Developments in dust sampling and counting techniques in the asbestos industry

Our plain-English summary of Developments in dust sampling and counting techniques in the asbestos industry, by S. Holmes (Annals of the New York Academy of Sciences, 1965).

The study

• Author: S. Holmes
• Journal: Annals of the New York Academy of Sciences
• Published: 1965;132(1):288-97
• Cited by: 8 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy.

In plain English

This article was written by an author from Turner Brothers Asbestos Co. Ltd. in Rochdale, England, and the Asbestosis Research Council. It described how methods for sampling and counting airborne asbestos dust had developed in the author's company and in the Council. It was a methods paper, not a study of workers' health. The author explained that the older Thermal Precipitator rarely collected fibers longer than 10 microns. The Long Running Thermal Precipitator (the "Ottway" instrument) collected fibers up to 300 microns long but needed 30 minutes or more per sample. Work on membrane filters followed. Clearing filters with "Microil" gave low counts, because the cleared membrane's refractive index was close to that of chrysotile. Opaque membranes generally gave slightly higher counts than Ottway samples. Phase contrast increased counts compared with bright field. Opaque and Triacetin-cleared membrane counts had a correlation coefficient of 0.95. The Council then adopted a standard method that counted fibers 5 to 100 microns long, at least three times as long as wide. The author expected the membrane technique, especially personal samplers, to hold its own.

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: Descriptive methods paper reporting the development and comparison of dust sampling and counting techniques; not a health study
• Who was studied: No human subjects; airborne dust samples from the asbestos industry, mainly the asbestos textile operations of the author's company (Turner Brothers Asbestos Co. Ltd., Rochdale, England) and members of the Asbestosis Research Council
• Exposure: Airborne asbestos dust; laboratory illustrations used milled chrysotile asbestos; counted fibers were 5 to 100 microns long with length at least three times diameter
• Main results:
  • The original Thermal Precipitator rarely collected fibers above 10 microns in length
  • Long Running Thermal Precipitator (Ottway) deposits showed fibers up to 300 microns long
  • Membrane filters cleared with "Microil" gave low counts compared with Ottway samples taken at the same time
  • Opaque membrane filter samples generally gave slightly higher counts than Ottway samples
  • Phase contrast illumination increased the count on cleared membranes compared with bright field
  • Counts from Triacetin-cleared membranes agreed with opaque membrane counts, with a correlation coefficient of 0.95
  • Based on this work, the Asbestosis Research Council members adopted a standard membrane filter sampling and counting method
• The authors' conclusion: The author expected the membrane filter technique, particularly as a personal sampler, to hold its own, and considered personal samplers combined with a dust monitoring system likely to be the ideal arrangement for assessing the dust hazard in the asbestos industry
• Limitations the authors state:
  • The counting range was chosen on the assumption that the particle size spectrum was reasonably constant across textile processes, which later work suggested might not be strictly true
  • The definition of a fiber (length at least three times diameter) was arbitrary
  • Opaque filters tended to distort when mounted, making them difficult to count
  • The Ottway instrument was efficient only at a slow aspiration rate and needed 30 minutes or more per sample

Related studies

• Dust measurement and monitoring in the asbestos industry — C.G. Addingley (1965)
• A comparison of impinger and membrane filter techniques for evaluating air samples in asbestos plants — H.E. Ayer, J.R. Lynch, et al. (1965)
• Present threshold limit value in the U.S.A. for asbestos dust: a critique — E.L. Schall (1965)
• Economics of dust control — D.W. Hills (1965)
• Inter-laboratory comparisons of the counting of asbestos fibres sampled on membrane filters — S.T. Beckett, M.D. Attfield (1974)
• Reproducibility of dust disturbance techniques during clearance sampling after asbestos removal — J. Prentice, B. Gonsalves (1985)

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