Incidence of malignant mesothelioma in Aboriginal people in Western Australia

Our plain-English summary of Incidence of malignant mesothelioma in Aboriginal people in Western Australia, by P. Franklin, A. Reid, N. Olsen, et al (Australian and New Zealand Journal of Public Health, 2016).

The study

• Authors: P. Franklin, A. Reid, N. Olsen, S. Peters, N. de Klerk, F. Brims, T. Threlfall, R. