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PubMed1998

Radium and leukemia: is current dogma valid?

Current reviews have concluded that internal 226Ra appears not to give rise to leukemia in humans, a conclusion based on incidence in U.S. female radium dial workers. In fact, leukemias have occurred significantly early in female dial workers; males occupationally exposed to radium show an excess of leukemias; and the rare erythrocytic leukemias appear in male workers as they do in Thorotrast case series. It appears more reasonable that Thorotrast data are suitable for projection of leukemogenic risk from radium and plutonium than that no concern for leukemogenic risk is warranted.

Bone Marrow↗
PubMed1998

Dose-response analyses of osteonecrosis in New Jersey radium workers point to roles for other alpha emitters.

A previous study of 25 radium workers reported radium osteonecrosis to be common down to that study's lower limit of detection of 226Ra. This paper reanalyzes those data using Poisson and linear regression to obtain quantitative dose-response estimates for radium osteonecrosis. A quadratic, supralinear response of the necrosis ratio to skeletal dose and preterminal 226Ra burden was observed at a high level of statistical significance. At low dose the response was linear. Clearly observable necrosis, that appearing in 4% of tissue blocks, was seen in femurs at approximately 0.8 Gy skeletal dose. Comparable effects from plutonium in spongy bone might therefore be expected in the 0.01-0.02 Gy dose range. Prediction equations are presented for preterminal 226Ra burden, for skeletal dose, and, at low doses where the response can be taken as linear, for dose from and uptakes of both 226Ra and 228Ra. Male New Jersey workers in the radium refinery were observed to have necrosis not explained by the 226Ra uptakes, but compatible with skeletal doses from other internal emitters, in the range 0.25-1.2 Gy lifetime dose acquired per year of employment. 210Po, inhaled directly or from inhaled 210Pb, is the most likely source of this dose.

Body Burden↗
PubMed1999

Simple model for the reconstruction of radionuclide concentrations and radiation exposures along the Techa River.

The Techa River (Southern Urals, Russia) was contaminated in 1949-1956 by liquid radioactive wastes from the Mayak complex, the first Russian facility for the production of plutonium. The measurements of environmental contamination were started in 1951. A simple model describing radionuclide transport along the free-flowing river and the accumulation of radionuclides by bottom sediments is presented. This model successfully correlates the rates of radionuclide releases as reconstructed by the Mayak experts, hydrological data, and available environmental monitoring data for the early period of contamination (1949-1951). The model was developed to reconstruct doses for people who lived in the riverside communities during the period of the releases and who were chronically exposed to external and internal irradiation. The model fills the data gaps and permits reconstruction of external gamma-exposure rates in air on the river bank and radionuclide concentrations in river water used for drinking and other household needs in 1949-1951.

Body Burden↗
PubMed1999

Radiostrontium in the Savannah river site environment.

The Savannah River Site has produced plutonium, tritium, and other special nuclear materials for national defense, other government programs, and some civilian purposes. Strontium has been released to the environment during the operation of five reactors, two radiochemical processing facilities, and other supporting facilities. During the period 1954-1996, 110 GBq of 90Sr were released to the atmosphere and 5,400 GBq were released to site streams. The maximum individual effective dose equivalent at the site boundary was estimated to be 72 microSv from atmospheric releases and 25 microSv from liquid releases. The 80-km population dose was 0.3 person-Sv.

Air Pollutants, Radioactive↗
PubMed2000

Dose reconstruction system for the exposed population living along the Techa River.

The Mayak Production Association, which began operation in 1948, was the first facility in the former Soviet Union for the production of plutonium. Significant worker and population exposure occurred as a result of failures in the technological processes in the late 1940's and early 1950's. Members of the public were exposed via discharge of about 1017 Bq of liquid wastes into the Techa River during 1949-1956, an explosion in the radioactive waste-storage facility in 1957, and gaseous aerosol releases within the first decades of the facility's operation. Residents of many villages downstream on the Techa River were exposed via a variety of pathways; the more significant included drinking of water from the river and external gamma exposure due to proximity to sediments and shoreline. The specific aim of this project is to enhance the reconstruction of external and internal radiation doses for individuals in the Extended Techa River Cohort. The purpose of this paper is to present the details of the methods that are being used in this enhanced dose-reconstruction effort and to provide example and representative results of the calculations. The methods of dose assessment currently being developed for the exposed population [termed the Techa River Dosimetry System-2000 (TRDS-2000)], which are a significant improvement on past methods (TRDS-1996), are presented. The new TRDS-2000 doses from the ingestion of radionuclides are substantially higher for the gastrointestinal tract, due to consideration of short-lived radionuclides. The TRDS-2000 doses from external exposure are substantially lower due to improvements in several factors. Assessment of uncertainty and validation of the "new" doses are significant issues currently under investigation.

