Health Physics Society Meeting, Minneapolis, MN, July 12-16, 2009
On July 13th, USTUR’s Director received the distinct honor of delivering the R.S. Landauer Sr. Memorial Lecture at the Health Physics Society’s 54th Annual Meeting, Minneapolis, MN. This award is made for “distinguished contribution to the field of Radiological Physics and Radiation Health Protection.”
The U.S. Transuranium & Uranium Registries: Reaping the benefits of lifetime follow-up of plutonium worker health and internal α-dose
A.C. James (USTUR)
September 2008 was the 40th anniversary of the U.S. Atomic Energy Commission’s vision in establishing the National Plutonium Registry. Its successors, the U.S. Transuranium and Uranium Registries (USTUR), continue to follow into ‘old age’ individuals with documented accidental exposures to actinide elements who voluntarily permitted access to their employment, occupational exposure histories and medical records. To date, 326 past-worker volunteers have donated their tissues for scientific research, including 35 whole body donors. Each individual’s autopsy examination results (coded for primary and contributing causes of death), their exposure and medical records, together with USTUR’s results of radiochemical analyses of tissues and major organs, enable the Registries to compile a comprehensive and definitive collection of scientific data. The database and associated tissue materials serve to encapsulate the real human experience (including actual health outcomes) of accidental exposures to long-lived α-emitting actinides over the history of U.S. nuclear materials production. This USTUR resource is unique in that, in many cases, the quality and scope of the available in-vivo bioassay data and tissue analyses together enable ‘state-of-the-art’ assessments of tissue doses to be performed for individual persons – for reliable comparison with that individual’s long-term health outcome. The assessed tissue doses are anchored (testable) by directly measured physical quantities – the actual tissue contents of radionuclides at the time of death. This presentation illustrates how the donated (privacy-protected) case information and USTUR measurements are being applied to increase the credibility (level of certainty) in determining actual tissue doses received by accidentally-exposed weapons-site and other workers from intakes of all important forms of plutonium, americium and uranium. With the exception of rare cases with very high tissue doses, there are no indications of deleterious health outcomes among USTUR Registrants that may be associated with actinide exposure. [USTUR-0268-09]
Upgrading the United States Transuranium and Uranium Registries’ pathology database
S.L. McCord (USTUR), A.C. James (USTUR)
Initiated in the 1960’s with the mission of acquiring and providing precise information about the effects of plutonium and other transuranic elements in man, the United States Transuranium Registries (USTUR) have followed up to ‘old age’ almost 500 volunteer Registrants who worked at weapons sites and received measurable internal doses. As a part of this follow up, it is important to accurately track Registrant causes of death. To obtain consistent, reliable pathology data, the USTUR sub-contracted a professional nosologist to code all death certificates and autopsy reports using both revisions 9 and 10 of the World Health Organization’s International Classification of Diseases, ICD-9-CM and ICD-10 respectively. Accordingly, the USTUR have redesigned and significantly expanded the functionality of their internal pathology database in a manner that promotes these data. The upgraded database focuses on 1) obtaining and importing quality cause of death data for each deceased registrant, and 2) designing forms that enhance the accessibility of data by enabling the user to search by case number, keywords, ICD-9-CM code, and ICD-10 code. Forms, search criteria and results, and quality assurance measures are described. [USTUR-0262-09]
Elemental bio-imaging of actinides and beryllium in lymph nodes of former nuclear workers.
S.Y. Tolmachev (USTUR), D. Bishop (Bio-imaging Facility, University of Technology Sydney), P. Doble (Bio-imaging Facility, University of Technology Sydney), D. Hare (Bio-imaging Facility, University of Technology Sydney), and A.C. James (USTUR)
The U.S. Transuranium & Uranium Registries (USTUR) studies the uptake, translocation and biokinetics of actinides in humans. This study explored the application of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to elemental bio-imaging (EBI) of actinides [thorium (Th), uranium (U), plutonium (Pu), americium (Am)] and beryllium (Be) in samples of human tissue. The tissue samples were from occupationally exposed ‘nuclear weapons site’ workers, who had voluntarily donated their tissues to the USTUR. For this exploratory study, single sections of thoracic (respiratory tract) lymph nodes were mapped for actinide isotopes and 9Be. The aim of this work was to develop LA-ICP-MS protocols for elemental bio-imaging (elemental distribution) of actinides and beryllium isotopes in soft tissue samples from occupationally exposed individuals. [USTUR-0271-09]
USTUR Case 0102 CT image processing techniques for voxel phantom development
G. Tabatadze. (ISU), R. Brey (ISU), A. James (USTUR), D. Theel (Portneuf Medical Center), S. Todd (Portneuf Medical Center)
A 3D voxel model of the United States Transuranium and Uranium Registries’ (USTUR) Case 0102
