Human and experimental data on translocation of asbestos fibers through the respiratory system

Our plain-English summary of Human and experimental data on translocation of asbestos fibers through the respiratory system, by J. Bignon, G. Monchaux, P. Sebastien, et al (Annals of the New York Academy of Sciences, 1979).

The study

• Authors: J. Bignon, G. Monchaux, P. Sebastien, A. Hirsch, J. Lafuma
• Journal: Annals of the New York Academy of Sciences
• Published: 1979;330:745-50
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy.

Abstract

The translocation of fibrous dusts through the respiratory system is discussed on the basis of human and experimental data obtained with the transmission electron microscope. Comparison of the characteristics (numerical and mass concentrations, sizes, types) of asbestos fibers retained in different locations of the respiratory system in humans exposed to asbestos has shown that there is no relationship between the numerical concentrations in lung parenchyma and those in parietal pleura. Moreover, almost al fibers encountered in the pleura were ultimate, short fibrils of chrysotile. The animal data are from rats injected intrapleurally with different types of fibers (chrysotile, crocidolite and glass fibers) and sacrificed at different times. There was a progressive increase in the number and mass of fibers translocated into lung parenchyma from the pleural cavity that was particularly obvious after 90 days. After this time, the mean length of fibers, especially chrysotile, increased, indicating that more long fibers are retained in alveolar tissue than short fibers.

In plain English

In the first part, the authors summarized their own earlier electron-microscope measurements of asbestos fibers in human lung tissue, lung washings, parietal pleura and chest lymph nodes. They reported no relationship between fiber concentrations (number per amount of tissue) in lung tissue and in parietal pleura. In humans, fibers longer than 8 micrometers made up less than 2% of pleural fibers but 15% of lung fibers. Pleural fibers were mostly chrysotile, and lymph node fibers mostly amphibole. The second part gave preliminary results from an ongoing rat experiment. Male rats received 20 mg of chrysotile, crocidolite or glass fibers in the right pleural cavity and were killed 1 to 210 days later. Fibers reached the chest lymph nodes within one day, and at 90 days were found in all tissues analyzed. In the left lung, fibers found per unit of tissue, relative to the number injected, stayed about level for 90 days and then rose, and fibers became longer on average, especially chrysotile. The authors concluded that fibers may easily and rapidly migrate within the body. They noted that in humans the normal route is the reverse, from lung to pleura.

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: Two parts: a summary of the authors' earlier human tissue measurements by transmission electron microscopy, and preliminary results of an ongoing animal experiment (intrapleural injection in rats)
• Who was studied: Human part: subjects with different levels of asbestos exposure and different asbestos-related diseases, studied in the authors' earlier reports. The article does not give their number. Animal part: three groups of 14 male Sprague-Dawley SPF rats, six to eight weeks old, killed 1, 2, 7, 30, 90, 145 and 210 days after injection. Tissues from two animals at the different times were analyzed.
• Exposure: Humans: asbestos exposure at different levels, not specified here. Rats: 20 mg of UICC A chrysotile, UICC crocidolite or glass fibers JM 104 in 2 ml of saline, injected into the right pleural cavity. Mean lengths were 3.6 µm (chrysotile), 2.5 µm (crocidolite) and 5.9 µm (glass). Mean diameters were .05, .14 and .23 µm.
• Main results:
  • Humans: no relationship was found between the numerical concentrations of asbestos fibers in lung parenchyma and in parietal pleura.
  • Humans with heavy asbestos exposure: washing one lung segment recovered 100 times fewer fibers than digesting tissue from an equivalent lung volume.
  • Humans: fibers longer than 8 micrometers were less than 2% of fibers in the pleura, compared with 15% in lung parenchyma.
  • Humans: fibers in the pleura were short chrysotile fibrils. The article's body says the pleural fibers were mostly chrysotile; its summary says almost all.
  • Humans: fibers in thoracic lymph nodes were mostly of the amphibole type.
  • Rats, 90 days after injection: fibers were found in all tissues analyzed.
  • Rats, one day after injection: about 1% of the number of chrysotile fibers injected, and 10% of the crocidolite and glass fibers injected, were found in one gram of thoracic lymph nodes.
  • Rats: the translocation rate into the lung was defined as the number (or mass) of fibers recovered from a fixed unit of lung parenchyma divided by the total number (or mass) injected, expressed in ppm.
  • Rats: the translocation rate by number into lung parenchyma was 10 times higher for crocidolite than for chrysotile. It was also higher than for glass fibers, but to a lesser extent.
  • Rats: for each fiber type, the translocation rate by number stayed about the same for 90 days and then increased.
  • Rats: the translocation rate by mass was much higher for glass fibers than for crocidolite and chrysotile.
  • Rats: after one day, the mean length of fibers in lung parenchyma was lower than that of the injected fibers. After seven months it was higher than the initial length for all fiber types, especially chrysotile.
  • Rats: no significant difference was observed in fiber diameter distribution between injected fibers and fibers found in lung parenchyma.
• The authors' conclusion: The authors concluded that their results confirm that the vast majority of fibers may easily and rapidly migrate within the body, whatever the site of their penetration.
• Limitations the authors state:
  • The exact quantity of fibers translocated to the thoracic lymph nodes could not be measured, because the entire mass of lymph node tissue was not assessed.
  • The rat study was a secondary objective of an experiment designed to induce mesothelioma in rats.
  • The normal route for fibers in humans is the reverse of the one studied in rats: from lung parenchyma to pleura.
  • Data on changes in fiber number, mass and size over time were available only for the lung.
  • The absence of fibers in the pleura of some subjects must be interpreted cautiously, because fibers are not uniformly distributed in the parietal pleura.
  • The route the fibers take to the thoracic lymph nodes remains unclear.

Topics

Medical terms in this study, explained in our Lexicon: Translocation, Parenchyma, Parietal Pleura, Pleura, Fibril, Chrysotile, Crocidolite, Pleural Cavity.

Related studies

• 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 and cellular interaction of cancer-inducing particles in the human respiratory tract: Theoretical approaches and experimental data — R. Sturm (2010)
• Experimental asbestosis: an investigation of functional and pathological disturbances. II. Results for chrysotile and amosite exposures — D.M. Hiett (1978)
• 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 of inhaled asbestos and man-made mineral fibres in the respiratory tract — A. Morgan (1995)
• Translocation pathways for inhaled asbestos fibers — G. Miserocchi, G. Sancini, et al. (2008)

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