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.

The development of the plutonium lung clearance model for exposure estimation of the Mayak production association, nuclear plant workers.

The purpose of this study was to develop a biokinetic model that uses urinary plutonium excretion rate data to estimate the plutonium accumulation in the human respiratory tract after occupational exposure. The model is based on autopsy and urinalysis data, specifically the plutonium distribution between the respiratory tract and the remainder of the body, taken from 543 former workers of a radiochemical facility at the Mayak Production Association (MPA) plant. The metabolism of plutonium was represented with a compartmental model, which considers individual exposure histories and the inherent solubility properties of industrial plutonium aerosols. The transport properties of plutonium-containing aerosols were estimated by experimentally defining their in vitro solubility. The in vitro solubilities were found by dialysis in a Ringer's solution. Analysis of the autopsy data indicated that a considerable fraction of the inhaled plutonium is systemically redistributed rapidly after inhalation. After the initial dynamic period, a three-compartment model describes the retention in the respiratory tract. One compartment describes the nuclide retained in the lungs, the second compartment describes a plutonium lung concentration that exponentially decreases with time, and the third compartment describes the concentration in the pulmonary lymph nodes. The model parameters were estimated by minimizing sum squared of the error between the tissue and bioassay data and the model results. The parameters reflect the inverse relationship between plutonium retention in lungs and the experimentally derived aerosol transportability. The model was validated by comparing the autopsy results with in vivo data for 347 cases. The validation indicates that the model parameters are unbiased. This model is being used to estimate individual levels of nuclide accumulation and to compute radiation doses based upon the urinary excretion rates.