Exposure to asbestos and lung and pleural cancer mortality among pulp and paper industry workers

Our plain-English summary of Exposure to asbestos and lung and pleural cancer mortality among pulp and paper industry workers, by R. Carel, P. Boffetta, T. Kauppinen, et al (Journal of Occupational and Environmental Medicine, 2002).

The study

• Authors: R. Carel, P. Boffetta, T. Kauppinen, K. Teschke, A. Andersen, P. Jäppinen, N. Pearce, B.A. Rix, A. Bergeret, D. Coggon, B. Persson, I. Szadkowska-Stanczyk, D. Kielkowski, P. Henneberger, R. Kishi, L.A. Facchini, M. Sala, D. Colin, M. Kogevinas
• Journal: Journal of Occupational and Environmental Medicine
• Published: 2002;44(6):579-84
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

We studied the mortality from lung and pleural cancers in a cohort of 62,937 male workers employed for at least 1 year in the pulp and paper industry in 13 countries during 1945 to 1996. Mill departments were classified according to probability and level of exposure to asbestos on the basis of available dust measurements and mill-specific information on exposure circumstances. Thirty-six percent of workers were classified as ever exposed to asbestos. Standardized mortality ratios of lung cancer were 0.99 (95% confidence interval [CI], 0.90 to 1.08) among unexposed and 1.00 (95% CI, 0.90 to 1.11) among ever exposed workers. The number of pleural cancer deaths among unexposed workers was 10; that among exposed workers was 14, most of which occurred among maintenance workers. In internal analyses, a trend in mortality from either neoplasm was suggested for estimated cumulative exposure to asbestos, weighted for the individual probability of exposure within the department and for duration of exposure (relative risk for lung cancer for 0.78+ f/cc-years, as compared with < or = 0.01 f/cc-years: 1.44; 95% CI, 0.85 to 2.45; corresponding relative risk for pleural cancer: 2.43; 95% CI, 0.43 to 13.63). Despite a possible nondifferential misclassification of exposure and outcome, this study suggests that the carcinogenic effect of asbestos can be detected among workers employed in industries such as the pulp and paper industry, in which it is not considered to be a major hazard.

In plain English

This multinational cohort study followed 62,937 men employed at least 1 year in the pulp and paper industry in 13 countries, 1945 to 1996. Industrial hygienists estimated exposure by department and time period; asbestos type was unknown. 36% were classed as ever exposed. Compared with national rates (Brazil and South Africa excluded), the lung cancer standardized mortality ratio was 0.99 (95% CI 0.90 to 1.08) in never-exposed and 1.00 (0.90 to 1.11) in ever-exposed workers. Pleural cancer caused 14 deaths among exposed and 10 among unexposed workers, a relative risk for ever exposure of 2.53 (95% CI 1.03 to 6.23). At the highest weighted cumulative exposure (0.78 f/cc-years or more, versus 0.01 or less), relative risks were 1.44 (0.85 to 2.45) for lung and 2.43 (0.43 to 13.63) for pleural cancer; trend-test P values were 0.07 and 0.29. The authors concluded that their findings suggest a more than negligible asbestos effect in this industry and a particularly high risk for maintenance workers of dying from pleural cancer. They noted likely misclassification of exposure and cause of death.

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: Multinational cohort mortality study. It compared the cohort with national death rates (standardized mortality ratios) and made internal comparisons by estimated asbestos exposure (relative risks from Poisson regression).
• Who was studied: 62,937 male workers employed for at least 1 year in the pulp and paper industry in 13 countries, 1945 to 1996. The cohort covered 42 mills and 96 departments. Brazil and South Africa were excluded from the comparisons with national rates because reference rates were not available.
• Exposure: Asbestos exposure estimated by industrial hygienists for each mill, department and time period. Estimates covered probability, intensity, duration and weighted cumulative exposure in f/cc-years. The fiber type was unknown. 22,468 workers (36%) were classed as ever exposed and 40,107 (64%) as never exposed.
• Main results:
  • Lung cancer standardized mortality ratio, with Brazil and South Africa excluded: 0.99 (95% CI 0.90 to 1.08; 446 deaths) among never-exposed workers and 1.00 (95% CI 0.90 to 1.11; 349 deaths) among ever-exposed workers.
  • All-cause mortality was below national rates in both groups: SMR 0.93 (0.91 to 0.95) in never-exposed and 0.89 (0.86 to 0.91) in ever-exposed workers.
  • There were 14 pleural cancer deaths in the asbestos-exposed group. 13 of these were in non-production departments, including maintenance, storage, loading, transport and construction.
  • There were 10 pleural cancer deaths in the nonexposed group, three of them among maintenance workers.
  • Relative risk for ever exposure compared with never exposure: pleural cancer 2.53 (95% CI 1.03 to 6.23; 10 unexposed and 14 exposed cases); lung cancer 0.95 (95% CI 0.81 to 1.10; 450 and 351 cases).
  • After further adjustment for sulfur dioxide and formaldehyde, the lung cancer relative risk for ever exposure was 0.78 (95% CI 0.59 to 1.03). The pleural cancer relative risk became unstable.
  • Highest weighted cumulative exposure (0.78 f/cc-years or more) compared with 0.01 f/cc-years or less: lung cancer relative risk 1.44 (95% CI 0.85 to 2.45; 25 deaths), trend P value 0.07; pleural cancer relative risk 2.43 (95% CI 0.43 to 13.63; 3 deaths), trend P value 0.29.
• The authors' conclusion: The authors concluded that their findings suggest an effect of asbestos exposure in the pulp and paper industry that is more than negligible. They also concluded there was a particularly high risk for maintenance workers of dying from pleural cancer.
• Limitations the authors state:
  • Exposure was estimated at department level, almost always without measurements from the mill in question.
  • The type of asbestos was unknown.
  • Underestimation and misclassification of asbestos exposure were likely.
  • Pleural cancer was identified from the underlying cause of death, and death certificates have limited specificity and sensitivity.
  • Little follow-up time fell more than 35 years after first exposure, so the full effect may not yet have been expressed.
  • Maintenance workers may also have been exposed to asbestos in other industries.
  • A link with lung cancer may go undetected because lung cancer is affected by confounders such as smoking.

Topics

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

Medical terms in this study, explained in our Lexicon: standardized mortality ratio (SMR), Lung Cancer, confidence interval, Neoplasm, Cumulative Exposure, Relative Risk, Carcinogenic.

Related studies

• Cohort mortality study of pulp and paper mill workers in British Columbia, Canada — P.R. Band, N.D. Le, et al. (1997)
• Health effects of working in pulp and paper mills: malignant diseases — K. Torén, B. Persson, et al. (1996)
• Pleural mesotheliomas and asbestos exposure in the pulp and paper industries: a new risk group identified by linkage of official registers — B. Järvholm, H. Malker, et al. (1988)
• Cancer incidence among Swedish pulp and paper mill workers: a cohort study of sulphate and sulphite mills — E. Andersson, H. Westberg, et al. (2013)
• Asbestos fibers in ovarian tissue from Norwegian pulp and paper workers — H. Langseth, B.V. Johansen, et al. (2007)
• Mortality among shipbreaking workers in Taiwan--a retrospective cohort study from 1985 to 2008 — W.T. Wu, Y.H. Lu, et al. (2013)

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