Fibers in Human Lung Dust Samples - A Scanning Electron Microscope Study

Our plain-English summary of Fibers in Human Lung Dust Samples - A Scanning Electron Microscope Study, by K.H. Friedrichs, H. Otto (1981).

The study

• Authors: K.H. Friedrichs, H. Otto
• Published: American Industrial Hygiene Association Journal 42:150-156 February (1981)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

In the Federal Republic of Germany, mesothelioma was recognized as an occupational disease when workplace asbestos exposure could be proven. This study used a scanning electron microscope to examine lung dust from 100 necropsy (autopsy) cases. The six groups were 22 normal lungs without occupational asbestos exposure, 22 cases the authors called spontaneous mesothelioma, 22 occupationally caused mesothelioma cases, 12 asbestosis with mesothelioma, 8 asbestosis with bronchial carcinoma, and 14 asbestosis. Fibers were counted and measured but not chemically identified. Average fiber concentration rose from the normal-lung group to the asbestosis group. It was 10 times higher in occupationally caused than spontaneous mesothelioma, but values scattered too widely for concentration alone to separate them. Fiber diameters showed no significant difference among groups, but fiber length distribution differed between the normally exposed groups and the occupationally asbestos-exposed groups. For fibers longer than 5 micrometers, the transition between the two mesothelioma groups occurred at about 0.4 fibers per ng of dust. The authors concluded that counting longer fibers can distinguish the two kinds of cases, and that counting fibers longer than 5 micrometers was apparently essential.

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: Laboratory study of lung dust from necropsy (autopsy) cases, comparing fiber concentration and fiber size by scanning electron microscopy (SEM) across six groups of cases
• Who was studied: 100 necropsy lung dust specimens: 22 normal lungs (no occupational asbestos exposure, used as controls), 22 spontaneous mesothelioma, 22 occupationally caused mesothelioma, 12 asbestosis with additional mesothelioma, 8 asbestosis with additional bronchial carcinoma, 14 asbestosis. Cases were assigned to groups on histopathology and on light-microscope counts of fibers 20 micrometers long and/or asbestos bodies. The readable text does not clearly state where and when the cases were collected.
• Exposure: Occupational asbestos exposure compared with no known occupational exposure. Fibers were counted at 10,000 times magnification by SEM and sorted by length and diameter. A fiber was defined as an elongated particle with a length-to-width ratio above 3 and parallel sides. Fiber types were not identified because microchemical analysis (EDXA) was not done.
• Main results:
  • Mean fiber concentration in lung dust increased from category 1 (normal lungs) to category 6 (asbestosis cases)
  • Fiber concentration in the occupationally caused mesothelioma cases was 10 times higher than in the spontaneous mesothelioma cases
  • Despite the different means, concentration could not practically distinguish spontaneous from occupationally caused mesothelioma, because the values were widely scattered. Standard deviations were high in most groups.
  • Fiber diameter distribution showed no significant difference among the groups
  • Fiber length distribution differed between the normally exposed groups and the categories occupationally exposed to asbestos. The article does not report a test of statistical significance for this difference.
  • For fibers longer than 5 micrometers, the transition between spontaneous and occupationally caused mesothelioma cases occurred at about 0.4 fibers per ng of dust
  • The range of overlap (transition) between the two groups became smaller as longer fibers were counted
• The authors' conclusion: The authors concluded that spontaneous and occupationally caused mesothelioma cases can be distinguished by counting the longer fibers in lung dust. They wrote that it is apparently essential to count fibers longer than 5 micrometers, and that it is not necessary to distinguish asbestos from non-asbestos fibers.
• Limitations the authors state:
  • Concentrations could not be expressed per total dust or per gram of dried lung, because in many cases only small portions of lung tissue were available, especially in exhumation cases
  • Fibers were not chemically analyzed (no EDXA), so fiber types were not identified

Topics

Medical terms in this study, explained in our Lexicon: Mesothelioma, Occupational Disease, Asbestos Exposure, Autopsy, Carcinoma, Fiber Length.

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