Investigation and analysis of asbestos fibers and accompanying minerals in biological materials

Our plain-English summary of Investigation and analysis of asbestos fibers and accompanying minerals in biological materials, by L. Le Bouffant (Environmental Health Perspectives, 1974).

The study

• Author: L. Le Bouffant
• Journal: Environmental Health Perspectives
• Published: 1974;9:149-53
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

A method is described for isolating asbestos fibers contained in biological tissues. It consists in incinerating the biological material in activated oxygen at 150 degrees C, and attacking the ash by 1N HC1 for 18 hr. The residue is then filtered on a membrane covered with a carbon film. Electron microscope examination of the deposit makes it possible to determine fiber concentrations when the weight or volume of primary material is known, and to make size analyses. By x-ray diffraction, the mineralogical nature of the asbestos is determined by comparison with an aluminum reference diagram. For x-ray diffraction, a micromethod is used, with an ash sample of about 10 mug. These techniques are used for identifying and counting asbestos fibers in small fragments of lungs or other organs. It was found that asbestos fibers generally go along with other minerals which may be abundant. Most fibers found in lung are less than 5 mum long. Counts on lungs of asbestos workers give concentrations often greater than 10(7) particles per gram of dry tissue. The evolution of inhaled chrysotile seems to be different from that of amphiboles. In the case of pleural mesothelioma, a comparison of fibers within the tumor with fibers in the adjacent parenchyma shows only slight differences in the particle sizes, but marked differences in their nature, with a chrysotile enrichment in the pleural zone. Pleural plaques were analyzed in the same way. After decalcification, many small sized asbestos fibers were found. The same technique is now being used for determining ingested particles. A great number of observations concerning fiber counts, their nature and sizes, and the presence of various clays minerals will be necessary to establish the role of the different factors in the formation of lesions caused by the inhalation or the ingestion of asbestos fibers.

In plain English

This 1974 article described a laboratory method for finding, counting and identifying asbestos fibers in body tissue, and gave early results from it. Tissue was burned away at a low temperature (150°C) in activated oxygen. Tests showed no apparent change in the shape or crystal structure of chrysotile at this temperature, while heating to 450°C markedly changed it. The ash was then treated with mild hydrochloric acid for 18 hours to remove other minerals, and fibers were examined by electron microscopy and X-ray diffraction. In the lungs of asbestos-industry workers with bronchial carcinoma or pleural mesothelioma, fibers came with other minerals such as talc, kaolinite, chlorite or quartz. Most fibers were under 5 micrometres long, and counts were frequently 10 to 50 million particles per gram of dry tissue. Chrysotile was rare compared with amphiboles in lung tissue. In several pleural mesotheliomas, however, the tumor showed a chrysotile enrichment. In the pleural plaques examined, calcified zones had higher fiber concentrations per gram of dry tissue than fibrohyaline zones. The author presented these findings as illustrations of the method's possibilities.

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 methods paper describing a tissue preparation and analysis technique, with illustrative analyses of human tissue samples and a rat inhalation clearance experiment
• Who was studied: Lungs of workers with bronchial carcinoma or pleural mesothelioma who had many years of dust exposure in the asbestos industry; three pleural mesothelioma cases with adjacent lung; two cases of pleural plaques; rats in a clearance experiment. The total number of people examined, the location and the dates were not stated.
• Exposure: Occupational dust exposure in the asbestos industry, including mixed chrysotile and amphibole exposure. Laboratory tests used chrysotile and amosite samples. Rats inhaled chrysotile, quartz and titanium oxide dust at 300 mg/m3 for 6 hours.
• Main results:
  • Chrysotile heated at 150°C showed no apparent change, either morphological or crystallographical. At 450°C the appearance and crystal structure of the fibers were markedly modified, which led the author to adopt ashing at 150°C in active oxygen.
  • An 18-hour treatment with 1N hydrochloric acid was chosen to remove other minerals from the ash.
  • In the workers' lungs, asbestos fibers were generally accompanied by other minerals, which were often present in greater concentrations than the asbestos itself.
  • Most fibers found in the lungs were less than 5 micrometres long.
  • Electron microscope counts in asbestos workers, even within tumors, were frequently 10 to 50 million particles per gram of dry tissue.
  • Chrysotile was rare compared with amphiboles in the lung parenchyma, even in workers exposed much longer to chrysotile than to amphiboles.
  • In rats, the rate of alveolar clearance of chrysotile was significantly different from that of the other, insoluble or slightly soluble, minerals tested.
  • In pleural mesotheliomas, fiber sizes within the tumor were not very different from those in the lung parenchyma. In several cases of mixed chrysotile-amphibole dusts, the tumor showed a significant chrysotile enrichment.
  • In three pleural mesothelioma cases, fibers per gram of tissue were: case 1, 17.4 million in lung and 18.6 million in tumor; case 2, 1600 million in lung and 13 million in tumor; case 3, 34 million in lung and 1.2 million in tumor.
  • In pleural plaques from two cases, fibers per gram of dry tissue were 6 million and 3.6 million in fibrohyaline tissue, and 30 million and 40 million in calcified tissue (fiber length 0.1 to 2 micrometres). The corresponding lungs held 10 million and 1.6 million. The fiber concentration was greater in the calcified zone than in the fibrohyaline zone.
• The authors' conclusion: The author concluded that these few findings illustrate the method's possibilities for qualitative and quantitative determination of asbestos fibers in lung and other tissues, including ingested particles. The author suggested there seems to be a preferential drainage of chrysotile towards the pleura. The author also stated that many more counts and analyses are needed to establish the statistical significance of fiber number, mineral type, fiber size and accompanying minerals in lesion formation.
• Limitations the authors state:
  • The mesothelioma findings come from a limited series of examinations.
  • The reason chrysotile disappears from the lung was not yet clear to the author.

Topics

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

Medical terms in this study, explained in our Lexicon: X-Ray Diffraction (XRD), Chrysotile, Amphibole Group, Pleural Mesothelioma, Parenchyma, Pleural Plaques.

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