Mineral fiber content of lungs in patients with mesothelioma seeking compensation in Québec

Our plain-English summary of Mineral fiber content of lungs in patients with mesothelioma seeking compensation in Québec, by A. Dufresne, R. Bégin, A. Churg, et al (American Journal of Respiratory and Critical Care Medicine, 1996).

The study

• Authors: A. Dufresne, R. Bégin, A. Churg, S. Massé
• Journal: American Journal of Respiratory and Critical Care Medicine
• Published: 1996;153(2):711-8
• Cited by: 31 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos fibers (AF) and ferruginous bodies (FB) in lung parenchyma from 50 workers seeking compensation from the Workers' Compensation Board of Québec for pleural or peritoneal mesothelioma were analyzed using transmission electron microscopy (TEM) equipped with energy-dispersive spectrometer (EDS) and phase-contrast microscopy (PCM). These workers had been occupationally exposed in mining and milling activities (12 were from Asbestos Township and 11 from Thetford Mines) and 27 were from other types of industry (asbestos factory, shipyard, etc.). For comparison, analyses of lung tissue at autopsy were done in a group of 49 subjects from a reference population. A 95% confidence interval upper limit of 540 AF < 5 microns/mg and a 95% confidence interval upper limit of 161 AF > or = 5 microns/mg dried lung tissue were found for the reference population. Similarly, a concentration of FB of 142 FB/g constituted the upper limit of detectable FB in the lungs of the reference population. Forty-eight of the 50 workers with mesothelioma had either a ferruginous body or total asbestos fiber count greater than the 95% confidence interval for the reference population; the remaining two had amosite and/or crocidolite concentrations greater than the 95% confidence interval for the reference population. The fiber types were different in the three groups, with the lungs of workers from Thetford Mines containing only chrysotile and tremolite, those from Asbestos Township containing chrysotile, tremolite, amosite, and crocidolite, and those in other industries containing largely amosite and crocidolite. We conclude that in this population of workers seeking compensation for mesothelioma, fiber analysis confirmed occupational asbestos exposure in every case. The fiber types responsible for the tumors are probably different in the three different groups.

In plain English

The authors measured asbestos fibers and ferruginous bodies in lung tissue from 50 Québec workers with pleural or peritoneal mesothelioma who sought workers' compensation. Twelve were miners and millers from the chrysotile mining region of Asbestos Township, 11 from Thetford Mines, and 27 worked in other industries such as asbestos factories and shipyards. They were compared with 49 men with no known asbestos exposure who were autopsied at Sherbrooke University Hospital Centre in 1990 to 1992. Chrysotile and tremolite were the only asbestos fiber types found in the lungs of Thetford Mines workers. Lungs of Asbestos Township workers also contained amosite and crocidolite. Workers from other industries had mainly amosite and crocidolite. Forty-eight of the 50 workers (96%) had asbestos fiber or ferruginous body levels above the upper 95% limit for the reference group. The other two had amosite and/or crocidolite levels above it. The authors concluded that fiber analysis confirmed occupational asbestos exposure in every case, and that the fiber types responsible for the tumors probably differed among the groups. They noted that the method may fail when exposure is to relatively pure chrysotile, which does not persist in lung tissue.

