Cancer incidence among marine engineers, a population-based study (Iceland)

Our plain-English summary of Cancer incidence among marine engineers, a population-based study (Iceland), by V. Rafnsson, P. Sulem (Cancer Causes & Control, 2003).

The study

• Authors: V. Rafnsson, P. Sulem
• Journal: Cancer Causes & Control
• Published: 2003;14(1):29-35
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Marine engineers are in their occupation exposed to different chemicals, organic solvents, exhaust gases, oils, and petroleum products, and were formerly exposed to asbestos. The aim was to study the cancer pattern, with particular attention to lung and bladder cancer, in an Icelandic cohort of marine engineers, indirectly controlling for their smoking habits.

Methods: A cohort of 6603 male marine engineers was followed up from 1955 to 1998, a total of 167,715 person-years. The cohort was record linked by the engineers' personal identification numbers to population-based registers containing the vital and emigration status and cancer diagnosis. Standardized incidence ratios (SIRs) were calculated for all cancers and different cancer sites in relation to different lag time and year of graduation. Information on smoking habits was obtained by administering a questionnaire to a sample of the cohort (n = 1,501).

Results: In the total cohort 810 cancers were observed, whereas 794 were expected (SIR 1.0, 95% CI 1.0-1.1), and significantly increased risk of stomach cancer (SIR 1.3, 95% CI 1.0-1.5) and lung cancer (SIR 1.2, 95% CI 1.0-1.5) was found. Increased risk of all cancers (SIR 1.2, 95% CI 1.1-1.3), stomach cancer (SIR 1.5, 95% CI 1.1-1.9), lung cancer (SIR 1.4, 95% CI 1.2-1.8), pleural mesothelioma (SIR 4.8, 95% CI 1.3-12.3), and urinary bladder cancer (SIR 1.3, 95% CI 1.0-1.8) were observed when a 40-year lag time was applied. The engineers' smoking habits were similar to those in a sample of the general population. The predictive value for lung cancer was 1.03.

Conclusions: The increased risk for mesothelioma is possibly attributable to the previous asbestos exposure. The excess of lung cancer could also be related to asbestos exposure. The high incidence of stomach cancer, lung cancer, and bladder cancer may be related to exposure to chemical risk factors, such as oils and petroleum products, as confounding due to smoking seems to be ruled out. In the light of the limited exposure information in the present study the importance of the different occupational exposures needs to be evaluated in further studies.

In plain English

This cohort study followed 6603 male Icelandic marine engineers for cancer from 1955 to 1998 through national registries, comparing them with Icelandic men. Exposure was not known for each man, but a questionnaire answered by 1501 cohort members covered smoking, years worked as machinists and skin contact with oils. Earlier graduation was taken to mean a greater chance of past asbestos exposure. Overall, 810 cancers were observed against 794 expected, with stomach and lung cancer significantly raised. Four pleural mesotheliomas occurred versus 1.4 expected, and there was no peritoneal mesothelioma. With counting starting 40 years after graduation, all cancers, stomach, lung, pleural mesothelioma (standardized incidence ratio 4.8, 95% CI 1.3 to 12.3) and bladder cancer were raised. Surveyed engineers smoked similarly to the general male population; 57% reported daily skin contact with oils or petroleum products. The authors concluded that the mesothelioma excess points to previous asbestos exposure and that lung cancer could also be related to asbestos. They added that stomach, lung and bladder cancer may relate to oils and petroleum products, and that further study is needed.

