Chemical Characteristics of Asbestos and Associated Trace Elements

Our plain-English summary of Chemical Characteristics of Asbestos and Associated Trace Elements, by A. Morgan, L.J. Cralley (1973).

The study

• Authors: A. Morgan, L.J. Cralley
• Published: BIOLOGICAL EFFECTS OF ASBESTOS (J.C. WAGNER, EDITOR), LYON: IARC SCIENTIFIC PUBLICATIONS, VOLUME 8, PP. 113-118 (1973)
• 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This paper was mainly a review, though it also reported some unpublished acid-leaching results from Morgan and colleagues. The authors summarised information on the chemistry of asbestos minerals and their associated trace metals, with particular reference to the UICC standard reference samples. They noted that trace metals can occur as substitutes within the crystal structure, as fragments of host rock and accessory minerals, or as alloy particles worn from processing equipment. Compiled measurements showed that trace metal levels in chrysotile samples fell within well-defined ranges, so a sample's source did not appear identifiable from them. Chromium, nickel and cobalt were generally one or two orders of magnitude lower in amosite and crocidolite than in chrysotile, while anthophyllite levels were similar to chrysotile. In cited rat experiments, about 30% of chrysotile's magnesium had dissolved after 2 months. Amphiboles resisted acid better; in rats injected with amosite and crocidolite, structural iron dissolved much more slowly than chrysotile's magnesium. The authors concluded that correlating carcinogenicity with trace metal concentration alone was pointless, and called for study of how magnesium loss affects chrysotile's cytotoxicity and carcinogenicity.

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 of published laboratory work on the chemical composition, trace metal content and solubility of asbestos minerals. It also includes some unpublished leaching data from Morgan and colleagues.
• Who was studied: No people were studied. The review covered asbestos samples, mainly the UICC standard reference samples, along with samples from Rhodesia, Canadian (Quebec) mines, Cyprus, South Africa and Finland, as compiled from earlier studies.
• Exposure: Chrysotile, amosite, crocidolite and anthophyllite asbestos, and the trace metals chromium, cobalt, iron, manganese, nickel and scandium associated with them
• Main results:
  • Trace metals in asbestos can be present as substitutes in the crystal structure, as fragments of host rock and accessory minerals, or as fine alloy particles produced when the asbestos wears down processing equipment (citing Cralley et al., 1967).
  • In earlier work by Morgan et al. (1971b) on samples of chrysotile, the fraction of iron present as magnetite varied from 19 to 58%.
  • Trace metal levels in all the chrysotile samples in Table 1 fell within well-defined ranges, so it did not appear that a sample's source could be identified from its trace elements.
  • The UICC standard reference samples did not appear to have been significantly contaminated during milling, with the possible exception of manganese in Chrysotile A.
  • Levels of chromium, nickel and cobalt in amosite and crocidolite were generally one or two orders of magnitude lower than in chrysotile.
  • Levels of chromium, nickel and cobalt in anthophyllite were very similar to those in chrysotile.
  • In the leaching work of Morgan et al. (1971b), virtually all the scandium in chrysotile appeared to be present as a substitute for magnesium in all the samples examined.
  • In rats injected intrapleurally with radioactive chrysotile (Morgan et al., 1971a), about 30% of the magnesium had dissolved after 2 months. After that, further leaching was very slow.
  • Amphiboles were much more resistant to attack by acids than chrysotile.
  • In unpublished leaching studies by Morgan et al. on the UICC reference samples in dilute hydrochloric acid, the structural iron of amosite was slightly more soluble than that of crocidolite.
  • In rats injected intrapleurally with radioactive amosite and crocidolite (Holmes & Morgan, 1968), the structural iron dissolved in the body, but much more slowly than the magnesium of chrysotile.
• The authors' conclusion: The authors concluded that trying to correlate carcinogenicity with trace metal concentration alone is pointless, because the metals occur in many chemical and physical forms with varying solubility. They said more information is needed on how the metals are distributed between fibre and contaminants, and that the effect of magnesium removal on chrysotile's cytotoxicity and carcinogenicity should be investigated.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos, UICC, Crystal Structure, Accessory Mineral, Chrysotile, Amosite, Crocidolite, Anthophyllite.

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