Health Physics↗
PubMed2000

The basic directions and results of activities of branch no. 1 of the state research center of the Russian Federation "Biophysics Institute" (FIB-1).

During the 1950's, in the early years at the Mayak Production Association (MAYAK) in the Southern Urals, there was a rapid expansion of plutonium output. This was carried out when nuclear technology was still being developed and knowledge of the effects of radiation exposure on humans was not well understood. As result of the discharge of liquid waste into the Techa River, there was large scale overexposure to both the workers at the facility and the population of riverside localities on the Techa River. There were also other environmental discharges, due to an accident and problems of waste storage, which contributed to exposure of other populations around MAYAK. Although all information on the MAYAK operation and its consequences for both workers and population was kept secret, studies on nuclear technology improvement, the handling of radioactive waste, of medical sequence of radiation exposure, radiation safety improvement, and prevention and treatment of radiation injuries were initiated virtually from the onset the of nuclear weapons production program.

Academies and Institutes↗
PubMed2000

Reconstruction of radionuclide contamination of the Techa River caused by liquid waste discharge from radiochemical production at the Mayak Production Association.

Because of its importance to reconstructing radiation doses for ongoing epidemiological studies, a feasibility study was undertaken to determine if the source term of radioactive materials released to the Techa River from the Mayak Production Association, the first facility in the former Soviet Union for the production of plutonium, could be reconstructed from historical measurements made at a limited number of downriver locations. The feasibility study used historically measured water flow rates and total-beta radioactivity measurements, and considered the processes of radioactive decay and of sorption/desorption. A simple radionuclide mass balance approach was used. To determine the rate of input of radionuclides to the Techa River system, the Techa River was depicted as a series of segments for which measurements are available. For each segment of the river, a system of recurrent (with time) equations was compiled for radioactivity balance accounting for the radioactivity inflow at the inflowing end, activity discharge with water at the outflowing end, and the reduction of activity because of radioactive decay. The equations change with time to account for the changing nature of the river regime. Effective sorption constants for 90Sr and 137Cs, which characterize the transport of radionuclides among the river system components (water and bottom sediments), were defined based on the inventory of these radionuclides deposited at each of the studied river segments and data on water concentration and radioactive removal. All the information on radioactive contamination of the river system components during the period 1949-1996 was used. Solution of the series of equations provided information on the rate of input of these radionuclides into the upper end of the river. The pilot study indicated that it is possible to determine the historical releases of a wider suite of radionuclides using the historical monitoring data from numerous locations along the river, rather than relying on a more uncertain reconstruction of quantities released at the point of discharge. Radionuclides considered include 90Sr, 106Ru, 137Cs, and 144Ce. Estimated concentrations of selected radionuclides at various times are presented.

Feasibility Studies↗
PubMed2000

The Techa River dosimetry system: methods for the reconstruction of internal dose.

The Mayak Production Association (MPA) was the first facility in the former Soviet Union for the production of plutonium. Significant worker and population exposures occurred as a result of failures in the technological processes in the late 1940's and early 1950's. Residents of many villages downstream on the Techa River were exposed via a variety of pathways; the more significant included drinking of water from the river and external gamma exposure due to proximity to contaminated bottom sediment and shoreline. After the extent of the major contamination of the Techa River became known, several villages on the upper part of the Techa River were evacuated. Organ doses are being reconstructed on the basis of derivation of an historical source term and a simple river model used to simulate the transport of radionuclides downstream and their retention on sediments; measurements of 90Sr content in teeth and the whole body of half of the members of the cohort; and development of the "Techa River Dosimetry System" for computation of the doses.

