Topographic Distribution Of Asbestos Fibres In Human Lung In Relation To Occupational And Non-Occupational Exposure

Our plain-English summary of Topographic Distribution Of Asbestos Fibres In Human Lung In Relation To Occupational And Non-Occupational Exposure, by P. Sebastien, A. Fondimare, J. Bignon, et al (1977).

The study

• Authors: P. Sebastien, A. Fondimare, J. Bignon, G. Monchaux, J. Desbordes, G. Bonnaud
• Published: Inhaled Particles Iv (W.H. Walton And B. Mcgovern, Editors), Oxford: Pergamon Press, Part 2, Pp. 435-446 (1977)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library, J-M no. 004012. The article is still under copyright, so we describe it here rather than post it.

In plain English

The authors studied autopsy lungs from a small number of people, 18 in all, who had lived and worked in the Le Havre area. Group I was six heavily exposed asbestos workers. Group II was six people who had handled small amounts of asbestos at work. Group III was six people with no known exposure, randomly chosen from fifty consecutive autopsies. Fibres were counted by light microscopy in four sites of one lung, and in parietal pleural plaques when present. Electron microscopy identified fibre types and counted lung fibres at four sites in five cases each from groups I and II. Asbestos fibres were found in every case. In the electron microscope cases, light microscopy showed only 10% of lung fibres in group I and 0.20% in group II. All five group II cases counted by electron microscopy had chrysotile. Chrysotile proportions were higher in peripheral than central lung areas. Pleural plaque fibres, mostly short chrysotile fibrils, varied much less between groups than lung fibres did. The authors suggested this might explain mesothelioma in people living near asbestos mines or factories.

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: Autopsy study comparing asbestos fibre content at different lung sites and in pleural plaques across three exposure groups, using light and electron microscopy
• Who was studied: 18 autopsy cases of people who had lived and worked in the Le Havre area. Group I was six asbestos workers with heavy exposure. Group II was six subjects who had handled small amounts of asbestos at work. Group III was six cases chosen at random from fifty consecutive autopsies, with no known asbestos exposure history. Dates are not given.
• Exposure: Occupational asbestos exposure ranging from heavy to small amounts, plus a group with no known exposure. Fibres in the lungs were identified as amphibole or chrysotile. The authors stated in discussion that the different amphibole varieties could not be distinguished.
• Main results:
  • Asbestos fibres were found by electron microscopy in the peripheral lower lobe of every case in each of the three groups.
  • In group III, only coated fibres were found under light microscopy.
  • Across all cases of the three groups, the mean local concentration index (light microscopy) in the peripheral lower lobe was significantly higher than the mean for the other three sites together: 1.24 vs. 0.92.
  • Mean length of coated fibres in the lung was 51, 45 and 37 micrometres in groups I, II and III respectively. These values were significantly different.
  • Coated fibres were found in all pleural plaque samples by light microscopy. They were shorter than lung fibres, with an average length of 28 micrometres.
  • Coated fibre concentrations in pleural plaques, measured by light microscopy, ranged from 5 to 300 per cubic centimetre of plaque.
  • The quantitative electron microscope study covered the four lung sites in five cases from group I and five from group II. The work on group III was still in progress.
  • In the cases studied by quantitative electron microscopy, light microscopy revealed only 10% of the total lung fibre content in the heavily exposed group I subjects and 0.20% in group II. The discussion says 'the other groups', but the electron microscope comparison covered only group II, and Table 3 gives group II a whole-lung mean of 0.21%.
  • In group I, when electron microscope counts were included, mean local concentration index values were significantly higher in the upper lobe, with the lowest value in the peripheral lower lobe.
  • In group II, there was no statistically significant upper vs. lower lobe difference, but fibres accumulated in peripheral areas.
  • All five group II cases analysed quantitatively by electron microscopy contained chrysotile in their lungs. In three of these cases chrysotile made up more than 90%, and in two cases about 50%.
  • Mean proportions of chrysotile were significantly higher in peripheral than in central lung areas.
  • Among more than 5000 fibres measured by electron microscopy, the proportion shorter than 5 micrometres ranged from 0% to 90%.
  • Optical and electron microscope examination of pleural plaques showed much less variation in fibre content between the three groups than in lung tissue. Electron microscopy found chrysotile to be the variety most commonly present in plaques, mostly as short ultimate fibrils.
• The authors' conclusion: The authors suggested that the number of fibres reaching the pleura may be roughly similar whatever the lung content. They proposed that this preferential localization in the pleura might explain non-occupational mesothelioma in people living near asbestos mines or factories. They also stated that the effects of short fibres should be studied further in humans.
• Limitations the authors state:
  • Only a small number of autopsy cases was studied, because the measurements were numerous and tedious.
  • The quantitative electron microscope study of group III was not finished.
  • The first electron microscope method was not suitable for good quantitative evaluation.
  • Light microscopy can be used for first screening but is unsuitable for studying dose-effect relationships.
  • In the discussion, the author stated that the different amphibole varieties could not be distinguished by diffraction pattern.
  • Because the study was retrospective, air samples of the dust originally inhaled could not be taken.

Topics

Medical terms in this study, explained in our Lexicon: Non-Occupational Exposure, Autopsy, Pleural Plaques, Chrysotile, Fibril, Mesothelioma.

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