Malignancy In Relation To Crocidolite And Amosite

Our plain-English summary of Malignancy In Relation To Crocidolite And Amosite, by I. Webster (1973).

The study

• Author: I. Webster
• Published: Biological Effects Of Asbestos (J.C. Wagner, Editor), Lyon: Iarc Scientific Publications, Volume 8, Pp. 195-198 (1973)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library, J-M no. 002413. The article is still under copyright, so we describe it here rather than post it.

In plain English

This South African conference paper described where cancers occurred among people exposed to different types of asbestos. It drew on two sets of records and did not calculate rates. The first consisted of records of the Asbestos Tumour Reference Panel and the tumour registry at the National Research Institute for Occupational Diseases: of 375 confirmed mesothelioma cases, 360 were pleural. Eighty-eight had been linked to mining, mostly in Cape crocidolite (Cape Blue) mines. Two had worked with amosite only, and 47 had no known asbestos exposure. The second was autopsy examinations of miners' heart and lung organs. Bronchogenic (lung) carcinoma was found in 9 of 262 amosite miners, 6 of 61 Transvaal crocidolite miners and 3 of 74 chrysotile miners. The author said that if the figures were significant, which was unproven, lung cancer occurred in all asbestos areas, at percentages similar to gold miners'. Mesothelioma was confined mainly to the south and central Cape Blue fields. The author noted that not all deceased miners were represented, many had other mineral exposures, and most with smoking histories smoked.

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: Descriptive analysis of two case series: mesothelioma cases from tumour panel and registry records, and malignancies found in autopsy examinations of cardio-respiratory organs. No rates were calculated.
• Who was studied: South Africa. 375 confirmed mesothelioma cases (360 pleural) from records of the Asbestos Tumour Reference Panel and the tumour registry at the National Research Institute for Occupational Diseases. 1165 autopsy specimens examined since 1959. Asbestos miners' specimens from 1965 to 1971 were compared with gold miners.
• Exposure: Cape crocidolite (Cape Blue), Transvaal crocidolite (Transvaal Blue), amosite and chrysotile, through mining, other industry and environmental exposure in the northern Cape. No dose measurements were given.
• Main results:
  • 375 mesothelioma cases had been confirmed and registered; 360 of them were pleural mesotheliomas.
  • 88 of the 360 pleural mesothelioma cases had been associated with the mining industry, the majority with crocidolite mines of the northern Cape.
  • Two pleural mesothelioma cases had definitely had amosite service only.
  • 47 pleural mesothelioma cases had no known history of asbestos exposure, and this number was increasing.
  • Only three people with mesothelioma had worked at the most northern mine (Pomfret), although Pomfret and Koegas in the south had about the same workforce, about 1250 each.
  • Of 1165 autopsy specimens examined since 1959, 94 showed malignant disease: 61 bronchogenic carcinomas and 33 mesotheliomas.
  • Amosite miners, 1965 to 1971: bronchogenic carcinoma in 9 of 262 examined.
  • Transvaal crocidolite (Transvaal Blue) miners, 1965 to 1971: bronchogenic carcinoma in 6 of 61 examined (9.8 per cent).
  • Chrysotile miners, 1965 to 1971: bronchogenic carcinoma in 3 of 74 examined.
  • Although the series were small, the author described the percentages of bronchogenic carcinoma among those exposed to Transvaal crocidolite and South African chrysotile as high.
  • According to the author, the percentages of bronchogenic carcinoma in a comparable group of gold miners were similar to those in the asbestos areas.
• The authors' conclusion: The author stated these conclusions only on the condition that the figures were significant, which the author said had not been proven. On that basis, the author concluded that bronchogenic carcinoma occurred in all South African asbestos areas, while mesothelioma was confined mainly to the south and central parts of the Cape Blue fields. The author also noted that the manganese content of the asbestos rises from the southern Cape fields to the amosite area.
• Limitations the authors state:
  • The author stated the conclusions only if the figures were significant, and said this had not been proven.
  • Not all deceased miners were represented in the autopsy series.
  • The series was weighted toward ex-employees who attended mission hospitals or other health services.
  • Autopsies were more likely when tuberculosis was suspected.
  • 16 of the 29 lung cancer cases diagnosed in 1965 to 1971 had a history of exposure to other minerals.
  • A smoking history was available for only 14 patients; only two of them were non-smokers.
  • Mesotheliomas appeared to occur in family groups, but shared environmental exposure could not be excluded.

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Amosite, Cancer Registry, Occupational Disease, Mesothelioma, Cape Blue, Asbestos Exposure, Autopsy.

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