Asbestos dust deposition and retention in rats

Our plain-English summary of Asbestos dust deposition and retention in rats, by J.C. Wagner, J.W. Skidmore (Annals of the New York Academy of Sciences, 1965).

The study

• Authors: J.C. Wagner, J.W. Skidmore
• Journal: Annals of the New York Academy of Sciences
• Published: 1965;132(1):77-86
• Cited by: 40 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 preliminary animal experiment, from the Medical Research Council Pneumoconiosis Research Unit in Penarth, Glamorgan, tested a method for depositing asbestos dust in rat lungs by inhalation. Wistar albino rats (57 male, 58 female) were split into five groups: unexposed controls, and groups breathing Rhodesian chrysotile, South African crocidolite, South African amosite, or powdered glass (a non-fibrous comparison dust), 5 days a week for 6 weeks. Rats were killed 1, 29 and 58 days after exposure ended. Crocidolite and amosite fibers were seen in scavenger cells in air sacs next to the smallest airways. Chrysotile-exposed lungs showed only occasional fiber fragments, and no visible dust by day 58. One day after exposure, chrysotile uptake was about one-third that of crocidolite and amosite. Chrysotile was cleared from the lung at a rate about three times that of the other dusts. The authors concluded that this suggests an explanation for chrysotile's previously observed lower fibrogenicity (tendency to cause scarring). They added that the reason for the difference remains to be determined.

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: Preliminary animal inhalation experiment in rats, carried out to test a newly devised method of producing asbestos dust clouds
• Who was studied: 57 male and 58 female Wistar albino rats, randomly allocated into 5 groups: four exposed groups of 12 male and 12 female rats each, plus an unexposed control group. The work was done at the MRC Pneumoconiosis Research Unit, Llandough Hospital, Penarth, Glamorgan, Great Britain. Groups of 4 male and 4 female rats from each dust group were killed 1, 29 and 58 days after the last exposure. The date of the experiment is not given.
• Exposure: Airborne clouds of Rhodesian chrysotile, South African crocidolite or South African amosite, each in the most finely ground commercial grade and further ground in a mill. Powdered glass was used as an inert nonfibrous comparison dust. Exposure was on 5 days a week over 6 weeks, a total of 30 daily sessions. The number of hours per day is garbled in the scanned text.
• Main results:
  • In rats exposed to crocidolite and amosite and killed 24 hours after the final exposure, fibers and dust particles were seen in alveolar phagocytes (scavenger cells). These cells were concentrated in the alveoli arising directly from the respiratory bronchioles. At 29 and 58 days there was progressive organization in the alveoli, and some phagocytes had fused into giant cells.
  • In chrysotile-exposed rats, only occasional small fiber fragments were seen at 24 hours. By the 58th day, no evidence of the dust was observed, although the tissue organization was similar to that in the crocidolite and amosite groups.
  • Uptake was measured as lung dust one day after exposure, expressed as a percentage of the dust collected by the size-selective sampler. Chrysotile uptake was about one-third that of crocidolite and amosite, and powdered glass uptake was described as twice as great. Table 3 lists 2.3 (chrysotile), 7.5 (crocidolite), 8.8 (amosite) and 15.8 (glass).
  • The elimination (clearance) rate slopes were -0.09 for glass, -0.07 for amosite and -0.11 for crocidolite. These three were not significantly different at the 5 per cent level. The slope for chrysotile was -0.26, practically three times greater.
  • In the crocidolite and amosite chambers, the air samplers collected fibers up to 250 microns long. No fibers longer than 50 microns were found in dust extracted from the rats' lungs.
  • Two rats died of bronchiectasis during the 6-week exposure period.
• The authors' conclusion: The authors concluded that the dusts tend to accumulate in the alveoli arising directly from the respiratory bronchioles. They found that the elimination rate of Rhodesian chrysotile was three times greater than that of amosite and crocidolite, which they said suggests an explanation for the previously observed reduced fibrogenicity of chrysotile.
• Limitations the authors state:
  • The authors state that the reason for chrysotile's faster elimination rate remains to be determined.
  • The authors note that the size-selecting sampler (horizontal elutriator) does not account for particle shape except as it affects falling speed.

Topics

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

Medical terms in this study, explained in our Lexicon: Deposition.

Related studies

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• Accumulation of mixed mineral dusts in the lungs of rats during chronic inhalation exposure — C.H. McMillan, A.D. Jones, et al. (1989)
• Effects of fiber characteristics on lung deposition, retention, and disease — M. Lippmann (1990)
• A striking deposition of mineral particles in the lungs of a farmer: a case report — B. Gylseth, L. Stettler, et al. (1984)
• Inhalation toxicity study of disk-shaped potassium octatitanate particles (terracess TF) in rats following 90 days of aerosol exposure — S. Sakai, K. Inada, et al. (2010)
• Enhanced lipid peroxidation and lysosomal enzyme activity in the lungs of rats with prolonged pulmonary deposition of crocidolite asbestos — J. Jajte, I. Lao, et al. (1987)

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