Lung asbestos content in chrysotile workers with mesothelioma

Our plain-English summary of Lung asbestos content in chrysotile workers with mesothelioma, by A. Churg, B. Wiggs, L. Depaoli, et al (The American Review of Respiratory Disease, 1984).

The study

• Authors: A. Churg, B. Wiggs, L. Depaoli, B. Kampe, B. Stevens
• Journal: The American Review of Respiratory Disease
• Published: 1984;130(6):1042-5
• Cited by: 107 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001647).

Abstract

The role of chrysotile asbestos in the genesis of mesotheliomas in humans is disputed. We analyzed the asbestos content of the lung in 6 long-term chrysotile miners and millers who had pleural mesotheliomas. In five patients, only chrysotile ore components (chrysotile and tremolite/actinolite/anthophyllite types of amphibole asbestos) were found, while the sixth patient presented both chrysotile ore components and amosite, a type of asbestos that is not derived from the mining process. The mean number of fibers/g dry lung for the 5 patients with mesothelioma containing only chrysotile ore components was higher (chrysotile 64 X 10(6) and tremolite group 540 X 10(6] than in a group of long-term chrysotile miner control subjects who had no asbestos-related disease (chrysotile 23 X 10(6), tremolite group 58 X 10(6], but some patients with mesothelioma had fiber burdens near the mean of the control range. Fiber sizes and aspect ratios in the mesothelioma group were approximately the same as those in the control subjects, and analysis of fiber distribution failed to show any preferential localization in the periphery of the lung. However, the concentration ratio of tremolite in the lungs of the mesothelioma cases compared to the control cases was 9.3, while the ratio of chrysotile was only 2.8. Our findings provide strong evidence that chrysotile mine dust (chrysotile and amphibole components) can produce mesotheliomas in humans; the greater relative amounts of tremolite group amphiboles present in the patients with mesothelioma raise the possibility that these fibers may be important in the pathogenesis of the tumors.

In plain English

The authors measured asbestos fibers in autopsy lung tissue from 6 long-term Quebec chrysotile miners and millers with pleural mesothelioma. These were all the mesotheliomas among about 90 sequential autopsies of such workers, done from late 1980 through 1983. Five had only "chrysotile ore components": chrysotile plus the tremolite, actinolite and anthophyllite amphiboles that occur naturally in the ore. The sixth also had amosite and was left out of the averages. In the 5, the means were 64 million chrysotile fibers and 540 million tremolite-group fibers per gram of dry lung. The comparison group, 9 previously studied chrysotile workers without mesothelioma or asbestos-related fibrosis, had 23 million and 58 million. The two groups overlapped, and two mesothelioma patients had levels at or below the comparison mean. Fiber size and shape did not differ, and fibers were not concentrated in the outer lung. Compared with the comparison group, tremolite-group fibers were 9.3 times higher and chrysotile 2.8 times higher. The authors concluded that chrysotile mine dust can produce mesothelioma, and that the tremolite-group amphiboles may be important in causing it.

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: Autopsy lung fiber-burden (mineralogic) analysis of a small case series, compared with a previously published group of chrysotile workers without mesothelioma
• Who was studied: 6 men aged 52 to 68 with pleural mesothelioma, who were long-term workers in the Quebec chrysotile industry. They were all the mesotheliomas among about 90 sequential autopsies performed from late 1980 through 1983 at Thetford Mines, Quebec. The comparison group was 9 previously published long-term chrysotile workers from the same autopsy series who had neither mesothelioma nor asbestos-induced fibrosis.
• Exposure: Chrysotile mine dust: chrysotile plus the amphiboles tremolite, actinolite and anthophyllite that occur in the chrysotile ore. Workers had 10 to 47 years of employment in the chrysotile industry, in jobs including mine mechanic, underground miner, mill fiber bagger and fiber separator. One patient also had amosite in the lungs.
• Main results:
  • Five of the 6 mesothelioma patients had only chrysotile ore components in their lungs. The sixth also had amosite (70 x 10 to the 6th fibers per gram of dry lung), which does not come from the mining process.
  • In the 5 mesothelioma patients with only chrysotile ore components, the mean was 64 plus or minus 65 x 10 to the 6th chrysotile fibers and 540 plus or minus 840 x 10 to the 6th tremolite-group fibers per gram of dry lung.
  • In the 9 comparison chrysotile workers without asbestos-related disease, the means were 23 x 10 to the 6th chrysotile fibers and 58 x 10 to the 6th tremolite-group fibers per gram of dry lung.
  • The mesothelioma and comparison groups overlapped considerably. Two mesothelioma patients (Patients 2 and 4) had fiber concentrations at or below the comparison-group mean.
  • Fiber size distribution and fiber aspect (length to width) ratios did not differ between the mesothelioma and comparison groups, or between central and peripheral lung samples. Mean chrysotile aspect ratios were 92 in the mesothelioma patients and 96 in the comparison group; for the tremolite group they were 14 and 13.
  • Fibers did not show any preferential concentration in the periphery of the lung in the mesothelioma patients.
  • Compared with the comparison group, the ratio of fiber numbers in the 5 mesothelioma patients was 9.3 for tremolite-group fibers and 2.8 for chrysotile.
  • Two of the 5 patients with detailed occupational histories appear to have worked only in the mines, not the mills (for example, Case 4 was an underground miner only).
• The authors' conclusion: The authors concluded that their findings provide strong evidence that chrysotile mine dust (chrysotile and its amphibole components) can produce mesotheliomas in humans. They added that the greater relative amounts of tremolite-group amphiboles in the patients raise the possibility that these fibers may be important in causing the tumors.
• Limitations the authors state:
  • Because chrysotile does not accumulate in lung tissue as amphiboles do, the authors could not determine what chrysotile load may originally have been present in these lungs.
  • For Patient 6, who had amosite, the authors could not obtain enough occupational details to confirm the suspected work in a factory that used amosite.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Actinolite, Anthophyllite, Chrysotile, Lung cancer, Mesothelioma, Tremolite.

Medical terms in this study, explained in our Lexicon: Chrysotile, Mesothelioma, Pleural Mesothelioma, Tremolite, Actinolite, Anthophyllite, Amphibole Asbestos, Amosite.

Related studies

• Fiber size and number in workers exposed to processed chrysotile asbestos, chrysotile miners, and the general population — A. Churg, B. Wiggs (1986)
• Mineralogic correlates of fibrosis in chrysotile miners and millers — A. Churg, J.L. Wright, et al. (1989)
• Sumas Mountain chrysotile induces greater lung fibrosis in Fischer344 rats than Libby amphibole, El Dorado tremolite, and Ontario ferroactinolite — J.M. Cyphert, A. Nyska, et al. (2012)
• Environmental pleural plaques in residents of a Quebec chrysotile mining town — A. Churg, L. DePaoli (1988)
• Asbestos fiber concentrations in the lungs of brake repair workers: commercial amphiboles levels are predictive of chrysotile levels — G.M. Marsh, A.O. Youk, et al. (2011)
• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part III. Radiographic findings — H.E. Amandus, R. Althouse, et al. (1987)

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