Asbestiform and acicular mineral fragments

Our plain-English summary of Asbestiform and acicular mineral fragments, by T. Zoltai (1979).

The study

• Author: T. Zoltai
• Published: Annals of the New York Academy of Sciences, pp. 621-?; (ISSN 0077-8923/79/0330-0621) (1979)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This 1979 article by a University of Minnesota mineralogist was a survey and commentary on minerals, not a study of people or disease. The author argued that the definition of asbestos used in regulation rested mainly on a commercial argument. That definition was limited to five minerals: chrysotile, actinolite-tremolite, anthophyllite, cummingtonite-grunerite and riebeckite. It also counted as asbestos, or asbestos-like, any fragment of these minerals at least three times longer than wide. As a result, it covered non-asbestiform cleavage fragments of the amphiboles but left out other asbestiform minerals. The author reviewed published electron-microscope work and added new observations. A search of the university's mineral collection found asbestiform pyrophyllite, muscovite, lepidolite and glauconite. Asbestiform enstatite fibers looked indistinguishable from top-quality amphibole asbestos. X-ray photographs showed a South African "amosite" fiber was made of many small fibrils. For non-serpentine layered silicates, the author noted no quantitative measurements of their asbestos properties existed. The author concluded that the carcinogenic factor of asbestos lies in the fibers' "asbestos properties", with the particles' mineral identity of secondary importance, and that the definition should be replaced.

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: Review and commentary on mineralogy and the definition of asbestos, with some original observations of mineral specimens (light, SEM and X-ray diffraction photographs); no human or animal health data
• Who was studied: Mineral specimens, not people: samples from the University of Minnesota mineral collection, a 50 um diameter "amosite" fiber from Penge, South Africa, and minerals described in earlier published studies
• Exposure: Not an exposure study. The subject was the regulatory definition of asbestos. That definition covered five minerals: chrysotile, actinolite-tremolite, anthophyllite, cummingtonite-grunerite and riebeckite. It also counted any fragment of these minerals with an axial ratio of at least 3:1 as asbestos or asbestos-like. The author compared this with asbestiform and acicular (needle-like) forms of these and other silicate minerals.
• Main results:
  • The author stated that the current regulatory definition of asbestos was arbitrary and based primarily on a commercial argument
  • Under that definition, fragments of the five minerals were treated as asbestos whether or not they had crystallized in the asbestiform habit or had the properties of asbestos
  • A search of the University of Minnesota mineral collection found asbestiform varieties of other layered silicates: pyrophyllite, and the micas muscovite, lepidolite and glauconite
  • An SEM mount of the asbestiform muscovite sample showed fibers composed of smaller fibrils, as in chrysotile
  • Precession and Weissenberg X-ray photographs of a 50 um diameter South African "amosite" fiber indicated it was composed of many small fibrils with preferred orientation (the author wrote "hundreds of thousands")
  • Enstatite fibers came from a specimen that looked like poor-quality amphibole asbestos. Once separated, they turned out to be indistinguishable from the best quality amphibole asbestos. Their identity was checked by X-ray diffraction.
• The authors' conclusion: The author concluded that the current definition of asbestos should be abandoned and replaced by a scientific one (for example, a mineral crystallized in the asbestiform habit). The author also concluded that the carcinogenic factor of asbestos lies in the fibers' "asbestos properties", with the mineralogical identity of the particles of secondary importance. The biological properties of each type of asbestos need to be determined independently. A joint research program by mineralogists, biologists, and medical and public health scientists should be started.
• Limitations the authors state:
  • The author stated that there were no quantitative measurements of the asbestos properties of the non-serpentine layered silicate fibers described
  • The author stated that no quantitative studies had yet compared the density of surface defects in asbestiform fibers with that in acicular crystals or cleavage fragments of amphibole
  • Other biological and epidemiological studies indicated that cleavage fragments differ from asbestos fibers and may not be carcinogenic. The author stated that these indications could not yet be considered proof.

Topics

Medical terms in this study, explained in our Lexicon: Asbestiform, Acicular, Chrysotile, Actinolite, Tremolite, Anthophyllite, Cummingtonite-Grunerite, Riebeckite.

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