Insulation workers in Belfast. 3. Mortality 1940-66

Our plain-English summary of Insulation workers in Belfast. 3. Mortality 1940-66, by P.C. Elmes, M.J. Simpson (British Journal of Industrial Medicine, 1971).

The study

• Authors: P.C. Elmes, M.J. Simpson
• Journal: British Journal of Industrial Medicine
• Published: 1971;28(3):226-36
• Cited by: 72 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001357).

Abstract

Elmes, P. C., and Simpson, Marion J. C. (1971).Brit. J. industr. Med.,28, 226-236. Insulation workers in Belfast. 3. Mortality 1940-66. One hundred and seventy men were identified as making up the total population of insulation workers in Belfast in 1940. This is an analysis of all the information about deaths that has emerged from tracing these men up to the end of 1966. Five remain untraced, and the mortality experience of the remainder is compared with that of other men in Northern Ireland over the period. There were 98 deaths when only 37 were expected. The number of deaths occurring exceeded those expected throughout the period 1940-66 and the increase was statistically significant during the period 1950-55 and onwards. There was an especially high mortality (compared with other Northern Ireland males) due to cancer of the lung, mesothelioma of the pleura and peritoneum, cancer of the gastrointestinal tract, and fibrotic lesions of the lungs. The ratio of observed over expected deaths was 2·6 for all causes, 3·9 for all cancers, and 17·6 for cancers of the lower respiratory tract and pleura. Those men finally classified as dying from lung cancer showed evidence of lung fibrosis whereas those classified as dying from mesothelioma did not. Comparisons within the group failed to show any relationship between age at first exposure or duration of exposure and the excessive mortality. There were too few non-smokers to show the significance of smoking.

In plain English

The authors identified 170 men working as Belfast insulators or pipe coverers in 1940 and traced them to the end of 1966. Five could not be traced, leaving 165. The authors compared their deaths with those expected among Northern Ireland men of the same ages. The men were known to have been exposed to chrysotile, amosite and crocidolite. There were 98 deaths against 37 expected, with the excess clearly significant after 1950. Cancer caused 45 deaths against 6.8 expected. Of these, 28 were cancers of the larynx, lung or pleura, about 17 times the expected number. Seven mesotheliomas were confirmed (four pleural, three peritoneal), though the official register recorded only one. Other cancers, mostly gastrointestinal, and non-cancer lung disease deaths were also in excess. Of 24 lung cancer deaths, five lacked fibrosis information; 11 showed extensive and eight some fibrosis. Mesothelioma cases had little or none. Allowing for the men's home area, social class and smoking did not remove the excess. Within the group, no consistent link with age at starting work was found. The authors concluded the excess appears due to inhaling asbestos dust.

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: Historical cohort mortality study: all men employed as insulators in 1940 were traced to the end of 1966, and their deaths were compared with expected deaths for Northern Ireland males (age-adjusted), plus comparisons within the group
• Who was studied: 170 men employed as insulators or pipe coverers in 1940 (Belfast, Northern Ireland); 5 untraced, 165 analysed; followed 1940 to 1966
• Exposure: Insulation and pipe-covering work. The men were known to have been exposed to chrysotile, amosite and crocidolite, and were unlikely to have had much anthophyllite exposure. There was no quantitative dust measurement.
• Main results:
  • All causes: 98 deaths among the 165 traced men (59.5%), compared with 37 expected for Northern Ireland males
  • By the end of 1966, 41% (67 men) of the insulators survived, compared with 73% (121 men) expected
  • The excess of deaths over expectation became clearly significant after 1950
  • Cancers of all types: 45 deaths (revised diagnoses; 41 on death certificates) against 6.8 expected. From 1950 onwards, cancer deaths were nearly eight times more frequent than expected.
  • Cancers of the larynx, lung or pleura: 28 of the 45 cancer deaths (26 on death certificates), against 1.639 expected; about 17 times more frequent than expected
  • Mesothelioma: seven confirmed cases (four pleural, three peritoneal). The Registrar General recorded only one pleural case; the others were diagnosed from postmortem findings. Expected incidence was described as negligible.
  • Non-respiratory cancers: 17 deaths against 5.16 expected (a threefold excess). Of these, 15, including three peritoneal mesotheliomas, were gastrointestinal in origin.
  • Non-malignant disease: 53 deaths against 30.9 expected. The excess lay among the 26 deaths from lung disease other than tuberculosis. Asbestosis was named on the death certificate as a contributory cause in nine cases.
  • Of the 24 men finally classified as dying of lung carcinoma, there was no information on fibrosis for five. Eleven showed extensive fibrosis and the remaining eight showed some fibrosis. None was known to have no lung fibrosis.
  • Of the seven mesotheliomas, one pleural case showed no lung fibrosis. The others showed minimal fibrosis on histology only, and none showed fibrosis on x-ray.
  • After the authors' combined adjustment for domicile, social class and smoking, respiratory cancer deaths were 28 (or 26 by registered cause) against a predicted 4.64. For all causes the adjusted prediction was 40.6 against 98 observed. For all cancers it was 8.35 against 45. All differences remained P less than 0.0005.
  • Within the group, apart from the late-entry (over 40) group, there was no consistent difference in mortality by age at entry or duration of exposure
  • Smoking: only five of the men with known habits did not smoke; neither of the two deaths among non-smokers was due to cancer. There was no significant difference in respiratory cancer deaths between those smoking more or less than 20 cigarettes a day.
• The authors' conclusion: The authors concluded that the excess mortality could not be accounted for by smoking, domicile or social class, and appears to be due to the inhalation of asbestos dust
• Limitations the authors state:
  • No control group of working men could be selected and followed in the same way
  • The basic comparison with the general population could not allow for precise domicile, social class or smoking. Only fragmentary data were available for the later adjustment, which the authors call an overestimate of the combined effect.
  • The numbers were small, so the standardized mortality ratios lack precision
  • Retrospective diagnosis was uncertain; some lung cancers may have been pleural mesotheliomas
  • No quantitative information on dust exposure was available
  • Employer and union records used to build the list of workers were incomplete
  • There were too few non-smokers to assess the role of smoking in lung cancer

Topics

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

Medical terms in this study, explained in our Lexicon: Insulator, Mesothelioma, Pleura, Peritoneum, Lung Cancer, Fibrosis.

Related studies

• Insulation workers in Belfast. A further study of mortality due to asbestos exposure (1940-75) — P.C. Elmes, M.J. Simpson (1977)
• Insulation workers in Belfast. 1. Comparison of a random sample with a control population — W.F. Wallace, J.H. Langlands (1971)
• Influence of age at death on accuracy of death certificate disease diagnosis: findings in 475 consecutive deaths of mesothelioma among asbestos insulation workers and asbestos factory workers — I.J. Selikoff (1992)
• Mortality experience of insulation workers in the United States and Canada, 1943--1976 — I.J. Selikoff, E.C. Hammond, et al. (1979)
• Analysis of mortality patterns and workers' compensation awards among asbestos insulation workers in Ontario — M.M. Finkelstein (1989)
• Cause-specific mortality among male chemical workers — G.G. Bond, E.A. McLaren, et al. (1987)

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