Occupational asbestos exposure and digestive cancers - a cohort study

Our plain-English summary of Occupational asbestos exposure and digestive cancers - a cohort study, by B. Clin, F. Morlais, B. Dubois, et al (Alimentary Pharmacology & Therapeutics, 2009).

The study

• Authors: B. Clin, F. Morlais, B. Dubois, A.V. Guizard, N. Desoubeaux, M.F. Marquignon, C. Raffaelli, C. Paris, F. Galateau-Salle, G. Launoy, M. Letourneux
• Journal: Alimentary Pharmacology & Therapeutics
• Published: 2009;30(4):364-74
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Although the role of asbestos in the genesis of mesothelioma and primary bronchopulmonary cancers has been established, results from studies focusing on the relationship between occupational exposure to asbestos and digestive cancer remain contradictory.

Aim: To determine whether occupational asbestos exposure increases the incidence of digestive cancers.

Methods: Our study was a retrospective morbidity study based on 2024 subjects occupationally exposed to asbestos. The incidence of digestive cancer was calculated from 1st January 1978 to 31st December 2004 and compared with levels among the local general population using Standardized Incidence Ratios. Asbestos exposure was assessed using the company's job exposure matrix.

Results: Eighty-five cases of digestive cancer were observed within our cohort, for an expected number of 66.90 (SIR = 1.27 [1.01; 1.57]). A significantly elevated incidence, particularly notable among women, was observed for peritoneal mesothelioma, independently of exposure levels. A significantly elevated incidence was also noted among men for cancer of small intestine and oesophagus, for cumulative exposure indexes for asbestos above 80 fibres/mL x years. A significantly elevated incidence of cancer of the small intestine was also observed among men having been exposed to asbestos for periods in excess of 25 years and for mean exposure levels in excess of 4 fibres/mL.

Conclusions: This study suggests the existence of a relationship between exposure to asbestos and cancer of the small intestine and of the oesophagus in men.

In plain English

This retrospective cohort study followed 2024 workers (1604 men, 420 women) from an asbestos textile and friction-lining plant in Calvados, France. About 65% had been exposed only to chrysotile and about 35% to both chrysotile and amphibole. Using local cancer registry data, the authors compared digestive cancers diagnosed in the cohort from 1978 to 2004 with the number expected from age- and sex-specific Calvados population rates. There were 85 digestive cancers against 66.90 expected (SIR 1.27, 95% CI 1.01 to 1.57). These included 8 peritoneal mesotheliomas (SIR 29.65, 12.77 to 58.42), with a higher ratio in women than men. With peritoneal mesothelioma excluded, the excess was not statistically significant (SIR 1.16, 0.91 to 1.44). Among men with cumulative exposure above 80 fibres/mL x years, small intestine cancer (3 cases, SIR 6.93, 1.39 to 20.25) and oesophageal cancer (SIR 1.85, 1.08 to 2.96) were significantly raised. The authors concluded that the study suggests a relationship between asbestos and these two cancers in men, while noting it could not firmly establish cause, partly because smoking and alcohol data were lacking.

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 morbidity (cancer incidence) cohort study comparing the cohort with the local general population using Standardized Incidence Ratios (SIR)
• Who was studied: 2024 workers (1604 men, 420 women) at an asbestos reprocessing plant south of Calvados, Normandy, France. Included were workers who were alive in 1978, had worked at least 1 year in the plant and had lived in Calvados during the study period. Follow-up ran from 1 January 1978 to 31 December 2004.
• Exposure: Occupational asbestos exposure in the production of textile materials and friction linings. 65.22% were exposed to chrysotile only and 34.74% to mixed chrysotile and amphibole. Exposure was measured as a cumulative exposure index (fibres/mL x years) from the company's job exposure matrix, plus exposure duration and mean exposure level. Medians were 80 fibres/mL x years, 25 years and 4 fibres/mL.
• Main results:
  • Whole cohort, both sexes: 85 digestive cancers observed versus 66.90 expected, SIR 1.27 [1.01; 1.57]. Expected numbers were based on age- and sex-standardized Calvados incidence rates.
  • Whole cohort: 8 peritoneal mesotheliomas, SIR 29.65 [12.77; 58.42]
  • Whole cohort, after excluding peritoneal mesothelioma: SIR 1.16 [0.91; 1.44], not statistically significant
  • Men, all exposure levels: oesophageal cancer significantly elevated, SIR 1.63 [1.02; 2.48] (22 observed versus 13.46 expected)
  • Peritoneal mesothelioma, all exposure levels: SIR 61.30 [19.76; 143.06] in women (5 cases) and SIR 15.93 [3.2; 46.55] in men (3 cases)
  • Men with cumulative exposure above 80 fibres/mL x years: small intestine cancer SIR 6.93 [1.39; 20.25] (3 observed versus 0.43 expected) and oesophageal cancer SIR 1.85 [1.08; 2.96] (17 observed versus 9.19 expected)
  • Cumulative exposure above 80 fibres/mL x years: peritoneal mesothelioma SIR 97.66 [31.47; 227.91] in women and 22.63 [4.55; 66.13] in men
  • Men: small intestine cancer was also significantly elevated with exposure duration over 25 years (SIR 9.49 [1.07; 34.26], 2 cases) and mean exposure level over 4 fibres/mL (SIR 5.86 [1.18; 17.13], 3 cases)
  • Men: by exposure duration and by mean exposure level, oesophageal cancer was not significantly elevated
  • Colorectal cancer, whole cohort: 24 observed versus 26.48 expected, SIR 0.91 [0.58; 1.35]
• The authors' conclusion: The authors concluded that the study suggests a relationship between asbestos exposure and cancer of the small intestine and of the oesophagus in men. They added that their results do not firmly establish a causal link.
• Limitations the authors state:
  • The authors could not account for potential confounders such as alcohol and tobacco use or other occupational exposures.
  • Small numbers gave the study low statistical power.
  • About 25% of subjects were excluded from follow-up after moving out of the department, which further reduced statistical power.
  • There were no data on cancers before 1978, which may have led to underestimation of cancer incidence.
  • Some workers included in the cohort had not been exposed to asbestos, for example those in administrative jobs.
  • The results do not allow a causal link to be firmly established.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Cohort Study, Mesothelioma, Occupational Exposure, Standardized Incidence Ratio (SIR), Peritoneal Mesothelioma, Cumulative Exposure.

Related studies

• Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers — M. Boulanger, F. Morlais, et al. (2015)
• Incidence of digestive cancers and occupational exposure to asbestos — S. de La Provôté, N. Desoubeaux, et al. (2002)
• Asbestos exposure, pleural plaques and digestive cancers — B. Clin, C. Gramond, et al. (2025)
• Cancer incidence within a cohort occupationally exposed to asbestos: a study of dose--response relationships — B. Clin, F. Morlais, et al. (2011)
• A graphical analysis of the interrelationships among waterborne asbestos, digestive system cancer and population density — M.E. Tarter, R.C. Cooper, et al. (1983)
• Answers to some questions raised by the presentation on the graphical analysis of the interrelationships between waterborne asbestos, digestive system cancer and population density — M.E. Tarter (1983)

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