Cancer incidence among members of the Norwegian trade union of insulation workers

Our plain-English summary of Cancer incidence among members of the Norwegian trade union of insulation workers, by B. Ulvestad, K. Kjaerheim, J.I. Martinsen, et al (Journal of Occupational and Environmental Medicine, 2004).

The study

• Authors: B. Ulvestad, K. Kjaerheim, J.I. Martinsen, G. Mowe, A. Andersen
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2004;46(1):84-9
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Insulation work has been described as an occupation with high exposure to asbestos. A cohort of members of the Norwegian Trade Union of Insulation Workers (n = 1116), hired between 1930 and 1975, was established. During 2002, the cohort was linked to the Cancer Registry of Norway. The standardized incidence ratio (SIR) of pleural mesothelioma was 12.9 (95% confidence interval [CI] = 6.0-24.6). Two cases with peritoneal mesotheliomas were found (SIR, 14.8; 95% CI = 1.8-53.4). The SIR of lung cancer was 3.0 (95% CI = 2.3-3.8). Four cases of lung cancer were observed among cork workers without any exposure to asbestos, but to cork dust and tar smoke (SIR, 5.3; 95% CI = 1.5-13.6). Our study showed a high risk of mesothelioma and an elevated risk of lung cancer among members of the Trade Union of Insulation Workers.

In plain English

This Norwegian cohort study followed 1116 men who had belonged to the Trade Union of Insulation Workers for at least one year, hired 1930 to 1975. Records were linked to the Cancer Registry (1953 to 1999) and compared with rates for all Norwegian men. Insulation work mainly used Canadian chrysotile, with some crocidolite; an expert panel ranked jobs by asbestos exposure. No exposure measurements or smoking data were available. The cohort had 63 lung cancers versus 21.3 expected (standardized incidence ratio 3.0, 95% CI 2.3 to 3.8). It had 9 pleural mesotheliomas (12.9, 6.0 to 24.6) and 2 peritoneal mesotheliomas (14.8, 1.8 to 53.4). Insulators had the highest mesothelioma risk and the highest lung cancer risk among asbestos-exposed job groups. Thirty-seven cork workers, exposed to cork dust and tar smoke but not asbestos, had 4 lung cancers versus 0.8 expected. Among workers first employed in 1970 or later, no mesothelioma occurred, and lung cancer (4 cases, 2.7 expected) was not significantly elevated. The authors concluded that mesothelioma incidence was high and lung cancer risk elevated in these insulation workers.

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: Cohort study linked to the national cancer registry, comparing observed with expected cancer cases (standardized incidence ratios, SIR). Expected numbers came from rates for the entire male population of Norway.
• Who was studied: 1116 men who had been members of the Norwegian Trade Union of Insulation Workers for at least 1 year and were hired between 1930 and 1975. The starting group was 1143; 27 lacked a personal identification number. The cohort was established in 1976 and followed for cancer from 1953 to 1999 (33,471 person-years).
• Exposure: Asbestos in insulation work, mainly Canadian chrysotile. In a 1980 questionnaire, 15% of insulation workers reported also using crocidolite sometimes or often. An expert panel of experienced workers and foremen classified job groups (insulators, assistants, storesmen, capsulators, chauffeurs/shopmen/welders) into high, moderate, low or no asbestos exposure; no exposure measurements were available. A subgroup of 37 cork workers was exposed to cork dust and tar smoke but not to asbestos.
• Main results:
  • Whole cohort, lung cancer: 63 observed versus 21.3 expected. SIR 3.0 (95% CI 2.3 to 3.8).
  • Whole cohort, pleural cancer: 9 cases, all malignant mesotheliomas. SIR 12.9 (95% CI 6.0 to 24.6).
  • Whole cohort, peritoneal mesothelioma: 2 observed versus 0.1 expected. SIR 14.8 (95% CI 1.8 to 53.4).
  • Whole cohort, all cancers combined: 240 observed versus 157.1 expected. SIR 1.5 (95% CI 1.4 to 1.7).
  • Job group 'insulators' (highest mesothelioma risk of any job group; highest lung cancer risk among the asbestos-exposed job groups):
• Mesothelioma: 6 observed versus 0.2 expected, SIR 35.0 (95% CI 12.8 to 76.1).
• Lung cancer: 25 observed versus 5.1 expected, SIR 4.9 (95% CI 3.2 to 7.3).
  • Job group 'assistants':
• Mesothelioma: 3 observed versus 0.5 expected, SIR 6.2 (95% CI 1.3 to 18.1).
• Lung cancer: 28 observed versus 11.8 expected, SIR 2.4 (95% CI 1.6 to 3.4).
  • Cork workers (no asbestos exposure; exposed to cork dust and tar smoke):
• Lung cancer: 4 observed versus 0.8 expected, SIR 5.3 (95% CI 1.5 to 13.6). This point estimate is higher than the insulators' 4.9.
• Mesothelioma: no cases.
  • Timing of mesothelioma: no case among workers with less than 15 years since first employment.
  • Timing of mesothelioma: 9 of the 11 cases occurred in workers with 30 years or more since first employment.
  • Workers first employed 1970 to 1976:
• Mesothelioma: no cases observed.
• Lung cancer: 4 observed versus 2.7 expected, SIR 1.5 (95% CI 0.4 to 3.8), not statistically significant.
  The authors describe this as no elevated risk of either cancer.
  • Whole cohort, colorectal cancer: 33 observed versus 21.6 expected. SIR 1.5 (95% CI 1.1 to 2.2).
  • Colorectal cancer by duration of employment: the highest risk was among workers employed 20 years or more, SIR 2.7 (95% CI 1.4 to 4.8). The authors also report it was not significantly elevated in the group with the highest asbestos exposure.
• The authors' conclusion: The authors concluded the study showed a high incidence of mesothelioma and an elevated risk of lung cancer in insulation workers exposed to a mix of chrysotile and crocidolite. They also found elevated lung cancer risk in a subgroup exposed to cork dust and tar smoke but not asbestos. Colorectal cancer incidence was increased, but not only in the highly exposed job groups.
• Limitations the authors state:
  • No measurements of exposure levels were available; exposure was assigned by job group.
  • No information on smoking habits was available.
  • Pathology slides were not reviewed again, so diagnostic bias cannot be excluded.
  • The degree of the cork workers' exposure to cork dust and tar smoke could not be evaluated retrospectively.

Topics

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

Medical terms in this study, explained in our Lexicon: Insulator, Cancer Registry, Standardized Incidence Ratio (SIR), Pleural Mesothelioma, confidence interval, Peritoneal Mesothelioma, Lung Cancer, Mesothelioma.

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