Comparison of the results of asbestos fibre dust counts in lung tissue obtained by analytical electron microscopy and light microscopy

Our plain-English summary of Comparison of the results of asbestos fibre dust counts in lung tissue obtained by analytical electron microscopy and light microscopy, by F.D. Pooley, D.L. Ranson (Journal of Clinical Pathology, 1986).

The study

• Authors: F.D. Pooley, D.L. Ranson
• Journal: Journal of Clinical Pathology
• Published: 1986;39(3):313-7
• Cited by: 30 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 003638).

Abstract

The efficiency of the light microscope with that of the electron microscope in detecting asbestos fibres in human lung tissue was computed. Necropsy material from 55 patients who had died from asbestos related diseases was analysed independently by phase contrast microscopy and electron microscopy. As expected the number of fibres identified using electron microscopy was higher than that identified by light microscopy. By adjusting the electron allow for the limited resolving power of the light microscope, however, a significant correlation of the number of fibres identified using the two methods was obtained. The best correlation was found with specimens containing crocidolite (correlation coefficient 0.79) and amosite (correlation coefficient 0.74), while chrysotile gave a much lower correlation (correlation coefficient 0.15). The cumulated fibre diameter distribution obtained using the electron microscope suggests that the light microscope is able to visualise only 5% of crocidolite, 26.5% of amosite, and 0.14% of chrysotile present in lung tissue. Therefore, although it is possible, using the electron microscope, to predict the asbestos fibre count that would be obtained by light microscopy, the reserve prediction cannot be made: it is impossible to determine the proportion of the various asbestos mineral types using the light microscope.

In plain English

This study compared phase contrast light microscopy and analytical electron microscopy for counting asbestos fibres in autopsy lung tissue. Tissue from 55 patients, mostly people who died of asbestos related disease, was examined independently in two laboratories. Four specimens were recounted by light microscopy, giving 59 sets of results. Electron microscopy found far more fibres. The authors assumed that the light microscope used could not show fibres thinner than its working resolution. Using electron microscope fibre diameters, they estimated it could see only 5% of crocidolite, 26.5% of amosite and 0.14% of chrysotile fibres. After adjusting the electron microscope counts for this, the correlation between the logarithms of the two counts was 0.56 overall (p less than 0.001). It was 0.79 in crocidolite-predominant specimens, 0.74 in amosite-predominant specimens and 0.15 in chrysotile-predominant specimens. The light microscope counts also included ferruginous bodies. The authors said the reason for the poorer chrysotile agreement was unclear but might be this. They concluded that electron microscopy can predict the approximate light microscope count, but the reverse is impossible. They did not assess non-asbestos fibres in the light microscope counts.

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 comparison study. Necropsy lung tissue from the same patients was counted independently by phase contrast light microscopy in one laboratory and by analytical electron microscopy in another.
• Who was studied: Necropsy lung tissue from 55 patients. Most had died from asbestos related disease; the rest had died from cardiovascular disease or bronchial carcinoma. There were 59 sets of results because four specimens were re-examined by light microscopy. Light microscopy was done at City Hospital, Nottingham, and electron microscopy in the department of mineral exploitation, University College, Cardiff. Dates are not given.
• Exposure: Asbestos and other mineral fibres in lung tissue, expressed as fibres per gram of dried tissue. Specimens were grouped by the predominant asbestos mineral found by electron microscopy: crocidolite, amosite or chrysotile.
• Main results:
  • Total mineral fibre counts and asbestos fibre counts by electron microscopy were very much higher than light microscope counts.
  • The authors assumed a working resolution for the light microscope used in this study. Fibres with diameters below this would not be seen or counted. The scan prints the resolution as '03gm', which appears to be 0.3 micrometres; this reading is inferred from the garbled text, not printed clearly.
  • On that assumption, and based on fibre diameter distributions from electron microscopy, only 5% of crocidolite, 26.5% of amosite and 0.14% of chrysotile fibres were estimated to be visible with the light microscope.
  • For all specimens combined, the correlation between the logarithms of the light microscope counts and the adjusted electron microscope counts was 0.56 (p less than 0.001).
  • Correlation coefficients by predominant fibre type were 0.79 for crocidolite, 0.74 for amosite and 0.15 for chrysotile.
  • Specimens in which chrysotile was the predominant asbestos mineral deviated most from perfect agreement.
  • About 70% of the results lay within a factor of 4 difference between the two methods, and 30% within a factor of 2.
  • The light microscope counts included both naked fibres and ferruginous bodies.
  • In a separate light microscope recount of six specimens, ferruginous bodies were relatively numerous when the fibre count was low, and in one case they outnumbered the fibres.
• The authors' conclusion: The authors concluded that electron microscopy can predict the approximate fibre concentration that light microscopy would give, but that the reverse prediction is impossible, because light microscopy cannot determine the proportions of the different asbestos mineral types.
• Limitations the authors state:
  • The authors made no attempt to assess how much non-asbestos mineral fibres contributed to the light microscope counts.
  • The two methods used tissue from different areas of the lung, although the authors note that fibre counts within a lung can vary by as much as 50%.
  • The authors said the reason for the larger discrepancy in chrysotile-predominant specimens was not clear. They suggested that including ferruginous bodies in the light microscope count might explain it.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite, Chrysotile, Crocidolite.

Medical terms in this study, explained in our Lexicon: Autopsy, phase contrast microscopy (PCM), Crocidolite, Amosite, Chrysotile.

Related studies

• Determination of mineral fibre in human lung tissue by light microscopy and transmission electron microscopy — A.J. Rogers (1984)
• A technical comparison of evaluating asbestos concentration by phase-contrast microscopy (PCM), scanning electron microscopy (SEM), and analytical transmission electron microscopy (ATEM) as illustrated from data generated from a case report — R.F. Dodson, S.P. Hammar, et al. (2008)
• Comments on Dodson et al., A technical comparison of evaluating asbestos concentration by phase contrast microscopy (PCM), scanning electron microscopy (SEM), and analytical transmission electron microscopy (ATEM) as illustrated from data generated from a case report — V.L. Roggli, T.A. Sporn, et al. (2008)
• A comparison of light microscopy and transmission electron microscopy results in the evaluation of the occupational exposure to airborne chrysotile fibres — A. Marconi, E. Menichini, et al. (1984)
• Comparison of light and electron microscopy for defining occupational asbestos exposure in transbronchial lung biopsies — R.F. Dodson, G.A. Hurst, et al. (1988)
• Assessment of occupational exposure to asbestos fibers: Contribution of analytical transmission electron microscopy analysis and comparison with phase-contrast microscopy — C. Eypert-Blaison, A. Romero-Hariot, et al. (2018)

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