Lithuania) were discharged into Lake Druksiai cooling pond. Additional radionuclide migration and recharge to this lake from a hypothetical near-surface, low-level radioactive waste disposal, to be situated 1.5 km from the lake, had been simulated using RESRAD-OFFSITE code. This paper uses ERICA Integrated Approach with associated tools and databases to compare the radiological dose to freshwater reference organisms. Based on these data, it can be concluded that background dose rates to non-human biota in Lake Druksiai far exceed those attributable to anthropogenic radionuclides. With respect the fishery and corresponding annual committed effective human dose as a result of this fish consumption Lake Druksiai continues to be a high-productivity water body with intensive angling and possible commercial fishing.     

Occurrence and behaviour of radionuclides in the Moselle River-Part II: Distribution of radionuclides between aqueous phase and suspended matter

Most of the radionuclides released from nuclear power plants ( NPPs) into rivers are primarily adsorbed onto suspended matter. To describe this nuclide transfer, a model was used which takes the total suspended matter load as solid phase into account. The necessary partition factors of various radionuclides were determined in river water/suspended matter of the Moselle in laboratory investigations. By use of this model, a conservative estimate of the radionuclide concentration of the solid phase could be obtained which proved to be more realistic than the results based on the distribution law.Furthermore, the influence of grain-size on the specific activity of single fractions of a Moselle sediment was demonstrated using ¹³⁷Cs, ¹⁰⁶Ru and ¹⁴⁴Ce from the Chernobyl nuclear accident as tracers. The grain-size pattern is considered to be a main factor which may seriously distort the determination of distribution coefficients and concentration factors that are needed in applying the model based on the distribution law.