[Assessment of Erythropoiesis Status in Roach (Rutilus rutilus) of the Radioactively Contaminated Techa River].

At present volumetric activity of ß-emitting radionuclides in water at various locations of the Techa River ranges from 5 to 40-Bq/L; a specific activity of ß-emitting radionuclides in the bottom sediments at various locations ranges 10 Ito 106 Bq/kg dry weight. A significant increase of the erythroblast content in blood as compared to that in the roach from the reference watercourse (the Miass River) was observed during spawning in the spring. Due to this fact the number of erythrocytes was equal to that in the control animals under chronic radiation exposure at the dose rates of 0.9 and 16 µGy/day, and was insufficient at the dose rate of 108 gGy/day. During summer feeding no changes in the indexes of erythropoiesis in roach were observed under chronic radiation exposure at the dose rate of 0.9 µGy/day; the number of erythrocytes in the peripheral blood declines when the dose rates are 16 and 108 µGy/day. When performing a regression analysis, we revealed a dose-rate-dependent decrease in the absolute number of erythrocytes, normocytes, polychromatocytes, dividing and non-dividing erythroid cells in the peripheral blood of roach from the Techa River and an increase of a relative number of normochromatophylic erythrocytes.

Overview of dose assessment developments and the health of riverside residents close to the "Mayak" PA facilities, Russia.

The Norwegian Radiation Protection Authority (NRPA) has been involved in studies related to the Mayak PA and the consequences of activities undertaken at the site for a number of years. This paper strives to present an overview of past and present activities at the Mayak PA and subsequent developments in the quantification of health effects on local populations caused by discharges of radioactive waste into the Techa River. Assessments of doses to affected populations have relied on the development of dose reconstruction techniques for both external and internal doses. Contamination levels are typically inhomogeneous and decrease with increasing distance from the discharge point. Citations made in this paper give a comprehensive, though not exhaustive, basis for further reading about this topic.

[Intergrated assessment of the radioecological state of the biota in Moscow water objects].

The paper presents the results of studying the regularities and distribution pattern of natural radionuclides (potassium-40, thorium-232), as well as the representatives of the uranium family (radium-226, polonium-210) and the technogenic isotope cesium-137 in different objects of the water ecosystem in the North-Western District of Moscow (bottom sediment, hydrobiota). Some radiation parameters of these objects (the total alpha- and beta-activities of the radionuclides, their specific effective activity are given. On the basis of the experimental findings, the authors have made an assessment of the radioecological situation in the water pool of the district examined.

Dose distribution measurements and calculations for Dounreay hot particles.

Discrete fragments of irradiated nuclear fuel have been discovered on the foreshore at the Dounreay nuclear site in Scotland, offshore on the seabed and at nearby beaches which have public access. The fragments contain mainly (137)Cs and (90)Sr/(90)Y and for particles recovered to date, (137)Cs activities are within the range of 10(3) to 10(8) Bq. The most active particles found at Sandside Beach contain approximately 3 x 10(5)Bq (137)Cs. Direct measurements of the spatial dose distributions from 37 fuel fragments were measured in detail for the first time using radiochromic dye film as part of a national evaluation of the associated potential radiological hazard. Monte Carlo code calculations of the doses are in good agreement with measurements, taking into account variations to be expected due to differences in shape and the increasing importance of self-absorption for the larger, more active fragments. Dose measurements provide little evidence for wide variations in the (137)Cs:(90)Sr/(90)Y ratio between fragments. Specific attention is given to the evaluation of skin dose, averaged over an area of 1 cm(2) at a depth of 0.07 mm, since this is of major radiological concern. There is no obvious dependence of skin dose on the site of origin of the fragments (foreshore, seabed or beaches) for a given (137)Cs activity level. A dose rate survey instrument (SmartION) was shown to provide a rapid and convenient method for skin dose assessment from fuel fragments in the (137)Cs activity range measured (2 x 10(5) to 2 x 10(7) Bq). A conversion factor multiplier of 240 can be applied to the open window SmartION scale reading to estimate the skin dose rate within +/-25%.

Science, policy, and stakeholders: developing a consensus science plan for Amchitka Island, Aleutians, Alaska.

