Some investigations into the nature and cause of massive fibrosis (MF) in the lungs of South African gold, coal, and asbestos mine workers

Our plain-English summary of Some investigations into the nature and cause of massive fibrosis (MF) in the lungs of South African gold, coal, and asbestos mine workers, by M.C. Leibowitz, B. Goldstein (American Journal of Industrial Medicine, 1987).

The study

• Authors: M.C. Leibowitz, B. Goldstein
• Journal: American Journal of Industrial Medicine
• Published: 1987;12(2):129-43
• Cited by: 5 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. 000982).

Abstract

Samples from fibrotic lung lesions greater than 1 cm in diameter macroscopically (by definition, massive fibrosis; MF) were taken from the lungs of 9 randomly selected post-mortem cases of mine workers all showing a background of a pneumoconiosis. These samples were studied histologically, biochemically, and by X-ray diffraction and electron microscopy. As controls for the biochemical and X-ray diffraction investigations, nonfibrosed lung tissue was taken from the same specimens. The findings suggest that the higher quartz content may be the primary cause responsible for the MF formation in this series of cases, while other factors such as tuberculosis may play a part according to some relevant literature on MF. Although an area of MF appears macroscopically to be a solid lesion, on microscopy this is not the case and the lesion is composed of dense and sparse collagen bundles and cellular elements.

In plain English

The authors studied lung tissue from 9 randomly selected South African gold, coal and asbestos mine workers, examined after death at the National Centre for Occupational Health in Johannesburg. All had massive fibrosis (scarred lung lesions larger than 1 cm across) on a background of pneumoconiosis. Lesion samples were compared with apparently unscarred tissue from the same lungs. On chemical analysis, the average silica content of the fibrotic tissue was 2.33 times that of the comparison tissue, and the average collagen content was 1.2 times; both differences were reported as statistically significant. X-ray diffraction of tissue ash found an average of 1.4% quartz in ash from the fibrotic tissue, against no trace or no clear indication in ash from the comparison tissue. Stains for tuberculosis bacteria were negative in all lesions; one worker had active tuberculosis elsewhere in the lung. Asbestos fibers were counted in lesions from two cases. The authors concluded that higher quartz content may be an important cause of massive fibrosis in these cases. They noted the quartz findings apply only to these nine cases.

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: Post-mortem pathology case series comparing massive fibrosis tissue with nonfibrosed tissue from the same lungs (histology, chemical analysis, X-ray diffraction of tissue ash, electron microscopy)
• Who was studied: 9 randomly selected deceased mine workers with massive fibrosis (lesions over 1 cm) on a background of pneumoconiosis. Their cardiorespiratory organs were submitted under South African law to the National Centre for Occupational Health, Johannesburg. Dates of death are not stated; the average age at death was 66 years.
• Exposure: Work in South African gold, coal and asbestos mining (the case table also lists other substances mined). Quartz (crystalline silica) content of lung tissue was measured. Asbestos fiber types are not named.
• Main results:
  • On chemical analysis, the average silica percentage in massive fibrosis tissue was 2.33 times that in the comparison tissue from the same lungs. The average collagen percentage was 1.2 times.
  • The silica difference was reported as significant at p less than 0.01 (one-tailed test).
  • The collagen difference was reported as significant at p less than 0.05.
  • The tissues were burned to ash, and the ash was analysed by X-ray diffraction. Ash from the massive fibrosis tissue contained an average of 1.4% crystalline silica (quartz). Ash from the comparison tissue showed no trace or no clear indication of quartz.
  • Birefringent particles, probably quartz, were seen in all massive fibrosis sections.
  • Stains for acid- and alcohol-fast bacilli and for amyloid were negative in all massive fibrosis tissues.
  • One case (case 8) showed active tuberculosis in other lung sections, but not in the massive fibrosis lesions.
  • Although the lesions looked solid to the naked eye, under the microscope they were made of dense and less dense collagen and cellular areas.
  • In the massive fibrosis tissue of case 2 (moderate asbestosis, 28 years of asbestos exposure), there were 102,213 coated and 765,543 uncoated fibers per g dry tissue.
  • In the massive fibrosis tissue of case 8 (slight asbestosis, 29.8 years of exposure), there were 15,348 coated and 291,151 uncoated fibers per g dry tissue.
• The authors' conclusion: The authors concluded that the higher quartz content in the massive fibrosis tissue may be an important cause of massive fibrosis in the gold, coal and asbestos miners in this series. Drawing partly on other literature, they suggested tuberculosis as a secondary localising factor. They also suggested that a combination of factors, which may differ from person to person, is responsible.
• Limitations the authors state:
  • More cases are needed to determine the significance of the quartz finding.
  • Conclusions from the quartz figures apply only to these nine cases.
  • Variation in quartz content may reflect whether a sample came from a quartz-rich or quartz-poor area of the lesion.
  • Rheumatoid factor could not be tested because only post-mortem tissue was available.
  • The cells seen on electron microscopy could not be identified because of tissue breakdown (autolysis).
  • No conclusion could be drawn about cumulative dust exposure and massive fibrosis.

Topics

Medical terms in this study, explained in our Lexicon: Fibrosis, Pneumoconiosis, X-Ray Diffraction (XRD), Collagen.

Related studies

• Discussion paper: asbestos fiber exposures in a hard rock gold mine — J.M. Dement, R.D. Zumwalde, et al. (1976)
• Relationships between simultaneous airborne dust samples taken with five types of instruments at South African asbestos mines and mills — R.S. Du Toit, L.W. Isserow, et al. (1983)
• Mortality patterns among hard rock gold miners exposed to an asbestiform mineral — J.D. Gillam, J.M. Dement, et al. (1976)
• Particle toxicology: from coal mining to nanotechnology — P.J. Borm (2002)
• Does occupational exposure to brown coal dust cause a decline in lung function? — C. Finocchiaro, A. Lark, et al. (1997)
• Asbestosis in South African asbestos miners — G.K. Sluis-Cremer (1970)

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