Fiber toxicology

Our plain-English summary of Fiber toxicology, by J.P. Leineweber (Journal of Occupational Medicine., 1981).

The study

• Author: J.P. Leineweber
• Journal: Journal of Occupational Medicine.
• Published: 1981;23(6):431-4
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This article was a narrative review, not a new study. It was presented at a 1980 occupational health congress by an author from Johns-Manville Corp. The author argued that the disease-producing potential of asbestos and other natural and man-made fibers depends on three factors: fiber dimensions, dose, and durability in the body. Drawing on other researchers' animal experiments, the author cited Stanton's report that fibers longer than 8 micrometers and thinner than 1.5 micrometers had the greatest biological activity. The author listed fibers that had produced tumors after being implanted in the pleural or peritoneal cavities of animals, including chrysotile, amosite, crocidolite, tremolite and borosilicate glass. The author said this research on fiber dimensions provided no data relating to bronchogenic cancer and only scant data on fibrogenesis. The author added that very little was known about fiber durability. The author proposed that, once agreement was reached on the main factors, a particular mineral in a particular situation could be judged against them. Where not all requirements were met, the author said, one could presume an operation could be permitted without any significant hazard to workers.

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: Narrative review and discussion paper presented at a conference. It reports no original data.
• Who was studied: No study population. The author reviewed other researchers' animal implantation experiments (Stanton, Pott, Wagner, Davis), a guinea pig study by Wright and Kuschner, and fiber-deposition work by Timbrell and others.
• Exposure: Asbestos (including chrysotile, amosite, crocidolite, anthophyllite, tremolite) and other natural and man-made fibers: zeolites, clay minerals, man-made vitreous fibers such as glass fiber and mineral wool, and high-performance reinforcing fibers.
• Main results:
  • The author stated that the main determinants of fibers' biological activity and disease-producing potential are fiber dimensions, dose, and durability in the biological system.
  • Citing Stanton's animal work, the author reported that fibers longer than 8 micrometers and thinner than 1.5 micrometers had the greatest biological activity. The author added that Pott put the diameter for maximal activity at about 0.25 micrometers.
  • Table 1 listed fibers shown to produce malignant fibrous neoplasms after implantation in animals' pleural or peritoneal cavities. These included mineral wool, amosite, anthophyllite, aluminum oxide, potassium titanate, chrysotile, crocidolite, silicon carbide, tremolite, borosilicate glass, wollastonite and attapulgite.
  • The author stated that analysis of the available data showed no consistent cause of biological activity other than fiber dimensions. The author also stated that trace-metal or organic contamination hypotheses had not been substantiated by animal experiments.
  • Citing Timbrell, the author reported that the limiting diameter for fiber respirability was about 3 micrometers. The author added that fibers as long as 200 micrometers had a finite probability of reaching the alveoli.
  • The author noted a suggestion by others that fibers longer than 10 micrometers cannot be removed by alveolar macrophages.
  • The author noted that Wright and Kuschner suggested the reduced activity of long, very thin glass fibers could be due to lower durability. The author also described durability studies that had only been started at Johns-Manville and at Tulane University, with no results reported.
• The authors' conclusion: The author proposed a conditional framework. If agreement could be reached on the major factors responsible for biological activity, it should be simple to judge whether a particular mineral in a particular situation fulfills the requirements. If not all requirements are met, one could presume the operation could be permitted without significant hazard. The author also argued against broad, asbestos-based definitions of fibers.
• Limitations the authors state:
  • The author noted that the animal experiments used very artificial means of bringing fibers into contact with tissue.
  • In the discussion of the animal research on fiber dimensions, the author stated there were no data relating to bronchogenic cancer and only scant data on fibrogenesis.
  • The author stated that dose, in terms of host entry, biological availability and duration, could not yet be quantified.
  • The author stated that very little is known about the biological durability of fibers.

Related studies

• Efficacy of screens in removing long fibers from an aerosol stream--sample preparation technique for toxicology studies — B.K. Ku, G.J. Deye, et al. (2014)
• Evaluation of the dose-response and fate in the lung and pleura of chrysotile-containing brake dust compared to chrysotile or crocidolite asbestos in a 28-day quantitative inhalation toxicology study — D.M. Bernstein, B. Toth, et al. (2018)
• Synthetic vitreous fibers: a review of toxicology research and its impact on hazard classification — T.W. Hesterberg, G.A. Hart (2001)
• Contemporary issues in fiber toxicology — D.B. Warheit, K.E. Driscoll, et al. (1995)
• Natural mineral fibers: conducting inhalation toxicology studies - part A: Libby Amphibole aerosol generation and characterization method development — A. Wang, A. Gupta, et al. (2023)
• Natural mineral fibers: conducting inhalation toxicology studies-part B: development of a nose-only exposure system for repeat-exposure in vivo study of Libby amphibole aerosol — A. Wang, A. Gupta, et al. (2023)

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