Fiber analysis in lungs of residents of a Japanese town with endemic pleural plaques

Our plain-English summary of Fiber analysis in lungs of residents of a Japanese town with endemic pleural plaques, by Y. Murai, M. Kitagawa, T. Hiraoka (Archives of Environmental Health, 1997).

The study

• Authors: Y. Murai, M. Kitagawa, T. Hiraoka
• Journal: Archives of Environmental Health
• Published: 1997;52(4):263-9
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The authors analyzed various types of fibers in lung-tissue samples, which were obtained from 50 cases (46 surgical resections and 4 autopsies) at Kumamoto-Minami Hospital in Matsubase, where the occurrence of pleural plaques is endemic. Lung cancer necessitated surgical resection in 44 cases. Eleven of the 50 cases were residents of Matsubase; 15 resided in the region around the town, where the frequency of pleural plaques was slightly higher; and 24 cases lived in a region with normal plaque frequency. The number of anthophyllite fibers in the lungs of town residents was significantly higher than in residents of the region with normal plaque frequency. In 6 cases, the authors found accompanying pleural plaques, and the anthophyllite fiber count in the lungs in these cases was significantly higher than in cases without plaques. In addition, the anthophyllite fiber counts in 2 cases with severe plaques were significantly higher in 4 cases with only mild plaques. These results suggested that anthophyllite fiber might be responsible for the increased prevalence of pleural plaques in Matsubase. Even though the anthophyllite fibers were quite long (mean length = 25.1 microm), the width of most anthophyllite fibers were thick (mean diameter = 0.84 microm). Therefore, the aspect ratio of anthophyllite (mean = 38.7) was lower than that of amosite (mean = 81.8), which, in a previous report, was found predominantly in cases of pleural mesothelioma. Perhaps these differences in fiber size are related to the strength of the carcinogenicity to the pleura.

In plain English

This Japanese study measured asbestos bodies and fibers in lung tissue from 50 patients at Kumamoto-Minami Hospital in Matsubase, a town with endemic pleural plaques and three former asbestos mines (one anthophyllite, two chrysotile). Most samples came from lung cancer surgery, and 4 came from autopsies. Eleven patients lived in Matsubase, 15 in the surrounding area, and 24 in a region with normal plaque frequency. Only 1 patient had been exposed to asbestos at work. Matsubase residents had significantly more anthophyllite fibers than residents of the normal-frequency region. Six patients had pleural plaques. In them, anthophyllite made up 90.2% of asbestos fibers. In patients without plaques it made up 13.7%, and their fibers were mostly tremolite-actinolite (81.4%). The 2 patients with severe plaques had significantly more anthophyllite than the 4 with mild plaques. The authors concluded that anthophyllite might be responsible for the town's plaques. They speculated that its cancer-causing effect may be weaker than amosite's. They noted that their method would have overlooked short fibers and long, thin fibers.

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: Lung-tissue fiber analysis (asbestos body counts by light microscopy, fiber counts and sizing by electron microscopy) comparing hospital patients grouped by area of residence and by presence and severity of pleural plaques
• Who was studied: 50 patients at Kumamoto-Minami Hospital, Kumamoto Prefecture, southwestern Japan. Samples came from 44 lung cancer resections, 2 resections for bronchial inflammatory polyp and bronchiectasia, and 4 autopsies. Group A was 11 residents of Matsubase, group B was 15 residents of the surrounding region (slightly higher than normal plaque frequency), and group C was 24 residents of a region with normal plaque frequency. Many patients were farmers.
• Exposure: Mainly non-occupational, residential exposure. Matsubase formerly had one anthophyllite and two chrysotile asbestos mines. Fibers measured were anthophyllite, tremolite-actinolite (not distinguished from each other), amosite, crocidolite, chrysotile and nonasbestos fibers. Only 1 patient, a Matsubase resident with pleural plaques, had occupational asbestos exposure.
• Main results:
  • Compared with group C (normal plaque frequency), group A (Matsubase residents) had significantly higher numbers of asbestos bodies, anthophyllite fibers, total asbestos fibers and nonasbestos fibers. Group B had significantly more nonasbestos fibers than group C.
  • Pleural plaques were found in 6 of the 50 cases: 5 in group A, 1 in group B and none in group C. Plaque frequency differed significantly between the three regions (chi-square 15.335).
  • The 6 cases with plaques were significantly older than the 44 without plaques. They also had significantly more asbestos bodies, anthophyllite, amosite, total asbestos and nonasbestos fibers. In cases with plaques, anthophyllite was 90.2% of asbestos fibers. In cases without plaques, tremolite-actinolite was 81.4% and anthophyllite 13.7%.
  • The 2 cases with severe plaques had significantly higher anthophyllite and total asbestos fiber counts than the 4 cases with mild plaques. Mean anthophyllite per 5 g wet lung tissue was 1.0 x 10^6 in severe cases versus 1.6 x 10^5 in mild cases (p less than .01). Asbestos body counts did not differ significantly by plaque severity.
  • Anthophyllite fibers had a mean length of 25.1 micrometres, a mean diameter of 0.84 micrometres and a mean aspect ratio of 38.7. This aspect ratio was lower than that of amosite (81.8) and crocidolite (165.3). The share of fibers with an aspect ratio over 100 was 5.7% for anthophyllite, 31.1% for amosite and 47.0% for crocidolite.
• The authors' conclusion: The authors concluded that anthophyllite fibers might be responsible for the increased prevalence of pleural plaques in Matsubase. Comparing these cases with their earlier report on pleural mesothelioma cases, they speculated that anthophyllite's carcinogenic effect may be less than amosite's, and that differences in fiber size may relate to the strength of carcinogenicity to the pleura.
• Limitations the authors state:
  • The lower magnification used for screening would have missed short fibers and long, thin fibers. Chrysotile fibers are usually short with small diameters.
  • No standard sample was available for tremolite and actinolite, so these two fiber types were not distinguished.
  • Fiber length or diameter could not be measured for some fibers, for example when their edges were hidden by other minerals or the fibers were totally coated.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Endemic, Pleural Plaques, Surgical Resection, Matsubase, Lung Cancer, Anthophyllite, Aspect Ratio (Length-to-diameter ratio), Amosite.

Related studies

• Environmental pleural plaques in residents of a Quebec chrysotile mining town — A. Churg, L. DePaoli (1988)
• Lung asbestos content in long-term residents of a chrysotile mining town — A. Churg (1986)
• Significant relationship between the extent of pleural plaques and pulmonary asbestos body concentration in lung cancer patients with occupational asbestos exposure — T. Yusa, K. Hiroshima, et al. (2015)
• Coated and uncoated lung mineral fibres in subjects with and without pleural plaques at autopsy — A. Andrion, D. Bellis, et al. (1984)
• Pulmonary asbestos and non-asbestos fiber concentrations in autopsied inhabitants in Pohang, Korea — H.S. Lim, J.Y. Kim, et al. (2004)
• A retrospective study on radiological findings of diffuse pleural thickening with benign asbestos pleural effusion in Japanese cases — T. Kishimoto, K. Kato, et al. (2022)

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