An updated mortality study of workers at a petroleum refinery in Beaumont, Texas

Our plain-English summary of An updated mortality study of workers at a petroleum refinery in Beaumont, Texas, by G.K. Raabe, K.W. Collingwood, O. Wong (American Journal of Industrial Medicine, 1998).

The study

• Authors: G.K. Raabe, K.W. Collingwood, O. Wong
• Journal: American Journal of Industrial Medicine
• Published: 1998;33(1):61-81
• Cited by: 40 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The mortality experience of 7,119 workers who were employed at a Beaumont, Texas, refinery for at least 1 year between 1945 and 1987 was investigated. Mortality analyses based on standardized mortality ratios (SMRs) and 95% confidence intervals (95% CI) showed overall mortality was significantly lower than expected compared with the U.S. general population (SMR = 82, 95% CI = 79-86). Total cancer mortality was also lower than expected (SMR = 92, 95% CI = 84-100). Significant mortality deficits from several malignant and nonmalignant diseases were reported. A significant mortality increase in the broad category of lymphatic and hematopoietic cancers was found (SMR = 133, 95% CI = 103-170). This increase was attributed to a nonsignificant elevation in leukemia of all cell types combined (SMR = 139, 95% CI = 92-201) and a borderline significant increase in other lymphatic tissue cancer (SMR = 158, 95% CI = 101-235). The elevation in leukemia was confined to workers hired before 1950. Furthermore, the leukemia excess was shown to have peaked during the 1960s, with mortality no longer elevated post-1980. Analyses of cell type-specific leukemias showed a similar temporal pattern for acute myeloid leukemia (AML) which was not significantly elevated (SMR = 136, 95% CI = 59-268). Mortality from other leukemia cell types was similar to or lower than expected. Mortality from non-Hodgkin's lymphoma (NHL) (SMR = 140, 95% CI = 88-211) and multiple myeloma (MM) (SMR = 121, 95% CI = 55-230) were increased, but neither was statistically significant nor likely to be related to refinery employment. No death from asbestosis was reported, and mortality from mesothelioma and pulmonary fibrosis was lower than expected. Lung cancer mortality for the overall cohort was similar to expected. For the overall cohort, analyses by duration of employment and time since first employment showed no evidence of any trends for increasing cause-specific mortality. Separate analyses of male workers employed in operator jobs showed mortality patterns that were more favorable than those of the total cohort. Maintenance craftworkers showed statistically significant elevations in mortality for prostate cancer (SMR = 145, 95% CI = 107-194), leukemia (SMR = 179, 95% CI = 111-273), and other lymphatic tissue cancer (SMR = 233, 95% CI = 138-368). Detailed analyses indicated that, among maintenance craftworkers, mortality was elevated for AML, NHL, and MM, but none was significant. Furthermore, no upward trend by duration of maintenance jobs was observed. A small increase of lung cancer was observed among maintenance craftworkers (SMR = 120, 95% CI = 99-145), which was borderline significant. No relationship between lung cancer and duration of maintenance employment was found. In contrast, a deficit of pulmonary fibrosis was reported among maintenance craftworkers (SMR = 62, 95% CI = 17-159). These findings are discussed in conjunction with results from other refinery studies, and the limitations of the study are discussed.

In plain English

This historical cohort study followed 7,119 people who worked at least one year at the Beaumont, Texas, petroleum refinery between 1945 and 1987. Deaths were tracked through 1987 and compared with U.S. national death rates as standardized mortality ratios (SMRs), where 100 means as many deaths as expected. There were 2,294 deaths against 2,782.5 expected (SMR 82). Because asbestos was used at the refinery in the past, the authors examined asbestos-related diseases separately. No death certificate showed asbestosis. Among all men, pulmonary fibrosis caused 4 deaths versus 12.0 expected. One mesothelioma death was found, versus 3.1 expected. Among 5,360 male maintenance craftworkers, whom the authors considered likely to have had past asbestos exposure, there were 109 lung cancer deaths versus 90.8 expected (SMR 120, 95% CI 99 to 145). The authors called this borderline significant and found no upward trend with years in maintenance jobs. This group also had significantly raised leukemia and prostate cancer deaths. The authors concluded these excesses were most likely unrelated to maintenance work. They noted they had no asbestos measurements and no information on smoking or on asbestos exposure in other jobs.

