Mortality of 196,826 Men and Women Working in U.S.-Based Petrochemical and Refinery Operations: Update 1979 to 2010

Our plain-English summary of Mortality of 196,826 Men and Women Working in U.S.-Based Petrochemical and Refinery Operations: Update 1979 to 2010, by N.C. Wojcik, E.M. Gallagher, M.S. Alexander, et al (Journal of Occupational and Environmental Medicine, 2022).

The study

• Authors: N.C. Wojcik, E.M. Gallagher, M.S. Alexander, R.J. Lewis
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2022;64(3):250-262
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To describe mortality trends of men and women working in various petrochemical and refinery operations of a U.S.-based company.

Methods: The cohort consists of full-time employees with at least 1 day of service during 1979 through 2010. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) were calculated for 111 possible causes of death studied.

Results: SMRs for malignant mesothelioma and asbestosis were highest for the 1940s decade of hire. Increased SMRs were observed for malignant melanoma and motor neuron disease with no obvious work patterns. Decreasing mortality patterns were observed for aplastic anemia and acute nonlymphocytic leukemia.

Conclusions: Mortality surveillance of this large established cohort aids in assessing the chronic health status of the workforce. Identifying methods for incorporating job-exposure matrices and nonoccupational risk factors could further enhance interpretations for some findings such as motor neuron disease.

Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Occupational and Environmental Medicine.

In plain English

This retrospective cohort study followed 196,826 full-time ExxonMobil U.S. employees (141,742 men, 55,084 women) who worked at least one day between 1979 and 2010. The authors compared deaths with numbers expected from U.S. general population rates; for mesothelioma deaths in 1979 to 1998, expected numbers came from SEER cancer incidence rates. All-cause deaths were 30% lower than expected in men and 22% lower in women. Men had 120 malignant mesothelioma deaths, a standardized mortality ratio (SMR) of 1.61 (95% CI 1.34 to 1.92). The SMR was highest for men hired in the 1940s (2.36, 95% CI 1.78 to 3.08). Mesothelioma risk was concentrated in downstream operations, skilled craftsmen and managers/supervisors. Men also had 27 asbestosis deaths (SMR 1.97, 95% CI 1.30 to 2.87). Women had 3 mesothelioma deaths against 3.9 expected. Melanoma and motor neuron disease deaths exceeded expected in both sexes. Asbestos exposure was not measured; the authors used job title, operating segment and employment length as stand-ins and lacked smoking data. The authors concluded that mesothelioma and asbestosis risk was highest among men hired in the 1940s.

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 occupational cohort mortality study (update of an earlier cohort study), comparing cohort deaths with expected deaths based on U.S. general population rates (standardized mortality ratios). For mesothelioma deaths coded under ICD-9 (1979 to 1998), expected numbers used SEER mesothelioma incidence rates.
• Who was studied: 196,826 men and women employed full-time in ExxonMobil U.S. operations for at least one day between January 1, 1979 and December 31, 2010 (141,742 men, 55,084 women), contributing 4,473,909 person-years
• Exposure: Employment in petrochemical, refinery and other company operations. Asbestos exposure was not measured and no fiber types are named. The authors used operating segment, job title and duration of employment as stand-ins for exposure. They described downstream operations as the segment where higher asbestos exposures were more likely to have occurred.
• Main results:
  • Men: all-cause mortality was 30% lower than for men in the U.S. general population over 1979 to 2010
  • Women: all-cause mortality was 22% lower than for women in the U.S. general population
  • Men: 120 malignant mesothelioma deaths (up from 64 in the original study), SMR 1.61 (95% CI 1.34 to 1.92)
  • Men: mesothelioma SMR was highest for those hired in the 1940s, SMR 2.36 (95% CI 1.78 to 3.08)
  • Men: mesothelioma risk was concentrated in downstream operations, SMR 2.62 (95% CI 2.11 to 3.23). It was also concentrated among skilled craftsmen, SMR 2.90 (95% CI 2.10 to 3.91), and managers/supervisors, SMR 1.88 (95% CI 1.33 to 2.57).
  • Women: 3 observed versus 3.9 expected malignant mesothelioma deaths
  • Men: 27 asbestosis deaths, SMR 1.97 (95% CI 1.30 to 2.87)
  • Men in downstream operations: asbestosis SMR 2.97 (95% CI 1.76 to 4.70)
  • Male skilled craftsmen (all operating segments combined): asbestosis SMR 5.27 (95% CI 2.81 to 9.02)
  • Malignant melanoma: men SMR 1.17 (95% CI 1.02 to 1.33)
  • Malignant melanoma: women SMR 1.44 (95% CI 1.01 to 1.99)
  • Motor neuron disease: men SMR 1.21 (95% CI 1.00 to 1.44)
  • Motor neuron disease: women SMR 1.64 (95% CI 1.11 to 2.34), based on 30 deaths
• The authors' conclusion: The authors concluded that mortality risk for malignant mesothelioma and asbestosis was highest among men hired in the 1940s.
• Limitations the authors state:
  • No information on smoking and other lifestyle factors, exposures from other jobs or outside work, or genetics
  • No systematic link between the cohort and exposure sampling data for specific chemical exposures
  • No data on use of personal protective equipment
  • No data to evaluate talcum powder use as a possible risk factor for mesothelioma
  • Causes of death taken from death certificates may be misclassified
  • A strong healthy worker effect likely explains the lower SMRs for several causes, and findings based on small numbers are more prone to chance

Topics

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

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

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• Update of the Texaco mortality study 1947-93: Part II. Analyses of specific causes of death for white men employed in refining, research, and petrochemicals — B.J. Divine, C.M. Hartman, et al. (1999)
• Long-term follow-up mortality study of petroleum refinery and chemical plant employees — S.P. Tsai, E.L. Gilstrap, et al. (1996)
• Update of mortality and cancer incidence in the Australian petroleum industry cohort — R.T. Gun, N. Pratt, et al. (2006)
• Asbestos exposure and cancer mortality among petroleum refinery workers: a Poisson regression analysis of updated data — F. Montanaro, M. Ceppi, et al. (2004)

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