Applying DOE's Graded Approach for assessing radiation impacts to non-human biota at the INL

In July 2002, The US Department of Energy (DOE) released a new technical standard entitled A Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota. DOE facilities are annually required to demonstrate that routine radioactive releases from their sites are protective of non-human receptors and sites are encouraged to use the Graded Approach for this purpose. Use of the Graded Approach requires completion of several preliminary steps, to evaluate the degree to which the site environmental monitoring program is appropriate for evaluating impacts to non-human biota. We completed these necessary activities at the Idaho National Laboratory (INL) using the following four tasks: (1) develop conceptual models and evaluate exposure pathways; (2) define INL evaluation areas; (3) evaluate sampling locations and media; (4) evaluate data gaps. All of the information developed in the four steps was incorporated, data sources were identified, departures from the Graded Approach were justified, and a step-by-step procedure for biota dose assessment at the INL was specified. Finally, we completed a site-wide biota dose assessment using the 2002 environmental surveillance data and an offsite assessment using soil and surface water data collected since 1996. These assessments demonstrated the environmental concentrations of radionuclides measured on and near the INL do not present significant risks to populations of non-human biota.     

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.     

Derivation of a screening methodology for evaluating radiation dose to aquatic and terrestrial biota

The United States Department of Energy (DOE) currently has in place a radiation dose standard for the protection of aquatic animals, and is considering additional dose standards for terrestrial biota. These standards are: 10 mGy/d for aquatic animals, 10 mGy/d for terrestrial plants, and, 1 mGy/d for terrestrial animals. Guidance on suitable approaches to the implementation of these standards is needed. A screening methodology, developed through DOE's Biota Dose Assessment Committee (BDAC), serves as the principal element of DOE's graded approach for evaluating radiation doses to aquatic and terrestrial biota. Limiting concentrations of radionuclides in water, soil, and sediment were derived for 23 radionuclides. Four organism types (aquatic animals; riparian animals; terrestrial animals; and terrestrial plants) were selected as the basis for development of the screening method. Internal doses for each organism type were calculated as the product of contaminant concentration, bioaccumulation factor(s) and dose conversion factors. External doses were calculated based on the assumption of immersion of the organism in soil, sediment, or water. The assumptions and default parameters used provide for conservative screening values. The screening methodology within DOE's graded approach should prove useful in demonstrating compliance with biota dose limits and for conducting screening assessments of radioecological impact. It provides a needed evaluation tool that can be employed within a framework for protection of the environment.     

Derivation of hazardous doses for amphibians acutely exposed to ionising radiation

Derivation of effect benchmark values for each taxonomic group, which has been difficult due to lack of experimental effects data, is required for more adequate protection of the environment from ionising radiation. Estimation of effects doses from nuclear DNA mass and subsequent species sensitivity distribution (SSD) analysis were proposed as a method for such a derivation in acute irradiation situations for assumed nuclear accident scenarios. As a case study, 5% hazardous doses (HD₅s), at which only 5% of species are acutely affected at 50% or higher lethality, were estimated on a global scale. After nuclear DNA mass data were obtained from a database, 50% lethal doses (LD₅₀s) for 4.8 and 36% of the global Anura and Caudata species, respectively, were estimated by correlative equations between nuclear DNA mass and LD₅₀s. Differences between estimated and experimental LD₅₀s were within a factor of three. The HD₅s obtained by the SSD analysis of these estimated LD₅₀s data were 5.0 and 3.1 Gy for Anura and Caudata, respectively. This approach was also applied to the derivation of regional HD₅s. The respective HD₅s were 6.5 and 3.2 Gy for Anura and Caudata inhabiting Japan. This HD₅ value for the Japanese Anura was significantly higher than the global value, while Caudata had no significant difference in global and Japanese HD₅s. These results suggest that this approach is also useful for derivation of regional benchmark values, some of which are likely different from the global values.     

Gamma radiation doses to people living in Western Sweden

Indoor environments contribute to gamma radiation in the general population. The aims of the present study were to investigate average gamma radiation doses in a rural and an urban area of Sweden, compare indoor dose rates with personal exposure, and study the effects of building characteristics on radiation levels. Radiation was measured with thermoluminescence dosimeters (TLDs). Repeated measurements were performed with TLDs worn by participants (n=46) and placed in their dwellings. Personal dose rates were 0.092muSv/h (rural) and 0.096muSv/h (urban). The mean effective gamma dose rates in dwellings were 0.091muSv/h (rural) and 0.11muSv/h (urban), which are higher than the world average. Dose rates in apartments were higher than in detached houses and higher for concrete than wooden dwellings. Personal dose rates were strongly associated with dwelling dose rates (r(p)=0.68, p<0.01) and could be modelled. Within-participant variability was low.     