Aging↗
PubMed2000

Stochastic effects of environmental radiation exposure in populations living near the Mayak Industrial Association: preliminary report on study of cancer morbidity.

The Mayak Industrial Association, located in the South Ural Mountains, began operation in 1948 and was the first Russian site for the production and separation of plutonium. During the early days of operation, technological failures resulted in the release of large amounts of radioactive waste into the Techa River. Residents who lived in villages on the banks of the Techa and Iset Rivers were exposed to varying levels of radioactivity. The objective of this study is to assess stochastic (carcinogenic) effects in populations exposed to offsite releases of radioactive materials from the Mayak nuclear facility in Russia. Subjects of the present study are those individuals who lived during the period January 1950 through December 1960 in any of the exposed villages along the Techa River in Chelyabinsk Oblast. Death certificates and cancer incidence data have been routinely collected in the past from a five-rayon catchment area of Chelyabinsk Oblast. The registry of exposed residents along the Techa River assembled and maintained by the Urals Research Center for Radiation Medicine for the past 40 y is the basis for identifying study subjects for this project. Specific study objectives are to evaluate the incidence of cancer among current and former residents of Chelyabinsk Oblast who are in the exposed Techa River cohort; integrate results from the dose-reconstruction study to estimate doses for risk assessment; and develop a structure for maintaining continued follow-up of the cohort for cancer incidence. In the earlier part of our collaborative effort, the focus has been to enhance the cancer morbidity registry by updating it with cancer cases diagnosed through 1997, to conduct a series of validation procedures to ensure completeness and accuracy of the registry, and to reduce the numbers of subjects lost to follow-up. A feasibility study to determine cancer morbidity in migrants from the catchment area has been proposed. Our preliminary analyses of cancer morbidity underscore the importance of examining both cancer mortality and cancer morbidity in conducting a comprehensive analysis of the occurrence of cancer in this important cohort.

Age Distribution↗
PubMed2001

What views and uses of radiation sources in the 21st century?

Considering that in 1899 neither biotechnology nor the electronic revolution were foreseen, some humility might be advisable when one looks into the crystal ball for the future role of radiation sources. In the past 50 years, nuclear medicine, nuclear weapons, and nuclear power have had a huge impact in the world. In the next 50 years, nuclear weapons may be phased out, nuclear power revived, and nuclear medicine may continue, especially for diagnostic purposes. Conflicts between great powers and blocks will no longer be about territorial or ideological domination but about trade, finance, information, and the environment and the weapons used will not be bombs but investments, credits, and control of information. Nuclear power-still based on fission-will be relaunched and get more uses, e.g., to propel ships, to produce heat for industry and for space heating, and perhaps to desalinate water. The public will be more at ease with radiation as it is better educated, as nuclear safety continuously improves and new types of nuclear power plants emerge, as waste sites fail to cause any problems, and as no other energy source is found to deliver so much energy at reasonable cost with negligible impact on climate and environment. One kilogram of oil corresponds to 4 kWh of electricity. One kilogram of uranium fuel corresponds to 50,000 kWh, and 1 kg of plutonium 6,000,000 kWh! In nuclear medicine, radiation may give way to other treatments as the understanding of cancer advances. On the other hand, the extreme ease with which sources of radiation can be identified is unmatched and likely to make them useful tools as tracers and markers in medicine-and other fields-for a long time. For certain uses--perhaps food irradiation--radiation sources, such as cobalt, may be replaced by accelerators which may be switched on and off at will. As more sources are used, registration and control of them must be made very effective around the whole world. Very high natural emissions of radon will continue to call for cautionary measures, but many other nonradiating substances will be identified as hazardous to health and call for vigorous intervention.

Forecasting↗
PubMed2001

Former radiation worker Medical Surveillance Program at Rocky Flats.

