Experimental asbestosis with four types of fibers: importance of small particles

Our plain-English summary of Experimental asbestosis with four types of fibers: importance of small particles, by P.F. Holt, J. Mills, D.K. Young (Annals of the New York Academy of Sciences, 1965).

The study

• Authors: P.F. Holt, J. Mills, D.K. Young
• Journal: Annals of the New York Academy of Sciences
• Published: 1965;132(1):87-97
• Cited by: 52 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

In this animal experiment, researchers at the University of Reading, England, exposed guinea pigs to dust of four kinds of asbestos (chrysotile, crocidolite, amosite and anthophylite) and examined their lungs under the microscope. The article gives no total number of animals. The authors stated that dust concentration could not be expressed precisely, since much of the dust was too small to see by light microscope. The earliest damage was inflammation of the small airways. Coated fibers (asbestos bodies) appeared as early as seven days after first exposure. Later, lungs showed widespread fibrosis and the tracheal lymph glands became enlarged. In a group of six guinea pigs given very finely divided chrysotile, the authors reported widespread fibrosis 226 days after first exposure, with little visible dust and few asbestos bodies; how many of the six were examined then is not stated. Untreated control animals also developed asbestosis after asbestos dust spread through the room where they were kept, which the authors called an accident. The authors concluded that fine dust particles too small to see under the light microscope will produce asbestosis in the guinea pig.

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: Animal inhalation experiment with descriptive microscopic examination of lung tissue (no statistical comparisons)
• Who was studied: Guinea pigs, studied at the University of Reading, England. The total number is not stated. Four were examined after three days (two exposed to chrysotile, two to crocidolite). Six were used in the first chrysotile experiments. Untreated control animals were also kept. Dates are not given.
• Exposure: Airborne dust of chrysotile, crocidolite, amosite and anthophylite from a dust generator, breathed in a tunnel. Early experiments lasted as long as 78 days. Later experiments lasted 5 to 10 days, with the generator running about 100 hours. Dust concentration was not measured precisely, and much of the dust was too small to see by light microscope.
• Main results:
  • In four animals examined after three days in the tunnel, dust had already reached the terminal bronchioles in large amounts.
  • The earliest lesion was a bronchiolitis (inflammation of the small airways), illustrated in a guinea pig after 14 days of exposure to chrysotile.
  • Coated asbestos fibers (asbestos bodies) were found as early as seven days after first exposure.
  • Collagen was seen in one animal killed 15 days after first exposure to anthophylite.
  • In later stages there was widespread, progressive lung fibrosis and adenoid proliferation of the bronchiolar epithelium. There was also reticulinosis and fibrosis of the tracheal lymph glands, which became grossly enlarged.
  • Six guinea pigs received very finely divided chrysotile by chance (one for 14 days, the rest for 78 days). The authors reported widespread fibrosis in these animals 226 days after first exposure, with very little dust visible by light microscope and only a few asbestos bodies. The article does not say how many of the six were examined at 226 days.
  • Even where asbestos bodies were numerous, they were vastly outnumbered by small particles inside macrophages.
  • Untreated control animals in one experiment, kept in the room where asbestos dust had spread, developed asbestosis. It was less severe than in the exposed animals, with one or two asbestos bodies per whole-lung section.
  • After the animal room was changed, a cage of untreated guinea pigs kept for 12 months developed interstitial pneumonia. Electron microscopy found asbestos dust in their lungs, which the authors presumed was the cause.
• The authors' conclusion: The authors concluded that fine dust particles, too small to be seen under the light microscope, will produce asbestosis in the guinea pig. They also concluded that the guinea pig lung is a very sensitive indicator of asbestos dust, and that the spread of dust is difficult to control.
• Limitations the authors state:
  • The authors stated that the dust concentration breathed by the guinea pigs could not be expressed with any precision.
  • Dust spread through the animal room and untreated control animals were inadvertently exposed, which the authors called an accident.
  • The authors noted that the first chrysotile experiments were done when experience with the dust generator was limited, and that those animals received very finely divided dust by chance.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Related studies

• Biochemical components of bronchoalveolar lavage in early experimental asbestosis of the sheep: phospholipase A2 activity, prostaglandin E2 and proteins — P. Sirois, G. Drapeau, et al. (1983)
• Characterization of the bronchoalveolar cellular response in experimental asbestosis. Different reactions depending on the fibrogenic potential — I. Lemaire (1985)
• Fiber deposition in the tracheobronchial region: experimental measurements — Y. Zhou, W.C. Su, et al. (2007)
• Pathologic changes in the small airways of the guinea pig after amosite asbestos exposure — D. Filipenko, J.L. Wright, et al. (1985)
• Pulmonary and systemic immunoregulatory changes during the development of experimental asbestosis — M. Rola-Pleszczynski, S. Gouin, et al. (1984)
• Small animals in the study of pathological effects of asbestos — P.F. Holt (1974)

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