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 (historical) cohort mortality study, an update of an earlier study of the same refinery. Deaths were compared with U.S. national rates using standardized mortality ratios.
• Who was studied: 7,119 Mobil employees (91% male, 83% white) who worked a year or more at the Beaumont, Texas, refinery between January 1, 1945 and December 31, 1987. Vital status was followed to December 31, 1987. Subcohorts were 1,240 male operators and 5,360 male maintenance craftworkers.
• Exposure: Refinery employment, with potential exposure to petroleum hydrocarbons, benzene and other substances, and past use of asbestos at the refinery. No fiber type is named and no asbestos exposure measurements were available. Exposure was approximated by duration of employment, period of hire, and job category (operators versus maintenance craftworkers, the latter considered likely to have had past asbestos exposure).
• Main results:
  • Whole cohort: 2,294 deaths observed versus 2,782.5 expected (SMR 82, 95% CI 79 to 86), a statistically significant deficit.
  • Whole cohort: lymphatic and hematopoietic cancer deaths were significantly raised (SMR 133, 95% CI 103 to 170).
  • Whole cohort: a review of death certificates in the nonmalignant respiratory disease category found no asbestosis death.
  • All male cohort members: 4 pulmonary fibrosis deaths observed versus 12.0 expected. The article prints the SMR as 33 (95% CI 0 to 84) and reports it as statistically significant.
  • Whole cohort: one death attributed to mesothelioma, versus 3.1 expected (SMR 32, 95% CI 0 to 179).
  • All males: lung cancer SMR 92 (95% CI 78 to 108), similar to expected.
  • Male maintenance craftworkers: 109 lung cancer deaths versus 90.8 expected (SMR 120, 95% CI 99 to 145), borderline significant.
  • Male maintenance craftworkers: no upward trend in lung cancer with duration of maintenance employment (chi-square for trend 1.85), although the 20 to 29 year group showed a significant increase (46 observed versus 29.8 expected, SMR 154, 95% CI 113 to 206).
  • Male maintenance craftworkers hired 1940 to 1949: significant lung cancer increase (43 observed versus 30.5 expected, SMR 141, 95% CI 102 to 190).
  • Male maintenance craftworkers hired in or after 1950: 3 lung cancer deaths versus 9.3 expected, a significant deficit (SMR 32, 95% CI 7 to 95).
  • Male maintenance craftworkers: no death attributed to asbestosis. Pulmonary fibrosis: 4 deaths versus 6.43 expected (SMR 63, 95% CI 17 to 160). Mesothelioma: 1 death versus 1.84 expected.
  • Male maintenance craftworkers: deaths significantly higher than expected for prostate cancer (SMR 145, 95% CI 107 to 194), leukemia (SMR 179, 95% CI 111 to 273) and other lymphatic tissue cancer (SMR 233, 95% CI 138 to 368).
• The authors' conclusion: The authors concluded that the updated study confirmed a favorable overall mortality experience compared with the U.S. population. They found no relationship between lung cancer and refinery employment for the overall cohort. They judged that the excesses among maintenance craftworkers (prostate cancer, leukemia, other lymphatic tissue cancer, and a small lung cancer increase) were most likely unrelated to work in maintenance craft jobs.
• Limitations the authors state:
  • No information on smoking or on employment elsewhere with potential exposure to asbestos and other carcinogens, which the authors say a complete evaluation of lung cancer would need.
  • No specific asbestos exposure measurements were available.
  • Little quantitative exposure data were available, so analyses by quantitative exposure were not possible.
  • The exposure surrogates used (duration, period of first exposure, broad job class) might lack sensitivity and specificity.
  • Asbestosis deaths could have been recorded simply as pulmonary fibrosis if certifying physicians did not know of asbestos exposure.
  • Causes of death relied on death certificates, with their problems of diagnostic accuracy.
  • About 2% had unknown vital status and about 2% of death certificates were not obtained, so some deaths of interest might have been missed.
  • Too few deaths among women for detailed analyses.

Topics

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

Related studies

• Retrospective exposure assessment of airborne asbestos related to skilled craftsmen at a petroleum refinery in Beaumont, Texas (1940-2006) — P. Williams, D. Paustenbach, et al. (2007)
• Asbestos exposure and cancer mortality among petroleum refinery workers: a Poisson regression analysis of updated data — F. Montanaro, M. Ceppi, et al. (2004)
• Mortality and cancer morbidity in a cohort of Canadian petroleum workers — R.J. Lewis, A.R. Schnatter, et al. (2003)
• Long-term follow-up mortality study of petroleum refinery and chemical plant employees — S.P. Tsai, E.L. Gilstrap, et al. (1996)
• An updated study of mortality among workers at a petroleum manufacturing plant — Y. Honda, E. Delzell, et al. (1995)
• Updated mortality among diverse operating segments of a petroleum company — R.J. Lewis, A.R. Schnatter, et al. (2000)

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