241Am phantom has been developed. The phantom which was created using half the skeleton from Case 0102 has served as a unique standard for intercomparison of external counting systems at United States DOE facilities and other laboratories world-wide. High resolution (0.5mm) Computed Tomography (CT) images of the USTUR Case 0102 phantom provide the physical basis for precisely defining the internal structure of the bones in the donor subject. DICOM (Digital Imaging and Communications in Medicine) images of the phantom (head, torso, arm, and leg) have been segmented using the Eclipse® radiotherapy planning software. This has a robust automatic segmentation feature. The three-step segmentation procedure involved: defining the regions of interest and CT numbers for different anatomical structures; auto-segmenting the Dicom images, and; manually correcting any errors in the auto segmentation results. Each Dicom image was segmented into the following regions of interest: air pockets, cortical bone, bone cavities (marrow/trabecular spongiosa), and soft tissue. Soft tissue was subdivided into ‘light’ and ‘regular’ regions to represent inhomogeneities (artifacts) that occurred when the phantom was cast in nominal ICRU tissue equivalent plastic. The range of CT numbers in each region of interest was replaced by a single characteristic CT number. All structures of the phantom were exported to the DICOM-RT format. The voxel representation of the phantom is now ready for use in the Geant4 Monte Carlo code to simulate the experimental response of external planar germanium detectors. [USTUR-0263-09]
Inhalation of Highly Insoluble Plutonium: Case Studies from the Rocky Flats Plutonium Fire
Maia Avtandilashvili (ISU), Richard Brey (ISU), Anthony C. James (USTUR), Alan Birchall (HPA)
The United States Transuranium and Uranium Registries (USTUR) includes several whole- and partial-body donations from workers involved in the Rocky Flats Plutonium fire of 1965. This fire resulted in Pu contamination over about 6,500 m2 of working area with airborne Pu concentrations ranging from 3.7×10-2 Bq/m3 to greater than 3.7×104 Bq/m3. About 400 workers were monitored for their potential exposure to highly insoluble “high fired” plutonium dioxide particles with a measured mass median physical particle diameter (MMD) of 0.32 micrometer. Several of the employees had intakes exceeding the contemporary permissible lung burden of 592 Bq (16 nCi) by a factor of 1 to 17. The USTUR’s follow-up of relatively highly exposed individuals over several decades indicates that the inhaled plutonium is retained in the lungs significantly longer than expected for insoluble “Type S” plutonium [as characterized by the International Commission on Radiological Protection’s (ICRP) Publication 66 Human Respiratory Tract Model (HRTM)]. This phenomenon has been referred to as “Type Super S” absorption behavior, although the mechanism for this very long particle retention has not yet been established. Several cases with long follow-up and minimal influence of additional exposures were selected from the USTUR database. These are being used to evaluate simultaneously the intake amounts, lung absorption rates and long-term particle transport (clearance) rates from the lungs, with their associated uncertainty distributions. The preliminary results of one of these case studies are discussed. [USTUR-0264-09]
Critical evaluation of 239PuO2 wound and lymph node retention predicted by NCRP 156’s recommended biokinetic transfer rates
Nino Chelidze (ISU), Richard Brey (ISU)
A Powerbasic (PBCC 4.03) code has been developed to implement explicitly the general structure of the NCRP Publication 156 recycling biokinetic wound model, which partitions accidentally injected material into four characteristic initial states: (1) soluble, (2) colloid & intermediate state, (3) particles, aggregates & bound state, and (4) fragment. This was bench-marked (quality assured) against compartmental retention values calculated separately for each of the four possible material states for 239Pu (as a function of time after intake) by several European institutions. The new code also implements simultaneously the ICRP Publication 67 systemic biokinetic model for plutonium, to calculate the daily excretion of plutonium in urine and liver as a function of time resulting from the combined blood uptake kinetics (from the wound ) and that of plutonium subsequently transferred to body organs. The utility of the NCRP wound model structure (and recommended inter-compartmental transfer rates) for predicting the wound and axillary lymph node retention measured for USTUR Case 0262 was examined. This worker died 33 y after receiving an accidental finger-puncture wound contaminated with 239PuO2 particles and other plutonium material. A previously published empirical analysis of the data available in this case yielded four distinguishable phases of wound clearance, varying in characteristic rate over 5 orders of magnitude. The ‘mechanistic’ analysis carried out here examines the hypothetical fractionation between material states represented in the NCRP 156 wound model that is needed to ‘fit’ the USTUR Case 0262 data and the goodness-of-fit so obtained. [USTUR-0265-09]
An updated evaluation of data from the 1980 statistical analysis of plutonium in U.S. autopsy tissue
D.C. Mecham (ISU), J.J. Shonka (Shonka Research Associates, Inc.), R.R. Brey (ISU), A.C. James (USTUR)
In a 1980 paper in Health Physics, T. Fox et al. analyzed the results from tissues of over 900 individuals from various regions in the United States. The objective was to determine the level of 239Pu in these tissues due to global fall-out from weapons testing. A comparison was made between 7 regions, including non-worker residents in the vicinity of Los Alamos National Laboratory (LANL). It was concluded that “…no geographic difference in any of the tissue concentrations of plutonium was observed amongst the regions.” This study discusses a re-evaluation of the data from the Fox study. A regrouping of the residents living near LANL into pre and post 1960 sample groups, a reassessment of excluded outliers and an evaluation of liver to bone ratios of plutonium is evaluated to examine the hypothesis: Higher concentrations of 239Pu are present in residents living near LANL in the 1948-1960 time frame in comparison to those in the post-1960 time frame and residents living in the 7 other regions. [USTUR-0274-09]