A kinetic-allometric approach to predicting tissue radionuclide concentrations for biota

Allometry, or the biology of scaling, is the study of size and its consequences. It has become a useful tool for comparative physiology. There are several allometric equations that relate body size to many parameters, including ingestion rate, lifespan, inhalation rate, home range and more. While these equations were originally derived from empirical observations, there is a growing body of evidence that these relationships have their origins in the dynamics of energy transport mechanisms. As part of an ongoing effort by the Department of Energy in developing generic methods for evaluating radiation dose to biota, we have examined the utility of applying allometric techniques to predicting radionuclide tissue concentration across a large range of terrestrial and riparian species of animals. This particular study examined 23 radionuclides. Initial investigations suggest that the allometric approach can provide a useful tool to derive limiting values of uptake and elimination factors for animals.     

Dynamic model for the assessment of radiological exposure to marine biota

A generic approach has been developed to simulate dynamically the uptake and turnover of radionuclides by marine biota. The approach incorporates a three-compartment biokinetic model based on first order linear kinetics, with interchange rates between the organism and its surrounding environment. Model rate constants are deduced as a function of known parameters: biological half-lives of elimination, concentration factors and a sample point of the retention curve, allowing for the representation of multi-component release. The new methodology has been tested and validated in respect of non-dynamic assessment models developed for regulatory purposes. The approach has also been successfully tested against research dynamic models developed to represent the uptake of technetium and radioiodine by lobsters and winkles. Assessments conducted on two realistic test scenarios demonstrated the importance of simulating time-dependency for ecosystems in which environmental levels of radionuclides are not in equilibrium.     

Estimation of radiation doses from (137)Cs to frogs in a wetland ecosystem

Currently, there is no established methodology to estimate radiation doses to non-human biota. Therefore, in this study, various dose models were used to estimate radiation doses to moor frogs (Rana arvalis) in a wetland ecosystem contaminated with (137)Cs. External dose estimations were based on activity concentrations of (137)Cs in soil and water, considering changes in habitat over a life-cycle. Internal doses were calculated from the activity concentrations of (137)Cs measured in moor frogs. Depending on the dose model used, the results varied substantially. External dose rates ranged from 21 to 160 mGy/y, and internal dose rates varied between 1 and 14 mGy/y. Maximum total dose rates to frogs were below the expected safe level for terrestrial populations, but close to the suggested critical dose rate for amphibians. The results show that realistic assumptions in dose models are particularly important at high levels of contamination.     

Adaptive response in frogs chronically exposed to low doses of ionizing radiation in the environment

Using the micronucleus assay, decreased levels of DNA damage were found after high dose ionizing radiation exposure of liver cells taken from frogs inhabiting a natural environment with above-background levels of ionizing radiation, compared to cells taken from frogs inhabiting background areas. The data obtained from a small number of animals suggest that stress present in the above-background environment could induce an adaptive response to ionizing radiation. This study did not reveal harmful effects of exposure to low levels of radioactivity. On the contrary, stress present in the above-background area may serve to enhance cellular defense mechanisms.     

An estimation of radiation doses to benthic invertebrates from sediments collected near a Canadian uranium mine.

A new method is described for calculating radiation doses to benthic invertebrates from radionuclide concentrations in freshwater sediment. Both internal and external radiation doses were estimated for all 14 principal radionuclides of the uranium-238 decay series. Sediments were collected from three sites downstream of a uranium mining operation in northern Saskatchewan, Canada. Sediments from two sites, located approximately 1.6 and 4.4 km downstream from mining operations, yielded absorbed doses to both larval midges, Chironomus tentans, and adult amphipods, Hyalella azteca, of 59-60 and 19 mGy/year, respectively, compared to 3.2 mGy/year for a nearby control site. External beta radiation from protactinium-234 (234Pa) and alpha radiation from uranium (U) contributed most of the dose at the impacted sites, whereas polonium-210 (210Po) was most important at the control site. If a weighting factor of 20 was employed for the greater biological effect of alpha vs. beta and gamma radiation, then total equivalent doses rose to 540-560 mGy/year at the site closest to uranium operations. Such equivalent doses are above the 360-mGy/year no-observed-effect level for reproductive effects in vertebrates from gamma radiation exposure. Data are not available to determine the effect of such doses on benthic organisms, but they are high enough to warrant concern. Detrimental effects have been observed in H. azteca at similar uranium concentration in laboratory toxicity tests, but it remains unclear whether the radiotoxicity or the chemotoxicity of uranium is responsible for these effects.     

