Mortality and cancer incidence among marine engineers and machinists in Iceland

Our plain-English summary of Mortality and cancer incidence among marine engineers and machinists in Iceland, by V. Rafnsson, S.G. Jóhannesdóttir, H. Oddsson, et al (Scandinavian Journal of Work, Environment & Health, 1988).

The study

• Authors: V. Rafnsson, S.G. Jóhannesdóttir, H. Oddsson, H. Benediktsson, H. Tulinius, G. Magnússon
• Journal: Scandinavian Journal of Work, Environment & Health
• Published: 1988;14(3):197-200
• Cited by: 24 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. 000931).

Abstract

A retrospective cohort study of mortality and cancer morbidity was carried out among 295 marine engineers and 182 machinists with special regard to cancer of the lung. The cohort was defined as all graduates from engineering and machinists school in Iceland during 1936-1955. During vocational training, as well as in their professional lives, marine engineers and machinists are exposed to asbestos, different kinds of mineral oils, and exhaust gases with marked individual variation as regards mode and magnitude of exposure. For deaths occurring between 1951 and 1982 information was obtained from the Statistical Bureau of Iceland. Significantly increased standardized mortality ratios were determined for cancer of the trachea, bronchus, and lung for the entire cohort. Record linkage with the Cancer Register revealed 36 cancers in the period 1955-1982. No statistically significant excess was found for the overall cancer incidence or for the incidence of cancer at any particular site. A special survey of smoking status showed that cigarette smoking was not as common among the subjects of the cohort as among the general male population in Reykjavik. These results support the suggestion that the increased mortality of lung cancer in the study group had a causal relationship to occupational exposure, particularly to asbestos exposure.

In plain English

This retrospective cohort study followed 295 marine engineers and 182 machinists in Iceland who graduated or completed courses in 1936 to 1955. The authors wrote that both groups were presumably exposed to varying amounts of asbestos in training, with exposure continuing at work, alongside mineral oils, organic solvents and exhaust gases. Deaths were traced to 1 December 1982 and compared with rates for Icelandic men. For the whole group, 7 lung cancer deaths gave a standardized mortality ratio of 205 (95% confidence interval 83 to 423). The authors called this significant on a one-tailed test, as for machinists alone. All-cause deaths in 1951 to 1982 numbered 85 against 93.9 expected. Over 1936 to 1982, drowning in water transport accidents was raised (9 observed versus 4.0 expected). Among 461 subjects, 36 cancers were registered in 1955 to 1982 against 34.71 expected, with no significant excess at any site, including lung (6 versus 4.94 expected). Of 184 men surveyed, 26% smoked cigarettes, versus 30% of all male survey participants. The authors concluded that the lung cancer excess supported a causal relationship with occupational exposure, particularly asbestos.

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 of mortality and cancer incidence
• Who was studied: 477 men: 295 marine engineers and 182 certified machinists recorded in the Register of Icelandic Engineers, born 1905 to 1945, who graduated from the Engineers School of Iceland or completed Fishing Association of Iceland courses in 1936 to 1955. Vital status was traced as of 1 December 1982.
• Exposure: The authors stated that both groups were presumably exposed to a variable amount of asbestos (fiber type not specified) during apprenticeship or training, and that asbestos exposure continued in their later careers. They were also exposed to mineral oils, organic solvents and exhaust gases, with marked individual variation in mode and magnitude. No exposure measurements were given.
• Main results:
  • Lung cancer (trachea, bronchus and lung) mortality, 1951 to 1982, all subjects: 7 deaths, SMR 205 (95% CI 83 to 423). The authors reported this as significant at the 5% level on a one-tailed test. The same was true for machinists alone (4 deaths, SMR 234), with no latency requirement.
  • Lung cancer SMR for subjects with a 20-year latency was 195 (6 deaths), and with a 30-year latency 255.
  • All causes of death, 1951 to 1982: 85 observed against 93.9 expected. The SMR for all causes over the whole period 1936 to 1982 was 94, not statistically significant.
  • Drowning in water transport accidents, whole study period 1936 to 1982: SMR 225 (9 observed versus 4.0 expected), statistically significant at the 5% level.
  • SMRs for bladder cancer (299) and cerebrovascular diseases (155) were raised for all subjects, 1951 to 1982.
  • Cancer incidence for 461 subjects, 1955 to 1982: 36 cancers observed against 34.71 expected. SIRs were generally low and in no case statistically significant.
  • Lung cancer incidence: 6 observed versus 4.94 expected (SIR 121), not significant at the 5% level (one-tailed).
  • Smoking: 184 of the 477 cohort members took part in a Heart Association survey (1967 to 1981). Twenty-six percent of them currently smoked cigarettes, compared with 30% of all male participants.
• The authors' conclusion: The authors concluded that the results supported the suggestion that the increased lung cancer mortality had a causal relationship to occupational exposure, particularly asbestos exposure. They said it could hardly be ascribed to more cigarette smoking than in the general population.
• Limitations the authors state:
  • Misreading of information identifying the subjects could cause errors in vital status and cancer data. The authors compared the register information twice to prevent this.
  • Smoking might be a serious confounding factor if the cohort's smoking habits differed from those of the general population. Smoking data were available for only 184 of the 477 subjects.
  • Records before 1951 were incomplete, and some death certificates were attested by clergymen. For that period, only deaths from all causes, from accidents, poisoning and violence, and from drowning were studied.
  • When the cohort was split into marine engineers and machinists, the groups were small and the cases few. Confidence intervals were wide, and no SMR was statistically significant.

Topics

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

Medical terms in this study, explained in our Lexicon: Cohort Study, standardized mortality ratio (SMR), Bronchus, Lung Cancer, Occupational Exposure, Asbestos Exposure.

Related studies

• Cancer incidence among marine engineers, a population-based study (Iceland) — V. Rafnsson, P. Sulem (2003)
• Exposure to mineral oil mist and respiratory symptoms in marine engineers — K. Svendsen, B. Hilt (1997)
• Incidence of cancer among welders, platers, machinists, and pipe fitters in shipyards and machine shops — S. Tola, P.L. Kalliomäki, et al. (1988)
• Cancer incidence among Danish seafarers: a population based cohort study — L. Kaerlev, J. Hansen, et al. (2005)
• Cancer incidence among seafarers and fishermen in the Nordic countries — K. Ugelvig Petersen, E. Pukkala, et al. (2020)
• Asbestos exposure and mesothelioma incidence and mortality in Bulgaria — K. Vangelova, I. Dimitrova (2016)

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