Correlation between the tissue response and asbestos fiber content

Our plain-English summary of Correlation between the tissue response and asbestos fiber content, by A.G. Heppleston (Environmental Health Perspectives, 1974).

The study

• Author: A.G. Heppleston
• Journal: Environmental Health Perspectives
• Published: 1974;9:295-6
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos fiber concentration increases in proportion to the degree of pulmonary fibrosis as far as the moderate grade. No such correlation occurs with severe asbestosis, nor with the morphological form which the fibrosis assumes, and here secondary factors may be concerned. Electron microscopy suggests that optically visible fibers constitute a reasonably constant proportion of the total irrespective of the pathological reaction. Light microscopy may thus afford a guide to the total asbestos concentration. Finally, the development of mesothelioma, whether of the pleura or the peritoneum, appears to be unrelated to the concentration of coated or uncoated asbestos fibers residing in the lung.

In plain English

This short report described lung fiber counts that the author made with a colleague, T. Ashcroft, in lung tissue from 35 people whose lungs contained asbestos bodies. All but one had a definite or probable history of occupational asbestos exposure. Coated and uncoated asbestos fibers were counted by light microscopy, and fiber diameters were measured by electron microscopy in samples from six cases. Mean fiber counts showed statistically significant 6- to 10-fold increases between the nil-mild and mild-moderate asbestosis groups. The five cases of severe asbestosis showed no further increase, and fiber levels varied widely within the same lung. Cases with nil, mild or moderate asbestosis were all associated with mesothelioma of the pleura or peritoneum; the severe cases were not. Grade of asbestosis was not related to how long exposure lasted or to time since exposure. Optically visible fibers made up between 12% and 30% of all fibers. Amphibole asbestos predominated over chrysotile. The author concluded that secondary processes may underlie severe asbestosis and that mesothelioma appeared unrelated to lung fiber concentration.

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: Laboratory study counting asbestos fibers in human lung tissue by light and electron microscopy, reported briefly here (the full study is cited as Ashcroft and Heppleston)
• Who was studied: Lung tissue from 35 individuals with asbestos bodies in lung sections, including five necropsy cases of severe asbestosis; electron microscopy was done on samples from six cases. Place and dates of the cases are not stated.
• Exposure: Definite or probable occupational asbestos exposure in all but one case. Coated and uncoated asbestos fibers were measured in the lung. Electron micrographs showed mostly amphibole asbestos, with relatively few chrysotile fibers.
• Main results:
  • Mean counts of coated, uncoated and total fibers showed successive, statistically significant 6- to 10-fold increases between the groups of cases with nil-mild and mild-moderate asbestosis.
  • The mean proportion of uncoated fibers rose slightly with increasing fibrosis, but the differences between grades were not statistically significant.
  • Grade of asbestosis was not related to duration of asbestos exposure, time from first exposure to death, or time from last exposure to death.
  • Cases with nil, mild or moderate asbestosis, which had widely varying lung fiber concentrations, were all associated with mesothelioma of the pleura or peritoneum.
  • The severe asbestosis cases were not associated with mesothelioma. Three severe cases (the 'low' group) had fiber concentrations in the range seen with mild asbestosis.
  • The other two severe cases (the 'high' group) had concentrations in the range for moderate asbestosis, so progression to severe asbestosis was not accompanied by a further rise in fiber concentration.
  • Asbestos concentration varied widely between areas of the same lung showing no fibrosis, fibrocystic change or solid fibrosis.
  • By electron microscopy, less than a third, and usually less than a fifth, of fibers were optically visible (diameter 0.4 micrometres or over). This did not vary between grades of asbestosis, and the proportion stayed between 12% and 30% of the total.
  • Electron micrographs showed a preponderance of amphibole asbestos with relatively few chrysotile fibers. The author commented that it seemed unlikely all the patients had been exposed almost exclusively to amphibole.
• The authors' conclusion: The author concluded that fiber concentration rises with fibrosis up to the moderate grade, and that the changes of severe asbestosis are due to one or more secondary pathological processes. The author also concluded that an optical count gives a fair indication of total asbestos concentration, and that mesothelioma of the pleura or peritoneum appears unrelated to the concentration of coated or uncoated fibers in the lung.
• Limitations the authors state:
  • The number of cases examined by electron microscopy was small.

Topics

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

Medical terms in this study, explained in our Lexicon: Pulmonary Fibrosis, Fibrosis, Mesothelioma, Pleura, Peritoneum.

Related studies

• Malignant mesothelioma and duration of asbestos exposure: correlation with tissue mineral fibre content — V.L. Roggli (1995)
• Discrepancies of asbestos body and fiber content between formalin-fixed and corresponding paraffin embedded lung tissue — B.K. Kuhn, F. Barresi, et al. (2021)
• Mineral fiber content of lung tissue in patients with environmental exposures: household contacts vs. building occupants — V.L. Roggli, W.E. Longo (1991)
• Asbestos content of lung tissue in asbestos associated diseases: a study of 110 cases — V.L. Roggli, P.C. Pratt, et al. (1986)
• Correlation of asbestos fiber burdens in fallopian tubes and ovarian tissue — D.S. Heller, R.E. Gordon, et al. (1999)
• Silica and asbestos: contrasts in tissue response — A.G. Heppleston (1979)

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