On the utility of dark-field electron microscopy in the determination of the degree of deformation in chrysotile asbestos: an environmental research application

Our plain-English summary of On the utility of dark-field electron microscopy in the determination of the degree of deformation in chrysotile asbestos: an environmental research application, by K. Seshan (Environmental Research, 1978).

The study

• Author: K. Seshan
• Journal: Environmental Research
• Published: 1978;16(1-3):383-92
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy.

In plain English

This laboratory study, by a single author, tested whether a high-resolution "dark-field" electron microscope technique could show how damaged (deformed) chrysotile asbestos fibers are. The author noted that earlier studies disagreed on whether chrysotile survives in automobile brake drum dust. Four samples were examined:

• undeformed chrysotile ore from Calaveras County, California;
• UICC reference samples of Canadian chrysotile, milled during preparation;
• unused brake lining dust collected during burnishing before new brake shoes were installed;
• brake drum dust from a State vehicle, collected during brake service.

The natural ore fibers showed uniform contrast, as expected for undeformed crystals. In the UICC fibers, the crystal structure appeared broken into many tiny regions, which the author attributed to ball milling. Fibers in the unused brake lining dust were less deformed than the UICC samples. Used brake drum dust contained heavily deformed fibers, whose exact cause could not yet be determined. It also contained undeformed chrysotile, confirmed by diffraction measurements. The author concluded that the method can distinguish degrees of deformation and may help environmental researchers trace the origins of asbestos fibers. The author described the work as preliminary.

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 electron microscopy study (methods demonstration) comparing high-resolution dark-field images and electron diffraction patterns of four chrysotile-containing samples
• Who was studied: Four samples, not people: (A) undeformed chrysotile ore from serpentine outcrops in Calaveras County, California; (B) UICC reference standards of Canadian chrysotile; (C) unused brake lining dust collected during burnishing before installation of new brake shoes; (D) brake drum dust from the front and rear brake drums of a State vehicle, collected during brake shoe service
• Exposure: Chrysotile asbestos in different states of deformation: natural ore, UICC Canadian chrysotile milled during preparation, unused brake lining dust, and used automobile brake drum dust
• Main results:
  • Natural chrysotile (sample A) showed uniform contrast in dark-field images, consistent with undeformed crystals
  • In the UICC standard chrysotile (sample B), the internal canals seen in undeformed fibers were destroyed. The diffraction patterns changed to those of a polycrystal, which the author attributed to ball milling
  • Fibers in unused brake shoe burnishing dust (sample C) were less deformed than the UICC standard samples, because some intact internal canals could still be seen
  • Used brake drum dust (sample D) contained heavily deformed chrysotile with inhomogeneous, mottled contrast. The author listed possible causes, including transformation of local areas into a new crystalline phase such as forsterite, but did not determine which applied
  • Used brake drum dust (sample D) also contained undeformed and unaltered chrysotile. This was confirmed by indexed electron diffraction patterns calibrated against a gold standard
• The authors' conclusion: The author concluded that dark-field electron microscopy can distinguish the degree of deformation in chrysotile, and that UICC standard chrysotile was microdeformed by ball milling. The author suggested the method may be used to trace the origins of asbestos fibers
• Limitations the authors state:
  • The author described the study as preliminary
  • The crystallographic and microstructural nature of the deformation was not clear
  • The cause of the mottled appearance of heavily deformed fibers in used brake drum dust could not be determined without further work
  • Chrysotile is damaged by the electron beam, so care is needed when making the images

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile.

Related studies

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• Electron microscopy: a brief history and review of current clinical application — R.E. Gordon (2014)
• The crocidolite fibres interaction with human mesothelial cells as investigated by combining electron microscopy, atomic force and scanning near-field optical microscopy — L. Andolfi, E. Trevisan, et al. (2013)
• Electron microscope characteristics of inhaled chrysotile asbestos fibre — F.D. Pooley (1972)
• The utility of electron microscopy in cytopathology — D. Etit, M. Selig, et al. (2010)

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