Asbestos fiber analysis in 27 malignant mesothelioma cases

Our plain-English summary of Asbestos fiber analysis in 27 malignant mesothelioma cases, by Y. Murai, M. Kitagawa (American Journal of Industrial Medicine, 1992).

The study

• Authors: Y. Murai, M. Kitagawa
• Journal: American Journal of Industrial Medicine
• Published: 1992;22(2):193-207
• Cited by: 17 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The asbestos body counts per 5 gm wet lung tissue in 27 (23 pleural and 4 peritoneal) malignant mesothelioma cases derived from 19 autopsy and 8 surgical cases were, according to our own criteria, low level exposure in 13 cases (48.2%), moderate level exposure in 2 cases (7.4%), and high level exposure in 12 cases (44.4%). In our previous study on 235 consecutive autopsy cases, the low level exposure was considered to be environmental, the moderate level was secondary or blue collar, and the high level was occupational. In the present study, about half of the cases examined (44.4%, high level exposure) are closely related to some occupational asbestos exposure and the other half (48.2%) to environmental exposure. The type and size of asbestos fibers from the 12 cases of high level exposure were analyzed and the characteristics were compared with those of cases of low level exposure without lung cancer or mesothelioma. Most fibers analyzed (98%) were longer than 5 microns and thicker than 0.10 micron by our counting rules. In the control group, predominant fibers were tremolite or actinolite. In all the 11 pleural mesothelioma cases, the content of amosite fibers was significantly higher than in the controls. In one case of peritoneal mesothelioma, incipient asbestosis was found and the predominant fibers were crocidolite. It is suggested that the presence of amosite and crocidolite is linked to mesothelioma. The mean lengths of amosite and crocidolite, as detected by our resolution capabilities, were 36.0 and 20.9 microns, and the mean diameters were 0.51 and 0.27 micron, respectively. Both amosite and crocidolite fibers had high aspect ratios (94.2 and 115.4).

In plain English

This Japanese study measured asbestos in the lungs of 27 people with malignant mesothelioma (23 pleural, 4 peritoneal). By their own asbestos-body cut-offs, the authors rated 13 cases (48.2%) low, 2 (7.4%) moderate and 12 (44.4%) high exposure. Based on an earlier study, they considered high-level counts occupational and low-level counts environmental. For the 12 high-exposure cases only, they compared fiber types with 30 autopsy controls with low-level exposure and no lung cancer or mesothelioma. Of these, the 11 pleural cases averaged 51.3% amosite, 31.9% tremolite-actinolite and 14.6% crocidolite. Amosite was significantly higher than in controls in all 11. In the controls, most fibers were tremolite-actinolite (74%). The one peritoneal case among them, an insulation worker with asbestosis, had 89% crocidolite. For fibers meeting the counting rules (at least 5 microns long and 0.10 micron thick), mean lengths were 36.0 microns for amosite and 20.9 microns for crocidolite. Little chrysotile was found, possibly because the magnification was too low to detect it. The authors suggested that amosite and crocidolite are associated with the development of mesothelioma.

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: Case series measuring lung asbestos burden in mesothelioma cases. Asbestos bodies were counted by light microscopy in all 27 cases. Fiber type and size were analyzed by electron microscopy in the 12 high-exposure cases and compared with low-exposure autopsy controls.
• Who was studied: 27 malignant mesothelioma cases (23 pleural, 4 peritoneal; 19 autopsy, 8 surgical; 22 men and 5 women, mean age 60.9). Twenty came from Toyama Medical and Pharmaceutical University Hospital and affiliated hospitals in Toyama, Japan, and 7 from consultations. The 30 controls (12 male, 18 female, mean age 64.7) were low-exposure autopsy cases without lung cancer or mesothelioma.
• Exposure: Asbestos bodies per 5 g wet lung tissue, grouped by the authors' criteria as low (40 or fewer), moderate (41 to 150) and high (151 or more). In the 12 high-exposure cases, fibers were typed as amosite, crocidolite, tremolite-actinolite, anthophyllite and chrysotile. Occupations in the high group included former Japan National Railway workers, ironworkers and an insulation worker.
• Main results:
  • By asbestos body counts, 13 of the 27 cases (48.2%) were low-level exposure, 2 (7.4%) moderate-level and 12 (44.4%) high-level.
  • Asbestos body counts and asbestos fiber counts correlated (r = 0.858, p less than 0.01), although their ratio was not always constant.
  • In the 11 high-exposure pleural mesothelioma cases, mean fiber percentages were amosite 51.3%, tremolite-actinolite 31.9% and crocidolite 14.6%, with a wide range between cases.
  • Compared with controls, amosite was significantly higher in all 11 high-exposure pleural cases and crocidolite was significantly higher in seven. Tremolite-actinolite fell within the controls' range in about half the cases.
  • In the 30 controls, tremolite-actinolite was the most frequent fiber type (74%).
  • In the single high-exposure peritoneal case (a 50-year-old former insulation worker of 11 years, the only case with asbestosis, 2.72 million asbestos bodies per 5 g), 89% of fibers were crocidolite and the next most common was amosite.
  • Only fibers at least 5 microns long and at least 0.10 micron in diameter were included in the counting procedure, and fiber sizes were measured on those fibers.
  • In the high-exposure cases, 98% of analyzed fibers were longer than 5 microns and thicker than 0.10 micron. Among the counted fibers, mean lengths were 36.0 microns (amosite) and 20.9 microns (crocidolite), and mean diameters were 0.51 and 0.27 micron. Mean aspect ratios were 94.2 (amosite) and 115.4 (crocidolite), compared with 21.0 for tremolite-actinolite.
  • Chrysotile was found only in small quantity, and no asbestos bodies formed on chrysotile fibers were found.
  • No clear-cut relationship was seen between the tumor's microscopic type and the level of asbestos exposure.
  • At the two hospitals, mesothelioma was found in 8 of 2,107 adult autopsies (0.38%) from October 1979 to December 1988. The authors described this frequency as high, for reasons not yet known.
• The authors' conclusion: The authors suggested that the presence of amosite and crocidolite is associated with mesothelioma development. They also said it is possible that at least half the cases in their series are related to asbestos exposure.
• Limitations the authors state:
  • At the 2,000-times magnification used, most fibers shorter than 2 to 3 microns could not be seen.
  • The small amount of chrysotile found may reflect chrysotile breaking down in the body, or a magnification too low to detect it.
  • Tremolite and actinolite could not be told apart and were reported together.
  • The ratio of asbestos body counts to fiber counts was not always constant.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma, Peritoneal mesothelioma.

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Asbestos Body Formation, Autopsy, Asbestos Exposure, Environmental Exposure, Lung Cancer, Mesothelioma, Tremolite.

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