Predicted mortality from malignant mesothelioma among women exposed to blue asbestos at Wittenoom, Western Australia

Our plain-English summary of Predicted mortality from malignant mesothelioma among women exposed to blue asbestos at Wittenoom, Western Australia, by A. Reid, G. Berry, J. Heyworth, et al (Occupational and Environmental Medicine, 2009).

The study

• Authors: A. Reid, G. Berry, J. Heyworth, N.H. de Klerk, A.W. Musk
• Journal: Occupational and Environmental Medicine
• Published: 2009;66(3):169-74
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Introduction: Nearly 3000 women and girls were documented to have lived at the blue asbestos mining and milling town of Wittenoom in Western Australia between 1943 and 1992. Eight per cent of deaths among these women to the end of 2004 have been from malignant mesothelioma of the pleura.

Aim: To predict future mortality from mesothelioma to 2030 in this cohort.

Methods: Mesothelioma mortality rates incorporating parameters for cumulative exposure, a power of time since first exposure and annual rates of fibre clearance from the lung were calculated from maximum likelihood estimates. These rates plus age specific mortality rates for Western Australian females incorporating an excess lung cancer risk were then applied to all Wittenoom cohort women surviving to the end of 2004, in yearly increments, to predict the future numbers of cases of mesothelioma to 2030.

Results: There were 40 deaths from mesothelioma among the Wittenoom women to the end of 2004. Using a range of models that incorporate time since first exposure, competing risks from other diseases, latency periods and clearance of mesothelioma from the lungs we predict 66 (lowest estimate) to 87 (highest estimate) deaths from mesothelioma until 2030. This represents one and a half to two and a half times the number of deaths that have already occurred to the end of 2004.

Conclusion: The high toll from mesothelioma in this cohort of women and girls will continue well into the future.

In plain English

This study used records on women and girls who lived or worked at Wittenoom, a blue asbestos (crocidolite) mining and milling town in Western Australia, to predict how many would die of malignant mesothelioma between 2005 and 2030. The authors followed 2968 women through cancer and death registers. Of these, 416 had worked for the asbestos company, mostly in the shop, hotel or offices, and 2552 were residents. There were 40 mesothelioma deaths from 1950 to 2004: 10 among workers and 30 among residents. The authors fitted nine statistical models that differed in the assumed lag period and in how fast fibres clear from the lungs. They applied them to the 2402 women not known to be dead at the end of 2004. The models predicted between 66 and 87 further mesothelioma deaths up to 2030. The yearly numbers were not predicted to decline. The authors noted the figures may be overestimates, because 27% of the women were lost to follow-up and age at first exposure was not included. They also said some underestimation was possible. The authors concluded that the toll would continue well into the future.

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 prediction (modelling) study based on a cohort of women and girls exposed at Wittenoom; nine models varying the lag period (zero, 5 or 10 years) and the yearly rate of fibre clearance from the lungs (none, 6.7% or 15%)
• Who was studied: 2968 women and girls who lived or worked at Wittenoom, Western Australia, between 1943 and 1992 (416 asbestos company workers and 2552 residents), followed to the end of 2004; predictions were applied to the 2402 not known to be dead at the end of 2004, including 650 (27%) lost to follow-up
• Exposure: Blue asbestos (crocidolite) at Wittenoom, mostly from living in the town. Residents were assigned 1.0 f/ml from 1943 to 1957 and 0.5 f/ml from 1958 to 1966, falling to 0.010 f/ml by 1992. The 416 women company workers mostly worked in the shop, hotel or offices rather than in mining or milling.
• Main results:
  • 40 deaths from malignant mesothelioma occurred among the Wittenoom women between 1950 and 2004: 10 among workers and 30 among residents
  • Among residents, the mesothelioma rate was still rising: the rate at 40 or more years since first exposure was 43% greater than at 30 to 39 years
  • Across the nine models, 66 to 87 mesothelioma deaths were predicted to 2030 among the 2402 women not known to be dead at the end of 2004
  • The lowest prediction (66 mesothelioma deaths) came from the model with a 10-year lag and 15% yearly clearance
  • The model that best matched the pattern seen in male Wittenoom workers (5-year lag, 15% clearance) predicted 69 further mesothelioma deaths up to 2030
  • Under that model, mesothelioma deaths per 5-year period stayed relatively stable, rising slightly from 12 in 2005 to 2009 to 16 in 2025 to 2030
• The authors' conclusion: The authors concluded that the legacy of blue asbestos mining in Western Australia will continue to take a high toll well into the future
• Limitations the authors state:
  • Age at first exposure was not built into the models. 41% of the women were aged 14 or younger when first exposed. The authors listed this as a reason the predictions may be overestimates.
  • 27% of the women included in the predictions were lost to follow-up, and some may already be dead. The authors listed this as a reason the predictions may be overestimates.
  • Using current death rates instead of projected falling death rates from all causes could lead to some underestimation of future cases
  • The models diverged markedly beyond 45 years since first exposure because there were fewer observations
  • Women lost to follow-up were assumed to be alive, which likely overestimated person-years at risk and lowered the estimated rates

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: Crocidolite, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Crocidolite, Wittenoom, Pleura, Mesothelioma, Cumulative Exposure, Lung Cancer, Latency.

Related studies

• Cancer incidence among women and girls environmentally and occupationally exposed to blue asbestos at Wittenoom, Western Australia — A. Reid, J. Heyworth, et al. (2008)
• Retinol supplementation and mesothelioma incidence in workers earlier exposed to blue asbestos (Crocidolite) at Wittenoom, Western Australia — H.S. Alfonso, A. Reid, et al. (2010)
• Migration and work in postwar Australia: mortality profile comparisons between Australian and Italian workers exposed to blue asbestos at Wittenoom — A. Reid, E. Merler, et al. (2018)
• 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)
• Gynecologic and breast cancers in women after exposure to blue asbestos at Wittenoom — A. Reid, A. Segal, et al. (2009)

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