Cancer mortality in merchant seamen

Our plain-English summary of Cancer mortality in merchant seamen, by M. Greenberg (Annals of the New York Academy of Sciences, 1991).

The study

• Author: M. Greenberg
• Journal: Annals of the New York Academy of Sciences
• Published: 1991;643:321-32
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004877).

Abstract

Cancer mortality excess has been reported repeatedly over the past hundred years to occur in merchant seamen. More recently lung cancer has been found to account for some of this excess and the question of the contribution made by cigarette smoking raised. In the one study where there was some information on smoking habit, it did not appear that cigarettes would have accounted for all the excess cancer observed. In other mortality studies, where excess cancer mortality was observed, the other cigarette-linked causes of death were not prominent. In a preliminary mortality analysis of a small population of merchant seamen, two cases of malignant mesothelioma have so far been identified, and in a national mesothelioma register 28 cases have been reported in seamen: both instances constitute abnormal occurrences. The presence of substantial amounts of asbestos-containing materials in naval construction which are continuously subjected to vibration and intermittently disturbed during servicing, and the detection of radiological stigmata consistent with asbestos exposure, add plausibility to the hypothesis that occupational asbestos exposure contributes to the apparent excess cancer mortality in merchant seamen. Methodologic deficiencies in epidemiologic studies reported to date make for uncertainty. Properly designed studies will be needed to quantify disease excess and to identify potentially causal associations. Even in the absence of such data it would be prudent to contain the asbestos currently installed and to promote smoking cessation programs.

In plain English

This article was a single-author review of published and official data, from the 1890s onward, on cancer deaths among merchant seamen and on evidence of asbestos exposure at sea. Many of the reviewed mortality statistics showed more cancer deaths than expected. For example, England and Wales figures for 1930-1932 listed 654 cancer deaths in merchant seamen against 552 expected. A Swedish study of active seamen found 157 deaths from neoplasms against 151 predicted. A Norwegian study of 9,763 seamen that recorded smoking found overall cancer risk some 50% higher in seamen, and higher in smoking seamen than in smoking non-seamen. Chest X-ray studies found pleural abnormalities in 12% of 5,041 U.S. marine engineers. A U.K. register listed 28 mesothelioma cases in seamen, and two confirmed mesotheliomas had so far been found in an ongoing follow-up of 3,324 U.S. seamen. The author concluded that these findings made it plausible that asbestos contributed to the apparent cancer excess. The author also judged the data suggestive but inconclusive, citing uncertain numbers of seamen at risk and smoking.

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: Narrative review of published studies and official occupational mortality statistics on merchant seamen
• Who was studied: Merchant seamen covered by reviewed studies from the late nineteenth century onward, in England and Wales, Germany, the United States, Sweden, Norway, Greece, Italy and the U.K.
• Exposure: Asbestos in ship construction (fireproof paint and jointing, packing and insulating materials), disturbed by vibration and repairs, especially in engine rooms. Cigarette smoking was also considered. No fiber type was named and no exposure measurements were available.
• Main results:
  • Registrar General for England and Wales, 1930-1932: 654 cancer deaths observed in merchant seamen versus 552 expected, a ratio of 118%
  • Swedish merchant marine study (1945-1954, active seamen): 157 deaths from neoplasms recorded versus 151 predicted
  • Norwegian study of 9,763 seamen with smoking status recorded: overall cancer risk some 50% higher for seamen than for a comparison group
  • Norwegian study: smoking seamen had a greater cancer risk than smoking non-seamen, which the author took as suggesting an occupational contribution
  • U.S. Public Health Service hospitals, 1973-1978: 46.2% of deaths in seamen and 37.1% in non-seamen were from cancer
  • Chest radiographs of 5,041 U.S. marine engineers: overall prevalence of pleural abnormalities was 12%
  • 141 retired Greek merchant seamen: 37 (26.2%) had pleural abnormalities
  • 3,324 U.S. merchant seamen in long-term service: 601 (18.1%) had pleural changes only and 227 (6.8%) had combined changes
  • Among the same 3,324 U.S. seamen, abnormalities were more frequent in engine-room workers (42.5%) than in deck workers (36.6%) or stewards (28.4%)
  • Genoa, 1960-1973: among 60 malignant mesothelioma cases, job titles indicating merchant mariners included sailors (3), stokers (3), naval greaser (1), ship's electrician (1) and ship's engineer (1). None of these job titles appeared among 120 control subjects.
  • U.K. Health and Safety Executive mesothelioma register, 1968 to 1986: 28 cases with seamen's occupations on death certificates, which the author judged markedly excessive
  • Ongoing mortality follow-up of the 3,324 U.S. merchant seamen: two confirmed cases of malignant mesothelioma so far
• The authors' conclusion: The author concluded that asbestos-containing materials on ships and radiographic signs consistent with asbestos exposure add plausibility to the hypothesis that occupational asbestos exposure contributes to the apparent excess cancer mortality in merchant seamen.
• Limitations the authors state:
  • The author judged the available data suggestive but inconclusive because of the design and quality of the analyses
  • The numbers of seamen employed (denominators) were hard to determine accurately in all studies
  • The consistent cancer excess might partly result from common biases in how numerators and denominators were derived
  • Cigarette smoking is a confounding factor that still needs to be accounted for
  • No data were found on systematic measurement of asbestos exposure aboard ship
  • No adequate epidemiologic study has been carried out to determine the true size of the occupational cancer hazard

Topics

The National Library of Medicine indexes this study under subjects our site covers: Shipyards and maritime work, The Navy.

Medical terms in this study, explained in our Lexicon: Lung Cancer, Habit, Malignant Mesothelioma, Mesothelioma, Asbestos-Containing Material (ACM), Asbestos Exposure.

Related studies

• Asbestotic radiological abnormalities among United States merchant marine seamen — I.J. Selikoff, R. Lilis, et al. (1990)
• Historical state of knowledge of the health risks of asbestos posed to seamen on merchant ships — D.G. Dodge, B.D. Beck (2016)
• Asbestos related abnormalities among United States merchant marine seamen — P.J. Barrett (1990)
• Asbestos in strange places: two case reports of mesothelioma among merchant seamen — G. Varouchakis, E.G. Velonakis, et al. (1991)
• A mortality cohort study of seamen in Italy — E. Rapiti, E. Turi, et al. (1992)
• Mortality among shipyard workers in Genoa, Italy — R. Puntoni, M. Vercelli, et al. (1979)

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