Analysis of amphibole asbestos in chrysotile and other minerals

Our plain-English summary of Analysis of amphibole asbestos in chrysotile and other minerals, by J. Addison, L.S. Davies (The Annals of Occupational Hygiene, 1990).

The study

• Authors: J. Addison, L.S. Davies
• Journal: The Annals of Occupational Hygiene
• Published: 1990;34(2):159-75
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Chrysotile asbestos and many other mineral raw materials contain amphibole minerals which may be asbestiform. There is currently no analytical method which will detect the presence of amphibole at sufficiently low limits to preclude the possibility of inadvertent exposure of persons handling these materials to hazardous airborne fibre concentrations. A method of chemical digestion of chrysotiles has been tested with regard to the determination of their tremolite contaminant content and this has been applied to a range of chrysotile and other minerals. The method improves the sensitivity of the amphibole analysis at least 10-fold giving detection limits of 0.01-0.05% in chrysotile by X-ray diffractometry (XRD). The difficulties arising from compositional and morphological variations are discussed in the context of the potential hazards from airborne fibres and the relative values of analyses by XRD, infrared spectrophotometry (IR) and electron microscopy. It is concluded that XRD and IR are useful as screening methods for the detection of amphibole in chrysotile but other materials should be analysed by optical or electron microscopy.

In plain English

This was a laboratory methods study, not a study of people. The authors tested a way to find small amounts of tremolite, an amphibole mineral, mixed into chrysotile asbestos and other minerals. Samples were heated to 600°C, then boiled in acid and then in alkali to dissolve the chrysotile. The tremolite left in the residue was measured by X-ray diffraction (XRD), infrared spectrophotometry (IR) and microscopy. In five chrysotile samples spiked with known amounts of tremolite, recovery exceeded 85% in every test and averaged 95%. The authors reported at least a 10-fold gain in sensitivity. Of eight commercial chrysotiles, XRD found tremolite in three: 0.02%, 0.20% and 0.08% after a correction for measurement effects. Electron microscopy found appreciable fibrous tremolite only in one of these. Tremolites from different sources gave different instrument readings, which the authors said could cause large errors. In 14 further chrysotiles, 40% had tremolite detectable by XRD. The authors concluded that XRD or IR could screen chrysotile, but other materials needed optical or electron microscopy.

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 method development and validation: chemical digestion (heating, then acid and alkali) to remove chrysotile and other matrix minerals, followed by XRD, IR, optical microscopy and scanning electron microscopy (SEM) of the residues
• Who was studied: No human subjects. Mineral samples were tested: a nominally tremolite-free Johns Manville chrysotile (Grade 4T-30) spiked with tremolite, and eight commercial chrysotiles digested in duplicate. Five asbestiform tremolites (Rajasthan; California; Italy; Libby, Montana; Korea) were examined, three as possible calibration standards. Further chrysotile, vermiculite and other mineral samples were analysed routinely. The work was done at the Institute of Occupational Medicine, Edinburgh.
• Exposure: Tremolite (amphibole) present as a contaminant in chrysotile and in other minerals (vermiculite, talc, wollastonite, attapulgite, sepiolite, mullite, kyanite). This was measured in bulk samples, not as human exposure.
• Main results:
  • In five chrysotile samples spiked with tremolite, every sample recovered better than 85% of the added tremolite, with an average recovery of 95%.
  • Of the eight commercial chrysotiles, XRD detected tremolite in only three (samples 3, 5 and 8). Table 5 gives the tremolite percentages in these samples. By XRD with mass absorption correction they were 0.02%, 0.20% and 0.08% (0.01%, 0.09% and 0.04% without correction). By IR they were 0.03%, 0.69% and 0.48%.
  • In the commercial chrysotile analyses, correcting the XRD results for mass absorption roughly doubled the measured tremolite.
  • For samples 5 and 8, the IR results were considerably higher than the XRD results, using the same calibration mineral.
  • By scanning electron microscopy, only sample 5 contained appreciable fibrous tremolite (0.24% in Table 5), close to its XRD result. In samples 3 and 8, the SEM mass estimate was much lower than the XRD result.
  • Tremolites from different sources gave different calibrations. By XRD, the Californian tremolite gave a calibration about 40% higher than the Korean tremolite. Korean tremolite was used for all later analyses.
  • In routine use on 14 further chrysotile samples, 40% contained tremolite detectable by XRD. The average tremolite content was 0.15% (range 0.1 to 0.33%).
  • In eighteen vermiculites, XRD recorded amphibole contents of up to 3.7% in about half of them, but many of these amphiboles were not asbestiform.
  • The authors reported that, after digestion, the method improved detection sensitivity at least 10-fold.
• The authors' conclusion: The authors concluded that XRD or IR could be useful as a screening method for digestion residues and would be satisfactory for chrysotile. For other materials, they considered optical or electron microscopy essential.
• Limitations the authors state:
  • Tremolites from different sources responded differently to XRD and IR, so quantitative results may carry a large error.
  • XRD and IR measure fibrous and non-fibrous tremolite together; only electron microscopy could identify the fibrous amphibole content.
  • Quantitative XRD and IR analysis would be difficult if more than one amphibole were present, for example tremolite and actinolite in vermiculite.
  • Possible interference from other minerals in the IR spectra was not evaluated in detail.
  • Semi-quantitative estimation of fibrous tremolite by optical microscopy was not possible.
  • The XRD and IR detection limit may not be adequate for nuisance dust minerals such as vermiculite.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Amphibole Asbestos, Chrysotile, Amphibole Group, Asbestiform, Tremolite.

Related studies

• Mesotheliomas in rats following inoculation with acid-leached chrysotile asbestos and other mineral fibres — G. Monchaux, J. Bignon, et al. (1981)
• Amphibole fibers in a taconite mine and in the lungs of the miners — B. Gylseth, T. Norseth, et al. (1981)
• Does qualitative examination of Elongated Mineral Particles (EMP) recovered from human and animal lungs provide reliable information on their carcinogenic and other effects? — B.W. Case (2018)
• Tremolite, other amphiboles, and mesothelioma — J.C. McDonald (1988)
• Solubility of asbestos and man-made mineral fibers in vitro and in vivo: its significance in lung disease — A. Morgan, A. Holmes (1986)
• Biological in vitro and in vivo responses of chrysotile versus amphiboles — J. Bignon, M.C. Jaurand (1983)

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