Analyses of radiation and mesothelioma in the US Transuranium and Uranium Registries

Our plain-English summary of Analyses of radiation and mesothelioma in the US Transuranium and Uranium Registries, by H. Gibb, K. Fulcher, S. Nagarajan, et al (American Journal of Public Health, 2013).

The study

• Authors: H. Gibb, K. Fulcher, S. Nagarajan, S. McCord, N.A. Fallahian, H.J. Hoffman, C. Haver, S. Tolmachev
• Journal: American Journal of Public Health
• Published: 2013;103(4):710-6
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: We examined the relationship between radiation and excess deaths from mesothelioma among deceased nuclear workers who were part of the US Transuranium and Uranium Registries.

Methods: We performed univariate analysis with SAS Version 9.1 software. We conducted proportionate mortality ratio (PMR) and proportionate cancer mortality ratio (PCMR) analyses using the National Institute for Occupational Safety and Health Life Table Analysis System with the referent group being all deaths in the United States.

Results: We found a PMR of 62.40 (P < .05) and a PCMR of 46.92 (P < .05) for mesothelioma. PMRs for the 4 cumulative external radiation dose quartiles were 61.83, 57.43, 74.46, and 83.31. PCMRs were 36.16, 47.07, 51.35, and 67.73. The PMR and PCMR for trachea, bronchus, and lung cancer were not significantly elevated.

Conclusions: The relationship between cumulative external radiation dose and the PMR and PCMR for mesothelioma suggests that external radiation at nuclear facilities is associated with an increased risk of mesothelioma. The lack of a significantly elevated PMR and PCMR for trachea, bronchus, and lung cancer suggests that asbestos did not confound this relationship.

In plain English

This study examined deaths among 329 deceased donors to the US Transuranium and Uranium Registries, mostly defense nuclear workers. The authors compared each cause's share of all deaths (PMR) and each cancer's share of cancer deaths (PCMR) with US figures. Dosimeter records of cumulative external radiation dose existed for 293 donors. The 7 mesothelioma deaths gave a PMR of 62.40 (95% CI 25.09 to 128.57) and a PCMR of 46.92 (18.60 to 88.11). Across four dose groups, mesothelioma PMRs were 61.83, 57.43, 74.46 and 83.31; PCMRs rose from 36.16 to 67.73. Confidence intervals were wide (lowest-dose PMR 1.57 to 344.52; highest 17.18 to 243.48), and the two lowest groups had one mesothelioma death each. No dose-response was found for lung dose rate from internal alpha emitters. Lung cancer was not significantly elevated. Asbestosis was significantly elevated (2 deaths; PMR 23.22, 95% CI 2.81 to 83.90). Four of the 7 mesothelioma cases reported asbestos exposure. The authors concluded that the dose pattern suggests external radiation at nuclear facilities is associated with increased mesothelioma risk; they noted their analysis was limited by size.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Proportionate mortality analysis of deceased registry donors (PMR and PCMR, adjusted for age, race, sex and calendar time, with all US deaths as the reference), with analysis by quartile of cumulative external radiation dose
• Who was studied: 329 deceased US Transuranium and Uranium Registries donors (332 minus 3 people who were medically exposed to Thorotrast). Of these, 317 worked at a defense nuclear facility (126 at Rocky Flats and 116 at Hanford), 10 at a uranium mine or mill, and 2 at a source manufacturing facility. Deaths occurred between 1967 and 2010.
• Exposure: Two radiation measures were studied. The first was cumulative and annual external (penetrating) radiation dose in mSv, taken from work site dosimeter records: 279 registrants had records for their whole employment, 14 had partial records and 36 had none. The second was the terminal dose rate to the lung from internally deposited alpha emitters (plutonium, americium, uranium). Asbestos exposure was known only from a questionnaire item: 60 of 329 donors said they had worked with or around asbestos.
• Main results:
  • Mesothelioma, all registrants: 7 deaths, PMR 62.40 (95% CI 25.09, 128.57).
  • Mesothelioma, all registrants: PCMR 46.92 (95% CI 18.60, 88.11).
  • Mesothelioma by quartile of cumulative external radiation dose (1, 1, 2 and 3 mesothelioma deaths): PMRs were 61.83, 57.43, 74.46 and 83.31, and PCMRs were 36.16, 47.07, 51.35 and 67.73.
  • The quartile confidence intervals were wide. In the lowest dose quartile (0.17 to 23.84 mSv) the PMR was 61.83 (95% CI 1.57, 344.52) and the PCMR was 36.16 (95% CI 0.03, 242). In the highest quartile (187.75 to 1829.70 mSv) the PMR was 83.31 (95% CI 17.18, 243.48) and the PCMR was 67.73 (95% CI 15.71, 204.31).
  • Mesothelioma deaths had an average cumulative external radiation dose of 191.68 mSv (median 129.90), compared with 110.54 mSv for other cancer deaths and 146.80 mSv for noncancer deaths.
  • No dose-response was found between terminal dose rate to the lung and mesothelioma PMRs or PCMRs.
  • Cancer of the trachea, bronchus and lung (35 deaths) was not significantly elevated: PMR 1.16 (95% CI 0.81, 1.62); PCMR 0.87 (95% CI 0.60, 1.18).
  • Asbestosis was significantly elevated: 2 deaths, PMR 23.22 (95% CI 2.81, 83.90). Amosite, crocidolite, tremolite and anthophylite (as spelled in the article) fibers were found at autopsy in the lungs of one of these workers.
  • Self-reported asbestos exposure among the 7 mesothelioma deaths: 4 said yes, 2 said no and 1 did not respond.
• The authors' conclusion: The authors concluded that the relationship between cumulative external radiation dose and the mesothelioma PMR and PCMR suggests that external radiation at nuclear facilities is associated with an increased risk of mesothelioma. They also concluded that the lack of elevated lung cancer suggests asbestos did not confound this relationship.
• Limitations the authors state:
  • The analysis was limited by size: there were only 7 mesothelioma deaths, which makes the dose-response evaluation problematic.
  • Four of the mesothelioma cases had previously worked in occupations associated with increased mesothelioma risk, which could have confounded the results.
  • Participation in the registry was voluntary, and its effect on the results is unknown.
  • External dose records are presumed less accurate for smaller doses and for doses recorded in the facilities' early years.
  • Terminal dose rate to the lung may be a poor stand-in for cumulative dose to the pleura from internal alpha emitters.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Bronchus, Lung Cancer.

Related studies

• A Monte Carlo t Test to Evaluate Mesothelioma and Radiation in the US Transuranium and Uranium Registries — J.Y. Zhou, S.L. McComish, et al. (2019)
• USTUR Special Session Roundtable-US Transuranium and Uranium Registries (USTUR): A Five-decade Follow-up of Plutonium and Uranium Workers — S.Y. Tolmachev, M.J. Swint, et al. (2019)
• Gibb et al. respond — H. Gibb, K. Fulcher, et al. (2014)
• Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS) — D.B. Richardson, E. Cardis, et al. (2015)
• Impact of chemical exposure on cancer mortality in a French cohort of uranium processing workers — S. Zhivin, D. Laurier, et al. (2013)
• Bias in the proportionate mortality ratio analysis of small study populations: a case on analyses of radiation and mesothelioma — J.Y. Zhou (2014)

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