The effects of chrysotile and crocidolite asbestos on the lower respiratory tract: analysis of bronchoalveolar lavage constituents

Our plain-English summary of The effects of chrysotile and crocidolite asbestos on the lower respiratory tract: analysis of bronchoalveolar lavage constituents, by E. Kagan, Y. Oghiso, D.P. Hartmann (Environmental Research, 1983).

The study

• Authors: E. Kagan, Y. Oghiso, D.P. Hartmann
• Journal: Environmental Research
• Published: 1983;32(2):382-97
• Cited by: 34 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This study was designed to evaluate the effects of amphibole and serpentine asbestos inhalation on the constituents of the lower respiratory tract. Bronchoalveolar lavage (BAL) analyses were performed on three groups of rats: one group was exposed to chrysotile (serpentine) asbestos, another group was exposed to crocidolite amphibole asbestos, while a third group was sham-exposed. Intermittent inhalational exposures lasted three months. The total BAL cell yields and the macrophage content of BAL cells were significantly lower after asbestos exposure, especially in the chrysotile-exposed group. These effects persisted for as long as 1 year after the cessation of exposure. Multinucleated macrophages were seen in BAL cells from both asbestos-exposed groups. Striking ultrastructural alterations of macrophage morphology were noted in BAL cells from both groups of asbestos-exposed rats. Chrysotile fibers were not seen in any BAL cells from chrysotile-exposed animals. However, 15 months after terminating the exposure regimen, a sizeable proportion of BAL macrophages from crocidolite-exposed rats contained phagocytosed asbestos fibers. Significantly higher beta-glucuronidase and lactate dehydrogenase activity was found in BAL fluids from both asbestos-exposed groups and was detected 17-18 months after exposure had ceased. These observations have served as useful correlates of asbestos-mediated injury to the lower respiratory tract. They have also provided evidence of continual pathological sequelae occurring long after withdrawal from asbestos exposure.

In plain English

In this animal experiment, the authors exposed young male Fisher-344 rats by inhalation to chrysotile asbestos (average 10.7 mg/m3), crocidolite asbestos (average 11.2 mg/m3) or clean air (sham exposure) for 6 hours a day, 5 days a week, for 91 days. In the months after exposure ended, they washed out the rats' lungs (bronchoalveolar lavage) and examined the recovered cells and fluid. Both asbestos groups yielded fewer total cells and fewer macrophages, a type of scavenger cell, than sham-exposed rats. The lowest cell yields came from chrysotile-exposed rats. Both asbestos groups had more macrophages with several nuclei. At 14-15 months after exposure, 41-64% of macrophages from crocidolite-exposed rats contained crocidolite fibers. No chrysotile fibers were found in macrophages from chrysotile-exposed rats. At 17-18 months, activity of two enzymes, lactate dehydrogenase and beta-glucuronidase, measured per milligram of lavage-fluid protein, was significantly higher in both asbestos groups. Total protein content of the fluid showed no significant difference between groups. The authors concluded that the enzyme findings gave further evidence of persistent inflammation caused by asbestos fibers remaining in the lungs.

