Deposition pattern and clearance pathways of inhaled chrysotile asbestos

Our plain-English summary of Deposition pattern and clearance pathways of inhaled chrysotile asbestos, by A.R. Brody, L.H. Hill (Chest, 1981).

The study

• Authors: A.R. Brody, L.H. Hill
• Journal: Chest
• Published: 1981;80(1 Suppl):64-7
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

The authors noted that little was known about where inhaled asbestos is deposited in the most distal regions of the lung, or about the early events of particle translocation and cell injury. They studied how the initial deposition and subsequent movement of inhaled chrysotile asbestos related to the earliest lesions of asbestosis. White rats were exposed nose-only for one hour to aerosolized chrysotile at a respirable mass concentration of 4.0 mg per cubic metre of air. Animals were killed immediately afterwards and at five hours, 24 hours, four days and eight days after exposure. Lung tissue was examined by light, transmission and scanning electron microscopy. Asbestos deposition at alveolar duct bifurcations was scored from 0 to 3 according to the number of fibres seen. Most particles inhaled beyond the terminal bronchioles first landed on alveolar duct bifurcations. Immediately after exposure, mean scores were 2.44, 1.65 and 1.42 at the first, second and third bifurcations. After five hours in room air they were 1.80, 0.93 and 0.56. Small fibrils were taken into type I epithelial cells from the first hour onward. By 24 hours, asbestos was found in epithelial, interstitial and endothelial cells, basement membranes, connective tissue, capillaries and numerous alveolar macrophages. By four and eight days, few fibres remained on duct surfaces. The parenchyma approximately doubled in volume between one and eight days. The authors proposed that this was the initial lesion of asbestosis.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This was a short report of a rat experiment, presented at the 23rd Aspen Lung Conference. White rats breathed chrysotile asbestos through the nose for one hour, at a respirable mass concentration of 4.0 mg per cubic meter of air. The report did not state how many rats were used. Rats were killed immediately or at five hours, 24 hours, four days and eight days later, and their lungs examined by microscopy. Most fibers inhaled beyond the terminal bronchioles (the smallest conducting airways) landed first on the branching points of alveolar ducts. Less asbestos was seen at branch points farther from the bronchiole, and after five hours' recovery in room air. Small fibrils were taken up into type I epithelial cells from the first hour through eight days. By 24 hours, asbestos was in epithelial, interstitial and endothelial cells, connective tissue, capillaries and macrophages. By four and eight days, fibers were rarely seen on duct surfaces; lung tissue roughly doubled in volume between days one and eight. The authors proposed that fiber impact at duct branch points, where macrophages had gathered by 24 hours, was the initial lesion of asbestosis.

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 in rats with microscopic examination of lung tissue at set times after a single one-hour exposure (short conference report)
• Who was studied: White rats (number not stated), studied at the Laboratory of Pulmonary Function and Toxicology, National Institute of Environmental Health Sciences, North Carolina. They were killed immediately after exposure and at 5 hours, 24 hours, 4 days and 8 days afterward.
• Exposure: Chrysotile asbestos aerosol, nose-only, for one hour at a respirable mass concentration of 4.0 mg per cubic meter of air (printed as 'm8', an OCR error for cubic meters)
• Main results:
  • Most particles inhaled beyond the terminal bronchioles landed first on alveolar duct bifurcations (branching points)
  • Less asbestos was seen at bifurcations farther from the bronchiole. Immediately after exposure, mean deposition scores (0 to 3 scale) were 2.44 (SD .70; N=48) at the first bifurcation, 1.65 (SD .90; N=41) at the second and 1.42 (SD .60; N=19) at the third.
  • After five hours of recovery in room air, bifurcations had less asbestos. Mean scores were 1.80 (SD .90; N=41), .93 (SD .78; N=30) and .56 (SD .63; N=16) at the first, second and third bifurcations.
  • Small asbestos fibrils were taken into the cytoplasm of type I epithelial cells. This began during the first hour of exposure and continued through the eight-day study period.
  • At 24 hours, asbestos was found in epithelial cells, basement membranes, interstitial cells and connective tissue, endothelial cells and capillary lumina, and in many alveolar macrophages
  • At four and eight days after exposure, fibers were rarely seen on alveolar duct surfaces
  • The lung parenchyma of asbestos-exposed rats approximately doubled in volume between one and eight days after exposure (measured by image analysis)
• The authors' conclusion: The authors proposed that the impact of asbestos on alveolar duct bifurcations, with the build-up of macrophages there by 24 hours, is the initial lesion of asbestosis. They suggested that early clearance through the alveolar epithelium could carry small fibrils into the lung interstitium.

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, Chrysotile, Translocation, Scanning Electron Microscopy (SEM), Fibril, Interstitial, Alveolar Macrophage, Parenchyma.

Related studies

• Kinetics of deposition and clearance of inhaled mineral dusts during chronic exposure — J.H. Vincent, A.M. Johnston, et al. (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)
• Deposition, clearance, and translocation of chrysotile asbestos from peripheral and central regions of the rat lung — P.G. Coin, V.L. Roggli, et al. (1992)
• Lung proliferative and clearance responses to inhaled para-aramid RFP in exposed hamsters and rats: comparisons with chrysotile asbestos fibers — D.B. Warheit, S.I. Snajdr, et al. (1997)
• Studies on the deposition of inhaled fibrous material in the respiratory tract of the rat and its subsequent clearance using radioactive tracer techniques — A. Morgan, J.C. Evans, et al. (1975)
• Deposition and clearance of chrysotile asbestos — A. Churg (1994)

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