Early lung events following low-dose asbestos exposure

Our plain-English summary of Early lung events following low-dose asbestos exposure, by R. Bégin, M. Rola-Pleszczynski, P. Sirois, et al (Environmental Research, 1981).

The study

• Authors: R. Bégin, M. Rola-Pleszczynski, P. Sirois, I. Lemaire, D. Nadeau, M.A. Bureau, S. Massé
• Journal: Environmental Research
• Published: 1981;26(2):392-401
• Cited by: 33 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 001988).

Abstract

A conscious sheep model recently developed to study sequentially the bronchoalveolar milieu was applied to the investigation of the early lung events following very low dose asbestos exposure. UICC Canadian chrysotile fibers were administered in three monthly intratracheal injections of a suspension of 0 (controls), 1,2,4, 8, and 16 mg of asbestos in 50 ml saline. Three sheep per dose were repeatedly exposed to the same monthly doses and all were studied by serial pulmonary function (PF) tests, transbronchial lung biopsies (LB), and bronchoalveolar lavages (BAL). These low-dose exposures did not change the PF tests; routine lung histopathology was not altered except for the observation of occasional fibers in the alveoli, but there was a significantly higher yield in the total BAL cellular due to a marked increase in the macrophage and a small rise in the lymphocyte populations. These changes in the BAL cells occurred without significant changes in the biochemical analyses of the BAL supernatant. These data establish that very low dose asbestos exposure induces migration of macrophages and lymphocytes into the bronchoalveolar milieu. These cells have a major role in the lung defense and have been implicated in the development of asbestos-related diseases.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

In this animal experiment from the Université de Sherbrooke, Québec, Canada, 18 awake male sheep were split into groups of three. Once a month for 3 months, one group received saline injected into the windpipe and the others received saline containing 1, 2, 4, 8 or 16 mg of UICC Canadian chrysotile fibers. The sheep had repeated lung function tests, lung biopsies and bronchoalveolar lavage (washing cells out of the airways). Lung function did not differ significantly between exposed and control sheep. Biopsies were normal apart from occasional fibers in exposed animals. After the second exposure, lavage lymphocytes were significantly increased in exposed sheep (P less than 0.02). After the third, total cells, macrophages and lymphocytes were all significantly increased. These changes were not dose related. Chemical tests of the lavage fluid mostly showed no significant group differences. The authors concluded that low-dose exposure did not start lung function changes or cause interstitial fibrosis in the early days after exposure, but did start migration of macrophages and lymphocytes. They suggested biochemical changes may have been too small to detect.

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 experiment: repeated monthly intratracheal injections in a conscious (awake) sheep model, with serial lung function tests, transbronchial lung biopsies and bronchoalveolar lavage
• Who was studied: 18 male sheep (25 to 50 kg), studied unsedated and divided into six groups of three; Université de Sherbrooke, Québec, Canada (article received November 1980)
• Exposure: UICC Canadian chrysotile fibers at 0 (saline controls), 1, 2, 4, 8 or 16 mg in 50 ml saline, injected into the trachea monthly for 3 months
• Main results:
  • Lung volumes did not differ significantly between exposure groups in any period.
  • Gas exchange measurements did not differ significantly between exposed groups and controls in any period.
  • Total lung capacity and functional residual capacity fell significantly over the study (P less than 0.01). The authors attributed this largely to the sheep's weight gain, from 29.2 to 39.0 kg.
  • All lung biopsies were normal except for occasional fibers in the tissue of asbestos-exposed sheep.
  • After the second exposure, the only significant effect in lavage cells was an increase in lymphocytes in exposed sheep (P less than 0.02).
  • After the third exposure, total lavage cells, macrophages and lymphocytes were all significantly increased in exposed sheep compared with controls (P less than 0.05 per the figure legend).
  • The cell increases were not dose related, so exposed sheep were pooled and compared with controls.
  • Chemical analyses of the lavage fluid showed no significant differences between exposure groups.
  • When post-exposure data were averaged, the text reports a significant decrease in prostaglandin E2 and cyclic AMP (P less than 0.05) only in the 2 mg group.
• The authors' conclusion: The authors concluded that low-dose asbestos exposure did not start changes in lung respiratory function and did not cause interstitial fibrosis in the early days after exposure, but did start migration of macrophages and lymphocytes in the lung.
• Limitations the authors state:
  • The study did not count the alveolar or interstitial cells in the biopsies.
  • Biochemical changes may have been present but too small to detect by washing a single lung subsegment.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, UICC, Chrysotile, Bronchoalveolar Lavage (BAL), Histopathology, Alveoli, Macrophage.

Related studies

• The biological reactivity of calcium silicate composites: in vivo studies — R.J. Richards, T.D. Tetley, et al. (1981)
• Assessment of progression of asbestosis in the sheep model by bronchoalveolar lavage and pulmonary function tests — R. Bégin, M. Rola-Pleszczynski, et al. (1983)
• Asbestos-induced lung injury in the sheep model: the initial alveolitis — R. Bégin, M. Rola-Pleszczynski, et al. (1983)
• Translocation of inhaled dust to the pleura — P.F. Holt (1983)
• Morphologic features and function of the airways in early asbestosis in the sheep model — R. Bégin, S. Massé, et al. (1982)
• Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study — B. Hilt, J.T. Lien, et al. (1987)

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