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: Lung fiber burden study: electron microscopy analysis of lung tissue from mesothelioma cases, compared with an autopsy reference group analyzed in the same laboratory
• Who was studied: 50 workers with pleural or peritoneal mesothelioma who sought compensation from the Québec Workers' Compensation Board (CSST). Lung tissue was obtained for 50 of 120 workers compensated by the CSST: 12 from Asbestos Township, 11 from Thetford Mines and 27 from other industries. The reference group was 49 men who died accidentally or of acute myocardial infarction and were autopsied at Sherbrooke University Hospital Centre between 1990 and 1992, none with known asbestos exposure.
• Exposure: Occupational asbestos exposure in chrysotile mining and milling (Asbestos Township and Thetford Mines) or in other industries (asbestos factory, shipyard, etc.). Lungs were analyzed for chrysotile, tremolite, crocidolite, amosite, talc or anthophyllite, and other fibers.
• Main results:
  • In the reference population, the upper 95% confidence limit was 540 asbestos fibers shorter than 5 µm per mg of dried lung tissue, and 161 asbestos fibers 5 µm or longer per mg.
  • In the reference population, 142 ferruginous bodies per gram was the upper limit of detectable ferruginous bodies.
  • Among asbestos fiber types, workers from Thetford Mines retained only tremolite and chrysotile. Their lungs also contained talc or anthophyllite and other non-asbestos fibers.
  • Lungs of workers from Asbestos Township contained chrysotile, tremolite, amosite and crocidolite.
  • Workers from other industries retained mainly amosite and crocidolite fibers.
  • Very few amosite and crocidolite fibers were found in the reference group.
  • Concentrations of all fibers shorter than 5 µm were above the reference group's 95% limit in 12 of 12 Asbestos Township cases, 11 of 11 Thetford Mines cases, and 18 of 27 other-industry cases.
  • Concentrations of all fibers 5 µm or longer were above the reference group's 95% limit in 12 of 12 Asbestos Township cases, 9 of 11 Thetford Mines cases, and 21 of 27 other-industry cases.
  • Ferruginous body concentrations were above the reference group's 95% limit in 12 of 12 Asbestos Township cases, 8 of 11 Thetford Mines cases, and 23 of 27 other-industry cases.
  • Overall, 96% of the mesothelioma cases (48 of 50) had asbestos fibers of all sizes, or ferruginous bodies, in excess of the reference population.
  • The two workers not in that category had amosite and/or crocidolite concentrations greater than the reference population.
  • Median ferruginous body concentrations did not differ statistically among the three worker groups, but were statistically greater than in the reference population.
  • For asbestos fibers of any size, the 95% confidence interval of the reference population did not overlap with that of any of the three mesothelioma groups.
  • Length-to-diameter ratios of tremolite fibers from the lungs of Asbestos Township and Thetford Mines workers were comparable to known asbestiform tremolite and larger than cleavage fragments from Nytal talc.
• The authors' conclusion: The authors concluded that, in this population of workers seeking compensation for mesothelioma, fiber analysis confirmed occupational asbestos exposure in every case. They also concluded that the fiber types responsible for the tumors are probably different in the three groups.
• Limitations the authors state:
  • The authors stated that comparison with a reference population may fail when exposure is to relatively pure chrysotile, because chrysotile does not persist in lung tissue.
  • The authors described the Eastern Townships reference group as only probably a reasonable comparison group for the workers from other industries.

Topics

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

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Mesothelioma, Ferruginous body, Parenchyma, Peritoneal Mesothelioma, Transmission Electron Microscopy (TEM), Thetford Mines, Autopsy.

Related studies

• Lung mineral fibers of former miners and millers from Thetford-Mines and asbestos regions: a comparative study of fiber concentration and dimension — A. Nayebzadeh, A. Dufresne, et al. (2001)
• Pulmonary mineral fibers after occupational and environmental exposure to asbestos in the Russian chrysotile industry — A. Tossavainen, E. Kovalevsky, et al. (2000)
• Emphysema in silica- and asbestos-exposed workers seeking compensation. A CT scan study — R. Bégin, R. Filion, et al. (1995)
• Nonasbestos pulmonary mineral fibers in the general population — A. Churg (1983)
• Mineral fiber content of lung tissue in patients with environmental exposures: household contacts vs. building occupants — V.L. Roggli, W.E. Longo (1991)
• A trial on the quantitative risk assessment of man-made mineral fibers by the rat intraperitoneal administration assay using the JFM standard fibrous samples — S. Adachi, K. Kawamura, et al. (2001)

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