With the ending of the Cold War, the US Department of Energy is responsible for the remediation of radioactive waste and disposal of land no longer needed for nuclear material production or related national security missions. The task of characterizing the hazards and risks from radionuclides is necessary for assuring the protection of health of humans and the environment. This is a particularly daunting task for those sites that had underground testing of nuclear weapons, where the radioactive contamination is currently inaccessible. Herein we report on the development of a Science Plan to characterize the physical and biological marine environment around Amchitka Island in the Aleutian chain of Alaska, where three underground nuclear tests were conducted (1965-1971). Information on the ecology, geology, and current radionuclide levels in biota, water, and sediment is necessary for evaluating possible current contamination and to serve as a baseline for developing a plan to ensure human and ecosystem health in perpetuity. Other information required includes identifying the location of the salt water/fresh water interface where migration to the ocean might occur in the future and determining groundwater recharge balances, as well as assessing other physical/geological features of Amchitka near the test sites. The Science Plan is needed to address the confusing and conflicting information available to the public about radionuclide risks from underground nuclear blasts in the late 1960s and early 1970s, as well as the potential for volcanic or seismic activity to disrupt shot cavities or accelerate migration of radionuclides into the sea. Developing a Science Plan involved agreement among regulators and other stakeholders, assignment of the task to the Consortium for Risk Evaluation with Stakeholder Participation, and development of a consensus Science Plan that dealt with contentious scientific issues. Involvement of the regulators (State of Alaska), resource trustees (U S Fish and Wildlife Service), representatives of the Aleut and Pribilof Island communities, and other stakeholders was essential for plan development and approval, although this created tensions because of the different objectives of each group. The complicated process of developing a Science Plan involved iterations and interactions with multiple agencies and organizations, scientists in several disciplines, regulators, and the participation of Aleut people in their home communities, as well as the general public. The importance of including all parties in all phases of the development of the Science Plan was critical to its acceptance by a broad range of regulators, agencies, resource trustees, Aleutian/Pribilof communities, and other stakeholders.

Generic performance assessment for a deep repository for low and intermediate level waste in the UK--a case study in assessing radiological impacts on the natural environment.

Concentrations of radionuclides in soil and surface water, taken from a generic performance assessment of a repository for low and intermediate level radioactive waste, assumed to be located in the UK, have been used as the basis for a case study in assessing radiological impacts on the natural environment. Simplified descriptions of the terrestrial and aquatic ecosystem types likely to be impacted have been developed. A scoping assessment has identified (226)Ra, (210)Po, (234)U, (230)Th and (238)U as having the highest potential for impact, with doses from internally incorporated alpha emitters as being potentially of particular importance. These nuclides, together with (36)Cl and (129)I (which have proved to be of importance in radiological risk assessments for humans) were included in a more detailed dose assessment. A basic methodology for dose assessment of ecosystems is described, and has been applied for the defined impacted ecosystems. Paucity of published data on concentration factors prevented a more detailed assessment for terrestrial ecosystems. For the aquatic ecosystem, a more detailed assessment was possible and highest calculated absorbed dose rates (weighted for the likely higher biological effectiveness of alpha radiation) were about 6.5 microGy h(-1). We conclude that harm to the impacted ecosystems is unlikely and make the observation that the lack of concentration factor or transfer factor data for a sufficiently wide range of species, ecosystems and nuclides appears to be the principal obstacle to establishing a comprehensive framework for the application of radiological protection to ecosystems.

Uranium ores and depleted uranium in the environment, with a reference to uranium in the biosphere from the Erzgebirge/Sachsen, Germany.

The Erzgebirge ('Ore Mountains') area in the eastern part of Germany was a major source of uranium for Soviet nuclear programs between 1945 and 1989. During this time, the former German Democratic Republic became the third largest uranium producer in the world. The high abundance of uranium in the geological formations of the Erzgebirge are mirrored in the discovery of uranium by M. Klaproth close to Freiberg City in 1789 and the description of the so-called 'Schneeberg' disease, lung cancer caused in miners by the accumulation of the uranium decay product, radon, in the subsurfaces of shafts. Since 1991, remediation and mitigation of uranium at production facilities, rock piles and mill tailings has taken place. In parallel, efforts were initiated to assess the likely adverse effects of uranium mining to humans. The costs of these activities amount to about 6.5 10(9) Euro. A comparison with concentrations of depleted uranium at certain sites is given.

Depleted uranium residual radiological risk assessment for Kosovo sites.

