The locus of pathogenicity of asbestos dust: a theory

Our plain-English summary of The locus of pathogenicity of asbestos dust: a theory, by P. Gross, R.A. Harley (Archives of Environmental Health, 1973).

The study

• Authors: P. Gross, R.A. Harley
• Journal: Archives of Environmental Health
• Published: 1973;27(4):240-2
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy.

In plain English

This 1973 article proposed a theory about why asbestos dust harms the lungs. The authors argued that the harm lies in the 'polyfilamentous' structure of asbestos fibers, meaning bundles of fine fibrils packed side by side, rather than single strands. In support they cited earlier studies, many their own, of single-strand fibers and finely ground asbestos. They also described their own preliminary work. In this work, fibrils of asbestos were cemented together with lead or iron silicate. The cemented asbestos was injected into the windpipes of a few rats, whose lungs were examined three months later. The lung lesions after lead-cemented asbestos showed little reticulin and no collagen fibers. Unaltered asbestos produced lesions containing collagen. In a test-tube study, lead silicate-cemented crocidolite broke open 30% of human red blood cells, compared with 100% for unaltered crocidolite. Iron silicate reduced the effect of chrysotile less than lead silicate did. The authors called these cemented-asbestos results only suggestive and said they needed confirmation.

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• Design: Theory article combining earlier published and unpublished findings with preliminary animal experiments (injection into the windpipe of rats) and an in vitro red blood cell test
• Who was studied: A few rats (number not stated), with lungs examined three months after injection; human red blood cells in the in vitro test
• Exposure: Chrysotile and crocidolite asbestos, either unaltered or with fibrils cemented together chemically by lead silicate or iron (ferric) silicate. Figure captions mention doses of 10 mg iron silicate-cemented chrysotile and 7 mg unaltered chrysotile in individual rats.
• Main results:
  • In rats given lead-cemented asbestos, the main lung lesion was minimal: prominent giant cells, few histiocytes, little reticulin and no collagen fibers
  • In rats given unaltered asbestos, lesions of the same age contained collagen as well as reticulin fibers and histiocytes
  • In vitro, lead silicate-cemented crocidolite caused 30% hemolysis of human red blood cells, compared with 100% for unaltered crocidolite under identical conditions
  • Iron silicate was less effective than lead silicate in reducing the pathogenic potential of chrysotile
  • Electron micrographs of heated asbestos (chrysotile at 900 C, crocidolite at 1,000 C, amosite at 950 C) showed the fibrillar structure obliterated or the fiber bundle constituents fused
• The authors' conclusion: The authors proposed that the harmfulness of asbestos dust resides in the polyfilamentous (bundled-fibril) structure of its fibers, and that converting the fibers toward a single-strand state reduces their harmfulness
• Limitations the authors state:
  • The authors stated that the cemented-asbestos experiments had obvious inadequacies and that their results could be termed only suggestive
  • The authors stated that the preliminary experiments require confirmation

Related studies

• The ability of mineral dusts and fibres to initiate lipid peroxidation. Part I: parameters which determine this ability — M. Gulumian (1999)
• Cytotoxicity of respirable dusts from industrial minerals: comparison of two naturally occurring and two man-made silicates — D. Nadeau, L. Fouquette-Couture, et al. (1987)
• Lung cell toxicity experimentally induced by a mixed dust from Mexicali, Baja California, Mexico — A.R. Osornio-Vargas, N.A. Hernández-Rodríguez, et al. (1991)
• Analysis of particles from hamster lungs following pulmonary talc exposures: implications for pathogenicity — E. Sato, S.A. McDonald, et al. (2020)
• Experimental asbestosis. The development of lung cancer in rats with pulmonary deposits of chrysotile asbestos dust — P. Gross, R.T. DeTreville, et al. (1967)
• Studies of carcinogenesis of asbestos fibers and their natural oils — J.S. Harington, F.J. Roe (1965)

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