The US Transuranium and Uranium Registries (USTUR): A Five-Decade Follow-Up Of Plutonium and Uranium Workers.

Dedication: The research of the US Transuranium and Uranium Registries relies heavily upon postmortem autopsy findings and radiochemical analysis of tissues. The enormous debt owed to those now-deceased registrants who unselfishly voluntarily participated in the US Transuranium and Uranium Registries program through postmortem donation of their tissues and to those still-living registrants who have volunteered to be future postmortem tissue donors is hereby acknowledged with gratitude. The scientific findings derived from postmortem analysis of these tissues have been instrumental in advancing our understanding of the actinide elements in humans and have led to refinement, validation, and confidence in safety standards for those who work with these elements as well as for the general public. To these generous and anonymous persons who made this ultimate contribution, this paper is dedicated with great thanks and admiration.

Estimation of Total Skeletal Content of Plutonium and 241Am From Analysis of a Single Bone.

The skeleton is one of the major retention sites for internally deposited actinides. Thus, an accurate estimation of the total skeleton content of these elements is important for biokinetic modeling and internal radiation dose assessment. Data from 18 whole-body donations to the US Transuranium and Uranium Registries with known plutonium intakes were used to develop a simple and reliable method for estimation of plutonium and Am activity in the total skeleton from single-bone analysis. A coefficient of deposition Kdep, defined as the ratio of actinide content in the patella to that in the skeleton, was calculated for Pu, Pu, and Am. No statistical difference was found in Kdep values among these radionuclides. Variability in Kdep values was investigated with relation to skeleton pathology (osteoporosis). The average Kdep of 0.0051 ± 0.0009 for the osteoporotic group was statistically different from Kdep of 0.0032 ± 0.0010 for nonosteoporotic individuals. The use of Kdep allows for rapid estimation of the total skeletal content of plutonium and Am with up to 35% uncertainty. To improve accuracy and precision of total skeleton activity estimates, regression analysis with power function was applied to the data. Strong correlation (r > 0.9) was found between Pu, Pu, and Am activities measured in the patella bone and total skeleton activity. The results of this study are specifically important for the optimization of bone sample collection for US Transuranium and Uranium Registries partial-body donations.

USTUR Special Session Roundtable-US Transuranium and Uranium Registries (USTUR): A Five-decade Follow-up of Plutonium and Uranium Workers.

The US Transuranium and Uranium Registries is a human tissue program that collects tissues posthumously from former nuclear workers and radiochemically analyzes them for actinides such as plutonium, americium, and uranium. It was established in 1968 with the goal of advancing science and improving the safety of future workers. Roundtable participants recalled various aspects of this multidisciplinary research program, from establishing consistent autopsy protocols to comparing the registries' findings to those of other programs, such as the historical beagle dog studies and the Russian Radiobiological Human Tissue Repository. The importance of meeting ethical and legal requirements, including written consent forms, was emphasized, as was the need to know whether workers were exposed to nonradiological hazards such as beryllium or asbestos. At Rocky Flats, a bioassay program was established to follow workers after they terminated employment. The resulting data continue to help researchers to improve the biokinetic models that are used to estimate intakes and radiation doses. After 50 y, the US Transuranium and Uranium Registries continues to contribute to our understanding of actinides in humans, which is a testament to the vision of its founders, the generosity of its tissue donors, and the many dedicated scientists who have worked together to achieve a common goal.

Acute chemical toxicity of uranium.

Although human experience with uranium spans more than 200 years, the LD50 for acute intake in humans has not been well established. Large acute doses of uranium can produce death from chemical toxicity in rats, guinea pigs, and other small experimental animals, with variation in sensitivity among species. However, there has never been a death attributable to uranium poisoning in humans, and humans seem to be less sensitive to both acute and chronic toxic effects of uranium than other mammalian species studied. Highly relevant data on uranium toxicity in humans are available from the experience of persons administered large doses of uranium for therapy of diabetes and from acute accidental inhalation intakes. Although the data on which to establish oral and inhalation acute LD50 for uranium in humans are sparse, they are adequate to conclude that the LD50 for oral intake of soluble uranium compounds exceeds several grams of uranium and is at least 1.0 g for inhalation intakes. For intakes of uranium compounds of lesser solubility, acute LD50 values are likely to be significantly greater. It is suggested that 5 g be provisionally considered the acute oral LD50 for uranium in humans. For inhalation intakes of soluble compounds of uranium, 1.0 g of uranium is proposed as the provisional acute inhalation LD50.

Radioactivity in fossils at the Hagerman Fossil Beds National Monument.

Since 1996, higher than background levels of naturally occurring radioactivity have been documented in both fossil and mineral deposits at Hagerman Fossil Beds National Monument in south-central Idaho. Radioactive fossil sites occur primarily within an elevation zone of 900-1000 m above sea level and are most commonly found associated with ancient river channels filled with sand. Fossils found in clay rich deposits do not exhibit discernable levels of radioactivity. Out of 300 randomly selected fossils, approximately three-fourths exhibit detectable levels of natural radioactivity ranging from 1 to 2 orders of magnitude above ambient background levels when surveyed with a portable hand held Geiger-Muller survey instrument. Mineral deposits in geologic strata also show above ambient background levels of radioactivity. Radiochemical lab analysis has documented the presence of numerous natural radioactive isotopes. It is postulated that ancient groundwater transported radioactive elements through sand bodies containing fossils which precipitated out of solution during the fossilization process. The elevated levels of natural radioactivity in fossils may require special precautions to ensure that exposures to personnel from stored or displayed items are kept as low as reasonably achievable (ALARA).

The Health Physics Society: a 50-year chronology.

