Prediction of mesothelioma, lung cancer, and asbestosis in former Wittenoom asbestos workers

Our plain-English summary of Prediction of mesothelioma, lung cancer, and asbestosis in former Wittenoom asbestos workers, by G. Berry (British Journal of Industrial Medicine, 1991).

The study

• Author: G. Berry
• Journal: British Journal of Industrial Medicine
• Published: 1991;48(12):793-802
• Cited by: 43 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004147).

Abstract

Projections have been made of the number of mesotheliomas, lung cancers, and cases of asbestosis that might occur over the period 1987 to 2020 in former workers at the Wittenoom crocidolite asbestos mine in Western Australia. Predictions were based on the observed mortality to the end of 1986 and modelling of the mesothelioma rate. Elimination of crocidolite from the lungs was included in the model. Between the years 1987 and 2020 it is predicted that between 250 and 680 deaths will occur due to mesothelioma. This wide range is due to uncertainty on the functional form of the relation between mesothelioma rate and time, and insufficient data to estimate the elimination rate of crocidolite from the lungs. The most likely range is the lower half of this total range--that is, between 250 and 500. It is predicted that between 340 and 465 deaths will occur due to lung cancer. About 45% of these deaths would be attributable to exposure to asbestos. It is estimated that currently there are up to 200 cases of undiagnosed asbestosis. Of these about 50 will die of lung cancer or mesothelioma and are therefore also included in the figures above. Up to 60 former workers may develop the first signs of asbestosis in the future but any such cases are likely to progress to more serious disease at a much slower rate than the cases that have already been identified.

In plain English

This paper projected mesothelioma and lung cancer deaths and asbestosis cases for 1987 to 2020 among former Wittenoom crocidolite mine workers in Western Australia. Records covered 6501 men and 410 women to 1986, but vital status was unconfirmed for about a third of men and almost half of women. Among 6258 men followed over 10 years, 983 deaths were recorded, 122 from lung cancer and 84 from mesothelioma. Suspecting missed deaths, the author assumed 4982 men alive in 1987. Predicted mesothelioma deaths in men ranged from 255 to 654. The author rejected the zero-lag model giving 654 as unrealistic, and a lag of at least five years gave 573 at most. About 450 lung cancer deaths were predicted, or 336 if background rates fell 2% a year. About 45% were attributed to asbestos, assuming smoking habits like other men's. The author estimated 70 to 200 undiagnosed asbestosis cases and, at worst, 60 workers who might develop first signs, likely progressing slowly. The author concluded that mesothelioma would be the major continuing toll, while noting the wide range of predictions.

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: Mortality projection (modelling) study using cohort follow-up data, with Poisson modelling of observed mortality and year-by-year projection of future deaths
• Who was studied: Former workers employed in producing crocidolite asbestos at Wittenoom, Western Australia, between 1943 and 1966: 6501 men and 410 women, with follow-up to the end of 1986. After adjustment for probable undetected deaths, 4982 men were assumed alive on 1 January 1987.
• Exposure: Crocidolite asbestos from mining and milling at Wittenoom, measured as cumulative exposure in fibre-years/ml. This was calculated from total days worked and the average intensity of exposure.
• Main results:
  • Among 6258 men followed for more than 10 years after first employment, there were 983 recorded deaths: 122 from lung cancer and 84 from mesothelioma.
  • An apparent deficit of deaths at age 65 and older was attributed to undetected deaths. The men assumed alive on 1 January 1987 were therefore reduced from a maximum of 5172 to 4982.
  • If working at Wittenoom had caused no asbestos-related deaths, the model predicted 4088 deaths in men by 2020, 315 (7.7%) of them from lung cancer.
  • Predicted mesothelioma deaths in men by 2020 were 654 (15.1%), 573 (13.3%) and 441 (10.4%) for lag periods of zero, five and 10 years respectively.
  • The author regarded the zero-lag model, which gave 654, as unrealistic for prediction. Allowing a lag of at least five years reduced the upper limit to 573 mesotheliomas in men.
  • Models allowing for elimination of crocidolite from the lungs (6.8% and 15% per year) predicted 383 and 255 mesothelioma deaths respectively.
  • About 10 to 12 mesotheliomas were predicted in women by 2020.
  • About 450 lung cancer deaths were predicted in men by 2020 based on current background rates.
  • Assuming background lung cancer rates declined by 2% a year, 336 lung cancer deaths were predicted.
  • Using an overall lung cancer SMR of 1.79, about 45% of lung cancer deaths (about 200 of the predicted 450) were attributed to asbestos exposure. This assumed the workers had smoking habits similar to other men of the same age.
  • The author estimated 70 to 200 existing undiagnosed asbestosis cases.
  • Under a worst-case assumption, another 60 former workers could develop the first detectable signs of asbestosis in the future, and these cases would be expected to progress slowly.
• The authors' conclusion: The author concluded that, even using the lowest predicted number of mesotheliomas, deaths from mesothelioma would be the major continuing toll of the Wittenoom crocidolite mine. The article's abstract gives the most likely range of mesothelioma deaths as 250 to 500.
• Limitations the authors state:
  • The range of predictions is wide and will only narrow as more data accumulate.
  • The data could not determine whether a lag period should be included, because lags from zero to 10 years all fitted well.
  • The data were insufficient to estimate the rate of elimination of crocidolite from the lungs precisely.
  • Vital status was unconfirmed for about a third of the men and almost half of the women at the end of 1986.
  • The exposure measure was imperfect, and the absolute fibre concentrations were underestimates.
  • The lung cancer estimates assumed the workers had smoking habits similar to other men of the same age.
  • The agreement between the two asbestosis estimates was partly fortuitous, and the asbestosis predictions may be too high.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Wittenoom, Western Australia

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis, Crocidolite, Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, Lung Cancer, Wittenoom, Crocidolite.

Related studies

• The natural history of asbestosis in former crocidolite workers of Wittenoom Gorge — W. Cookson, N. De Klerk, et al. (1986)
• Prediction of mesothelioma, lung cancer, and asbestosis in former Wittenoom asbestos workers — A. Rogers (1992)
• Mortality of former crocidolite (blue asbestos) miners and millers at Wittenoom — A.W. Musk, N.H. de Klerk, et al. (2008)
• 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)
• The additional risk of malignant mesothelioma in former workers and residents of Wittenoom with benign pleural disease or asbestosis — A. Reid, N. de Klerk, et al. (2005)

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