A technique to prepare asbestos air samples for light and electron microscopy

Our plain-English summary of A technique to prepare asbestos air samples for light and electron microscopy, by T.W. Pang, A.E. Robinson (British Journal of Industrial Medicine, 1981).

The study

• Authors: T.W. Pang, A.E. Robinson
• Journal: British Journal of Industrial Medicine
• Published: 1981;38(4):389-93
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The direct transfer technique used in preparing waterborne asbestos for analysis by transmission electron microscopy is also suitable for preparing airborne asbestos collected on polycarbonate filters for light microscopy, scanning, and transmission electron microscopy. The same area and even the same fibre may be examined by the three microscopic methods and individual fibres identified by optical and electron-optical techniques and by x-ray microanalysis.

In plain English

This article described a laboratory method for preparing asbestos air samples for microscope analysis. It was not a study of people or disease. In the "direct transfer" method, air was drawn through a polycarbonate filter. The collected particles were coated with thin carbon, and the filter was dissolved in chloroform on an electron microscope grid. The authors showed the same grid openings viewed by light, scanning electron and transmission electron microscopy. Transmission electron microscopy gave the best resolution and showed fibres too small for the light microscope. When chrysotile and crocidolite were already known to be in a sample, they could be told apart under phase contrast in a liquid with a refractive index of 1.62: chrysotile looked whitish, crocidolite dark grey to greenish. No fibre counts were reported. The authors noted the method may undercount fibres shorter than 1 to 2 micrometres and thinner than 0.2 micrometres when sampling uses a polycarbonate filter with 0.2 micrometre pores. They concluded the method allows the accuracy of light microscopy to be checked, which might justify using it as a workplace screening procedure.

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 paper describing a sample preparation technique (direct transfer) for asbestos air samples, illustrated with micrographs. No human subjects and no statistical results.
• Who was studied: Airborne asbestos samples collected on polycarbonate filters, analysed by the Ontario Ministry of Labour Occupational Health Branch, Toronto, Canada. The number of samples and the sampling locations are not reported. The procedure calls for ten or more grid openings from each of five or more grids per filter.
• Exposure: Airborne asbestos fibres. The fibre types examined in this article's own work were chrysotile and crocidolite.
• Main results:
  • The same grid openings were examined and photographed by light microscopy, scanning electron microscopy and transmission electron microscopy.
  • Transmission electron microscopy gave the best resolution of the three methods and showed small asbestos fibres below the resolution of the light microscope.
  • Under light microscopy, the resolution and image quality on the carbon film were comparable with those from the chemically cleared cellulose membrane filter.
  • When chrysotile and crocidolite fibres were known to be in a sample, they could be differentiated using a liquid with a refractive index of 1.62. Under phase contrast illumination, chrysotile fibres appeared whitish (no colour) and crocidolite fibres dark grey to greenish. The authors stated this allowed the two fibre types to be distinguished and their concentrations determined separately.
• The authors' conclusion: The authors concluded that the direct transfer method prepares airborne asbestos samples suitable for both light and electron microscopy. They said that examining the same grid openings or fibres by both methods makes it possible to check the accuracy and precision of light microscopy. They also said correlations between the methods may be established, so that using light microscopy as a screening procedure for airborne asbestos in working environments may be justified.
• Limitations the authors state:
  • Citing earlier filter-collection measurements by other researchers, the authors stated that the technique may underestimate asbestos fibres below 1 to 2 micrometres in length and 0.2 micrometres in diameter when a polycarbonate filter with 0.2 micrometre pores is used for sampling.

Topics

Medical terms in this study, explained in our Lexicon: Transmission Electron Microscopy (TEM).

Related studies

• A total sample preparation method for the measurement of airborne asbestos and other fibers by optical and electron microscopy — N. Kohyama, S. Kurimori (1996)
• Techniques for microscopic detection of asbestos bodies in lung tissue — P. Bradbury (2005)
• Determination of mineral fibre in human lung tissue by light microscopy and transmission electron microscopy — A.J. Rogers (1984)
• 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)
• The sensitivity of lavage analysis by light and analytical electron microscopy in correlating the types of asbestos from a known exposure setting — R.F. Dodson, M. O'Sullivan, et al. (2003)
• Environmental scanning electron microscopy technique to identify asbestos phases inside ferruginous bodies — A. Croce, M. Musa, et al. (2013)

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