In 2005, the Health Physics Society celebrates its 50th anniversary. During its half century of existence, the Society has evolved from a small group of operationally oriented radiation protection scientists into an organization of several thousand with a recognized and respected peer reviewed journal. The bold decision to form an organization devoted to radiation safety in the United States spurred the formation of such societies in other countries and led to the formation of an international confederation of national societies, which has facilitated scientific communication and exchange worldwide. It also led to the formation of a separate body for the certification of health physicists, which in turn has grown into an academy with more than 1,000 members, and was instrumental in providing basic information establishing the need for a registry of radiation protection technologists.

The health physics society: a 50-year chronology.

In 2005, the Health Physics Society celebrates its 50th anniversary. During its half century of existence, the Society has evolved from a small group of operationally oriented radiation protection scientists into an organization of several thousand with a recognized and respected peer reviewed journal. The bold decision to form an organization devoted to radiation safety in the United States spurred the formation of such societies in other countries and led to the formation of an international confederation of national societies, which has facilitated scientific communication and exchange worldwide. It also led to the formation of a separate body for the certification of health physicists, which in turn has grown into an academy with more than 1,000 members, and was instrumental in providing basic information establishing the need for a registry of radiation protection technologists.

Natural Uranium Tissue Content of Three Caucasian Males.

Uranium content and concentrations were measured in the tissues of three Caucasian male whole body donors to the U.S. Transuranium and Uranium Registries with no known intake other than from natural environmental sources. Average total body uranium content in the three cases was 81.3 ± 22.3 µg, of which 37.2 ± 2.1 µg (46%) was in the skeleton. The skeleton had a mean concentration of 3.79 ± 0.45 µg U kg(-1) wet weight and 11.72 ± 1.49 µg U kg(-1) ash. Distribution was in bone volume and not predominately on bone surfaces. Soft tissue concentrations ranged over about an order of magnitude, averaging about 0.5 µg kg wet weight for all tissues except the thoracic lymph nodes, which averaged 32.3 times the mean for soft tissue of the three cases. Observed thyroid tissue concentrations were about an order of magnitude greater than the average soft tissue concentration in two of the three background cases, suggestive of a possible long-term depot in this organ. Kidney content of uranium averaged 0.38 ± 0.21 µg for the three cases, an order of magnitude lower than the 7 µg recommended for Reference Man. The lower content and concentration in the kidney do not support a significant long-term depot for uranium in that organ. Assuming equilibrium between intake and excretion, the tissue data suggest a transfer coefficient from blood to skeleton of 0.14 with a residence half-life in the skeleton of 4,950 d (13.56 y), significantly greater than the 1,500 d (4.1 y) half-time proposed by ICRP.

Six-year follow-up of an acute 241Am inhalation intake.

A 38-y-old Caucasian male who suffered an acute accidental inhalation intake of 6.3 kBq of 241Am was monitored over 2,135 d using periodic in vivo measurements of the activity in the lungs, liver, and skeleton. Lung clearance was described by a two-compartment exponential model with half-times of 110 d and 10,000 d. The observed uptake of 241Am in the liver (72 Bq) and skeleton (170 Bq) was significantly greater than predicted by the ICRP models for liver (5 Bq) and skeleton (8 Bq). The half-time in the liver was approximately 850 d. Estimates of skeletal activity based on head, wrist, and knee counts generally agreed within 25% over the course of the monitoring period. The half-time in the skeleton was approximately 20,000 d.

A review of contributions of human tissue studies to biokinetics, bioeffects and dosimetry of plutonium in man.

This paper briefly reviews the contributions made by human tissue studies to improved understanding of the biokinetics, dosimetry and potential bioeffects of plutonium in man. It includes consideration of tissue donations from both environmental and occupational populations, along with a brief history of human experience with plutonium and consideration of the bioethical aspects of post-mortem human tissue sampling.

Proposed standards for acute exposure to low enrichment uranium for compliance with 10 CFR 70.61.

Title 10, Code of Federal Regulations Part 70, puts forth requirements for licensure of special nuclear material including specific risk criteria for acute intakes based on biological effects. Standards for acute oral and inhalation intakes of soluble low enrichment are proposed for the three levels of biological effects given in the regulations. These levels were developed largely from available human data and have a large measure of conservatism. The proposed threshold for life endangerment was 500 mg for acute inhalation intakes and 2,500 mg for acute ingestion intakes. Acute intakes of 1,400 mg for ingestion and 100 mg for inhalation are proposed as thresholds for irreversible or serious long lasting health effects. For minor transient health effects, the proposed levels are 410 and 30 mg, respectively, for acute ingestion and inhalation intakes. For acute intakes below these levels, no demonstrable toxicological effects are anticipated.

Reconstruction of doses from occupationally related medical x-ray examinations.

Many nuclear weapons complex workers were required to undergo medical x-ray examinations as a condition of their employment. To ensure that their dose reconstructions are complete, it is necessary to include the contributions from these examinations. X-ray procedures that must be evaluated include: (1) posterior-anterior and lateral radiography, and/or photofluorography, of the chest; (2) anterior-posterior, lateral and oblique lumbar, cervical and thoracic radiography of the spine; and (3) radiography of the pelvis. Each is discussed in the context of conditions that existed during the time the worker was employed. For purposes of dose reconstruction, the x-ray beam size is especially important because the dose conversion factors (DCFs) for each specific body organ depend on whether it was in, or on the periphery of, the primary beam. The approach adopted was to use the DCFs, combined with the entrance kerma, to estimate the organ doses. In cases in which beam output data or information on the primary factors influencing the dose are not available, methods to provide conservative (i.e., claimant-favorable) entrance kerma and dose estimates are adopted. These include specific default values for chest radiography. To account for uncertainties, the estimated doses due to x-ray examinations are increased by 30%.