During the recent conflict in Yugoslavia, depleted uranium rounds were employed and were left in the battlefield. Health concern is related to the risk arising from contamination of areas in Kosovo with depleted uranium penetrators and dust. Although chemical toxicity is the most significant health risk related to uranium, radiation exposure has been allegedly related to cancers among veterans of the Balkan conflict. Uranium munitions are considered to be a source of radiological contamination of the environment. Based on measurements and estimates from the recent Balkan Task Force UNEP mission in Kosovo, we have estimated effective doses to resident populations using a well-established food-web mathematical model (RESRAD code). The UNEP mission did not find any evidence of widespread contamination in Kosovo. Rather than the actual measurements, we elected to use a desk assessment scenario (Reference Case) proposed by the UNEP group as the source term for computer simulations. Specific applications to two Kosovo sites (Planeja village and Vranovac hill) are described. Results of the simulations suggest that radiation doses from water-independent pathways are negligible (annual doses below 30 microSv). A small radiological risk is expected from contamination of the groundwater in conditions of effective leaching and low distribution coefficient of uranium metal. Under the assumptions of the Reference Case, significant radiological doses (>1 mSv/year) might be achieved after many years from the conflict through water-dependent pathways. Even in this worst-case scenario, DU radiological risk would be far overshadowed by its chemical toxicity.

Screening level dose assessment of aquatic biota downstream of the Marcoule nuclear complex in southern France.

Aquatic biota in the Rhone River downstream of the Marcoule nuclear complex in France are exposed to natural sources of radiation and to radioactivity released from the Marcoule complex. A simple conservative screening level model was used to estimate the range of concentrations in aquatic media (water, sediments, and aquatic organisms) of both artificial and natural radionuclides and the consequent absorbed (whole body) dose rates for aquatic organisms. Five categories of aquatic organisms were studied, namely, submerged aquatic plants (phanerogam), non-bottom-feeding fish, bottom-feeding fish, mollusca, and fish-eating birds. The analysis was based on the radionuclide concentrations reported in four consecutive annual radioecological monitoring reports published by French agencies with nuclear regulatory responsibilities. The results of this assessment were used to determine, qualitatively, the magnitude of any potential health impacts on each of the five categories of aquatic organisms studied. The range of dose rate estimates ranged over three orders of magnitude, with maximum dose rates estimated to be in the order of 1 to 10 microGy h(-1). These maximum dose rates are a factor 40 or more below the international guideline intended to ensure the protection of aquatic populations (about 400 microGy h(-1)), and a factor ten or more below the level which may trigger the need for a more detailed evaluation of potential ecological consequences to the exposed populations (about 100 microGy h(-1)). As a result, chronic levels of radioactivity, artificial and natural, measured in aquatic media downstream of Marcoule are unlikely to result in adverse health impacts on the categories and species of aquatic organisms studied. Thus, based on the screening level analysis discussed in this paper, a more detailed evaluation of the dose rates does not appear to be warranted.

Sensitivity of concentration and risk predictions in the PRESTO and MMSOILS multimedia models: regression technique assessment.

This paper describes the application of two multimedia models, PRESTO and MMSOILS, to predict contaminant migration from a landfill that contains an organic chemical (methylene chloride) and a radionuclide (uranium-238). Exposure point concentrations and human health risks are predicted, and distributions of those predictions are generated using Monte Carlo techniques. Analysis of exposure point concentrations shows that predictions of uranium-238 in groundwater differ by more than one order of magnitude between models. These differences occur mainly because PRESTO simulates uranium-238 transport through the groundwater using a one-dimensional algorithm and vertically mixes the plume over an effective mixing depth, whereas MMSOILS uses a three-dimensional algorithm and simulates a plume that resides near the surface of the aquifer. A sensitivity analysis, using stepwise multiple linear regression, is performed to evaluate which of the random variables are most important in producing the predicted distributions of exposure point concentrations and health risks. The sensitivity analysis shows that the predicted distributions can be accurately reproduced using a small subset of the random variables. Simple regression techniques are applied, for comparison, to the same scenarios, and results are similar. The practical implication of this analysis is the ability to distinguish between important versus unimportant random variables in terms of their sensitivity to selected endpoints.

Total system performance assessment for waste disposal using a logic tree approach.

