Chemical Detoxification of Asbestos Fibers

Our plain-English summary of Chemical Detoxification of Asbestos Fibers, by E.S. Flowers (1980).

The study

• Author: E.S. Flowers
• Published: National Workshop on Substitutes For Asbestos, Arlingotn VA. November 1980.
• 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 single-author conference paper described a proprietary process to detoxify asbestos fibers. The process used iron salts to add iron compounds such as ferric oxides to the fibers, imitating the 'ferruginous bodies' tissues form around asbestos. Treated chrysotile, amosite, crocidolite and anthophyllite were prepared; the process was extended to cobalt, manganese, chromium, aluminum and copper. Treated chrysotile and amosite were tested on human lung macrophage cells in culture. With UICC chrysotile B at 100 micrograms/ml, treated fibers left more living cells than untreated fibers, but fewer than in unexposed controls. Results with treated amosite were similar but less marked. No cell counts were printed in the text. Treatment lowered magnesium oxide content, changed fiber color and lowered cement strength at a high treatment level. It did not change acid resistance, alkali resistance or thermal insulation. The author concluded that the fibers kept their desirable properties. The fibers could serve as substitutes in appropriate applications only if further laboratory and animal tests showed lower toxicity and the treated material performed acceptably in products. The author noted the cell test stopped at 72 hours and did not examine whether cells engulfed the fibers.

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 (in vitro) cell-culture test and physical property testing of chemically treated asbestos, presented as a conference paper with a transcribed question-and-answer discussion
• Who was studied: Human lung macrophage cells in tissue culture, exposed to treated and untreated chrysotile and amosite; the number of cultures is not stated (five fields were counted per culture)
• Exposure: Asbestos fibers treated with an iron salt by a proprietary process that adds iron-containing compounds such as ferric oxides to the fiber. Chrysotile, amosite, crocidolite and anthophyllite were treated, and the process was also extended to cobalt, manganese, chromium, aluminum and copper. Cell tests used UICC chrysotile B and amosite at 100 micrograms/ml for 48 hours.
• Main results:
  • In cultures exposed to UICC chrysotile B, the average number of viable cells was highest in unexposed controls, next highest with treated chrysotile, and lowest with untreated chrysotile. The author interpreted this as decreased cytotoxicity. No numerical counts are given in the text.
  • Tests with treated amosite gave similar but less marked results.
  • Physical testing found decreases in magnetic rating, magnesium oxide content, spinning-solution viscosity and cement drainage rate, plus a color change. Cement strength fell at a high level of treatment but did not change at intermediate or low levels.
  • In the discussion, the author reported a slight increase in average fiber diameter after treatment (less than about 5 percent) and no change in length.
• The authors' conclusion: The author concluded that initial biological data showed reduced cytotoxicity and that physical test data indicated the fibers kept their desirable attributes. In appropriate applications, treated fibers could serve as substitutes if additional in vitro and in vivo tests showed decreased toxicity and the treated material performed acceptably in products.
• Limitations the authors state:
  • The cell test was a short-term assay ending at 72 hours, so effects beyond that time are unknown.
  • The study did not evaluate whether the cells engulfed (phagocytosed) the fibers.
  • The wet treatment process could not be scaled up beyond laboratory quantities.
  • Acoustic properties were not tested.
  • The color change may be unacceptable in some products, and the effect of the lower viscosity on textiles needs a production-line test.
  • The author agreed that much more work is needed.

Topics

Medical terms in this study, explained in our Lexicon: Ferruginous body, Chrysotile, Amosite, Crocidolite, Anthophyllite, Macrophage, UICC, Thermal System Insulation (TSI).

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