Observations on the distribution of asbestos fibers in human lungs

Our plain-English summary of Observations on the distribution of asbestos fibers in human lungs, by A. Churg, P. Wood (Environmental Research, 1983).

The study

• Authors: A. Churg, P. Wood
• Journal: Environmental Research
• Published: 1983;31(2):374-80
• Cited by: 35 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In an attempt to begin evaluating the distribution of mineral fibers within lung, multiple small adjacent samples were selected from peripheral portions of three normal and six asbestotic lungs, and analyzed for asbestos and nonasbestos fiber content. For both normal and fibrotic lungs there was marked variation in fiber concentration from site to site; the mean in-case ratio of maximum to minimum fiber concentration was 7.5 for amosite and crocidolite, 7.0 for tremolite, 3.8 for chrysotile, 4.0 for nonasbestos fibers, and 5.4 for asbestos bodies. In order to test the precision of the membrane filter method of quantitating particulates, multiple replicate samples of reference mineral standards were examined in a similar fashion; for these standard samples the ratio of maximum to minimum particle concentration varied from only 1.3 to 1.5. It is concluded that: (1) the membrane filter preparation technique used here for counting fibers provides reproducible results, and (2) there is marked variation in asbestos and nonasbestos fiber concentration from area to area within lung tissue. The latter finding implies that analysis of small subpleural lung biopsies may produce misleading results, and that larger pieces or several pieces should be analyzed when attempting to define total asbestos fiber content of the lung.

In plain English

This laboratory study examined how evenly asbestos and other mineral fibers are spread through small areas of human lung. The authors used lung tissue from nine people with a history of asbestos exposure: three whose lungs looked normal and six whose lungs were markedly scarred (asbestotic). For each person, five neighboring pieces from a strip of tissue just under the lung surface were analyzed. Counts varied much more from piece to piece than repeat tests of reference samples did (highest-to-lowest ratio 1.3 for reference amosite, 1.5 for talc). Within a person, the average highest-to-lowest ratio was 7.5 for amosite and crocidolite (seven cases), 7.0 for tremolite and 3.8 for chrysotile (two cases each), 4.0 for nonasbestos fibers (nine cases) and 5.4 for asbestos bodies (seven cases). The authors concluded that their counting method was reproducible and that small biopsies from the lung periphery may give misleading fiber counts. They noted there were too few cases to tell whether scarred lungs varied more.

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 of lung tissue from nine asbestos-exposed people, comparing fiber counts in adjacent small samples, plus a reproducibility test of the counting method using replicate reference mineral samples
• Who was studied: Lung tissue from nine individuals with a history of asbestos exposure. In three, the lung was grossly and microscopically normal. In six, the lung was markedly fibrotic (asbestotic). The work was done at the Department of Pathology, University of British Columbia. Dates of the cases are not given.
• Exposure: History of asbestos exposure; exposure details are not reported. In the lung tissue the authors measured amosite and crocidolite (counted as one group), tremolite, chrysotile, nonasbestos fibers and asbestos bodies.
• Main results:
  • In six replicate samples each of the reference minerals, the ratio of highest to lowest count was 1.3 for UICC amosite and 1.5 for cosmetic talc.
  • In the lung samples, every fiber type varied considerably more from site to site than the replicate reference samples did.
  • The mean within-case ratio of highest to lowest count was 7.5 for amosite and crocidolite over seven cases, and 4.0 for nonasbestos fibers over nine cases.
  • The mean within-case ratio was 7.0 for tremolite and 3.8 for chrysotile, each based on two cases.
  • The highest within-case ratio was 16.5, for amosite and crocidolite in case 1054.
  • For asbestos bodies, within-case ratios ranged from 1.5 to 15, with a mean of 5.4 over seven cases.
  • In seven cases, the concentration of amphibole asbestos fibers was not significantly correlated with the concentration of nonasbestos fibers.
  • The correlation between asbestos bodies and amosite and crocidolite fibers was not statistically significant.
• The authors' conclusion: The authors concluded that the membrane filter method gives reproducible counts and that fiber concentration varies markedly from area to area in the lung. They suggested that small peripheral biopsies may be misleading for measuring particle concentration, and that as large a piece as possible, or at least two pieces, should be analyzed.
• Limitations the authors state:
  • The data suggested more variation in fibrotic lungs, but there were too few cases for this to be statistically significant.
  • The reproducibility findings apply only to particles that do not tend to clump; clumped particles are likely to produce much greater counting errors.
  • Asbestos bodies were not evaluated in two cases because of technical problems in sample preparation.

Topics

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Amosite, Crocidolite, Tremolite, Chrysotile, Asbestos Bodies, Membrane Filter Method.

Related studies

• The distribution of amosite asbestos in the periphery of the normal human lung — A. Churg (1990)
• Cytotoxicity of a short-fiber chrysotile asbestos for human alveolar macrophages: preliminary observations — H. Yeager, D.A. Russo, et al. (1983)
• Distribution of asbestos bodies in the human lung as determined by bronchoalveolar lavage — H. Teschler, N. Konietzko, et al. (1993)
• The distribution and characteristics of asbestos fibers in the lungs of Finnish anthophyllite mine-workers — A. Morgan, A. Holmes (1984)
• Asbestos fibers in human pulmonary and extrapulmonary tissues — J. Huang, N. Hisanaga, et al. (1988)
• Some observations on the distribution of trace metals in chrysotile asbestos — A. Morgan, A.E. Lally, et al. (1973)

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