Chemo-physical properties of asbestos bodies in human lung tissues studied at the nano-scale by non-invasive, label free x-ray imaging and spectroscopic techniques

Our plain-English summary of Chemo-physical properties of asbestos bodies in human lung tissues studied at the nano-scale by non-invasive, label free x-ray imaging and spectroscopic techniques, by F. Bardelli, F. Brun, S. De Panfilis, et al (Toxicology Letters, 2021).

The study

• Authors: F. Bardelli, F. Brun, S. De Panfilis, P. Cloetens, S. Capella, E. Belluso, D. Bellis, A. Di Napoli, A. Cedola
• Journal: Toxicology Letters
• Published: 2021;348:18-27
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

In the lungs, asbestos develops an Fe-rich coating (Asbestos Body, AB) that becomes the actual interface between the foreign fibers and the host organism. Conventional approaches to study ABs require an invasive sample preparation that can alter them. In this work, a novel combination of x-ray tomography and spectroscopy allowed studying unaltered lung tissue samples with chrysotile and crocidolite asbestos. The thickness and mass density maps of the ABs obtained by x-ray tomography were used to derive a truly quantitative elemental analysis from scanning x-ray fluorescence spectroscopy data. The average mass density of the ABs is compatible with that of highly loaded ferritin, or hemosiderin. The composition of all ABs analyzed was similar, with only minor differences in the relative elemental fractions. Silicon concentration decreased in the core-to-rim direction, indicating a possible partial dissolution of the inner fiber. The Fe content in the ABs was higher than that possibly contained in chrysotile and crocidolite. This finding opens two opposite scenarios, the first with Fe coming from the fiber bulk and concentrating on the surface as long as the fiber dissolves, the second where the Fe that takes part to the formation of the AB originates from the host organism Fe-pool.

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In plain English

This laboratory study examined asbestos bodies, the iron-rich coatings that form around asbestos fibers in the lungs. The tissue was non-cancerous lung taken after death from two former fibre cement plant workers. One was an 81-year-old man exposed for 27 years and the other an 80-year-old woman exposed for more than 10 years. Both had asbestosis and pleural plaques. The man also had pleural mesothelioma and the woman lung cancer. Fiber analysis found crocidolite largely prevalent, and no chrysotile fibers were identified. Without extracting the bodies from the tissue, the authors used synchrotron x-ray tomography and x-ray fluorescence to measure nine asbestos bodies. Their average density was 2.2 g/cm3, plus or minus 0.2. The authors judged this compatible with the iron-storage proteins ferritin or hemosiderin. All bodies had similar composition. Silicon decreased from core to rim, which may indicate partial dissolution of the inner fiber. One body may have formed around a chrysotile fiber. Iron made up 32 to 51 percent, more than the authors cite for chrysotile or crocidolite. The authors described two possible sources for this iron: the fiber itself or the body's own iron supply. Only nine bodies could be measured.

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 analysis of post-mortem human lung tissue from two cases, using combined synchrotron x-ray phase-contrast holo-tomography and scanning x-ray fluorescence spectroscopy on the same tissue fragments
• Who was studied: Non-neoplastic lung tissue from the lower lobes of two former workers, obtained post-mortem. Case A: 81-year-old male, fibre cement plant, exposed 27 years (1962-1981), with asbestosis grade 3, pleural plaques and pleural mesothelioma, about 363 thousand asbestos bodies per gram of dry lung tissue. Case B: 80-year-old female, fibre cement plant, exposed more than 10 years, with asbestosis grade 4, pleural plaques and lung cancer, about 1195 thousand asbestos bodies per gram of dry lung tissue. Nine asbestos bodies were measured in total.
• Exposure: Prolonged occupational exposure (more than 10 years) to a mixture of asbestos types including the amphiboles crocidolite and amosite and the serpentine chrysotile, in fibre cement plants
• Main results:
  • Electron microscopy of fibers extracted from the tissue found crocidolite was largely the prevalent fiber. The presence of amosite was uncertain, and no fibers matching chrysotile were found.
  • The mass density of the asbestos bodies ranged from 2.0 to 2.5 g/cm3, with an average of 2.2 plus or minus 0.2 g/cm3
  • The authors interpreted the average density as compatible with highly loaded ferritin or hemosiderin. In their view, the bodies are mainly made of one of these iron-storage proteins, or most probably a mixture of them.
  • The composition of all asbestos bodies analyzed was similar. The major elements were silicon, phosphorus, sulfur, potassium, calcium and iron.
  • Silicon was found across the whole asbestos body, with concentration decreasing from core to rim. The authors said this may indicate partial dissolution of the inner fiber.
  • Iron content in all asbestos bodies analyzed was 32 to 51 percent. This is higher than the iron content of chrysotile (0.1 to 0.4 percent) and crocidolite (about 20 percent), figures the authors take from other studies.
  • The authors considered it reasonable to assume that one asbestos body (sample A2) developed around a chrysotile fiber. This was based on a silicon-rich, iron-depleted core.
• The authors' conclusion: The authors concluded that the high iron content leaves two possibilities. Either the iron comes from the fiber itself and concentrates on its surface as the fiber dissolves, or it comes from the body's own iron supply.
• Limitations the authors state:
  • Only nine asbestos bodies could be measured, because of long acquisition times and limited beamtime
  • The setup could not detect or quantify elements lighter than silicon, including sodium and magnesium, which are main constituents of asbestos fibers
  • Manganese could not be quantified because its signal overlapped with iron

Topics

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

Medical terms in this study, explained in our Lexicon: Asbestos Bodies, Asbestos Body Formation, Chrysotile, Crocidolite, Elemental Analysis, Ferritin.

Related studies

• A procedure for the isolation of asbestos bodies from lung tissue by exploiting their magnetic properties: a new approach to asbestos body study — V. Borelli, C. Brochetta, et al. (2007)
• Techniques for microscopic detection of asbestos bodies in lung tissue — P. Bradbury (2005)
• Minimally invasive, ionizing-free, and ultrasound-guided technique to biopsy anterior mediastinal masses: first 60 cases — B. Lorenzati, R. Cristofori, et al. (2018)
• Synchrotron soft X-ray imaging and fluorescence microscopy reveal novel features of asbestos body morphology and composition in human lung tissues — L. Pascolo, A. Gianoncelli, et al. (2011)
• Interobserver variability in analysis of asbestos fibres and asbestos bodies in human lung tissue — F. Roberts, J.L. Mackinnon, et al. (2004)
• Genotoxicity of chemical and physical agents in cultured human tissues and cells — A. Weston, S.M. Plummer, et al. (1986)

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