Preliminary assessment of current radiation doses to the population of Brodokalmak from contamination of the Techa River

Significant quantities of liquid radioactive waste were discharged to the Techa River in the southern Urals region of Russia in the early years of operation of the Mayak PA plant (1948–1951). A collaborative project is underway under contract to the European Commission to consider the radiological impact of radioactive contamination in the Southern Urals. Part of this project involves the calculation of radiation doses currently received by the population of Brodokalmak on the Techa river. The assessment made use of local data on the habits of the population and measurements of radionuclide activity concentrations in food and water. Exposure pathways included in the assessment were ingestion of foods and external exposure to gamma radiation from radionuclides deposited on the banks of the river. A range of doses was calculated for different age groups, firstly, assuming that the restrictions in place are retained and, secondly, assuming that there are no restrictions. These restrictions include bans on drinking river water, fishing and bathing in the river and the prohibition of use of the river and surrounding flood plains by humans and cattle. With restrictions the highest dose estimated was 0.56 mSv y⁻¹ for the most exposed adults and without restrictions this increased to 3.4 mSv y⁻¹.     

Ethics, genetics and dynamics: an emerging systematic approach to radiation protection of the environment

There is now a general consensus of opinion that an explicit approach is necessary to demonstrate radiation protection of the environment, and that this approach needs to be developed in a systematic way. The framework that is emerging links ethical and moral issues (anthropocentric, biocentric, and ecocentric) to broad-based principles and objectives of environmental protection (sustainable development, maintaining biological diversity, and habitat protection) and then links these, in turn, to the needs of current environmental management practices, such as environmental exploitation, pollution control, and nature conservation. The relevance of this to radiation is that its effects (such as causing early mortality, morbidity, reduced reproductive success, as well as resulting in observable (scorable) cytogenetic damage) are those that may have a bearing on these same environmental management practices. The devise that would appear to be most useful to bridge the gap between our disparate data on radiation effects and the needs of environmental management, is that of adding to the concept of Reference Man in the shape of a small set of Reference Animals and Plants. This approach has now been adopted by the ICRP, adding new dynamics-the motive forces, both moral and physical-to the subject. The way is now clear for rapid progress to be made on a number of fronts.     

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.     

The ecological relevance of current approaches for environmental protection from exposure to ionising radiation

This paper discusses the current approaches to environmental protection from ionising radiation from an ecological perspective, highlighting the need to understand fully what we are trying to protect. Ecologically relevant endpoints for environmental protection are discussed along with the need to integrate protection from ionising radiation with the approaches adopted for non-radioactive contaminants. A possible integrated assessment approach is outlined.     

Requirements for estimation of doses from contaminants dispersed by a ‘dirty bomb’ explosion in an urban area

The ARGOS decision support system is currently being extended to enable estimation of the consequences of terror attacks involving chemical, biological, nuclear and radiological substances. This paper presents elements of the framework that will be applied in ARGOS to calculate the dose contributions from contaminants dispersed in the atmosphere after a ‘dirty bomb’ explosion. Conceptual methodologies are presented which describe the various dose components on the basis of knowledge of time-integrated contaminant air concentrations. Also the aerosolisation and atmospheric dispersion in a city of different types of conceivable contaminants from a ‘dirty bomb’ are discussed.     

Learning for change: an educational contribution to sustainability science

Transition to sustainability is a search for ways to improve the social capacity to guide interactions between nature and society toward a more sustainable future and, thus, a process of social learning in its broadest sense. Accordingly, it is not only learning that is at issue but education and educational science, of which the latter is about exploring the preconditions of and opportunities for learning and education—whether individual or social, in formal or informal settings. Analyzing how educational science deals with the challenge of sustainability leads to two complementary approaches: the ‘outside-in’ approach sees the idea of sustainability influencing educational practice and the way the relationship of learning and teaching is reviewed, theoretically as well as within the social context. In an ‘inside-out’ approach, an overview is given of how educational science can contribute to the field of sustainability science. An examination of the literature on education and sustainability shows that, while sustainability features prominently in one form or another across all sectors, only little work can be found dealing with the contributions of educational science within sustainability science. However, as sustainability is a concept that not only influences educational practices but also invites disciplinary contributions to foster inter- and transdisciplinary research within the sustainability discourse, the question remains as to how and to what extent educational science in particular can contribute to sustainability science in terms of an ‘inside-out’ approach. In this paper, we reconstruct the emergence of education for sustainable development as a distinctive field of educational science and introduce and discuss three areas of sustainability research and throw into relief the unique contribution that educational science can make to individual action and behavior change, to organizational change and social learning, and, finally, to inter- and transdisciplinary collaboration.     

Using foraging honeybees to sample an area for trace metals

The metal contents of pollen loads gathered by honeybees have been determined in areas with known concentrations of soil-borne heavy metals. The manganese, zinc, copper, and lead contents of the pollen loads reflected those of the environment, indicating that honeybee colonies might be used to sample areas.