The United States Department of Energy (DOE), Office of Occupational Medicine and Medical Surveillance, has supported an ongoing Former Radiation Worker Medical Surveillance Program at the DOE Rocky Flats site since 1992. The program currently is managed for DOE by Oak Ridge Institute for Science and Education through a contract with Oak Ridge Associated Universities. Participation in the program is entirely voluntary and provides former Rocky Flats workers who were exposed to radiation with long-term medical monitoring and an update to the assessment of their radiation dose. Program participants receive medical examinations and in vivo and in vitro bioassay measurements of residual radioactivity. Radiation doses to participants are largely a result of internal depositions of plutonium and its radioactive decay products. The causes of many of the higher internal doses were accidents that generally are well documented. Former radiation workers are invited to participate in the program if they meet specific criteria for radiation exposure. Informed consent is documented using a consent form approved by an Institutional Review Board. Demographic, medical, and dosimetric information is maintained in a computer database and will be evaluated for any trends or correlations between exposure and health outcome.

Adult↗
PubMed2001

Radionuclides in Peconic River fish, mussels, and sediments.

For regulatory oversight and quality control of Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) actions, fish, mussels, and sediments were analyzed from the Peconic River system on Long Island, NY, downstream of the Brookhaven National Laboratory, as well as from control locations. The analyses were for photon-emitting radionuclides (notably 60Co and 137Cs), uranium, plutonium, and americium. Sediments were cored in 4 sections to 0.37 m depth, whole fish were analyzed, and mussels were separated into flesh and shells. Radioisotopes of the cited elements were detected in sediment, some of the fish contained 137Cs, 241Am, and uranium, and mussel flesh contained 137Cs and uranium. All of the 60Co, 233U, and enriched uranium, and some of the 137Cs and 241Am, can most likely be attributed to Brookhaven National Laboratory. The other radionuclides (and some of the 137Cs and 241Am) are believed to have either fallout or nature as their origin. The New York State Department of Health (NYSDOH) evaluated the radiological data in terms of adverse health implications due to consumption of fish with the levels of reported radioactivity. The NYSDOH determined that the added radiation doses likely to result from eating this fish are a small fraction of the radiation dose that normally results from radionuclides present in the body from natural sources.

Animals↗
PubMed2001

Non-invasive measurement of water content in lung phantom by neutrons: latest improvements to the technique.

The novel technique for measuring the water content in lungs based on the slowing down of fast neutrons has been improved making possible its clinical use on patients. This goal has been reached by performing computer simulations that closely mimic the experimental setup and by acquiring a new set of measurements obtained with a plutonium-beryllium (Pu-Be) neutron source provided of an activity suitable to clinical requirements. Finally, accurate radiation dose measurements have been carried out to ensure the acceptability of the technique.

Computer Simulation↗
PubMed2002

Influence of room geometry and ventilation rate on airflow and aerosol dispersion: implications for worker protection.

Knowledge of dispersion rates and patterns of radioactive aerosols and gases through workrooms is critical for understanding human exposure and for developing strategies for worker protection. The dispersion within rooms can be influenced by complex interactions between numerous variables, but especially ventilation design and room furnishings. For this study, dependence of airflow and aerosol dispersion on workroom geometry (furnishings) and ventilation rate were studied in an experimental room that was designed to approximate a plutonium laboratory. Three different configurations of simulated gloveboxes and two ventilation rates (approximately 6 and 12 air exchanges per hour) were studied. A sonic anemometer was used to measure airflow parameters including all three components of air velocity vectors and turbulence intensity distributions at multiple locations and heights. Aerosol dispersion rates and patterns were measured by releasing aerosols multiple times from six different locations. Aerosol particle concentrations resolved in time and space were measured using 16 multiplexed laser particle counters. Comparisons were made of air velocities, turbulence, and aerosol transport across different ventilation rates and room configurations. A strong influence of ventilation rate on aerosol dispersion rates and air velocity was found, and changes in room geometry had significant effects on aerosol dispersion rates and patterns. These results are important with regards to constant evaluation of placement of air sampling equipment, benchmarking numerical models of room airflow, and design of ventilation and room layouts with consideration of worker safety.

Aerosols↗
PubMed2002

A new graphical user interface for fast construction of computation phantoms and MCNP calculations: application to calibration of in vivo measurement systems.

