Elemental analysis of asbestos fibers by means of electron probe techniques

Our plain-English summary of Elemental analysis of asbestos fibers by means of electron probe techniques, by I.A. Rubin, C.J. Maggiore (Environmental Health Perspectives, 1974).

The study

• Authors: I.A. Rubin, C.J. Maggiore
• Journal: Environmental Health Perspectives
• Published: 1974;9:81-94
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The identification and characterization of microparticles has become an important field of study in recent years due to their presence in the environment and association with pathogenesis. Asbestos fibers have been intensively studied for these reasons. Since conventional microscopy has not provided unique identification of these materials, electron probe microanalysis, which yields chemical data, has been utilized in conjunction with other techniques to provide the necessary answers.The options now available to undertake electron probe analysis are discussed with relation to their utilization for microparticle analyses. Two types of electron sources are available, thermionic and field emission. The x-ray spectroscopy requires the use of either wavelength-dispersive focussing crystal spectrometers or an energy-dispersive Si(Li) x-ray detector. Data are presented to demonstrate the feasibility of asbestos identification by using modified raw data obtained with a scanning electron microscope and energy-dispersive x-ray spectrometer. Further, the extension of the technique to other microparticle identification problems is discussed.

In plain English

This technical article described how electron probe microanalysis, which measures the chemical elements in tiny particles, could be used to identify asbestos fibers. The authors reviewed the instrument options and presented data from a scanning electron microscope with an energy-dispersive x-ray detector. They used computer-filtered spectra from fibers of amosite, crocidolite, chrysotile, anthophyllite and tremolite. A sodium peak was statistically significant in the crocidolite spectrum and absent in the amosite spectrum. On triangular three-element plots, analyses of four asbestos types clustered. However, chrysotile, anthophyllite and fibrous talc could not be reliably separated by chemistry alone. With their system, and allowing about 100 seconds to collect each x-ray spectrum, the authors estimated a lower detection limit for silicate particles of about 0.05 micrometres in diameter. They noted that the method gives no crystal-structure information, cannot routinely detect elements lighter than sodium, and can pick up x-rays from nearby particles. The authors concluded that the technique had excellent utility for identifying and telling apart asbestos fibers in air, water and tissue samples. They added that conventional electron microscopy and electron diffraction might be needed for final determinations.

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: Technical methods article: a discussion of electron probe instrument options plus demonstration data on identifying asbestos types by their x-ray spectra; not a health study
• Who was studied: Individual mineral fibers (asbestos types and some other fibrous silicates) analyzed by scanning electron microscope with x-ray detector; the number of fibers analyzed is not stated
• Exposure: Fiber types analyzed: amosite, crocidolite, chrysotile, anthophyllite and tremolite asbestos, compared with fibrous talc
• Main results:
  • After digital filtering, the crocidolite spectrum showed a statistically significant sodium peak, while the amosite spectrum showed none
  • On a three-component diagram, analyses of four kinds of asbestos minerals showed clustering, each over a range of compositions
  • Chrysotile, anthophyllite and fibrous talc have similar elemental compositions, so chemistry alone did not allow certain differentiation between them
  • With the authors' system, collecting a spectrum typically took about 20 seconds for a particle larger than 0.5 micrometres in diameter
  • With the authors' system, and with the time to acquire each x-ray spectrum limited to about 100 seconds, their work indicated a lower limit of detectability for silicate particles of about 0.05 micrometres in diameter
• The authors' conclusion: The authors concluded that the electron microanalytical technique has excellent utility for identifying and differentiating asbestos fibers in air, water and tissue specimens. They added that conventional electron microscopy and selected area electron diffraction may be needed for final determinations.
• Limitations the authors state:
  • No crystal-structure information is obtained, so particles that differ only in crystal form cannot be accurately classified by microprobe analysis alone
  • The Si(Li) x-ray detector cannot routinely detect elements lighter than sodium
  • X-rays generated in nearby particles can contaminate the spectrum of the particle being analyzed
  • The program does not correct for absorption or fluorescence, so it does not give precise quantitative composition
  • Three-component diagrams cannot give a quantitative probability that a classification is correct

Topics

Medical terms in this study, explained in our Lexicon: Elemental Analysis.

Related studies

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• Chemical characterization of uncoated asbestos fibers from the lungs of asbestos workers by electron microprobe analysis — A.M. Langer, I.B. Rubin, et al. (1972)
• Fiber analysis vignettes: Electron microscopy to the rescue! — V.L. Roggli (2016)
• Chemical characterization of asbestos body cores by electron microprobe analysis — A.M. Langer, I.B. Rubin, et al. (1972)
• Pulmonary asbestos body counts and electron probe analysis of asbestos body cores in patients with mesothelioma: a study of 25 cases — V.L. Roggli, M.H. McGavran, et al. (1982)
• Oxygen incineration and electron microscope x-ray microanalysis of mineral particles in biological tissues — W.J. Henderson, C. Melville-Jones, et al. (1978)

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