Asbestos-related cancers in refinery workers in the Australian petroleum industry

Our plain-English summary of Asbestos-related cancers in refinery workers in the Australian petroleum industry, by R. Gun, N.L. Pratt, D.M. Roder, et al (Archives of Environmental & Occupational Health, 2006).

The study

• Authors: R. Gun, N.L. Pratt, D.M. Roder, P. Ryan
• Journal: Archives of Environmental & Occupational Health
• Published: 2006;61(1):11-6
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In this study of the incidence of asbestos-related cancer in the Australian petroleum industry, the authors traced a cohort of 16,543 petroleum industry workers for a total of 226,989 person-years. There were 18 cases of pleural mesothelioma; 12 occurred in refinery nonoffice workers, for whom the Standardized Incidence Ratio was 3.77 (95% confidence interval = 1.95-6.59). The incidence of lung cancer was significantly lower than that in the general male population. Lung cancer incidence was higher in maintenance workers than in nonmaintenance workers, but the excess was not statistically significant, as it was based on small numbers with wide confidence intervals. Lung cancer rates in refinery workers did not increase with duration of employment; however, they did tend to be higher in workers hired in earlier decades. Excess mesothelioma incidence in refinery workers is confirmed, but it is likely that there are few if any asbestos-related lung cancers.

In plain English

This cohort study looked at men in Health Watch, the Australian petroleum industry's health surveillance program. It followed 16,543 male workers for 226,989 person-years and compared their cancer rates with national rates. The authors believed the main asbestos type in Australian refineries was amosite, used mostly as insulation. There were 18 cases of pleural mesothelioma, a statistically significant excess (standardized incidence ratio, SIR, 1.76, 95% CI 1.05-2.79). Fifteen of the cases were refinery workers. Only refinery non-office workers had a significant excess: 12 cases, SIR 3.77 (95% CI 1.95-6.59). At least 2 of the refinery cases, and 1 of the 3 nonrefinery cases, had definite asbestos exposure before entering the industry. Lung cancer incidence was lower than in the general male population (SIR 0.69, 95% CI 0.57-0.83). Refinery maintenance workers had a higher lung cancer rate than other refinery workers, but the difference was not statistically significant and rested on small numbers. Lung cancer did not rise with years of employment. The authors concluded that the excess of mesothelioma was confirmed, but that there were likely few if any asbestos-related lung cancers.

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 (industry surveillance cohort) comparing cancer incidence and mortality with national rates, plus internal comparisons between job groups
• Who was studied: 16,543 men in the Australian petroleum industry (refineries, offshore and onshore production, terminals and airports), first enrolled 1980 to 1983 with further surveys up to 2000; 226,989 person-years of follow-up. The 1,356 women were not analyzed.
• Exposure: Asbestos in petroleum refining. The authors state that the predominant type was believed (not measured) to be amosite, mostly used as insulation on steam lines and as cladding on vessels and boilers. The work groups compared were refinery maintenance workers, other refinery non-office workers, nonrefinery workers and office workers.
• Main results:
  • Whole cohort: 18 cases of pleural mesothelioma, a statistically significant excess (SIR 1.76, 95% CI 1.05-2.79 in the text; Table 1 gives 1.77).
  • Of the 18 mesothelioma cases, 15 were refinery workers: 5 in maintenance, 6 operators, 3 office staff and 1 of unknown occupation.
  • Mesothelioma was significantly elevated only in refinery non-office workers: 12 observed vs 3.18 expected, SIR 3.77 (95% CI 1.95-6.59). Nonrefinery non-office workers had an SIR of 0.74 (0.15-2.16) and office workers 1.02 (0.21-2.97).
  • At least 2 of the refinery mesothelioma cases had a definite history of asbestos exposure before entering the industry. Among the other 13 refinery cases, prior exposure was judged probable in 5, possible in 6 and unlikely in 2.
  • For the 3 nonrefinery mesothelioma cases, asbestos exposure while in the industry appeared unlikely, and 1 of them had definite exposure before entering the industry.
  • There were no cases of primary peritoneal mesothelioma.
  • Lung cancer in the whole cohort was below general male population rates: incidence SIR 0.69 (95% CI 0.57-0.83) and mortality SMR 0.62 (95% CI 0.50-0.76).
  • Refinery maintenance workers compared with refinery nonmaintenance workers: lung cancer RIR 1.32 (95% CI 0.59-2.93) by longest-held job and 1.18 (0.56-2.52) by ever doing maintenance. Neither was statistically significant.
  • Compared with office workers, the lung cancer RIR was 1.40 (95% CI 0.83-2.35) for refinery non-office workers and 1.48 (0.91-2.41) for nonrefinery non-office workers. Both were nonsignificant and similar to each other.
  • Lung cancer showed no significant association with duration of employment, in either refinery or nonrefinery workers.
  • In refinery workers, lung cancer was higher the earlier the period of first employment: RIR 4.57 (95% CI 0.69-30.34) for those hired before 1954 compared with those hired after 1975. The trend was not statistically significant, and no such trend was seen in nonrefinery workers.
  • The age-standardized male smoking rate in the cohort was 24.1%, compared with 28.2% in the Australian population in the mid-1990s.
• The authors' conclusion: The authors concluded that excess mesothelioma incidence in refinery workers was confirmed, but that there were likely few if any asbestos-related lung cancers. They added that a small number of asbestos-related lung cancers in refinery maintenance workers could not be ruled out.
• Limitations the authors state:
  • Some mesothelioma cases were likely caused by asbestos exposure before the workers entered the petroleum industry.
  • For most mesothelioma cases there was not enough information to assess how likely or how great their asbestos exposure in the refinery had been.
  • The lung cancer comparisons rested on small numbers, with wide confidence intervals.

Topics

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

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

Related studies

• Update of mortality and cancer incidence in the Australian petroleum industry cohort — R.T. Gun, N. Pratt, et al. (2006)
• Update of a prospective study of mortality and cancer incidence in the Australian petroleum industry — R.T. Gun, N.L. Pratt, et al. (2004)
• Asbestos exposure and cancer mortality among petroleum refinery workers: a Poisson regression analysis of updated data — F. Montanaro, M. Ceppi, et al. (2004)
• An updated mortality study of workers at a petroleum refinery in Beaumont, Texas — G.K. Raabe, K.W. Collingwood, et al. (1998)
• Kidney cancer and hydrocarbon exposures among petroleum refinery workers — C. Poole, N.A. Dreyer, et al. (1993)
• 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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