Malignant mesotheliomas in former miners and millers of crocidolite at Wittenoom (Western Australia) after more than 50 years follow-up

Our plain-English summary of Malignant mesotheliomas in former miners and millers of crocidolite at Wittenoom (Western Australia) after more than 50 years follow-up, by G. Berry, A. Reid, P. Aboagye-Sarfo, et al (British Journal of Cancer, 2012).

The study

• Authors: G. Berry, A. Reid, P. Aboagye-Sarfo, N.H. de Klerk, N.J. Olsen, E. Merler, P. Franklin, A.W. Musk
• Journal: British Journal of Cancer
• Published: 2012;106(5):1016-20
• Cited by: 48 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: To report the number of malignant pleural and peritoneal mesotheliomas that have occurred in former Wittenoom crocidolite workers to the end of 2008, to compare this with earlier predictions, and to relate the mesothelioma rate to amount of exposure.

Methods: A group of 6489 men and 419 women who had worked for the company operating the former Wittenoom crocidolite mine and mill at some time between 1943 and 1966 have been followed up throughout Australia and Italy to the end of 2008.

Results: The cumulative number of mesotheliomas up to 2008 was 316 in men (268 pleural, 48 peritoneal) and 13 (all pleural) in women. There had been 302 deaths with mesothelioma in men and 13 in women, which was almost 10% of all known deaths. Mesothelioma rate, both pleural and peritoneal, increased with time since first exposure and appeared to reach a plateau after about 40 to 50 years. The mesothelioma rate increased with amount of exposure and the peritoneal mesotheliomas occurred preferentially in the highest exposure group, 37% compared with 15% overall.

Conclusion: By the end of 2008, the number of mesothelioma deaths had reached 4.7% for all the male workers and 3.1% for the females. Over the past 8 years the numbers were higher than expected. It is predicted that about another 60 to 70 deaths with mesothelioma may occur in men by 2020.

In plain English

This study followed 6489 men and 419 women employed between 1943 and 1966 by the company running Western Australia's Wittenoom crocidolite (blue asbestos) mine and mill. Follow-up ran to the end of 2008, but vital status of workers searched for in Italy was assessed at 31 December 2007. By end-2008, men had 316 mesotheliomas (268 pleural, 48 peritoneal) and women 13 (all pleural). Deaths with mesothelioma numbered 302 in men and 13 in women: 4.7% of male and 3.1% of female workers. The mesothelioma rate rose with time since first exposure, appearing to plateau after about 40 to 50 years. It also rose with cumulative exposure: about 4- to 5-fold from under 10 to 50 or more fibres per ml years, depending on counting method. In the highest exposure group, 37% were peritoneal, versus 15% overall. Male deaths closely matched the lowest earlier prediction, from a model allowing for crocidolite clearing from the lungs. However, the 74 deaths in the last 8 years exceeded it by 11. The authors predicted about 60 to 70 further deaths in men by 2020.

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: Cohort follow-up study of mesothelioma incidence and mortality in a former workforce, compared with earlier predictions
• Who was studied: 6489 men and 419 women employed by the company operating the Wittenoom crocidolite mine and mill (Western Australia) at some time between 1943 and 1966. They were followed to the end of 2008. Workers untraced in Australia were searched for in Italy, where vital status was assessed at 31 December 2007.
• Exposure: Crocidolite (blue asbestos) mining and milling at Wittenoom. Exposure was usually brief (74% worked less than a year). Cumulative exposure was grouped as under 10, 10 to under 50, and 50 or more fibres per ml years. Almost 90% of men worked in the mine or mill; most women worked in the town and had lower exposures.
• Main results:
  • Up to the end of 2008 there were 316 mesotheliomas diagnosed in men (268 pleural, 48 peritoneal) and 13 in women (all pleural)
  • There were 302 deaths with mesothelioma in men (255 pleural, 47 peritoneal) and 13 in women (all pleural)
  • Almost 10% of known deaths in men and 8% in women were due to mesothelioma. Mesothelioma deaths amounted to 4.7% of all male workers and 3.1% of all female workers.
  • The shortest time from starting at Wittenoom to diagnosis was 12 years and 9 months, the longest so far 58 years, and the average 35.4 years
  • 15 pleural mesotheliomas occurred within 20 years of first exposure, but no peritoneal mesotheliomas occurred in that time
  • Pleural and peritoneal mesothelioma rates rose with time since first exposure and appeared to plateau after about 40 to 50 years
  • The mesothelioma rate in the highest cumulative exposure group (50 or more fibres per ml years) was about 5-fold (Method 1) or about 4-fold (Method 2) the rate in the lowest group (under 10 fibres per ml years)
  • Overall 15% of mesotheliomas were peritoneal. In the highest exposure group the figure was 37%, compared with 6% and 7% in the two lower exposure groups (p less than 0.001).
  • Observed male mesothelioma deaths to 2008 (302) fitted closely the earlier model with the lowest predictions (Model 3, 297), which included an elimination rate of 15% per year. Models 1 and 2 predicted 509 and 371.
  • In the past 8 years, 74 male mesothelioma deaths were observed, 11 more than the 63 predicted
• The authors' conclusion: The authors concluded that models allowing for gradual elimination of crocidolite from the lungs are more realistic. They estimated there may be about a further 60 to 70 mesothelioma deaths in men by the end of 2020.
• Limitations the authors state:
  • Exposure estimates came from the only airborne dust study ever done, which the person who carried it out described as underestimates. The authors state the values are internally valid but the absolute level may be uncertain.
  • Follow-up relied on matching to death and cancer records, so workers without a match are not necessarily alive and cancer-free. Rates could only be estimated between the limits of two counting methods.
  • An unknown number of Italian workers returned to Italy after working at Wittenoom
  • The average lag time, and the numbers in the 40-plus year categories, will rise as follow-up continues

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, Peritoneal mesothelioma.

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

Related studies

• 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)
• Mortality of former crocidolite (blue asbestos) miners and millers at Wittenoom — A.W. Musk, N.H. de Klerk, et al. (2008)
• Prevalence of radiographic asbestosis in crocidolite miners and millers at Wittenoom, Western Australia — W.O. Cookson, N.H. De Klerk, et al. (1986)
• Predictions of future cases of asbestos-related disease among former miners and millers of crocidolite in Western Australia — N.H. de Klerk, B.K. Armstrong, et al. (1989)
• 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)
• Benign and malignant pleural effusions in former Wittenoom crocidolite millers and miners — W.O. Cookson, N.H. De Klerk, et al. (1985)

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