The identification of asbestos dust with an electron microscope microprobe analyser

Our plain-English summary of The identification of asbestos dust with an electron microscope microprobe analyser, by F.D. Pooley (The Annals of Occupational Hygiene, 1975).

The study

• Author: F.D. Pooley
• Journal: The Annals of Occupational Hygiene
• Published: 1975;18(3):181-6
• Cited by: 14 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

It is possible with the aid of a transmission electron microscope fitted with suitable X-ray analytical equipment, to identify submicroscopic particles of the various asbestos minerals. Identification of particles should depend upon the production of accurate chemical data and not upon spectrum morphology. Suitable pure mineral powders of known chemistry can be used as standards to calibrate equipment and the calibration used to obtain the chemistry of unknown particles for a positive identification. The transmission E.M. fitted with energy dispersive X-ray analytical equipment is more versatile than other combinations of electron optical machines and X-ray analytical equipment. This is due to the more versatile operating characteristics of the transmission E.M. and the ability to display the X-ray spectra obtained from a particle with an energy dispersive analysis system, thus showing the presence of all the major elements with higher atomic numbers than sodium 11.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

This laboratory methods study tested whether a transmission electron microscope fitted with an energy dispersive X-ray analyser could identify single fibres of different asbestos minerals by their chemistry. The author examined the U.I.C.C. reference samples of crocidolite, amosite, anthophyllite, chrysotile A and chrysotile B, plus a tremolite asbestos sample. The samples were dispersed in distilled water and mounted on gold grids. No people and no health outcomes were studied. Ten repeated analyses along one crocidolite fibre gave closely reproduced X-ray counts. Using conversion factors derived from powdered silicate minerals of known chemistry, the author calculated the chemistry of ten fibres per sample and compared it with bulk wet chemical analysis. The author reported that the agreement was good. Crocidolite, amosite and anthophyllite gave similar-looking spectra. The author therefore warned that identification should rest on calculated fibre chemistry, not on how a spectrum looks, because its appearance varies between machines and settings. The author concluded that the method can easily distinguish the asbestos mineral types, even in submicroscopic fibres. The author also concluded that the transmission microscope is more useful than the scanning microscope for this work.

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 study (analytical technique development); no human or animal subjects
• Who was studied: Asbestos mineral samples: the U.I.C.C. reference samples of crocidolite (South Africa), amosite (South Africa), anthophyllite (Finland), chrysotile A (Rhodesia) and chrysotile B (Canada), plus a tremolite asbestos sample supplied by the Cape Asbestos Company Limited; ten fibres analysed per sample
• Exposure: Not a health exposure study. Single fibres of crocidolite, amosite, anthophyllite, chrysotile and tremolite asbestos were analysed in a Philips 301 transmission electron microscope with an Edax energy dispersive analyser at 60 kV
• Main results:
  • Ten separate 60-second analyses along one crocidolite fibre gave these mean background-corrected X-ray counts and percentage standard deviations: silicon 1450 (2.2%), sodium 119 (10.3%), magnesium 126 (14.6%), iron 840 (4.8%)
  • The author interpreted the repeated analyses as showing that the X-ray spectrum from a single particle is very accurately reproduced
  • The X-ray spectra of crocidolite, amosite and anthophyllite fibres looked similar, so the author held that positive identification requires calculating fibre chemistry
  • Chemistry calculated from ten fibres per sample was compared with bulk wet chemical analysis, and the author reported good agreement
  • The author reported that the agreement between the electron microscope and bulk results was good and provided a positive method of fibre identification
  • Most of the fibres examined were submicroscopic
• The authors' conclusion: The author concluded that a transmission electron microscope with X-ray analytical equipment can give accurate chemical analysis of single, even submicroscopic, asbestos fibres and can easily distinguish the asbestos mineral types. Identification should not rest on visual examination of spectra, and equipment should be calibrated with minerals of known chemistry. The transmission instrument is more useful than the scanning instrument, mainly because of its electron diffraction capability.
• Limitations the authors state:
  • The calculated compositions do not account for water of crystallization, trace elements, or elements with atomic number lower than sodium
  • Spectrum appearance varies between machines and operating conditions
  • Other minerals with chemistry similar to the amphibole asbestos group could be confused with them on visual display alone

Topics

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

Related studies

• Quantitative assessment of inorganic fibrous particulates in dust samples with an analytical transmission electron microscope — F.D. Pooley, N.J. Clark (1979)
• 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)
• The effects of chrysotile asbestos dust on lung macrophages maintained in organ culture. An electron-microscope study — J.M. Davis (1967)
• An electron microscope study of the response of mesothelial cells to the intrapleural injection of asbestos dust — J.M. Davis (1974)
• The effect of different mineral dusts on the mechanism of phagocytosis: a scanning electron microscope study — K. Miller, R.I. Handfield, et al. (1978)
• Electron microscope characteristics of inhaled chrysotile asbestos fibre — F.D. Pooley (1972)

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