Cancer at sea: a case-control study among male Finnish seafarers

Our plain-English summary of Cancer at sea: a case-control study among male Finnish seafarers, by H. Saarni, J. Pentti, E. Pukkala (Occupational and Environmental Medicine, 2002).

The study

• Authors: H. Saarni, J. Pentti, E. Pukkala
• Journal: Occupational and Environmental Medicine
• Published: 2002;59(9):613-9
• Cited by: 31 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Aims: To study the possible work related reasons for the increased incidence of many cancers among seafarers.

Methods: A case-control study, nested in a cohort of all male seafarers (n = 30 940) who, according to the files of the Seamen's Pension Fund, had worked on board Finnish ships for any time during the period 1960-80. Cases of cancer of the lung, nervous system, kidney, and pancreas, leukaemia, lymphoma, and all cases histologically defined as mesotheliomas were identified from the Finnish Cancer Registry in 1967-92. The preceding numbers of years at sea in various occupational categories were collected according to the type of ship (dry cargo ship, tanker, passenger vessel, icebreaker, other vessel).

Results: The incidence for lung cancer among engine crew increased with the increase in employment time, the odds ratio (OR) after three years being 1.68 (95% CI 1.17 to 2.41). The OR of lung cancer for deck officers was 0.42 (95% CI 0.29 to 0.61). Deck personnel on icebreakers had a significantly increased risk of lung cancer > or =20 years after first employment (OR 3.41, 95% CI 1.23 to 9.49). The OR for mesothelioma among engine crew with a latency of 20 years was 9.75 (95% CI 1.88 to 50.6). The OR for renal cancer among deck officers after three years employment was 2.15 (95% CI 1.14 to 4.08), but there was no increase by employment time or by latency. A rise of OR for lymphoma was detected among deck personnel on tankers, if the employment had lasted over three years (OR 2.78, 95% CI 0.98 to 7.92). The risk pattern for leukaemia was similar to that of lymphoma, the OR among deck personnel on tankers varying from 2.26 (95% CI 1.01 to 5.06) to 6.86 (95% CI 1.62 to 28.8) depending on the length of employment.

Conclusions: Results indicate that occupational exposures of deck crews on tankers add to their risk of renal cancer, leukaemia, and possibly lymphoma. Engine crews have an asbestos related risk of mesothelioma, and the engine room conditions also seem to increase risk of lung cancer.

In plain English

This was a case-control study nested within a group of 30 940 men who had worked on Finnish ships at any time during the period 1960–80. Cancer cases came from the Finnish Cancer Registry. Each case was compared with three seafarers from the same group born in the same year (two for lung cancer). Exposure was measured as years worked in each shipboard job and on each type of ship. There were 10 mesothelioma cases and 30 controls. Engine crew had an odds ratio for mesothelioma of 7.50 (95% CI 1.53 to 36.7) using a 10-year latency, rising to 9.75 (1.88 to 50.6) with a 20-year latency. Engine crew with more than three years' service had a lung cancer odds ratio of 1.68 (1.17 to 2.41). Deck personnel who had worked over a month on tankers had a leukaemia odds ratio of 2.26 (1.01 to 5.06). The authors had no data on smoking or on work exposures ashore. They concluded that engine crews evidently had an asbestos related risk of mesothelioma, and that engine room conditions seemed to raise lung cancer risk.

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: Case-control study nested in a cohort of seafarers; controls randomly selected from the same cohort and matched on year of birth
• Who was studied: 30 940 male seafarers who worked on board Finnish ships at any time during the period 1960–80 and were alive on 1 January 1967, identified from the Seamen's Pension Fund files. Cancer cases came from the Finnish Cancer Registry. Each case was compared with three controls from the same cohort with the same year of birth (two controls for lung cancer). There were 299 lung cancer cases and 10 mesothelioma cases.
• Exposure: Years at sea by shipboard job (deck officer, engine officer, radio officer, deck crew, engine crew, catering) and by type of ship (dry cargo ship, tanker, passenger vessel, icebreaker, other vessel), taken from registers. Asbestos exposure was not measured directly; the authors linked engine room work to asbestos in their interpretation.
• Main results:
  • Mesothelioma among engine crew: odds ratio 7.50 (95% CI 1.53 to 36.7) with a 10-year latency. Six of the 10 cases and 5 of the 30 controls had worked more than one month as engine crew.
  • Mesothelioma among engine crew with a 20-year latency: odds ratio 9.75 (95% CI 1.88 to 50.6).
  • The mesothelioma odds ratio also tended to be raised among engine officers. For more than three years of work it was 4.33 (0.84 to 22.5), which was not statistically significant.
  • Lung cancer among engine crew with more than three years' employment: odds ratio 1.68 (95% CI 1.17 to 2.41), based on 63 cases and 82 controls. The odds ratio per 10 years of work was 1.22 (95% CI 1.00 to 1.63).
  • Lung cancer among deck officers: odds ratio 0.42 (95% CI 0.29 to 0.61). The authors regarded this as an artefact of differences in smoking.
  • Lung cancer among deck personnel who worked more than one month on icebreakers: odds ratio 3.41 (95% CI 1.23 to 9.49) with a 20-year latency. The increase was not seen with the 10-year latency, which the authors had chosen in advance as the most likely.
  • Kidney cancer among deck officers with more than three years' employment: odds ratio 2.15 (95% CI 1.14 to 4.08).
  • Leukaemia among deck personnel on tankers: odds ratio 2.26 (1.01 to 5.06) for more than one month of work (13 cases, 21 controls) and 6.86 (1.63 to 28.8) for more than three years (6 cases, 3 controls). The odds ratio per 10 years of work was 4.41 (95% CI 1.00 to 20.1).
  • Lymphoma/myeloma among deck personnel on tankers with more than three years' work: odds ratio 2.78 (0.98 to 7.92), based on 7 cases and 8 controls. The authors described this as borderline significant.
• The authors' conclusion: The authors concluded that work as deck crew on tankers added to the risk of kidney cancer, leukaemia and possibly lymphoma. They also concluded that engine crews evidently had an asbestos related risk of mesothelioma, and that asbestos or other agents in engine room air also seemed to increase their lung cancer risk.
• Limitations the authors state:
  • There were no data on smoking or on work exposures ashore. A planned interview of next of kin and a postal inquiry were not successful.
  • Smoking prevalence strongly affects the lung cancer odds ratios. The authors said it explains the apparently protective result for deck officers but hardly affects the rise in risk with working years among engine crew.
  • Work on coal-driven steamers could not be analysed separately from work on other ships.
  • There was no exact data on cargo contents, and crude oil and chemical tankers could not be analysed separately.

Topics

The National Library of Medicine indexes this study under subjects our site covers: The Navy.

Medical terms in this study, explained in our Lexicon: Case-Control Study, Mesothelioma, Cancer Registry, Lung Cancer, Odds Ratio, Latency, Occupational Exposure.

Related studies

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• Cancer incidence among Danish seafarers: a population based cohort study — L. Kaerlev, J. Hansen, et al. (2005)
• Past exposure to asbestos and combustion products and incidence of cancer among Finnish locomotive drivers — P. Nokso-Koivisto, E. Pukkala (1994)
• Asbestos-related cancers among 28,300 military servicemen in the Royal Norwegian Navy — L.A. Strand, J.I. Martinsen, et al. (2010)
• Occupational exposures and male breast cancer: A nested case-control study in the Nordic countries — M. Talibov, J. Hansen, et al. (2019)
• Cancer incidence and mortality among Finnish asbestos sprayers and in asbestosis and silicosis patients — P. Oksa, E. Pukkala, et al. (1997)

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