In December, the USTUR mailed its 2025 Registrant newsletter to living Registrants and deceased Registrants’ next of kin. This year’s newsletter included two guest articles from the scientific director of the Million Person Study, Lawrence Dauer. The first article introduced the MPS and the second discussed an observed association between Parkinson’s disease and radiation dose. The newsletter also included the USTUR director’s annual “Direct from the Director” letter, information about a proposal to create a Radiological and Nuclear Security Leadership Academy at WSU, an update on the USTUR’s follow-up urine collection program, a summary of the MPS special session at the 2025 American Public Health Association meeting, and a brief history of the Oak Ridge Associated Universities consortium, which WSU has been asked to join.

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One unique donation to the USTUR is that of a former nuclear worker who inhaled curium. His curium intake was minor in comparison to a much larger plutonium intake; however, relatively little direct human data about curium in humans is available. Curium is a minor actinide that has mostly been studied in animal models, or in terms of excretion of curium in urine after an intake. To our knowledge this is the first time that the curium biokinetic model has been combined with direct measurements of curium in human tissues.

This Registrant received an acute inhalation of curium-244 when a glove box failed. The worksite analyzed one urine sample for curium, but the amount of curium-244 in the sample was below the detection limit. Over five decades later, this individual passed away and donated selected tissues to the USTUR. The USTUR carried out post-mortem measurements to determine the amount of curium in 10 bones and 18 soft tissues. The results of these analyses confirmed that an intake had occurred. The worker was estimated to have inhaled approximately 840 mBq of curium-244, most of which was in the skeleton (90%), followed by muscle tissue (3.4%) and the liver (2.2%). The mass of the skeleton, and the muscular system, is much larger than that of the liver. This makes it useful to consider the concentration of radionuclides, such as curium, in tissues rather than the total activity. The highest concentration of curium-244 was observed in the tissues of the respiratory tract (182 mBq per kg), followed by the skeleton (77 mBq per kg) and the liver (15 mBq per kg).

Sergey Tolmachev presented this research at the 2025 Radiation Research Society meeting last September. A more comprehensive overview is available in the presentation slides from this meeting, which feature plots comparing the modeled retention of curium in various organs to the corresponding measured values. The slides also include a comparison between the distribution of curium to that of americium.

Presentation slides

USTUR research provides vital insights into the behavior of actinides in the human body, and USTUR faculty have been a consistent part of the conversation at both national and international radiation protection conferences. USTUR Director, Sergey Tolmachev, chaired a session on radionuclide decorporation agents and chelation therapy at the 2025 Radiation Research Society meeting and delivered a talk on a USTUR study involving a worker exposed to curium-244. This study is the most extensive work on the biokinetics and distribution of curium-244 in the human body. This is an example of the unique value that USTUR research has for the body of knowledge about actinides in humans. Two posters were also presented. George Tabatadze described the use of the ionizing radiation quantum imaging detector to quantify radium-226 in human bone, and Sara Dumit of Los Alamos National Laboratory summarized biokinetic modeling of plutonium decorporation in a female USTUR Registrant.

USTUR faculty have also been active at other scientific meetings nationally and internationally. Dr. Tolmachev presented a poster emphasizing the importance of human data to actinide research at the International Commission on Radiological Protection’s (ICRP) 8^th International Symposium on the System of Radiological Protection. Xirui Liu presented a simulation study on the impact of cause-of-death misclassification in radiation health risk models at both the annual Health Physics Society Meeting and the American Public Health Association Annual Meeting. Maia Avtandilashvili presented the findings of a study that used post-mortem organ measurements to validate a Bayesian approach to modeling dosimetric uncertainty. While biases in recruitment methods prevent the USTUR from directly conducting epidemiological studies, Dr. Avtandilashvili and Ms. Liu’s presentations demonstrate the USTUR’s unique ability to support epidemiological studies by shedding light on the uncertainties that are present in both the doses to workers and the causes of death reported on death certificates.

Xirui Liu gave an invited talk highlighting the USTUR history and research at the Occupational Internal Dosimetry Training and Meeting hosted by Georgia Institute of Technology (Atlanta, GA). This in-person training course for radiation protection professionals was focused on internal radiation dosimetry principles, tools, and regulatory applications.