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 cohort study using record linkage to national registries, with standardized incidence ratios (SIRs) compared to Icelandic male rates, plus a postal questionnaire given to a sample
• Who was studied: 6603 Icelandic men born 1900 or later who were alive in 1955 and had graduated from the Marine Engineering College of Iceland or completed Fishing Association of Iceland courses up to 1997; followed 1955 to 1998 (167,715 person-years). Women (fewer than 10) were excluded.
• Exposure: Work as marine engineers, and in the metal-work or mechanical training required before admission. The presumed exposures were varying amounts and types of asbestos (fiber types not specified), mineral oils and petroleum products, organic solvents and exhaust gases. Exposure information was not available for each person. A questionnaire answered by a sample gave self-reported work duration as machinists and skin contact with oils or petroleum products. Graduation period and 20- and 40-year lag times were used as proxies, with earlier graduation taken to mean a greater chance of asbestos exposure.
• Main results:
  • Whole cohort, no lag time: 810 cancers observed versus 794 expected (SIR 1.0, 95% CI 1.0 to 1.1).
  • Whole cohort, no lag time: stomach cancer SIR 1.3 (95% CI 1.0 to 1.5) and lung cancer SIR 1.2 (95% CI 1.0 to 1.5), both reported as significantly increased.
  • All pleural cancers were mesotheliomas: 4 observed versus 1.4 expected in the whole cohort (no-lag SIR 2.8, 95% CI 0.8 to 7.3, not significant). There was no peritoneal mesothelioma.
  • With a 40-year lag time (2348 men, 36% of the cohort): all cancers SIR 1.2 (95% CI 1.1 to 1.3), stomach 1.5 (1.1 to 1.9), lung 1.4 (1.2 to 1.8), pleural mesothelioma 4.8 (1.3 to 12.3) and urinary bladder 1.3 (1.0 to 1.8).
  • Men who graduated in 1940 or earlier, with a 20-year lag: significantly high stomach cancer (SIR 1.3, 95% CI 1.0 to 1.7) and lung cancer (61 observed versus 39.51 expected, SIR 1.5, 95% CI 1.2 to 2.0).
  • Men who graduated 1941 to 1960, with a 20-year lag: bladder cancer 41 observed versus 26.47 expected (significant), and 3 pleural mesotheliomas versus 0.68 expected.
  • Whole cohort: brain cancer was lower than expected (11 observed versus 24.67 expected, SIR 0.4, 95% CI 0.2 to 0.8).
  • Among surveyed cohort members, 57% reported daily skin contact with oils or petroleum products and 92% at least weekly. Glove use was rarely reported.
  • Smoking habits of the 1501 surveyed engineers were similar to those of a general male population sample. The calculated predictive value for lung cancer due to smoking was 1.03.
• The authors' conclusion: The authors concluded that the increased mesothelioma risk points to previous asbestos exposure and that the lung cancer excess could also be related to asbestos. They said the high stomach, lung and bladder cancer incidence may be related to oils and petroleum products, since confounding by smoking seemed ruled out. Because exposure information was limited, they said further studies are needed.
• Limitations the authors state:
  • Exposure information was not available for each person in the cohort, and the authors described the exposure information as limited.
  • The study could not separate the effects of asbestos and of oils and petroleum products on lung cancer risk.
  • There was no information on diet, N-nitroso compounds or Helicobacter pylori infection, which are relevant to stomach cancer.
  • Other bladder cancer risk factors, such as chemicals and diet, were not controlled for.
  • The most recent graduates had not yet reached the peak age for lung cancer, so a non-significant result in that group does not rule out risk.

Topics

Medical terms in this study, explained in our Lexicon: Habit, Standardized Incidence Ratio (SIR), Stomach Cancer, Lung Cancer, Pleural Mesothelioma, Mesothelioma, Asbestos Exposure, Confounding.

Related studies

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• Longitudinal analysis of respiratory symptoms in population studies with a focus on dyspnea in marine transportation workers — V.H. Arrandale, M. Koehoorn, et al. (2009)
• Historical cohort study of a New Zealand foundry and heavy engineering plant — H.M. Firth, J.M. Elwood, et al. (1999)
• Solitary fibrous tumors of the pleura: an estimation of population incidence — T. Thorgeirsson, H.J. Isaksson, et al. (2010)
• Cancer incidence among mild steel and stainless steel welders and other metal workers — K.S. Hansen, J.M. Lauritsen, et al. (1996)
• Cancer incidence among Danish seafarers: a population based cohort study — L. Kaerlev, J. Hansen, et al. (2005)

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