The evaluation of airborne asbestos fibres using a scanning electron microscope

Our plain-English summary of The evaluation of airborne asbestos fibres using a scanning electron microscope, by S.T. Beckett (The Annals of Occupational Hygiene, 1973).

The study

• Author: S.T. Beckett
• Journal: The Annals of Occupational Hygiene
• Published: 1973;16(4):405-8
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos fibres sampled on Nuclepore filters can be directly examined by scanning electron microscope in much greater detail than is possible using the conventional optical microscope/membrane filter technique. Results obtained by the two methods for fibres > 5 µm in length were in good agreement. The new technique could facilitate the development of automatic counting methods for asbestos fibres.

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

In plain English

This laboratory methods study, from the Asbestosis Research Foundation in Edinburgh, tested a way of counting and measuring airborne asbestos fibres with a scanning electron microscope. The author sampled clouds of UICC reference asbestos in animal exposure chambers on three kinds of filter: cellulose ester membrane, silver membrane and Nuclepore. The cellulose and silver filters had irregular surfaces that obscured the fibres. The smooth side of the Nuclepore filter gave a uniform background, while its dull side was more uneven. The author then took paired side-by-side samples, one on a membrane filter and one on a Nuclepore filter, in an asbestos textile factory and in the exposure chambers. The membrane filters were counted by the standard phase-contrast optical microscope method and the Nuclepore filters by scanning electron microscope. For fibres longer than 5 micrometres, the fibre length distributions for chrysotile and amosite agreed well, and the concentrations measured by the two methods were close. The author concluded that this good agreement suggests the two methods of evaluation are comparable.

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: a scanning electron microscope technique for evaluating asbestos fibres on Nuclepore filters, compared experimentally with the standard phase-contrast optical microscope and membrane filter method
• Who was studied: Airborne asbestos samples, not people. Clouds of UICC asbestos were sampled in animal exposure chambers at the Institute of Occupational Medicine, Edinburgh. Paired simultaneous samples on cellulose ester membrane and Nuclepore filters were also taken in an asbestos textile factory and in the chambers. At least 200 fibres were counted and sized per sample.
• Exposure: UICC reference asbestos samples dispersed into animal exposure chambers, with results reported for chrysotile and UICC amosite, plus airborne dust in an asbestos textile factory (the fibre type there is not stated). The comparison covered fibres longer than 5 micrometres, measured at 500 times magnification.
• Main results:
  • On the cellulose ester membrane and silver membrane filters, very irregular surfaces obscured the fibres, making them extremely difficult to count visually and of little use for automatic counting.
  • Nuclepore filters had a very smooth surface on which fibres were easily distinguished. The author judged them very suitable for visual or automatic evaluation.
  • The two surfaces of the Nuclepore filters differed. The dull surface was more uneven than the glossy side and less suitable for scanning electron microscopy.
  • Fibre length distributions (fibres longer than 5 micrometres) for chrysotile and amosite measured by the two methods were in good agreement.
  • Exposure chamber sample: the cellulose ester membrane filter, evaluated by two counters, gave 2.2 and 2.6 x 10^4 fibres per square centimetre, compared with 2.46 x 10^4 fibres per square centimetre on the Nuclepore filter.
  • Factory sample: the membrane filter gave 2.5 and 2.6 x 10^4 fibres per square centimetre, compared with 3.3 x 10^4 fibres per square centimetre on the Nuclepore filter.
• The authors' conclusion: The author concluded that the good agreement between the results suggests the two methods of evaluation are comparable, and that Nuclepore filters with the scanning electron microscope could help in developing automatic fibre counting.
• Limitations the authors state:
  • Nuclepore filters are not readily made transparent for direct evaluation by phase-contrast optical microscopy, so the same filter could not be counted both ways and separate paired samples had to be used.
  • Fields of view were chosen haphazardly with eyes averted from the screen. The author noted this procedure could be improved by using pre-determined random control settings.

Topics

Medical terms in this study, explained in our Lexicon: Membrane Filter Method.

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