Current Views On Pathological Aspects Of Asbestosis (The Unresolved Questions And Problems)

Our plain-English summary of Current Views On Pathological Aspects Of Asbestosis (The Unresolved Questions And Problems), by R.M.E. Seal (1980).

The study

• Author: R.M.E. Seal
• Published: Biological Effects Of Mineral Fibres (J.C. Wagner, Editor), Lyon: Iarc Scientific Publications, Volume 30, Pp. 217-235 (1980)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library, J-M no. 002579. The article is still under copyright, so we describe it here rather than post it.

In plain English

This paper discussed unresolved questions in diagnosing asbestosis, using 14 illustrative cases; it was not a formal study. The author defined asbestosis as asbestos-induced fibrosis (scarring) of the lung tissue itself, not pleural plaques. For each case the author described the fibrosis found. Where available, the author gave lung fibre counts by light microscopy (the Ashcroft method), by electron microscopy, or usually both. In two lung cancer cases, the cancer was accepted as an industrial malignancy. The Ashcroft counts in these cases were below one million fibres per gram dry weight. A third, borderline case was judged to involve previously undiagnosed mild asbestosis. In other cases, the author judged asbestos an unlikely cause of the fibrosis. Reasons included a high share of non-asbestos fibres such as mullite, or fibre levels like those found in urban male 'controls'. The author concluded that classical asbestosis, leading to respiratory disability, is likely to be associated with an Ashcroft count of over 1 million forms per gram dry weight. The author suggested that lesser degrees could be diagnosed with counts as low as 250,000, and called for further work.

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: Discussion paper presenting a series of illustrative cases (autopsy and lung tissue examinations with fibre counts), not a formal study
• Who was studied: 14 illustrative cases. They included UK patients with lung cancer or mesothelioma, cases from German asbestos workers and a Viennese case supplied by other pathologists, and two cases from the UK asbestos survey.
• Exposure: Mostly occupational asbestos exposure of varying degree and duration. Jobs included sheet-metal worker, chemical engineer, maintenance fitter, lagger and post-office engineer. One mesothelioma patient recalled only building an asbestos garage. Fibres identified in the lungs included amosite, chrysotile, crocidolite, actinolite and tremolite, along with non-asbestos fibres such as mullite.
• Main results:
  • Case 1 was a sheet-metal worker with lung cancer and slight fibrosis. Ashcroft counts were 292,000 and 425,000 fibres/g dry weight, and electron microscopy found 20.7 million fibres/g dry weight. The tumour was regarded as an industrial malignancy, and the Pneumoconiosis Panel accepted this opinion.
  • Case 2 was a chemical engineer with lung cancer. The Ashcroft count was 500,000 fibres/g dry weight, and electron microscopy found 157.5 million fibres/g dry weight, 65.4% of them crocidolite. The cancer was considered and accepted as an industrial malignancy.
  • Case 3 was a heavy smoker with lung cancer. Electron microscopy found 49.9 million fibres, a large share of them non-asbestos fibres. Because only a microscopic amount of fibrosis was found, the case was not considered an industrial malignancy.
  • Case 4 was a borderline lung adenocarcinoma case, regarded as arising in a patient with previously undiagnosed mild asbestosis. The finding of 39 million fibres, mostly crocidolite, was an important factor in this opinion.
  • Case 5 was a mesothelioma patient who recalled only trivial exposure. Electron microscopy found 5 million asbestos fibres, mostly chrysotile, plus many mullite fibres. The author said the case suggests that patients can occasionally be unaware of their exposure.
  • Case 12 had an Ashcroft count of 8000 and had kept budgerigars for 17 years. It was regarded as chronic extrinsic allergic alveolitis with asbestos plaques. No electron microscopy was done, and the author said they would now insist on it.
  • Case 13 was a mesothelioma case from the UK asbestos survey. Electron microscopy found 34 million total fibres, most of them mullite. The author judged that if the inhaled fibres caused the fibrosis, asbestos was unlikely to be the cause.
  • Case 14 had extensive fibrosis but 5.8 million fibres by electron microscopy. The author said these levels are found in many male urban 'controls' and were unlikely to have caused the fibrosis.
• The authors' conclusion: The author concluded that 'asbestosis' should refer only to asbestos-induced parenchymal fibrosis. Classical asbestosis, leading to respiratory disability, is likely to be associated with an Ashcroft count over 1 million forms/g dry weight. The author suggested that lesser degrees of asbestos-induced fibrosis, probably important when lung cancer develops, can be diagnosed with counts as low as 250,000. The author called for further work on whether still lesser grades matter and whether electron microscopy is mandatory in such cases.
• Limitations the authors state:
  • For one case (Herr N), the author noted that the evaluation was based on one small portion of lung rather than a whole lung.
  • The author stated that further work is needed to establish whether even lesser grades of asbestosis matter in lung cancer, and whether electron microscopic techniques are mandatory.

Topics

Medical terms in this study, explained in our Lexicon: Fibrosis, Pleural Plaques, Lung Cancer.

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