The paper reports on a new utility for development of computational phantoms for Monte Carlo calculations and data analysis for in vivo measurements of radionuclides deposited in tissues. The individual properties of each worker can be acquired for a rather precise geometric representation of his (her) anatomy, which is particularly important for low energy gamma ray emitting sources such as thorium, uranium, plutonium and other actinides. The software discussed here enables automatic creation of an MCNP input data file based on scanning data. The utility includes segmentation of images obtained with either computed tomography or magnetic resonance imaging by distinguishing tissues according to their signal (brightness) and specification of the source and detector. In addition, a coupling of individual voxels within the tissue is used to reduce the memory demand and to increase the calculational speed. The utility was tested for low energy emitters in plastic and biological tissues as well as for computed tomography and magnetic resonance imaging scanning information.

Calibration↗
PubMed2002

Influence of dust loading on the alpha-particle energy resolution of continuous air monitors for thin deposits of radioactive aerosols.

Alpha-particle continuous air monitors must sometimes be operated in dusty environments where significant dust loading of the filter can be anticipated. It is important to understand how this dust loading affects the response of the continuous air monitors. Not only must a filter be changed if there is a reduction in airflow, but a change may be necessary if the energy resolution deteriorates and the continuous air monitor loses sensitivity and specificity for the radioactive aerosols of interest. A series of experiments were conducted to investigate alpha-particle energy resolution of continuous air monitor filters, particularly under dust loading conditions. Aerosol particles of various sizes were tagged with radon decay products to serve as surrogates for radioactive aerosols of interest such as plutonium or uranium. While the size of radioactive aerosols, filter type, and dust type affected the energy resolution, the thickness of an underlying (nonradioactive) dust layer did not show significant effect for the materials studied and a loading range of 0.01-10 mg x cm(-2). Our results indicate that it is possible for continuous air monitors to detect the release of radioactive aerosols with little deterioration in energy resolution under conditions of significant dust loading provided that the deposited layer of radioactive aerosols remains thin (< or = 0.1 mg x cm(-2)).

Aerosols↗
PubMed2003

Results of a study to determine the impact of the new dosimetry performance standard, N13.11-2001.

Dosimeters were irradiated using the protocol described in the new ANSI HPS N13.11-2001 standard, "American National Standard for Dosimetry--Personnel Dosimetry Performance--Criteria for Testing." In particular, the following hypotheses were evaluated: (1) expanding the scope of testing fields in the x-ray category would not adversely impact the performance of dosimeter systems; (2) incorporating routine angular testing for medium-energy and high-energy photon fields would not adversely impact the performance of dosimeter systems; (3) implementing test criteria would adversely impact the performance of dosimeter systems; and (4) the narrow spectrum x-ray fields specified in the standard would provide adequate replacements for analogous k-fluorescence techniques previously used by DOELAP. The study tested only subcategories IIA, General photon fields, and IID, Plutonium-specific fields, and did not address mixed irradiations. The results of the study supported hypotheses (1) and (2) above. The results of the study indicated that the individual dosimeter performance test (10% rule) did not seriously impact the performance of dosimeter systems nor did results support the use of NS20 as a replacement x-ray field for the 17 keV k-fluorescence x-ray field.

Equipment Failure Analysis↗
PubMed2003

Comparison of doses and risks obtained from dose reconstructions for historical operations of federal facilities that supported the development, production, or testing of nuclear weapons.

Five dose reconstruction projects focusing on historical public exposures from U.S. government nuclear facilities have been completed in the last 12 y (Fernald, Hanford, Nevada Test Site, Oak Ridge, Rocky Flats). Using information available in published reports, doses and excess health risks of the most serious contaminants in each study are compared for representative maximally and typically exposed individuals. For both the representative maximally exposed individual and the representative typically exposed individual, the highest excess risks of cancer incidence were from 131I released from Hanford, Nevada Test Site, and Oak Ridge and 222Rn released from Fernald (with central estimates for maximally exposed individuals approaching or exceeding 10(-2)); the lowest risks for both maximally and typically exposed individuals were from 239/240Pu and carbon tetrachloride released from Rocky Flats. Excess health risks to the representative maximally exposed individual were at or below 10(-40 for releases from Rocky Flats. For representative typically exposed individuals, the excess risks from releases of mixed radionuclides in the Clinch River (Oak Ridge), PCBs in East Fork Poplar Creek (Oak Ridge), and both plutonium and carbon tetrachloride released from Rocky Flats were mostly below 10(-5).

Air Pollutants, Radioactive↗