Chrysotile asbestos and health in Zimbabwe: I. Analysis of miners and millers compensated for asbestos-related diseases since independence (1980)

Our plain-English summary of Chrysotile asbestos and health in Zimbabwe: I. Analysis of miners and millers compensated for asbestos-related diseases since independence (1980), by M.R. Cullen, R.S. Baloyi (American Journal of Industrial Medicine, 1991).

The study

• Authors: M.R. Cullen, R.S. Baloyi
• Journal: American Journal of Industrial Medicine
• Published: 1991;19(2):161-9
• Cited by: 21 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 003785).

Abstract

Data on the health effects caused by locally mined chrysotile asbestos in Zimbabwe have been very limited. The prevailing local view has been that risk is minimal. In this report we critically reassess the cases of 51 individuals with asbestos exposure who have been compensated by the Central Pneumoconiosis Bureau since independence in 1980. Results demonstrate that the major health risks of exposure reported elsewhere--morbid asbestosis, nonmalignant pleural disease, malignant mesothelioma, and lung cancer--all occur in Zimbabwe, at least among workers in the asbestos mines and mills. It is concluded that further investigation and control measures in the industry are warranted.

In plain English

The authors reviewed records of men certified by Zimbabwe's Pneumoconiosis Bureau since 1980 as having occupational lung disease, to see whether diseases linked to asbestos elsewhere occur among workers exposed to locally mined chrysotile. Of about 300 certified men, 54 had worked at an asbestos mining or manufacturing facility; full records existed for 51. Of these, 27 had findings consistent with asbestos-associated disease: three had pleural plaques, 21 had asbestosis, and three had features of chest cancer, one proven malignant mesothelioma and two without a pathologic diagnosis. Of 18 asbestosis cases exposed only in Zimbabwean mines or mills, eight had died by 1988: three from likely malignancies (one confirmed mesothelioma) and five from respiratory failure or cor pulmonale. Only two of the six apparent cancers, both mesotheliomas, were confirmed by pathology. The authors noted that compensation records miss many cases, especially milder ones and workers who left the industry, and that diagnoses relied on one clinician. They concluded that asbestosis, mesothelioma, nonmalignant pleural disease and lung cancer all appear to occur among workers exposed only to Zimbabwe's chrysotile industry, though little could be said about cancer rates.

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: review of workers' compensation records, X-ray files and medical records of men certified by the national Pneumoconiosis Bureau
• Who was studied: Of about 300 men certified by Zimbabwe's Pneumoconiosis Bureau as having occupational lung disease since 1980, 54 had worked at an asbestos mining or manufacturing facility. Complete records were available for 51, who formed the study population. The table covers cases certified between 1980 and 1987.
• Exposure: Work at Zimbabwean asbestos mines, mills or manufacturing facilities handling locally mined chrysotile asbestos. The final analysis was limited to men exposed exclusively at a Zimbabwe asbestos mine or mill. Among the 18 asbestosis cases with only Zimbabwe mine or mill exposure, exposure lasted 17 to 37 years (mean 22.3).
• Main results:
  • Among the 51 men, ten had tuberculosis, eight met radiographic criteria for silicosis, and six had diseases not primarily associated with dust or fiber exposure.
  • 27 of the 51 men had findings consistent with one or more asbestos-associated diseases.
  • Three men, all exposed only in Zimbabwean mines and/or mills, had asbestos-associated pleural plaques without parenchymal changes. All were alive and working, apparently without impairment.
  • Three men with otherwise normal X-rays presented with clinical and radiographic features of chest malignancies. One was proven at open resection to be malignant mesothelioma. The other two never received a pathologic diagnosis: one resembled mesothelioma on X-ray, the other a primary bronchogenic tumor.
  • Twenty-one men had asbestosis. One had been exposed making asbestos cement only, and two had been extensively exposed outside Zimbabwe. The other 18 had been exposed exclusively in Zimbabwe mines and/or mills.
  • Of the 18 asbestosis cases with only Zimbabwe mine or mill exposure, eight were dead by 1988: three from likely malignancies (one confirmed mesothelioma) and five from progressive respiratory failure and/or cor pulmonale.
  • Among the ten survivors in that group of 18, all but three had ILO profusion grade 1/2 or greater at diagnosis.
  • In the 18 asbestosis cases, exposure lasted 17 to 37 years (mean 22.3), and latency before the disease was recognized was 17 to 42 years (mean 27.2).
  • Of the six apparent malignancies in the series, only two, both malignant mesotheliomas, were pathologically confirmed.
• The authors' conclusion: The authors concluded that the data appear to confirm that asbestosis, mesothelioma, nonmalignant pleural disease and lung cancer all occur among Zimbabweans exposed exclusively to the domestic chrysotile industry. They stated that this was the first report to confirm these outcomes, and that it should prompt diagnostic vigilance among physicians and enhanced surveillance at the mines and nationally. They added that very little could be said quantitatively about the cancers.
• Limitations the authors state:
  • Compensation records under-recognize disease. Workers who quit or retired, most of whom return to their home regions, are not followed up.
  • Lung cancer and mesothelioma were not formally listed as compensable, which could further reduce reporting of these conditions.
  • The series severely underrepresents workers with milder (grade 1) X-ray changes. The Bureau tends to identify moderate or more severe cases.
  • Diagnoses relied on limited records and on a single clinician (one of the authors) as the diagnostic standard. Other causes of asbestosis could rarely be excluded.
  • Cancer case finding and confirmation were far from complete. There were also no adequate mortality data for unexposed men for comparison.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Asbestos Exposure, Pneumoconiosis, Mesothelioma, Lung Cancer.

Related studies

• Chrysotile asbestos and health in Zimbabwe: II. Health status survey of active miners and millers — M.R. Cullen, L. Lopez-Carrillo, et al. (1991)
• Fiber burden and patterns of asbestos-related disease in chrysotile miners and millers — A. Churg, J.L. Wright, et al. (1993)
• Prediction of Asbestos-Related Diseases (ARDs) and Chrysotile Asbestos Exposure Concentrations in Asbestos-Cement (AC) Manufacturing Factories in Zimbabwe — B. Mutetwa, D. Moyo, et al. (2022)
• The 1891-1920 birth cohort of Quebec chrysotile miners and millers: development from 1904 and mortality to 1992 — F.D. Liddell, A.D. McDonald, et al. (1997)
• The 1891-1920 birth cohort of Quebec chrysotile miners and millers: mortality 1976-88 — J.C. McDonald, F.D. Liddell, et al. (1993)
• Mineralogic correlates of fibrosis in chrysotile miners and millers — A. Churg, J.L. Wright, et al. (1989)

Browse more research in American Journal of Industrial Medicine, or return to medical research.