Epidemiology of malignant mesothelioma in Western Australia

Our plain-English summary of Epidemiology of malignant mesothelioma in Western Australia, by B.K. Armstrong, A.W. Musk, J.E. Baker, et al (The Medical Journal of Australia, 1984).

The study

• Authors: B.K. Armstrong, A.W. Musk, J.E. Baker, J.M. Hunt, C.C. Newall, H.R. Henzell, B.S. Blunsdon, M.D. Clarke-Hundley, S.D. Woodward, M.S. Hobbs
• Journal: The Medical Journal of Australia
• Published: 1984;141(2):86-8
• Cited by: 53 articles, as counted by NIH iCite
• Read it: PubMed
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 002551).

Abstract

Crocidolite was mined and milled at Wittenoom Gorge in Western Australia from 1943 to 1966. Between 1960-1964 and 1980-1982, the estimated incidence of malignant mesothelioma in Western Australia rose from 0.6/100 000 in men and less than 0.1/100 000 in women, aged 35 years or older, to 6.6/100 000 in men and 0.7/100 000 in women in this age group. Overall, 97 (70%) of 138 patients with malignant mesothelioma had definite or probable exposure to asbestos; 76 of these (55%) to Western Australian crocidolite. Of the latter 76 patients, 56 had worked in the mine or mill at Wittenoom and 4 had non-occupational exposure in the Wittenoom area; the remaining 16 had been exposed to crocidolite elsewhere in the State. There were only 4 (3%) patients with malignant peritoneal mesothelioma, of whom three had been exposed to crocidolite.

In plain English

This study described all cases of malignant mesothelioma diagnosed in Western Australia from 1960 to 1982. It examined the role of crocidolite mined and milled at Wittenoom Gorge, and of other asbestos. The authors identified 138 patients (125 men): 134 had malignant pleural mesothelioma and 4 had malignant peritoneal mesothelioma. Among people aged 35 or older, the estimated incidence rose between 1960–1964 and 1980–1982. In men it went from 0.6 to 6.6 per 100 000, and in women from less than 0.1 to 0.7 per 100 000. Of the 138 patients, 97 (70%) had definite or probable asbestos exposure, and 76 (55%) had exposure to Western Australian crocidolite. Of those 76, 56 had worked in the Wittenoom mine or mill, 4 had non-occupational exposure in the Wittenoom area, and 16 were exposed elsewhere in the State. Three of the four peritoneal cases had worked in the Wittenoom mine or mill. The authors concluded that the data showed an epidemic of pleural mesothelioma following the mining, milling and use of Wittenoom crocidolite. They noted that some cases may have been underdiagnosed, especially early on, and that exposure evidence may have been missed.

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: Population-based descriptive study of all diagnosed cases of malignant mesothelioma (incidence rates and asbestos exposure histories)
• Who was studied: 138 patients (125 men, 13 women) with malignant mesothelioma diagnosed in Western Australia between January 1, 1960 and December 31, 1982; 134 pleural and 4 peritoneal
• Exposure: Western Australian crocidolite from the Wittenoom Gorge mine and mill (mined and milled 1943 to 1966), through work there, non-occupational exposure near Wittenoom, or use elsewhere in the State; also other and unspecified asbestos
• Main results:
  • Among people aged 35 years or older, the estimated incidence in 1960–1964 was 0.6/100 000 in men and less than 0.1/100 000 in women.
  • By 1980–1982, the estimated incidence among people aged 35 or older had risen to 6.6/100 000 in men and 0.7/100 000 in women.
  • 97 (70%) of the 138 patients had definite or probable exposure to asbestos; 76 (55%) had exposure to Western Australian crocidolite.
  • Of the 76 patients exposed to Western Australian crocidolite, 56 had worked in the Wittenoom mine or mill, 4 had non-occupational exposure in the Wittenoom area, and 16 had been exposed to crocidolite elsewhere in the State.
  • Three of the four patients with malignant peritoneal mesothelioma had worked in the Wittenoom mine or mill; the fourth patient's exposure history was not known.
  • Over all ages in 1980–1982, incidence was 2.61/100 000 male population for men and 0.26/100 000 female population for women.
  • In 81 patients with certain asbestos exposure, the interval from first exposure to diagnosis ranged from 11 to 50 years (mean 25 years).
  • Duration of exposure at Wittenoom (occupational and environmental) ranged from two months to 29 years (mean 3.8 years).
  • Of the 13 women with malignant mesothelioma, four had been exposed to crocidolite at Wittenoom Gorge, three of them through environmental exposure.
• The authors' conclusion: The authors concluded that the data show the evolution of an epidemic of malignant pleural mesothelioma after the mining, milling and subsequent use of crocidolite from Wittenoom Gorge.
• Limitations the authors state:
  • Some underdiagnosis was possible, especially in the first 10 years of the study period, because clinicians and pathologists did not recognize the disease.
  • Occupational histories were not necessarily exhaustive, and evidence of exposure may have been missed in some cases.
  • Other patients may have had unidentified exposure to Western Australian crocidolite.
  • Peritoneal mesotheliomas may have been selectively underdiagnosed.

Topics

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

Medical terms in this study, explained in our Lexicon: Epidemiology, Mesothelioma, Crocidolite, Wittenoom, Non-Occupational Exposure, Peritoneal Mesothelioma.

Related studies

• Prevalence of radiographic asbestosis in crocidolite miners and millers at Wittenoom, Western Australia — W.O. Cookson, N.H. De Klerk, et al. (1986)
• Morphology of bronchogenic carcinoma in workers formerly exposed to crocidolite at Wittenoom Gorge in Western Australia — J.E. Baker, D.C. Reutens, et al. (1986)
• Malignant pleural and peritoneal mesotheliomas in former miners and millers of crocidolite at Wittenoom, Western Australia — G. Berry, N.H. de Klerk, et al. (2004)
• Malignant mesotheliomas in former miners and millers of crocidolite at Wittenoom (Western Australia) after more than 50 years follow-up — G. Berry, A. Reid, et al. (2012)
• Conventional treatment and its effect on survival of malignant pleural mesothelioma in Western Australia — A.W. Musk, S.D. Woodward (1982)
• Sputum asbestos bodies and radiographic changes in residents of Wittenoom, Western Australia — A.W. Musk, J.E. Baker, et al. (1983)

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