Techniques for the detection, identification and analysis of fibers

Our plain-English summary of Techniques for the detection, identification and analysis of fibers, by R.G. Keenan, J.R. Lynch (American Industrial Hygiene Association Journal, 1970).

The study

• Authors: R.G. Keenan, J.R. Lynch
• Journal: American Industrial Hygiene Association Journal
• Published: 1970;31(5):587-97
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001395).

In plain English

This 1970 article by two authors at the U.S. Public Health Service's Bureau of Occupational Safety and Health was a methods review, not a study of people. It described ways to detect, identify and analyze mineral fibers, including chrysotile, amosite and crocidolite asbestos, in bulk materials, in airborne dust and in lung tissue taken at autopsy, and the limits of each method. The authors reported that hydrochloric or nitric acid dissolved the metals in chrysotile but did not completely attack amosite, crocidolite or glass, so hydrofluoric acid was needed. They wrote that the light microscope shows only fibers wider than about 0.1 micron. They also wrote that X-ray diffraction cannot tell fibrous chrysotile from non-fibrous serpentine and needs about 1 mg of mineral. Measuring magnesium by atomic absorption let their laboratory analyze thousands of personal air samples for chrysotile, many with less than 0.1 mg of dust. That method works only when chrysotile is the only source of magnesium. The authors concluded that small samples and mixed materials often meant indirect sources of data had to be combined to characterize a fiber.

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: Methods review: a discussion of laboratory techniques for detecting, identifying and analyzing fibers, with some results from the authors' own laboratory
• Who was studied: No group of people was studied. The article discusses methods for three kinds of samples: bulk samples (raw materials, products and settled dust), airborne dust samples taken in the worker's breathing zone, and single fibers isolated from lung samples at autopsy.
• Exposure: Mineral fibers, mainly chrysotile, amosite and crocidolite asbestos. Fibrous glass and other man-made fibers (graphite, silicon carbide) are also mentioned.
• Main results:
  • Digestion in 5N hydrochloric or nitric acid for 20 to 30 minutes was adequate to dissolve the metals in chrysotile asbestos. It did not completely attack amosite, crocidolite or glass, so hydrofluoric acid was needed for those fibers. In Table I, for amosite, nickel was 'None' with hydrochloric acid and 50 micrograms per gram with hydrofluoric acid.
  • Table I, chrysotile, micrograms of element per gram of sample, hydrochloric acid versus hydrofluoric acid digestion: nickel 365 vs 380; chromium 197 vs 220; cobalt 37 vs 30; manganese 270 vs 270.
  • X-ray diffraction measured chrysotile, amosite and crocidolite in bulk or settled dust samples. Recoveries over the 1 mg to 10 mg range were 85% to 103%. Recovery varied with respirable dust samples of very small particle size, and the method was less reliable for them.
  • Atomic absorption measurement of magnesium in personal breathing-zone samples of workers exposed to chrysotile let the authors' laboratory run thousands of samples, including many with less than 0.1 mg of total dust. Compared with X-ray diffraction on a limited number of samples, results varied by no more than about 10% to 15%. The error on known samples was given as less than about 5%.
  • Table III compared neutron activation analysis with atomic absorption on duplicate portions of a chrysotile sample, in micrograms of element per gram of asbestos: nickel 1690 vs 1400; chromium 1090 vs 1060; cobalt 78 vs 80.
  • The light microscope can see only fibers with diameters greater than about 0.1 micron.
  • Citing another researcher (a personal communication), the authors reported that the electron microprobe found an amosite asbestos fiber at the core of an asbestos body from the lung of an asbestos worker. A look-alike 'pseudo-asbestos body' from the lung of a foundry worker had no asbestos fiber at its core.
• The authors' conclusion: The authors concluded that virtually all available methods had been applied to evaluating fiber health hazards and disease mechanisms. Because samples are small and fibers are mixed with other materials, indirect sources of data have often had to be combined to characterize a fiber, and new methods are being developed.
• Limitations the authors state:
  • X-ray diffraction cannot distinguish a fibrous mineral from the non-fibrous mineral with the same crystal structure. Its sensitivity of about 1 mg is generally not low enough for airborne dust exposure samples.
  • The atomic absorption magnesium method applies only when chrysotile is the only source of magnesium in the exposure. Like X-ray diffraction, it measures chrysotile and serpentine together.
  • Lung samples examined by microscope should not be assumed to be representative, because dust deposits are not evenly distributed through the lung.
  • The electron microprobe is not yet sensitive enough to analyze trace elements spread evenly throughout a fiber.
  • Counting fibers with the electron microscope is difficult because the field of view is very small.

Related studies

• Techniques for microscopic detection of asbestos bodies in lung tissue — P. Bradbury (2005)
• Approaches and constraints to identification and quantitation of asbestos fibers — A.M. Langer (1974)
• A comparison of impinger and membrane filter techniques for evaluating air samples in asbestos plants — H.E. Ayer, J.R. Lynch, et al. (1965)
• Developments in dust sampling and counting techniques in the asbestos industry — S. Holmes (1965)
• The detection and localization of mineral fibers in tissue — C. Berkley, J. Churg, et al. (1965)
• Mineral particles, mineral fibers, and lung cancer — A. Churg, B. Wiggs (1985)

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