Health Physics Society Meeting, Baltimore, MD, July 13-17, 2014
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USTUR faculty authored one presentation at the 59th Annual Meeting of the Health Physics Society (HPS) in Baltimore, MD, July 13-17, 2014. Maia Avtandilashvili presented a case study of a worker who was exposed to plutonium as a result of a wound in the workplace. Dr. Avtandilashvili tested the NCRP wound model by modeling the worker’s urinary excretion and organ retention using the Integrated Modules for Bioassay Analysis (IMBA) Professional Plus software.
Additionally, Joey Zhou (U.S. Department of Energy) presented a critique of a study on mesothelioma among USTUR registrants that was published in April 2013.
USTUR Whole-body Case 0212: Testing NCRP wound model
M. Avtandilashvili (USTUR), S.L. McComish (USTUR), S.Y. Tolmachev (USTUR)
The National Council of Radiation Protection and Measurements'(NCRP) wound model was applied to the data from United States Transuranium and Uranium Registries’ whole-body donor (Registrant). The Registrant (Case 0212) was exposed to plutonium nitrate as a result of occupational wound injury. Chelation treatment with intravenous injection of Ca-DTPA was administered on a bi-weekly basis over about six months. Two hundred and five urine samples were collected over about 3.5 years post-accident and analyzed for plutonium activity. A total of 916 Bq of plutonium was excreted in urine during the treatment period with maximum excretion rate of 73 Bq d-1 on the first day post-intake. The average post-treatment urinary excretion rate was 0.02 ± 0.01 Bq d-1. The individual died 17 years post-accident, at age 56, from severe pulmonary emphysema. At autopsy, all major soft tissues and bones were collected for radiochemical analyses of 238Pu, 239/240Pu and 241Am. From tissue radiochemical analyses, 239/240Pu retention in liver, skeleton and wound was estimated at 80.3 Bq, 114.5 Bq and 2.3 Bq, respectively. Total systemic 239/240Pu activity at the time of death was calculated at a magnitude of 229.4 Bq. Application of the NCRP wound model for strongly retained material resulted in a credible fit to the post-treatment (‘baseline’) urine data based on Chi-Square statistics (p = 0.246) and predicted plutonium liver and skeletal activity within 25% of the post-mortem activities. Using IMBA Professional Plus, the fraction of plutonium wound deposition not removed by DTPA therapy was estimated at 364 Bq. This resulted in the residual committed effective dose of 177 mSv. Accounting for plutonium eliminated with urine during the chelation therapy, a total ‘untreated’ intake of 1,280 Bq and the projected committed effective dose of 622 mSv were calculated. [USTUR-0361-14A]
Incorrect analysis of radiation and mesothelioma in the U.S. Transuranium and Uranium Registries
J. Zhou (DOE)
A recently published study, "Analyses of Radiation and Mesothelioma in the U.S. Transuranium and Uranium Registries", by Gibb et al. (American Journal of Public Health 103: 710-716; 2013) examines seven mesothelioma deaths among a population of 329 deceased registrants in the United States Transuranium and Uranium Registries (USTUR). The study finds a proportionate mortality ratio (PMR) of 62.40 for mesothelioma and suggests that cumulative external radiation is associated with an increased risk of mesothelioma. The reported PMR of 62.4 for mesothelioma is strikingly large and does not add up by quick examination. A PMR is defined as the proportion of observed deaths from a given cause in a study population divided by the proportion of deaths expected from this cause in a standard population. The proportion of observed deaths from mesothelioma among all USTUR deaths is 2.1% (7/329), while the proportion of deaths from mesothelioma among all U.S. deaths is approximately 0.1%, as cited by the Gibb study. Therefore, a crude estimate of the PMR for mesothelioma is only 21.0 (2.1% / 0.1%). Furthermore, mesothelioma is primarily an occupational disease, and the USTUR registrants were overwhelmingly adult male Caucasians. Since mesothelioma accounts for over 0.16% of all deaths in the population of American male Caucasians over age 30, a better estimate of the PMR for mesothelioma is 13.1 (2.1% / 0.16%). This presentation reveals that the Gibb study failed to consider the disease coding change for mesothelioma over the timeframe of the study, resulting in flawed results on radiation and mesothelioma. [USTUR-0362-14A]