The Organic Content of Canadian Chryotile

Our plain-English summary of The Organic Content of Canadian Chryotile, by G.W. Gibbs, H.Y. Hui (1971).

The study

• Authors: G.W. Gibbs, H.Y. Hui
• Published: American Industrial Hygiene Association Journal, August 1971
• 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 laboratory study by Gibbs and Hui measured the organic (carbon-based) material carried on commercially milled chrysotile asbestos from the Eastern Townships of Quebec, Canada. No people were studied. The authors collected samples at mills and extracted 105 samples of milled fiber with benzene. Organic content reached as high as 20.0 mg per 100 grams of fiber, depending on mine and fiber grade. In all but one case, milled fiber yielded more organic material than uncontaminated field specimens, which the authors took to indicate contamination from mining and milling. The extracts were mainly straight-chain hydrocarbons called n-alkanes. Fiber taken before and after the dryers showed an increase after drying in only one of four cases. Polycyclic aromatic hydrocarbons were exceedingly low: fluoranthene and pyrene were about 1/10,000 of the levels in smoke from rural England and Wales. The authors concluded that these compounds were in themselves unlikely to be important in chrysotile's biological action, and that total organic content may matter more. They noted they had too few dryer samples to show clearly how much contamination drying caused.

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 chemical analysis of asbestos fiber samples: solvent extraction, elemental analysis, infrared and ultraviolet spectra, gas chromatography, and polycyclic aromatic hydrocarbon analysis
• Who was studied: Commercially milled chrysotile fiber from mines and mills in the Eastern Townships of Quebec, Canada: 105 samples of milled fiber (20 to 100 gm each), plus fiber picked from ore entering and leaving dryers. Results were compared with field specimens.
• Exposure: Organic compounds present on Canadian chrysotile, whether occurring naturally or added as contamination during mining and milling (for example blasting with a fuel oil and ammonium nitrate mixture, and oil-fired or coal-fired dryers)
• Main results:
  • Organic content of commercially milled chrysotile ranged up to 20.0 mg per 100 gm, depending on source and fiber grade (the lower limit is unreadable in the scan).
  • Yields of organic matter from milled fiber exceeded those from uncontaminated field specimens in all but one case.
  • Longer fiber tended to have a higher organic content than shorter grades, except at two mills, which showed the reverse trend.
  • Fiber picked from ore before and after the dryers showed an increase in yield after drying in only one of four cases, and a slight loss in the other three.
  • The organic content of the dryer samples approximated that of the final milled fiber in all cases.
  • No difference in total organic yield was noted between coal-fired and oil-fired drying.
  • Dust from an experimental filter bag system on a dryer yielded at least twice the maximum amount of organic matter obtained from milled fiber from the same mill.
  • Infrared and gas chromatographic examination identified n-alkanes as the major constituents of the extracts.
  • In ultraviolet measurements, the difference between extracts from different mines was larger than could be expected from chance alone.
  • Concentrations of certain polycyclic aromatic hydrocarbons (fluoranthene, pyrene) in commercial chrysotile were approximately 1/10,000 of the levels in smoke from rural areas of England and Wales and 1/1000 of the levels in a Montreal smoke sample taken in July 1970.
  • Amounts of common polycyclic hydrocarbons on fiber dried in a coal-fired dryer were slightly higher than on fiber dried using oil.
• The authors' conclusion: The authors concluded that the polycyclic aromatic hydrocarbons identified in fiber at the final stage of milling are in themselves unlikely to be important in the biological action of chrysotile fiber. In their view the total organic content, especially n-alkanes, may be more important.
• Limitations the authors state:
  • Hand-picking fiber from ore was tedious, and too few samples could be analyzed to show clearly how much contamination the drying process caused.
  • Not every fiber group could be sampled at every mill.
  • The maximum n-alkane chain length detected may be an underestimate because of the temperature limit of the chromatography column.
  • The filter bag dust data came only from an oil-fired dryer; there was no comparable information for a coal-fired dryer.

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Eastern Townships.

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