Mortality Update of a US Cohort of Workers in Petrochemical and Refinery Operations

Our plain-English summary of Mortality Update of a US Cohort of Workers in Petrochemical and Refinery Operations, by M. Korre, E.M. Gallagher, M.A. Bach, et al (Journal of Occupational and Environmental Medicine, 2026).

The study

• Authors: M. Korre, E.M. Gallagher, M.A. Bach, N. Wojcik
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2026;68(9):740-755
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: This study updates mortality trends of over 214,000 men and women working in various petrochemical and refinery operations of a US-based company through December 31, 2020.

Methods: Standardized mortality ratios (SMRs) and 95% confidence intervals were calculated for 112 possible causes of death studied.

Results: SMRs for malignant mesothelioma are highest among men hired during the 1940s and 1950s. Increased SMRs are observed for Parkinson's disease and brain cancer in some subgroups with no consistent occupational pattern. Decreasing mortality trends observed for asbestosis, leukemias, motor neuron diseases, brain cancer in upstream men, and breast cancer among non-White women.

Conclusions: Updates of the mortality surveillance of this large, established cohort are useful in evaluating the chronic health status of this workforce. Additional follow-up time provides the statistical power to clarify earlier findings.

Copyright © 2026 The Author(s). Published by Wolters Kluwer Health, LLC. on behalf of the American College of Occupational and Environmental Medicine.

In plain English

This retrospective cohort study followed 214,327 ExxonMobil US employees, 1979 to 2020. Death rates were compared with US population rates using standardized mortality ratios (SMRs); 1.00 means equal. Asbestos exposure was not measured; job title, operating segment and employment length were stand-ins. Men had more malignant mesothelioma deaths than expected (164 deaths; SMR 1.54, 95% CI 1.31 to 1.79). Highest ratios, in overlapping groupings: men hired in the 1940s (2.29, 95% CI 1.73 to 2.97), downstream men (2.48, 2.03 to 3.01), skilled craftsmen (2.86, 2.15 to 3.72). Women had 5 mesothelioma deaths versus 6.42 expected (not significant). Men's asbestosis deaths were significantly raised (36 deaths; SMR 1.80, 95% CI 1.26 to 2.49). For 2011 to 2020 alone, 9 asbestosis deaths gave SMR 1.30 (95% CI 0.59 to 2.47), not statistically significant. Men's lung cancer deaths were below expected. The authors concluded the main finding was increased mesothelioma risk among downstream men, highest for 1940s to 1960s hires and still raised for 1970s hires (16 deaths; SMR 2.48, 95% CI 1.42 to 4.03). They lacked smoking data and could not quantify specific exposures.

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 study comparing cohort death rates with US general population rates (standardized mortality ratios)
• Who was studied: 214,327 men and women employed full-time for at least 1 day in ExxonMobil US operations (including the heritage Exxon and Mobil companies) between January 1, 1979 and December 31, 2020, followed for mortality through 2020; 5,996,497 person-years; 53,700 deaths
• Exposure: Work in petrochemical and refinery operations. Exposure was not measured. Duration of employment, operating segment (downstream, upstream, chemicals, coal and minerals, corporate global services) and job title were used as surrogates. No asbestos fiber type is named.
• Main results:
  • Men, 1979 to 2020: 164 observed malignant mesothelioma deaths (120 in the previous 1979 to 2010 study), SMR 1.54 (95% CI 1.31 to 1.79)
  • Men hired in the 1940s had the highest mesothelioma SMR by period of hire: 2.29 (95% CI 1.73 to 2.97), 57 deaths
  • Mesothelioma among men in downstream operations: SMR 2.48 (95% CI 2.03 to 3.01), 106 observed and 42.66 expected deaths
  • Mesothelioma among downstream men hired in the 1970s: 16 observed deaths, SMR 2.48 (95% CI 1.42 to 4.03)
  • Mesothelioma among male skilled craftsmen: SMR 2.86 (95% CI 2.15 to 3.72), 55 observed and 19.25 expected deaths
  • Men, 2011 to 2020 update period only: 43 mesothelioma deaths, SMR 1.35 (95% CI 0.98 to 1.82)
  • Women: 5 mesothelioma deaths against 6.42 expected, SMR 0.78 (95% CI 0.29 to 1.73), not statistically significant
  • Asbestosis, men only, 1979 to 2020: SMR 1.80 (95% CI 1.26 to 2.49), based on 36 deaths, statistically significant; there were no asbestosis deaths among women
  • Asbestosis, 2011 to 2020 update period: 9 deaths, SMR 1.30 (95% CI 0.59 to 2.47), not statistically significant
  • Lung cancer among all cohort men was below the general population rate: SMR 0.73 (95% CI 0.71 to 0.76)
  • Parkinson's disease among all cohort men, 1979 to 2020: SMR 1.23 (95% CI 1.13 to 1.32), 638 deaths
• The authors' conclusion: The authors concluded that the main finding was increased mesothelioma mortality among downstream men. It was highest among those hired in the 1940s through 1960s and still elevated among those hired in the 1970s, based on smaller numbers (16 observed deaths). They saw signals of a decreasing asbestosis trend in the update period, which they considered likely due in part to improved work practices and reduced potential exposures.
• Limitations the authors state:
  • No information on smoking, other lifestyle factors, exposures from other jobs or genetics
  • Exposure surrogates (duration, operating segment, job title) prevent quantifying exposure to specific workplace agents
  • Mixed manufacturing and nonmanufacturing work histories are a potential source of exposure misclassification
  • Many comparisons were made without adjustment, which can produce false positives or chance findings
  • A strong healthy worker effect likely accounts for lower SMRs for several broad causes of death
  • Use of personal protective equipment could not be quantified

Topics

The National Library of Medicine indexes this study under subjects our site covers: Refineries and petrochemical plants.

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

Related studies

• Mortality of 196,826 Men and Women Working in U.S.-Based Petrochemical and Refinery Operations: Update 1979 to 2010 — N.C. Wojcik, E.M. Gallagher, et al. (2022)
• 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)
• Systematic Review and Meta-Analysis of Selected Cancers in Petroleum Refinery Workers — A.R. Schnatter, M. Chen, et al. (2018)
• Mortality among maintenance employees potentially exposed to asbestos in a refinery and petrochemical plant — S.P. Tsai, L.C. Waddell, et al. (1996)
• Maintenance work and asbestos-related cancers in the refinery and petrochemical sector — M.M. Finkelstein (1999)
• Dangerous and cancer-causing properties of products and chemicals in the oil refining and petrochemical industry: Part V--Asbestos-caused cancers and exposure of workers in the oil refining industry — M.A. Mehlman (1991)

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