The Electric Power Research Institute (EPRI) has sponsored the development of a model to assess the long-term, overall "performance" of the candidate spent fuel and high-level radioactive waste (HLW) disposal facility at Yucca Mountain, Nevada. The model simulates the processes that lead to HLW container corrosion, HLW mobilization from the spent fuel, and transport by groundwater, and contaminated groundwater usage by future hypothetical individuals leading to radiation doses to those individuals. The model must incorporate a multitude of complex, coupled processes across a variety of technical disciplines. Furthermore, because of the very long time frames involved in the modeling effort (>> 10(4) years), the relative lack of directly applicable data, and many uncertainties and variabilities in those data, a probabilistic approach to model development was necessary. The developers of the model chose a logic tree approach to represent uncertainties in both conceptual models and model parameter values. The developers felt the logic tree approach was the most appropriate. This paper discusses the value and use of logic trees applied to assessing the uncertainties in HLW disposal, the components of the model, and a few of the results of that model. The paper concludes with a comparison of logic trees and Monte Carlo approaches.

Uncertainty and variability analysis in multiplicative risk models.

Currently, there is a trend away from the use of single (often conservative) estimates of risk to summarize the results of risk analyses in favor of stochastic methods which provide a more complete characterization of risk. The use of such stochastic methods leads to a distribution of possible values of risk, taking into account both uncertainty and variability in all of the factors affecting risk. In this article, we propose a general framework for the analysis of uncertainty and variability for use in the commonly encountered case of multireplicative risk models, in which risk may be expressed as a product of two or more risk factors. Our analytical methods facilitate the evaluation of overall uncertainty and variability in risk assessment, as well as the contributions of individual risk factors to both uncertainty and variability which is cumbersome using Monte Carlo methods. The use of these methods is illustrated in the analysis of potential cancer risks due to the ingestion of radon in drinking water.

Multimedia benchmarking analysis for three risk assessment models: RESRAD, MMSOILS, and MEPAS.

This paper is one in a series that describes results of a benchmarking analysis initiated by the Department of Energy (DOE) and the United States Environmental Protection Agency (EPA). An overview of the study is provided in a companion paper by Laniak et al. presented in this journal issue. The three models used in the study--RESRAD (DOE), MMSOILS (EPA), and MEPAS (DOE)--represent analytically-based tools that are used by the respective agencies for performing human exposure and health risk assessments. Both single media and multimedia benchmarking scenarios were developed and executed. In this paper, the multimedia scenario is examined. That scenario consists of a hypothetical landfill that initially contained uranium-238 and methylene chloride. The multimedia models predict the fate of these contaminants, plus the progeny of uranium-238, through the unsaturated zone, saturated zone, surface water, and atmosphere. Carcinogenic risks are calculated from exposure to the contaminants via multiple pathways. Results of the tests show that differences in model endpoint estimates arise from both differences in the models' mathematical formulations and assumptions related to the implementation of the scenarios.

Cancer risk from the lifetime intake of Ra and U isotopes.

From extensive human data on the induction of skeletal cancers (bone sarcomas and carcinomas of the head sinuses) by 226Ra, 228Ra and 224Ra, the cumulative lifetime risk to 1 million people, each ingesting 5 pCi of a Ra isotope per day, was calculated to be nine bone sarcomas plus 12 head carcinomas for 226Ra, 22 bone sarcomas for 228Ra, and 1.6 bone sarcomas for 224Ra. Assuming that the risk per rad of average skeletal dose is equal for 226Ra and the U isotopes with half-lives exceeding 1000 yr and that the equilibrium skeletal content is 25 times the daily ingestion of 226Ra, but 11 times the daily ingestion of long-lived U, the cumulative life-span risk to 1 million persons, each ingesting 5 pCi per day of 233U, 234U, 235U, 236U or 238U, is estimated to be about 1.5 bone sarcomas. The U risk is not well established and additional research is needed on the metabolism of U in humans and its carcinogenicity in laboratory animals. These estimates assume linear dose responses. However, if incidence varies with the square of dose, virtually no induced cancers would be expected from these levels of radioactivity.

Regulatory consideration in radiation protection.

A regulatory scheme is suggested that identifies regions labeled "unacceptable" and "safe" as the upper and lower bounds and "operational" region is identified as the continuum between the two extremes. These regions are associated with levels of annual risk of cancer death for a given level of lifetime exposure between 100 mrem/yr and 1 mrem/yr, upper and lower bounds, respectively. Concern is expressed with establishing public health standards at ALARA (as low as reasonably achievable) levels, which result in lower standards for reference, and views are presented on several issues of interest in regulations for protection of the public from radioactivity in drinking water. Based on the regulatory scheme suggested, the author concludes that existing standards for drinking water appear to be lower than necessary.