Update of mortality and cancer incidence in the Australian petroleum industry cohort

Our plain-English summary of Update of mortality and cancer incidence in the Australian petroleum industry cohort, by R.T. Gun, N. Pratt, P. Ryan, et al (Occupational and Environmental Medicine, 2006).

The study

• Authors: R.T. Gun, N. Pratt, P. Ryan, D. Roder
• Journal: Occupational and Environmental Medicine
• Published: 2006;63(7):476-81
• Cited by: 62 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objectives: To update the analysis of the cohort mortality and cancer incidence study of employees in the Australian petroleum industry.

Methods: Employees of Australian Institute of Petroleum member companies were enrolled in the cohort in four industry-wide surveys between 1981 and 1999. Mortality of 16,547 males and 1356 females was determined up to 31 December 2001 and cancer incidence to 31 December 2000. Cause specific mortality and cancer incidence were compared with those of the Australian population by means of standardised mortality ratios (SMRs) and standardised incidence ratios (SIRs). Associations between increased incidence of specific cancers and employment in the petroleum industry were tested by trends according to period of first employment, duration of employment, latency, and hydrocarbon exposure, adjusting for personal smoking history where appropriate.

Results: There was a significant elevation of the incidence of mesothelioma (SIR 1.77, 95% CI 1.05 to 2.79), melanoma (SIR 1.37, 95% CI 1.19 to 1.58), and prostate cancer (SIR 1.18, 95% CI 1.04 to 1.34). The SIRs of all leukaemias and of acute non-lymphocytic leukaemia (ANLL) were not significantly different from unity, but all 11 ANLL cases were clustered in the middle to high hydrocarbon exposure categories. Tanker drivers had a significantly elevated incidence of kidney cancer (12 cases v 5.84 expected, SIR 2.05, 95% CI 1.06 to 3.59). Lung cancer incidence was significantly reduced (SIR 0.69, 95% CI 0.57 to 0.83)

Conclusions: Most cases of mesothelioma are probably related to past exposure to asbestos in refineries. No occupational cause has been identified for the excess of melanoma, or prostatic or bladder cancer. The possibility of a causal relationship between cancer of the kidney and hydrocarbon exposure warrants further study. It is uncertain whether benzene exposures, particularly past levels of exposure, have been high enough to cause ANLL.

In plain English

This study updated an Australian cohort study (the Health Watch programme) of petroleum industry employees enrolled through industry-wide surveys. The authors followed 16 547 men and 1356 women, tracking deaths to 31 December 2001 and cancers to 31 December 2000, and compared these with national rates. Among men there were 18 mesotheliomas against 10.2 expected (SIR 1.77, 95% CI 1.05 to 2.79). Two were peritoneal, and 15 of the 18 occurred in refinery workers. Melanoma and prostate cancer incidence were also raised, and drivers had more kidney cancer than expected (12 cases v 5.84 expected). Lung cancer incidence among men was lower than in the general population (SIR 0.69, 95% CI 0.57 to 0.83). After adjusting for smoking, lung cancer in refinery maintenance workers did not differ significantly from refinery non-maintenance workers, office workers excluded (1.10, 95% CI 0.47 to 2.64). The authors concluded that most mesotheliomas were probably related to past asbestos exposure in refineries. They added that some were likely due to asbestos exposure before workers entered the industry. They described their hydrocarbon exposure ranking as crude.

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: Cohort study of mortality and cancer incidence (an update of an industry surveillance cohort), compared with national rates using standardised mortality and incidence ratios
• Who was studied: Employees of Australian Institute of Petroleum member companies (16 547 males and 1356 females), enrolled in industry-wide surveys from 1980–83 onward. Deaths were followed to 31 December 2001 and cancers to 31 December 2000. Head office staff and small facilities were excluded.
• Exposure: Employment in the Australian petroleum industry (refineries, terminals, drivers and other workplace types). Total hydrocarbon exposure was ranked from job codes into seven categories. The article reports no asbestos measurements and names no fiber type; asbestos is discussed as the likely explanation for mesothelioma.
• Main results:
  • Males: mesothelioma incidence was significantly raised, with 18 observed v 10.2 expected (SIR 1.77, 95% CI 1.05 to 2.79)
  • Of the 18 mesotheliomas, two were peritoneal and 15 occurred in refinery workers
  • Males: lung cancer incidence was significantly below the general population (SIR 0.69, 95% CI 0.57 to 0.83); the lung cancer mortality SMR was 0.62 (95% CI 0.50 to 0.76)
  • Refinery maintenance workers compared with refinery non-maintenance workers (office workers excluded), adjusted for smoking: lung cancer relative incidence 1.10 (95% CI 0.47 to 2.64)
  • Males: melanoma incidence SIR 1.37 (95% CI 1.19 to 1.58) and prostate cancer incidence SIR 1.18 (95% CI 1.04 to 1.34), both significantly raised
  • Drivers: kidney cancer incidence significantly raised, 12 cases v 5.84 expected (SIR 2.05, 95% CI 1.06 to 3.59)
  • Males: 11 acute non-lymphocytic leukaemias v 10.4 expected (SIR 1.06, 95% CI 0.53 to 1.90), not a significant excess
• The authors' conclusion: The authors concluded that most cases of mesothelioma are probably related to past exposure to asbestos in refineries
• Limitations the authors state:
  • The hydrocarbon exposure ranking is a crude measure of exposure, and uncoded jobs were assigned to a default category
  • Date of hire was self-reported by subjects at interview
  • Lower participation in the fourth survey (estimated at 73%) meant few recruits from offshore production
  • Complete matching of cancer registrations could not be guaranteed, and seven cancers not found in the national database were excluded
  • Some mesothelioma cases were likely due to asbestos exposure before workers entered the petroleum industry

Topics

Medical terms in this study, explained in our Lexicon: Standardized Incidence Ratio (SIR), Latency, Mesothelioma, Lung Cancer.

Related studies

• Update of a prospective study of mortality and cancer incidence in the Australian petroleum industry — R.T. Gun, N.L. Pratt, et al. (2004)
• Mortality and cancer morbidity in a cohort of Canadian petroleum workers — R.J. Lewis, A.R. Schnatter, et al. (2003)
• Mortality Update of a Cohort of Canadian Petroleum Workers — A.R. Schnatter, N.C. Wojcik, et al. (2019)
• Updated mortality among diverse operating segments of a petroleum company — R.J. Lewis, A.R. Schnatter, et al. (2000)
• Asbestos-related cancers in refinery workers in the Australian petroleum industry — R. Gun, N.L. Pratt, et al. (2006)
• Long-term follow-up mortality study of petroleum refinery and chemical plant employees — S.P. Tsai, E.L. Gilstrap, et al. (1996)

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