Clearing and mounting techniques for the evaluation of asbestos fibres by the membrane filter method

Our plain-English summary of Clearing and mounting techniques for the evaluation of asbestos fibres by the membrane filter method, by J.M. Le Guen, S. Galvin (The Annals of Occupational Hygiene, 1981).

The study

• Authors: J.M. Le Guen, S. Galvin
• Journal: The Annals of Occupational Hygiene
• Published: 1981;24(3):273-80
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This paper describes three clearing and mounting techniques used in the evaluation of fibres by the membrane filter method and puts forward new methods for clearing membrane filters made of mixed esters of cellulose. The paper also sets out criteria for assessing the relative merits of clearing and mounting techniques and shows that, judged by these criteria, one of the new methods offers considerable advantages over the other methods described.

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

In plain English

This laboratory study compared four ways of preparing membrane filters so that airborne asbestos fibres can be counted under a phase contrast microscope. Two methods were already used in the United Kingdom (triacetin and acetone/triacetin). Two were new (dimethylformamide/Euparal, called DMF/Euparal, and acetone/Euparal). Forty-eight gridded filters sampled chrysotile asbestos clouds in a test chamber and were divided into 12 sets of four. Three operators prepared filters by all four methods and graded the results. Triacetin gave a very granular background and needed considerable refocusing, though it gave the best contrast for chrysotile. DMF/Euparal showed negligible grid distortion and a very clear background. Its filters showed no detectable change over 24 months, while acetone/triacetin filters showed minor fibre movement within the first few weeks. The acetone methods were judged the most hazardous because acetone vapour is flammable. The authors concluded that DMF/Euparal best met their criteria for a versatile method, and that triacetin was adequate when a permanent slide is not needed. The study did not compare fibre counts between methods.

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 comparison of filter clearing and mounting methods
• Who was studied: 48 gridded membrane filters made of mixed esters of cellulose, divided into 12 sets of four and examined by three operators, over a period of 18 months (UK Health and Safety Executive laboratory)
• Exposure: Filters were used to sample homogeneous clouds of chrysotile asbestos generated in a test chamber, then cleared by four methods: triacetin, acetone/triacetin, DMF/Euparal and acetone/Euparal
• Main results:
  • Background clarity: triacetin-treated filters had a very granular background, acetone/triacetin gave varying clarity, and both acetone/Euparal and DMF/Euparal gave very clear backgrounds
  • Contrast: triacetin gave the best contrast for chrysotile fibres. All four techniques gave about the same contrast for amphiboles.
  • Refocusing: only the triacetin method demanded considerable refocusing during a fibre count
  • Filter distortion: DMF/Euparal produced negligible grid distortion
  • Keeping properties: DMF/Euparal filters showed no detectable change over 24 months, while acetone/triacetin filters showed minor fibre movement within the first few weeks
  • Hazard: the acetone vapour methods were considered the most hazardous. For DMF/Euparal, measured breathing-zone DMF concentrations did not exceed a small fraction of the TLV (threshold limit value).
  • Waiting time before analysis: the best results were obtained with DMF/Euparal and acetone/Euparal
• The authors' conclusion: The authors concluded that, of the methods tested, the new DMF/Euparal method best met their criteria for a versatile method. They considered triacetin clearing adequate when a permanent slide is not required.
• Limitations the authors state:
  • The authors state that relative fibre counts associated with the different mounting methods were not reported here and would be published independently

Topics

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

Related studies

• In situ identification of asbestos fibres collected on membrane filters for counting — N.P. Vaughan, S.J. Rooker, et al. (1981)
• The influence of external aerodymanic factors on the measurement of the airborne concentration of asbestos fibres by the membrane filter method — A.M. Johnston, A.D. Jones, et al. (1982)
• Performance of membrane filters used for TEM analysis of asbestos — J.S. Webber, A.G. Czuhanich, et al. (2007)
• A routine for the control of the performance of microscopists evaluating airborne asbestos fibre samples on membrane filters by phase contrast microscopy — J.R. Hoyes, R. Clayton (1980)
• The counting of small numbers of asbestos fibres on membrane filters: a comparison of results from some commercial laboratories — M.J. Duggan, E.W. Culley (1978)
• Conversion of the asbestos fibre concentration recorded by means of the konimeter and the thermal precipitator to that expected by means of the membrane filter method — R.S. du Toit, T.C. Gilfillan (1979)

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