Electron microscopy analysis of mineral fibers in human lung tissue

Our plain-English summary of Electron microscopy analysis of mineral fibers in human lung tissue, by K.H. Friedrichs, M. Brockmann, M. Fischer, et al (American Journal of Industrial Medicine, 1992).

The study

• Authors: K.H. Friedrichs, M. Brockmann, M. Fischer, G. Wick
• Journal: American Journal of Industrial Medicine
• Published: 1992;22(1):49-58
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In the present study, lung samples from 126 autopsied cases were examined to determine the content of mineral fibers using analytical transmission electron microscopy (ATEM). The cases were divided into four groups (22 lungs of persons exposed to ambient environmental pollution, 32 cases of mesothelioma, 38 cases of primary lung cancer, and 34 asbestosis cases, 13 of these with additional pleural plaques). Fibers were counted, measured, and mineralogically identified using a combination of X-ray microanalysis and electron diffraction of the non-oriented fiber. Concentration of fibrous particles (defined as particles above 1 micron in length with roughly parallel long sides and an aspect ratio of 5:1 and greater) was calculated as fibers 10(6)/g dry lung weight. The concentration of chrysotile was found to be similar throughout the groups except for two cases in the asbestosis group with comparably high numbers of chrysotile. However, a remarkable difference for amphiboles could be observed between the groups. Asbestos bodies were mostly found in the asbestosis group. There was a rather good correlation between numbers of amphibole fibers and asbestos bodies, with an average ratio of 10:1. For comparison purposes between occupationally exposed/non-exposed individuals, a transition was found in the concentration range of 3-10(7) asbestos fibers/g dried lung weight.

In plain English

The authors used analytical transmission electron microscopy to count, measure and identify mineral fibers in lung tissue from 126 autopsies in the German mesothelioma register in Bochum, 1989 to 1991. Cases were grouped by autopsy diagnosis: 22 exposed to ambient environmental pollution, 38 primary lung cancers, 32 pleural mesotheliomas, and 34 asbestosis cases, 13 also with pleural plaques. Only fibers longer than 1 micrometer were counted. The U-test found no significant chrysotile difference between groups, though an earlier passage reports one between two groups; amphibole differences were significant. Geometric mean amphibole concentrations, in millions of fibers per gram of dry lung, were 1.9 (environmental group), 3.7 (lung cancer), 16.6 (mesothelioma) and 106.1 (asbestosis). Asbestos bodies were found only in the three disease groups. They mostly had amphibole cores, with roughly ten amphibole fibers per body. The authors placed a zone of transition between occupationally exposed and non-exposed people at 20 to 50 million asbestos fibers per gram of dry lung (abstract: 30 million). The authors concluded that a single concentration value is not suitable as a limit between exposed and unexposed individuals.

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-tissue fiber-burden study comparing four diagnostic groups, using analytical transmission electron microscopy (ATEM)
• Who was studied: 126 autopsied cases from the German mesothelioma register in Bochum, 1989 to 1991, grouped by medical diagnosis at autopsy: 22 cases exposed to ambient environmental pollution ('normal lungs'), 38 cases of primary bronchial carcinoma, 32 cases of pleural mesothelioma, and 34 cases of asbestosis, 13 of them with pleural plaques
• Exposure: Lung content of chrysotile, amphiboles, other mineral fibers, and asbestos bodies. Amphiboles were not separated by type when counted; crocidolite and amosite are named as asbestos-body cores. Fibers were defined as longer than 1 micrometer with a length-to-diameter ratio of 5:1 or more. Occupational exposure status was based on anamnestic (history) data.
• Main results:
  • Geometric mean concentrations, in millions of fibers per gram dry weight (geometric SD in brackets). Amphiboles: normal lungs 1.9 (2.3), lung cancer 3.7 (4.4), mesothelioma 16.6 (6.6), asbestosis 106.1 (6.0). Chrysotile: normal lungs 4.5 (2.6), lung cancer 5.7 (3.6), mesothelioma 10.7 (4.7), asbestosis 7.2 (6.8).
  • By the Wilcoxon-Mann-Whitney U-test, there was no statistically significant difference in chrysotile concentration between the groups. An earlier results passage, however, reports a significant chrysotile difference between groups 1 and 3 at the 0.1% level. The article does not reconcile the two statements.
  • For amphibole fibers, the differences in median concentration between groups were mostly significant at the p = 0.005 level.
  • Asbestos bodies were found only in the mesothelioma, lung cancer and asbestosis groups. Their cores were mainly amphibole asbestos (crocidolite, amosite), and less than 5% were chrysotile.
  • The numbers of amphibole fibers and asbestos bodies were correlated, with an average ratio of about 10 fibers to 1 asbestos body.
  • The largest size differences were in amphibole fiber length. Geometric mean lengths were 2.6 micrometers in normal lungs, 4.4 in lung cancer, 6.0 in mesothelioma and 6.3 in asbestosis. The longest uncoated amphibole fiber measured 120.5 micrometers.
  • Two asbestosis cases had comparably high chrysotile counts and very few amphiboles. One of them had worked in a chrysotile mine some 25 years earlier.
  • The authors described a zone of transition between the occupationally exposed and non-exposed groups at 2 to 5 x 10^7 asbestos fibers per gram dry weight. They said this was about one order of magnitude above the mean of the environmental group, and attributed the increase to tumor cases with no ascertainable occupational exposure. The article's abstract gives 3 x 10^7 fibers per gram dried lung weight.
• The authors' conclusion: The authors concluded that the results suggest more asbestos in the lungs of occupationally exposed individuals than in non-exposed ones. They also concluded that setting one single concentration value as the limit between unexposed and exposed individuals does not seem suitable. They described the data as preliminary and intended to support medical judgment.
• Limitations the authors state:
  • In the mesothelioma and lung cancer groups, information about occupational history was incomplete in several cases.
  • The fibers reflect the lung at autopsy; nothing is known about when the fibers were deposited.
  • There is no standard for which part of the lung is sampled, and the sample locations in this study could not be exactly described for each case.
  • Short chrysotile fibrils contaminated even blank filters and could not be corrected for, so only fibers longer than 1 micrometer were evaluated.
  • Some fibers (7% to 21% per sample) could not be accepted as asbestos because one of the three analytical criteria failed. They were counted as 'other' fibers and may include asbestos.
  • Analytical sensitivity differs between laboratories, so calculated concentrations per gram dry weight will also vary.

Topics

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

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Analytical Transmission Electron Microscopy (ATEM), Mesothelioma, Lung Cancer, Pleural Plaques, Aspect Ratio (Length-to-diameter ratio), Chrysotile, Amphibole Group.

Related studies

• Pulmonary mineral dust. A study of ninety patients by electron microscopy, electron microanalysis, and electron microdiffraction — J.P. Berry, P. Henoc, et al. (1976)
• Determination of mineral fibre in human lung tissue by light microscopy and transmission electron microscopy — A.J. Rogers (1984)
• The detection and localization of mineral fibers in tissue — C. Berkley, J. Churg, et al. (1965)
• Scanning electron microscopy and x-ray microanalysis of mineral deposits in lungs of a patient with pleural mesothelioma — E.M. Ophus, G. Mowé, et al. (1980)
• Does qualitative examination of Elongated Mineral Particles (EMP) recovered from human and animal lungs provide reliable information on their carcinogenic and other effects? — B.W. Case (2018)
• Nonasbestos pulmonary mineral fibers in the general population — A. Churg (1983)

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