Cancer incidence in a chlorochemical plant in Isère, France: an occupational cohort study, 1979-2002

Our plain-English summary of Cancer incidence in a chlorochemical plant in Isère, France: an occupational cohort study, 1979-2002, by V. Bonneterre, G. Mathern, O. Pelen, et al (American Journal of Industrial Medicine, 2012).

The study

• Authors: V. Bonneterre, G. Mathern, O. Pelen, A.L. Balthazard, P. Delafosse, N. Mitton, M. Colonna
• Journal: American Journal of Industrial Medicine
• Published: 2012;55(9):756-67
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: A major French chlorine chemical plant (chlor-alkali process with diaphragm cell and manufacturing of organochlorine chemicals) has used or produced known or suspected carcinogenic compounds.

Methods: A cohort study, based on the plant occupational health service and the regional cancer registry, analyzed the standardized incidence ratios of malignant tumors for the period 1979-2002. Individual exposures were estimated from workers' occupational histories in a dual division of jobs into 9 sectors and 115 workshops with known exposures.

Results: Men (2,742) were followed, corresponding to 52,794 person-years. Primary tumors (304) were observed for 290 expected cases, a non-significant 5% excess. A significant excess was found of pleural mesothelioma and bladder cancer in employees hired before 1964.

Conclusion: Excesses of mesothelioma and bladder cancer were found, whereas there was no excess of hematopoietic cancers despite high benzene and dioxin exposures. Surprisingly, mesothelioma cases did not include workers who were the most exposed to asbestos.

Copyright © 2012 Wiley Periodicals, Inc.

In plain English

This cohort study followed cancer among men who worked at a chlorine chemical plant near Grenoble, Isère, France. The plant made chlorine in asbestos diaphragm cells and produced many organochlorine chemicals. Asbestos was used as a powder to make the diaphragm cells on site and was also present in insulation. Using the Isère cancer registry, the authors compared cancers in 2,742 men (52,794 person-years) from 1979 to 2002 with rates in the Isère population. Overall, 304 cancers occurred against 290 expected, a 5% excess that was not statistically significant. Pleural mesothelioma was significantly raised: 6 cases against 1.5 expected (standardized incidence ratio 4.01, 95% CI 1.46 to 8.73), all in men hired before 1964. Bladder cancer was significantly raised only in men hired before 1964. Lung cancer was not significantly raised. None of the mesothelioma cases had handled bulk asbestos for the diaphragms, and the authors suggested passive asbestos exposure across the plant. The authors noted that 28% of the men were lost to follow-up and that some cancers may not yet have had time to develop.

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: Occupational cohort study of cancer incidence. Cancers were identified through a regional cancer registry and compared with the population of Isère using standardized incidence ratios (SIRs) adjusted for age and sex.
• Who was studied: 2,742 men who worked at least 6 months at a chlorochemical plant in Isère, France, between 1979 and 2002 and were hired before the end of 1992. Together they contributed 52,794 person-years. The 217 women in the cohort were not analyzed because there were so few.
• Exposure: Work at a chlor-alkali and organochlorine chemical plant. Asbestos (fiber type not specified) was present in insulating material and was used in powder form to manufacture electrolysis diaphragm cells on site until the end of 2002. Asbestos exposure decreased from 1976 onward. Other exposures included benzene, dioxins and isocyanate precursors.
• Main results:
  • All cancers combined, men: 304 observed against 290 expected (SIR 1.05, 95% CI 0.93 to 1.17), a 5% excess that was not statistically significant.
  • Pleural mesothelioma, men: 6 observed against 1.5 expected (SIR 4.01, 95% CI 1.46 to 8.73, P = 0.01). This was the only cancer site with a statistically significant excess overall.
  • All 6 pleural mesothelioma cases were in men hired before 1964 (6 observed against 0.67 expected, SIR 8.94, 95% CI 3.26 to 19.45). The excess of cases was diagnosed only after 1987.
  • By sector, the mesothelioma excess was statistically significant for men who had worked at least once in petrochemistry (3 observed against 0.4 expected, SIR 6.92, 95% CI 1.39 to 20.21) or in the laboratory (2 observed against 0.1 expected, SIR 21.23, 95% CI 2.38 to 76.64). It was not associated with the minerals sector, which included electrolysis and had the greatest asbestos exposure.
  • None of the mesothelioma cases had occurred in workers handling bulk asbestos to make the diaphragms. All six cases were in workers whose work histories at the plant did not involve direct asbestos exposure. The authors suggested this may indicate passive asbestos exposure across the plant.
  • Bladder cancer: 20 observed against 13.1 expected overall (SIR 1.53, 95% CI 0.93 to 2.36, P = 0.09), which was borderline. The excess was statistically significant in men hired before 1964 (13 observed against 6.45 expected, SIR 2.02, 95% CI 1.07 to 3.45). All 20 bladder cancer cases were smokers.
  • Lung cancer, men: 55 observed against 50.5 expected (SIR 1.09, 95% CI 0.82 to 1.42), not statistically significant despite asbestos use.
• The authors' conclusion: The authors concluded that the study revealed a high excess of mesothelioma. They considered it probably due to contamination of the plant with bulk asbestos used in the diaphragm process, and possibly also related to asbestos used elsewhere in the plant, such as in heat insulation. They found it unexpected that the mesotheliomas did not occur among the most exposed workers.
• Limitations the authors state:
  • Men left the cohort when they moved outside Isère, so 28% were lost to follow-up.
  • The cohort had far more workers and employees (67%) than the Isère population (30%), and the SIRs could not be adjusted for socio-economic status. Social inequalities could partly explain the excess cancer incidence.
  • Some occupational cancers, such as pleural mesothelioma, may not yet have had time to develop, especially in more recently hired employees.
  • Workers moved between workshops and had multiple exposures. Subgroups were small, and no atmospheric or biological exposure measurements were available for the analysis.
  • The study did not include subcontractors.
  • Follow-up could not be continued beyond 2002. The authors stated that the negative and borderline results would have benefited from longer follow-up.

Topics

Medical terms in this study, explained in our Lexicon: Cohort Study, Diaphragm, Carcinogenic, Cancer Registry, Standardized Incidence Ratio (SIR), Pleural Mesothelioma, Mesothelioma.

Related studies

• Occupational exposure to chlorinated solvents and risk of head and neck cancer in men: a population-based case-control study in France — C. Barul, A. Fayossé, et al. (2017)
• Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers — M. Boulanger, F. Morlais, et al. (2015)
• Cancer incidence among asbestos-exposed chemical industry workers: an extended observation period — B. Hilt, A. Andersen, et al. (1991)
• A cancer incidence and mortality study of Dow Chemical Canada Inc. manufacturing sites — C. Burns, K. Harrison, et al. (2005)
• Occupational class, occupational mobility and cancer incidence among middle-aged men and women: a prospective study of the French GAZEL cohort* — M. Melchior, M. Goldberg, et al. (2005)
• Risk of cancer from occupational exposure to ionising radiation: retrospective cohort study of workers in France, the United Kingdom, and the United States (INWORKS) — D.B. Richardson, E. Cardis, et al. (2015)

Browse more research in American Journal of Industrial Medicine, or return to medical research.