Malignant pleural mesothelioma in parts of Japan in relationship to asbestos exposure

Our plain-English summary of Malignant pleural mesothelioma in parts of Japan in relationship to asbestos exposure, by T. Kishimoto, S. Ozaki, K. Kato, et al (Industrial Health, 2004).

The study

• Authors: T. Kishimoto, S. Ozaki, K. Kato, H. Nishi, K. Genba
• Journal: Industrial Health
• Published: 2004;42(4):435-9
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Malignant pleural mesothelioma is induced by asbestos exposure. Many reports have described this situation in America and European countries, but a few have been published in Japan. In this study malignant pleural mesothelioma cases in hospitals located in an area facing the Seto Inland Sea were evaluated. A total of 106 patients were examined with 100 patients having had occupational exposure to asbestos and 6 patients without such histories of asbestos exposure. Ninety seven were male and 9 were female. Ages ranged from 41 to 87 yr with mean of 64.8+/-5.3 yr. Thirty seven cases showed epithelial type of tumor, 25 biphasic type and 15 showed sarcomatous. The remaining 23 cases had insufficient evidence for typing the tumor. The mean survival rate for all cases was 9.2+/-11.6 months. Fifty-one patients had occupational histories of shipyard work, 16 patients worked in asbestos cement piping, and the remainder were employed in miscellaneous jobs related asbestos exposure. The duration of asbestos exposure ranged up to 20 yr or longer with the mean of 17.2+/-8.9 yr and the average latent period for the occurrence of malignant pleural mesothelioma was more than 31 yr with the mean of 37.0+/-13.3 yr. Quantification of asbestos bodies in the lungs indicated a high concentration in most patients and the major types of asbestos fibers were crocidolite and amosite. Six cases appeared after exposure to chrysotile. These results indicated that ninety four percent of malignant pleural mesothelioma appeared due to the exposure to asbestos including crocidolite and amosite. The remainder may be blamed on exposure to chrysotile.

In plain English

This hospital case series reviewed 106 patients with malignant pleural mesothelioma diagnosed from 1980 to 1998 at Japanese hospitals near the Seto Inland Sea: 100 with occupational asbestos exposure and 6 without. The commonest jobs were commercial shipbuilding (38), asbestos cement pipe manufacturing (16) and Kure naval shipyard work (14). Cement pipe workers were diagnosed younger than shipyard workers (mean 56.9 versus 69.5 years). In the 54 patients tabulated, mean survival from first hospital visit to death was 9.2 months, longer for epithelial than sarcomatous tumors. Mean exposure duration was 17.2 years (70 patients with data) and mean time from first exposure to mesothelioma 37.0 years (73 patients). Of 39 patients whose lungs were analyzed after surgery or autopsy, 38 had over 500 asbestos bodies per 5 grams of wet lung. The main fiber was crocidolite in 20, amosite in 13 and chrysotile in 6; those 6 also contained other asbestos types and tremolite. The authors concluded that chrysotile should be considered a cause of this disease. Some figures differ between the abstract, text and tables.

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: clinical review of hospital cases of malignant pleural mesothelioma, with lung asbestos body and fiber analysis in a subset
• Who was studied: 106 patients with malignant pleural mesothelioma (100 with occupational asbestos exposure, 6 without; 97 male, 9 female). They were diagnosed from 1980 to the end of December 1998 at several hospitals in prefectures facing the Seto Inland Sea, western Honshu, Japan.
• Exposure: Occupational asbestos exposure, mainly commercial shipbuilding (38), asbestos cement pipe manufacturing (16), the Japanese naval shipyard in Kure (14) and construction (7), plus other jobs. Lung fiber types (crocidolite, amosite, chrysotile, tremolite) were identified by electron microscopy in 39 cases.
• Main results:
  • Asbestos cement piping workers were younger at diagnosis than shipyard workers: mean 56.9 plus or minus 6.6 years versus 69.5 plus or minus 9.7 years (p less than 0.01).
  • Survival was measured from first hospital visit to death. The text calls 9.2 plus or minus 11.6 months the mean for all cases, but Table 1 gives this figure as the total for 54 patients. Survival ranged from 10 days to 60 months, and 43 cases (stated as 72%) died within 12 months.
  • Of the 54 cases in the survival table, epithelial-type tumors (26 cases, 12.3 plus or minus 5.7 months) had significantly longer survival than sarcomatous-type tumors (10 cases, 5.5 plus or minus 5.8 months), p less than 0.05.
  • Asbestosis was found in 14 asbestos cement piping workers (14 of 16, per the discussion) but in only 3 shipyard workers.
  • Among cases with full data, mean duration of asbestos exposure was 17.2 plus or minus 8.9 years (Table 3 covers 70 cases). Latency from first exposure to mesothelioma ranged from 15 to 72 years, averaging 37.0 plus or minus 13.3 years (Table 3 covers 73 cases).
  • Of the 39 cases with lung tissue analysis, 38 exceeded 500 asbestos bodies per 5 grams of wet lung tissue, and 23 exceeded 10,000.
  • 38 of the 39 cases had over 1 million asbestos fibers per gram of dry lung tissue.
  • Of the 39 analyzed cases, the main fiber was chrysotile in 6, crocidolite in 20 and amosite in 13.
  • The 6 chrysotile cases were 4 construction workers and 2 piping workers. All 6 had epithelial-type tumors, and their lungs also contained the other two asbestos types and tremolite.
  • The 6 cases without occupational asbestos exposure were 4 females and 2 males, aged 35 to 71 years (mean 54.2 plus or minus 6.8). Four were housekeepers, one a teacher and one a farmer.
  • 94 percent of the malignant pleural mesothelioma cases had a history of asbestos exposure.
• The authors' conclusion: The authors concluded that, besides crocidolite and amosite, chrysotile should be considered a cause of malignant pleural mesothelioma. They also said that construction and asbestos manufacturing workers should be examined earlier and more often.
• Limitations the authors state:
  • The authors said it should be re-examined whether all 6 'non-exposed' cases truly lacked asbestos exposure, for example the school teacher.
  • Chrysotile clears from the body easily, so lung asbestos content may not reflect the dose actually received.
  • Tumor type could not be determined in 23 cases because the tissue came only from needle biopsy.

Topics

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

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Asbestos Exposure, Occupational Exposure, Biphasic Mesothelioma, Asbestos-Cement, Asbestos Bodies, Crocidolite, Amosite.

Related studies

• Survival and prognostic factors in malignant pleural mesothelioma: a retrospective study of 314 patients in the west part of Japan — S. Nojiri, K. Gemba, et al. (2011)
• Incidence of interstitial lung disease in patients with mesothelioma in the west part of Japan — S. Nojiri, K. Gemba, et al. (2011)
• Clinical investigation of malignant mesothelioma in Japan — N. Fujimoto, K. Aoe, et al. (2010)
• Malignant mesotheliomas in Kure City, Japan: the relationship of asbestos exposure — T. Kishimoto, T. Sato, et al. (1989)
• Treatment and survival analyses of malignant mesothelioma in Japan — K. Gemba, N. Fujimoto, et al. (2013)
• National survey of malignant mesothelioma and asbestos exposure in Japan — K. Gemba, N. Fujimoto, et al. (2012)

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