Long-term retention and distribution of highly enriched uranium in an occupationally exposed female.

The United States Transuranium and Uranium Registries' (USTUR) female whole body tissue donor studied here was occupationally exposed to highly enriched uranium for 17 years. One hundred and twenty-nine tissue samples were collected at the time of death, 31 years post-exposure. These samples were radiochemically analyzed for uranium. The highest uranium concentration of 16.5 ± 2.0 µg kg-1 was measured in the lungs, and the lowest concentration of 0.11 ± 0.01 µg kg-1 in the liver. The thyroid had the highest concentration of 6.3 ± 2.9 µg kg-1 among systemic tissues. Mass-weighted average concentration in the entire skeleton was estimated to be 1.60 ± 0.19 µg kg-1. In the skeleton, uranium was non-uniformly distributed among different bones. Thirty-one years after the intake, approximately 40% of occupational uranium was still retained in the skeleton, followed by the kidneys (~ 30%), and the brain and liver (~ 10%). Systemic uranium was equally distributed between the skeleton and soft tissues. Uranium content in systemic organs followed the pattern: skeleton > > brain ≈ kidneys > heart ≈ liver > thyroid ≈ spleen. Uranium distribution in this female was compared to previously published USTUR data for male tissue donors. It is concluded that no difference in uranium systemic distribution was observed between female and male individuals. It is demonstrated that dose assessment based on the current ICRP biokinetic model overestimated the dose to the brain by 20%.

Forty-eight-year follow-up of a female worker exposed to highly enriched uranium via chronic and acute inhalation.

The United States Transuranium and Uranium Registries (USTUR) is a unique resource of data and materials for studying biokinetics of uranium in the human body. In this study, bioassay data and post-mortem organ activities from a female whole-body USTUR donor who was exposed to highly enriched uranium were analyzed using the IMBA Professional Plus® software to derive the best estimate of the total intake. The resulting radiation doses delivered to this individual's whole body and major target organs were calculated from estimated intake based on case-specific dose coefficients derived using the AIDE® software. Both intake and dose calculations were carried out using the biokinetic and dosimetric models recommended by the International Commission on Radiological Protection (ICRP) in its Occupational Intakes of Radionuclides publication series. Different exposure scenarios including chronic and acute inhalation intakes were tested. A combination of a chronic inhalation intake and two acute inhalation intakes appears to best describe the bioassay data. To fit this female individual's autopsy data, the transfer rate from the liver to the blood was increased by a factor of 8 and the transfer rate from the kidneys to the blood was decreased by a factor of 2.2. This resulted in the best fit to all data (p = 0.519). The total intake was estimated to be 44.1 kBq, and the committed effective dose was 211 mSv with 96.8% contributed by 234U. 96.6% of the committed effective dose was contributed by the lungs. The remaining 3.4% of the committed effective dose was contributed by all systemic tissues and organs with the highest contribution (0.40%) from the red bone marrow. It is concluded that the current ICRP models, with the adjustment for smoking status, adequately describe uranium biokinetics for this individual except retention in the liver and kidneys. However, this study was based on a single case and may not be sufficient to identify any apparent sex-specific differences in uranium biokinetics.