A Survey Of Black Mineworkers Of The Cape Crocidolite Mines

Our plain-English summary of A Survey Of Black Mineworkers Of The Cape Crocidolite Mines, by J.M. Talent, W.O. Harrison, A. Solomon, et al (1980).

The study

• Authors: J.M. Talent, W.O. Harrison, A. Solomon, I. Webster
• Published: Biological Effects Of Mineral Fibres (J.C. Wagner, Editor), Lyon: Iarc Scientific Publications, Volume 30, Pp. 723-729 (1980)
• Type of article: Conference paper
• Our copy: from Johns-Manville's own medical library, J-M no. 002187. The article is still under copyright, so we describe it here rather than post it.

In plain English

Begun in 1974, this survey studied Black employees and ex-employees of Cape crocidolite (blue asbestos) mines recruited before July 1962 and living near Kuruman, South Africa, an area the article placed in Bophuthatswana. Of 1185 people listed, 215 had died before the survey and 755 were fully examined. Some had also worked in gold, manganese or lime mines. X-rays of the 755 showed no abnormality in 66.1%, irregular small opacities only in 8.9%, pleural abnormalities only in 17.7%, and both in 7.3%. Four had pleural mesothelioma when first examined, a prevalence of 0.5%. Two more cases were found later. One lung cancer was found in the study group. Outside the study group, 11 of 947 other former mineworkers and 12 of 53 hand-cobbers examined had pleural mesothelioma. The authors cautioned that some of the 947 may have come forward feeling ill. The hand-cobber figure, they said, cannot be regarded as actual prevalence, since these cases presented as ill patients. With most causes of death unknown, no cohort study was possible. The authors considered the single mesothelioma death found an underestimate.

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: Clinical and radiological survey of employees and ex-employees (the authors state a cohort study was not possible)
• Who was studied: 1185 Black employees or ex-employees of Cape crocidolite mines recruited before July 1962. They were drawn from the registers of four mines and limited to citizens of Bophuthatswana (excluding migrant labour) living within 100 km of Kuruman, South Africa. The article described the area as part of Bophuthatswana. Of the 1185, 755 were examined with all parameters available.
• Exposure: Work on the Cape crocidolite (blue asbestos) mines before July 1962. Most had a relatively short exposure but a long time since first exposure; 65.0% were first exposed 16 to 20 years earlier. Some had also worked in gold, manganese and lime mining.
• Main results:
  • Of the 1185 in the study group, 215 (18.1%) had died before the survey and 755 (63.7%) were examined with all parameters available.
  • Among the 755 examined, 499 (66.1%) had no radiological abnormality.
  • Among the 755 examined, 8.9% had irregular small opacities only.
  • Among the 755 examined, 17.7% had pleural abnormalities only and 7.3% had both irregular small opacities and pleural abnormality.
  • Four of the 755 examined had pleural mesothelioma when they first presented, a prevalence of 0.5%. One more study-group member was diagnosed during the survey and another soon after it stopped, six cases in all.
  • Among 947 further ex-employees of the mining industry who were not on the study list, 11 had pleural mesothelioma.
  • 12 of 53 hand-cobbers examined had pleural mesothelioma. The authors said this figure cannot be regarded as the actual prevalence because these cases presented as ill patients.
  • One case of bronchogenic carcinoma was found in the study group, in an ex-smoker who had worked on the asbestos mines for 8.3 years and on the gold mines for 4.5 years.
• The authors' conclusion: The authors considered that the single mesothelioma death found among the 215 deceased was an underestimate, and that there were probably more mesothelioma deaths.
• Limitations the authors state:
  • The cause of death was known only if the employee died in hospital, so it was unknown for most of the 215 deceased and a cohort study could not be done.
  • Some ex-employees outside the study group may have come to the clinic more readily because they knew of the survey or felt ill.
  • The 12 of 53 figure for hand-cobbers cannot be regarded as their actual prevalence of mesothelioma, because these cases presented as ill patients.

Topics

Medical terms in this study, explained in our Lexicon: Crocidolite, Pleural Mesothelioma, Lung Cancer, Cohort Study, Mesothelioma.

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