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 comparing three groups of rats (chrysotile-exposed, crocidolite-exposed, sham-exposed)
• Who was studied: Male, inbred, albino Fisher-344 rats, 4 weeks old at the start (mean weight 124 g), in three groups; killed and lavaged between 6 and 18 months after exposure ended. The total number of rats is not stated.
• Exposure: Inhalation of chrysotile asbestos (Johns-Manville, Jeffrey Mine, Quebec; time-weighted average 10.7 mg/m3) or UICC reference crocidolite asbestos (time-weighted average 11.2 mg/m3), or clean air only for controls. Exposure ran 6 hours a day, 5 days a week for 91 consecutive days. The authors noted these concentrations were considerably higher than the 1972 OSHA standard but comparable with levels previously recorded in asbestos mines and mills.
• Main results:
  • About 6 months after exposure ended, sham-exposed rats gave significantly greater total lavage cell yields than chrysotile-exposed rats (P < 0.01) or crocidolite-exposed rats (P < 0.05). Chrysotile-exposed rats gave the lowest yields. Lower yields in both asbestos groups were seen from 3 to 12 months after exposure.
  • Cell viability was similar in the three groups: 90-94% in controls, 82-92% in chrysotile-exposed rats and 87-93% in crocidolite-exposed rats.
  • Macrophages made up most (more than 65%) of lavage cells in all three groups, with no significant difference in percentages. However, the absolute numbers of macrophages were significantly lower in both asbestos groups than in sham-exposed rats (P < 0.01).
  • The proportion of multinucleated macrophages and the fusion index were significantly higher in both asbestos groups than in sham-exposed rats (P < 0.01). Mean fusion index was 9% (chrysotile) and 6% (crocidolite) versus less than 1% (sham). Multinucleated giant cells were 4% (chrysotile) and 2% (crocidolite) versus less than 1% (sham).
  • Multinucleated giant cells and the fusion index were significantly higher in chrysotile-exposed rats than in crocidolite-exposed rats (P < 0.05).
  • Among freshly obtained lavage cells, the proportion that took up latex beads was significantly lower in chrysotile-exposed rats (mean 76%) than in crocidolite-exposed rats (83%, P < 0.05) or controls (86%, P < 0.01). Among macrophages that had attached to culture slides, there were no significant differences between groups (94% controls, 92% chrysotile, 95% crocidolite).
  • In lavage cells taken from three crocidolite-exposed and three chrysotile-exposed rats 14-15 months after exposure ended, 41-64% of macrophages from the crocidolite-exposed rats contained crocidolite fibers. No chrysotile fibers were identified in more than 100 consecutive macrophages per chrysotile-exposed rat.
  • Many macrophages from both asbestos groups showed swollen internal vacuoles (degenerative changes), more marked in chrysotile-exposed rats. A small percentage of macrophages from both asbestos groups were clearly nonviable or dying.
  • Total protein content of lavage fluid showed no significant difference between asbestos-exposed and sham-exposed rats. Means were 95 µg/ml (sham), 77 µg/ml (chrysotile) and 95 µg/ml (crocidolite).
  • In lavage fluid taken 17-18 months after exposure ended, lactate dehydrogenase activity, expressed per milligram of lavage protein, was significantly higher in both asbestos groups than in sham-exposed rats (P < 0.01). Means were 22 mU/mg protein for sham-exposed and 90 mU/mg protein for chrysotile-exposed rats.
  • Beta-glucuronidase activity in lavage fluid, expressed per milligram of lavage protein, was significantly higher in both asbestos groups than in controls (P < 0.01). Means were 21 U/mg protein in each asbestos group versus 9 U/mg protein in sham-exposed rats.
• The authors' conclusion: The authors concluded that the raised enzyme levels in lavage fluid 17-18 months after asbestos inhalation stopped provide further evidence of persistent inflammation caused by asbestos fibers remaining in the lungs. They also concluded that bronchoalveolar lavage is a useful tool for studying the effects of inhaled particles on the lower respiratory tract.
• Limitations the authors state:
  • The authors stated there is no obvious reason for the low macrophage yields after asbestos inhalation. They also stated that many cells breaking down inside the air spaces are likely not to be detected by the lavage procedure.
  • The airborne asbestos concentrations used were considerably higher than the maximum allowed under the 1972 OSHA asbestos standard.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Crocidolite.

Medical terms in this study, explained in our Lexicon: Chrysotile, Crocidolite, Bronchoalveolar Lavage (BAL), Amphibole Group, Serpentine Group, Amphibole Asbestos, Macrophage, Asbestos Exposure.

Related studies

• Alveolitis of pulmonary asbestosis. Bronchoalveolar lavage studies in crocidolite- and chrysotile-exposed individuals — B.W. Robinson, A.H. Rose, et al. (1986)
• Lymphocyte subpopulations in bronchoalveolar lavage fluid in asbestos workers — A.R. Gellert, M.G. Macey, et al. (1985)
• 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)
• Brief inhalation of asbestos compromises superoxide production in cells from bronchoalveolar lavage — J.M. Petruska, J. Marsh, et al. (1990)
• Characterization of the bronchoalveolar cellular response in experimental asbestosis. Different reactions depending on the fibrogenic potential — I. Lemaire (1985)
• Studies on the deposition of inhaled fibrous material in the respiratory tract of the rat and its subsequent clearance using radioactive tracer techniques. 1. UICC crocidolite asbestos — J.C. Evans, R.J. Evans, et al. (1973)

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