The Biological Effect of Dusts of Asbestos

Our plain-English summary of The Biological Effect of Dusts of Asbestos, by K. Robock (1976).

The study

• Author: K. Robock
• Published: 1976
• Type of article: Journal article
• 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 short paper combined a discussion of earlier research by others with the author's own laboratory cell tests. Scavenger cells from the lung (alveolar macrophages) were exposed to the five UICC standard asbestos samples, to dusts collected at four work sites in an asbestos cement factory, and to raw chrysotile and cement dust. One test of the UICC samples used scavenger cells from the abdominal cavity (peritoneal macrophages) instead. The two chrysotile samples damaged the cells much more than the three amphibole types, which did not differ from each other. In solution the chrysotiles released magnesium and raised the pH. Factory dusts A and B appeared more damaging than a standard quartz dust, and the factory dusts raised the pH of the solution. With extra buffering, the effect of dusts A and C became much weaker. Cement dust alone appeared rather damaging to cells. The author concluded that the harmfulness of asbestos dusts seems to depend on physical properties of the fibres rather than on their chemical composition. The author cautioned that the cell test must be interpreted critically and said animal experiments were still awaited.

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 cell (in vitro) experiments on macrophages, presented together with a discussion of other researchers' studies
• Who was studied: Alveolar (lung) macrophages were used in the oxygen-consumption tests with the UICC samples, the factory dusts, raw chrysotile and cement dust. Peritoneal (abdominal-cavity) macrophages were used in one test with the UICC samples. Rats were mentioned for related fibrogenicity tests done at the author's institute. Numbers of cells and animals were not given.
• Exposure: The five UICC standard asbestos dusts (chrysotile A and B and three amphibole types), with quartz DQ 12 as a comparison dust. Also dusts sampled at four working sites (A to D) in an asbestos cement factory, which contained chrysotile only (dust A 7 per cent, B 5 per cent, C 2 per cent, D 5 per cent). Also raw asbestos (chrysotile, E) and cement (F) from the factory stores.
• Main results:
  • The two UICC chrysotiles (A and B) showed a much stronger damaging effect on macrophages than the three amphibole fibre types, with B a little stronger than A.
  • The three amphibole fibre types did not differ from one another in their damaging effect on cells.
  • The author reported that the same relationship was found for fibrogenicity in intratracheal and intraperitoneal tests with rats at the author's institute. No figures were given.
  • After about one hour in a nutritive solution, 0.24 per cent magnesium separated from chrysotile A and 0.38 per cent from chrysotile B.
  • The magnesium release shifted the pH to 7.7 (chrysotile A) and 8.8 (chrysotile B). The author interpreted this as an additional toxic effect that did not apply to the amphiboles.
  • No chemiluminescence effect was observed when chrysotile A interacted with macrophages.
  • Without extra buffering, factory dust samples A and B appeared more damaging to alveolar macrophages than the standard quartz DQ 12.
  • The factory dusts shifted the pH of the solution from 6.9 to 10.2 (dust A), 9.66 (dust B), 10.3 (dust C) and 8.7 (dust D).
  • With additional buffering to prevent the pH shift, the damaging effect of dust A, and above all of dust C, became much weaker.
  • Raw chrysotile from the factory affected macrophage oxygen consumption in the same relation to quartz as the UICC standard chrysotile.
  • Cement dust alone appeared rather damaging to cells.
• The authors' conclusion: The author concluded that, on the findings available so far, the harmfulness of fibrous asbestos dusts seems not to be determined by their chemical composition or molecular structure. Instead, the author attributed it to certain properties of the fibre.
• Limitations the authors state:
  • Free fibres and their length and diameter distribution in the factory dust samples had not yet been examined.
  • The author stated that the cell test has to be handled critically to avoid false interpretations.
  • The author questioned whether the cell experiment can give a definitive answer on the harmfulness of asbestos cement dusts.
  • Results of corresponding animal experiments, and of further cell experiments, were still awaited.
  • No explanation could yet be given for the pH shift caused by the factory dusts.
  • The author stated that no definite statement was yet possible about co-factors in carcinogenicity.

Topics

Medical terms in this study, explained in our Lexicon: Alveolar Macrophage, UICC, Asbestos-Cement, Chrysotile, Macrophage, Amphibole Group.

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