Retention of asbestos fibres in lungs of workers with asbestosis, asbestosis and lung cancer, and mesothelioma in Asbestos township

Our plain-English summary of Retention of asbestos fibres in lungs of workers with asbestosis, asbestosis and lung cancer, and mesothelioma in Asbestos township, by A. Dufresne, R. Bégin, S. Massé, et al (Occupational and Environmental Medicine, 1996).

The study

• Authors: A. Dufresne, R. Bégin, S. Massé, C.M. Dufresne, P. Loosereewanich, G. Perrault
• Journal: Occupational and Environmental Medicine
• Published: 1996;53(12):801-7
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Objective: To conduct a mineralogical study on the particles retained in the necropsied lungs of a homogenous group of asbestos miners and millers from Asbestos township (and a local reference population) and to consider the hypothesis that there is a difference in size between fibres retained in the lungs of patients with asbestosis with and without lung cancer.

Methods: Samples of lung tissue were obtained from 38 patients with asbestosis without lung cancer, 25 with asbestosis and lung cancer, and 12 with mesothelioma, from necropsied Quebec chrysotile miners and millers from Asbestos township. Fibre concentrations in the lungs of these patients were compared with those in tissue from necropsies carried out on a local reference population: men who had died of either accidental death or acute myocardial infarction between 1990 and 1992. 23 were born before 1940 and 26 after 1940.

Results: Geometric mean (GM) concentrations were higher in cases than in the controls for chrysotile fibres 5 to 10 microns long in patients with asbestosis with or without lung cancer; for tremolite fibres 5 to 10 microns long in all patients; for crocidolite, talc, or anthophyllite fibres 5 to 10 microns long in patients with mesothelioma; for chrysotile and tremolite fibres > or = 10 microns long in patients with asbestosis; and crocidolite, talc, or anthophyllite fibres > or = 10 microns long in patients with mesothelioma. However, median concentrations of each type of fibre in the lungs did not show any significant differences between the three disease groups. Average length to diameter ratios of the fibres were calculated to be larger in patients with asbestosis and lung cancer than in those without lung cancer for crocidolite fibres > or = 10 microns long, for chrysotile, amosite, and tremolite fibres 5 to 10 microns long, and for chrysotile and crocidolite fibres < 5 microns long. However, there was no statistical difference in the median length to diameter ratios for any type of fibres across the disease groups when they were calculated in each patient. Cumulative smoking index (pack-years) was higher in the group with asbestosis and lung cancer but was not statistically different from the two other disease groups.

Conclusion: Lung cancers occurred in workers with asbestosis from Asbestos township who had an equal concentration of retained fibres but a tendency to a higher length to diameter ratio of amphiboles. These workers had a 29% higher average cumulative smoking index.

In plain English

This study examined mineral fibres in autopsy lung tissue from chrysotile asbestos miners and millers from Asbestos township, Quebec. From the autopsy records of a Sherbrooke hospital for 1976 to 1992, the authors identified 38 workers with asbestosis without lung cancer, 25 with asbestosis and lung cancer, and 12 with mesothelioma. They compared them with local men who had no known asbestos exposure and who died of accidental death or acute myocardial infarction between 1990 and 1992 (23 born before 1940, 26 after). Fibres were identified and measured by electron microscopy. All three disease groups had higher geometric mean fibre concentrations than the comparison men. Median concentrations of the different fibre types and sizes did not differ significantly between the three disease groups. Crocidolite appeared higher in the mesothelioma group, but this difference was not significant. Fibre length-to-diameter ratios showed no statistical difference between the disease groups. Cumulative smoking (pack-years) was higher in the asbestosis and lung cancer group, but not statistically different from the other two groups. The authors noted that cumulative exposure was not known and that asbestosis was not graded.