Presentation slides
Training and Meeting Website

The USTUR’s 2025 Annual Report has been completed and is available for download. The document summarizes organization, activities, and scientific accomplishments at the USTUR from April 1, 2024 to March 31, 2025 (fiscal year 2025). Research summaries include: impact of death certificate cause-of-death misclassification, vacuum drying to improve tissue sample preparation, and a curium-244 case study.

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The USTUR’s Assistant Director, George Tabatadze, was recently elected to the Health Physics Society (HPS) Board of Directors. He will take office at the 70th Annual Meeting of the HPS in July 2025 for a three-year term. Dr. Tabatadze is a long-time HPS member who has served on the International Collaboration, Science Support, and Academic Education Committees, as well as in the Columbia Chapter of the HPS, where he is a past president and continues to play an active role in its leadership. He is committed to advocating for sound radiation safety practices, supporting academic programs and students, and fostering professional development and mentoring. He looks forward to this opportunity to strengthen the HPS community, promote collaboration, and ensure that HPS continues to be a trusted source of expertise in the field of radiation protection.

USTUR faculty recently participated in the National Council on Radiation Protection and Measurements (NCRP) Annual Meeting, where they authored three presentations that highlighted the USTUR’s role in supporting epidemiological studies by helping to improve the reliability of both dose assessment and disease outcome data. This year’s NCRP meeting focused on the work that is being conducted by the Department of Energy’s Million Person Study (MPS). The million person study is investigating a range of health effects of low-dose radiation on American workers and veterans.

The USTUR’s presentations described several of the ways that the USTUR is supporting the MPS in their mission. USTUR director, Sergey Tolmachev’s invited podium presentation provided a brief introduction to the USTUR, and explored topics aimed at improving dose estimates. These included measuring the distribution on plutonium within the human heart, and investigating how well the standard biokinetic models predict the amount of plutonium that is retained in an individual worker’s organs. Xirui Liu presented a poster on her research to simulate the likelihood that mistakes on death certificates will lead to incorrect conclusions in epidemiological studies. Her work focused on the likelihood that over- and under-classification of cancer will lead to the conclusion that there is an association between cancer and radiation dose when in fact there was no association in the true distribution of diseases in a population. The simulated nature of the study means that her findings can be generalized to diseases other than cancer and exposures to non-radiological hazards. Additionally, Dr. Tolmachev was an author on a poster presentation that explored the distribution of radium in cardiac and bone samples from two radium-exposed individuals associated with the historical studies of radium in humans carried out at Argonne National Laboratory. This collaborative work was presented by Jessica Linson of the University of Missouri Department of Chemistry, and the samples were provided by the National Human Radiobiology Tissue Repository (NHRTR), a tissue collection associated with the USTUR that houses samples and records from several historical studies of radionuclides in humans. This work indicated that, for a single case, ²²⁶Ra was not uniformly distributed in the heart.

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Photo caption: Sergey Tolmachev, Kathryn Higley (NCRP President) and Xirui Liu at the National Council on Radiation Protection and Measurements Meeting.

George Tabatadze and Maia Avtandilashvili recently had the honor of being invited as ICRP experts to teach an internal dosimetry course for the UAE Federal Authority for Nuclear Regulation (FANR) in Abu Dhabi, October 14-18. The week-long course was organized jointly by FANR, ICRP, and the European Radiation Dosimetry Group (EURADOS). It included lectures that covered key concepts, such as intake routes and biokinetic models, as well as afternoon sessions dedicated to hands-on exercises that allowed participants to apply the concepts learned during the lectures. It was a privilege to be part of the world-renowned group of experts that were teaching the course. The discussions were insightful, and it was truly inspiring to see the level of engagement from the audience, with complete attention and participation throughout the entire day!

For more information, take a look at the official course webpage.

On September 9, 2024, the USTUR joined the CBRNResponder Network. CBRNResponder is a platform for all chemical, biological, radiological, and nuclear (CBRN) incident data sharing and multi-hazard event management. The decision to join this network was made following a discussion during 2024 Scientific Advisory Committee meeting.

As stated on their website: “CBRNResponder is a product of collaboration sponsored by Federal Emergency Management Agency (FEMA), Department of Energy (DOE)/National Nuclear Security Administration (NNSA), NA-84 and the Office of Radiological Security (ORS), the Environmental Protection Agency (EPA), the Defense Threat Reduction Agency (DTRA), and the Department of Homeland Security’s Science and Technology Directorate (DHS S&T), and is provided as a free service to all state, local, tribal, and territorial emergency response organizations.”