Mortality among workers at Oak Ridge National Laboratory

Our plain-English summary of Mortality among workers at Oak Ridge National Laboratory, by D.B. Richardson, S. Wing, A. Keil, et al (American Journal of Industrial Medicine, 2013).

The study

• Authors: D.B. Richardson, S. Wing, A. Keil, S. Wolf
• Journal: American Journal of Industrial Medicine
• Published: 2013;56(7):725-32
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Workers employed at the Oak Ridge National Laboratory (ORNL) were potentially exposed to a range of chemical and physical hazards, many of which are poorly characterized. We compared the observed deaths among workers to expectations based upon US mortality rates.

Methods: The cohort included 22,831 workers hired between January 1, 1943 and December 31, 1984. Vital status and cause of death information were ascertained through December 31, 2008. Standardized mortality ratios (SMRs) were computed separately for males and females using US and Tennessee mortality rates; SMRs for men were tabulated separately for monthly-, weekly-, and hourly-paid workers.

Results: Hourly-paid males had more deaths due to cancer of the pleura (SMR = 12.09, 95% CI: 4.44, 26.32), cancer of the bladder (SMR = 1.89, 95% CI: 1.26, 2.71), and leukemia (SMR = 1.33, 95% CI: 0.87, 1.93) than expected based on US mortality rates. Female workers also had more deaths than expected from cancer of the bladder (SMR = 2.20, 95% CI: 1.20, 3.69) and leukemia (SMR = 1.64, 95% CI: 1.09, 2.36). The pleural cancer excess has only appeared since the 1980s, approximately 40 years after the start of operations. The bladder cancer excess was larger among workers who also had worked at other Oak Ridge nuclear weapons facilities, while the leukemia excess was among people who had not worked at other DOE facilities.

Conclusions: Occupational hazards including asbestos and ionizing radiation may contribute to these excesses.

Copyright © 2013 Wiley Periodicals, Inc.

In plain English

This mortality study followed 22,831 workers (16,912 men, 5,919 women) hired at Oak Ridge National Laboratory in Tennessee before 1985, tracking deaths through 2008. The authors compared deaths with those expected from US rates and analyzed men by pay group. They had little information on individual exposure to hazards such as asbestos. Overall, the workers died at lower rates than the US population. Hourly-paid men, mainly laborers, machinists, pipefitters and other manual workers, had 6 pleural cancer deaths, a standardized mortality ratio (SMR) of 12.09 (95% CI 4.44 to 26.32). No pleural cancer deaths occurred before 1980. Mesothelioma, counted only for 1999 to 2008, had SMRs of 2.24 in weekly-paid and 1.37 in monthly-paid men, with confidence intervals that included 1. Pleural cancer and mesothelioma excesses were greater among men who had also worked at other Department of Energy facilities. Women had no deaths from pleural cancer or mesothelioma. Bladder cancer was elevated in hourly-paid men (SMR 1.89, 95% CI 1.26 to 2.71) and women (SMR 2.20, 95% CI 1.20 to 3.69). The authors concluded that occupational hazards including asbestos and ionizing radiation may contribute to these excesses.

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: Retrospective cohort mortality study comparing observed deaths with deaths expected from US (and Tennessee) mortality rates, as standardized mortality ratios (SMRs)
• Who was studied: 22,831 Oak Ridge National Laboratory workers (16,912 men, 5,919 women) hired between 1943 and 1984 who worked at least 30 days, followed for vital status through December 31, 2008; men were analyzed separately as monthly-, weekly- and hourly-paid workers
• Exposure: Employment at Oak Ridge National Laboratory, a US Department of Energy research facility, with potential exposure to ionizing radiation and non-radiological hazards such as asbestos, solvents and metals. There were no individual measurements of non-radiological exposures, so pay code (hourly-paid men were mainly laborers, machinists, pipefitters and operators) and work at other DOE facilities were used instead.
• Main results:
  • Hourly-paid men: 6 deaths from cancer of the pleura, SMR 12.09 (95% CI 4.44, 26.32). Weekly-paid men had 1 such death (SMR 1.44, 95% CI 0.04, 8.00) and monthly-paid men had 1 (SMR 0.87, 95% CI 0.02, 4.85).
  • Mesothelioma (1999 to 2008 only) among men: hourly-paid 1 death, SMR 0.78 (95% CI 0.02, 4.37); weekly-paid 4 deaths, SMR 2.24 (95% CI 0.61, 5.73); monthly-paid 5 deaths, SMR 1.37 (95% CI 0.44, 3.20)
  • Men who had worked at other DOE facilities as well as ORNL: pleural cancer SMR 4.25 (95% CI 1.16, 10.89) and mesothelioma SMR 2.72 (95% CI 1.09, 5.60). Men who worked only at ORNL: pleural cancer SMR 2.85 (95% CI 0.78, 7.30) and mesothelioma SMR 0.73 (95% CI 0.15, 2.12).
  • Among men there were no pleural cancer deaths before 1980; the pleural cancer SMR was above 1 from the 1980 to 1984 period through 1999.
  • Women: no deaths due to pleural cancer or mesothelioma were observed
  • Bladder and other urinary cancer: hourly-paid men 29 deaths, SMR 1.89 (95% CI 1.26, 2.71); women 14 deaths, SMR 2.20 (95% CI 1.20, 3.69)
  • Leukemia: women 28 deaths, SMR 1.64 (95% CI 1.09, 2.36); hourly-paid men 27 deaths, SMR 1.33 (95% CI 0.87, 1.93)
  • Deaths from all causes were below national rates: 10%, 15% and 45% lower among hourly-, weekly- and monthly-paid men; women's all-cause SMR was 0.85 (95% CI 0.81, 0.90)
• The authors' conclusion: The authors concluded that occupational hazards including asbestos and ionizing radiation may contribute to the excesses of pleural cancer, bladder cancer and leukemia they observed.
• Limitations the authors state:
  • There was little information on workers' exposure to non-radiological hazards such as asbestos.
  • Complete employment histories outside ORNL were not available; only employment at other DOE facilities was known.
  • Before ICD-10 there was no separate code for malignant mesothelioma, and specific reference rates for mesothelioma only began in 1999.
  • Excess deaths certified to symptoms and ill-defined conditions may bias SMRs for specific, less common causes, such as site-specific cancers, downward.
  • Smoking may have been less common than in the general population, which may have negatively confounded the bladder cancer SMRs.
  • Results for non-white workers were not reported because they were too imprecise.

Topics

Medical terms in this study, explained in our Lexicon: standardized mortality ratio (SMR), Pleura.

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