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: Mineralogical (fibre) analysis of autopsy lung tissue, comparing three asbestos-related disease groups with each other and with a local reference population
• Who was studied: Chrysotile miners and millers from the township of Asbestos, Quebec, selected from autopsy records of the Centre Hospitalier Universitaire de Sherbrooke from 1976 to 1992: 38 with asbestosis without lung cancer, 25 with asbestosis and lung cancer (8 adenocarcinoma, 17 epidermoid carcinoma), and 12 with mesothelioma (treated as positive controls). Negative controls were local men who died of accidental death or acute myocardial infarction between 1990 and 1992 (23 born before 1940, 26 after 1940).
• Exposure: Work as chrysotile miners and millers. The lungs were found to contain tremolite, chrysotile, crocidolite and amosite fibres, as well as talc or anthophyllite and other fibres. Fibres were counted in three length classes: under 5 micrometres, 5 to 10 micrometres, and over 10 micrometres.
• Main results:
  • Geometric mean concentrations of all sizes and types of fibres were higher in all three disease groups than in the controls.
  • Median fibre concentrations did not differ significantly between the three disease groups.
  • Crocidolite concentrations appeared higher in the mesothelioma group than in the two asbestosis groups, but the difference was not significant.
  • Ferruginous bodies were higher in the two asbestosis groups than in the mesothelioma group, but not significantly different.
  • Among the lung cancer patients, median asbestos fibre concentration (all sizes) did not differ statistically between adenocarcinoma (20 333 fibres/mg) and other lung cancer types (39 735 fibres/mg), or between upper-lobe (35 596 f/mg) and lower-lobe (36 315 f/mg) samples.
  • For certain fibre types and sizes, average length-to-diameter ratios were larger in the asbestosis with lung cancer group than in the asbestosis-only group. However, median ratios showed no statistical difference for any fibre type across the disease groups.
  • Cumulative smoking (pack-years) was higher in the asbestosis with lung cancer group, but not statistically different from the other two disease groups. Only six of the 75 workers were non-smokers.
• The authors' conclusion: The authors concluded that all patients had more fibres than the reference population; that the mesothelioma patients had accumulated more amphiboles, while patients with asbestosis with and without lung cancer had retained similar numbers of fibres; and that the patients with asbestosis and lung cancer had a 29% higher mean cumulative smoking index. They stated that their limited data failed to support a proposed fibre-size hypothesis (Lippmann's) and that further research is needed.
• Limitations the authors state:
  • The precise cumulative exposure of the workers was not known.
  • Asbestosis was not graded when patients were selected. Any selection bias was likely towards moderate and severe asbestosis, because compensated patients with a clear pattern of asbestosis were chosen.
  • Only tissue blocks were available, so the lobe and site each specimen came from could not be determined.
  • No group of exposed workers with lung cancer but without asbestosis could be found, and no exposed group without asbestos-related disease was included.
  • Most patients had more than one asbestos-related disease, which may have obscured differences in fibre concentrations between groups.
  • Reliable histories could not be obtained from the controls' next of kin.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec

All asbestos mines

Topics

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

Medical terms in this study, explained in our Lexicon: Lung Cancer, Mesothelioma, Quebec Chrysotile, Chrysotile, Tremolite, Crocidolite, Talc, Anthophyllite.

Related studies

• Retention patterns of asbestos fibres in lung tissue among asbestos cement workers — M. Albin, F.D. Pooley, et al. (1994)
• Fibers in lung tissues of mesothelioma cases among miners and millers of the township of Asbestos, Quebec — A. Dufresne, M. Harrigan, et al. (1995)
• Asbestos, carbon nanotubes and the pleural mesothelium: a review of the hypothesis regarding the role of long fibre retention in the parietal pleura, inflammation and mesothelioma — K. Donaldson, F.A. Murphy, et al. (2010)
• An epidemiological study of the respiratory health of workers in the European refractory ceramic fibre industry — H.A. Cowie, P. Wild, et al. (2001)
• Asbestos, asbestosis, and lung cancer: observations in Quebec chrysotile workers — B.W. Case, A. Dufresne (1997)
• Mass, number and size of lung fibres in the pathogenesis of asbestosis in sheep — P. Sébastien, R. Bégin, et al. (1990)

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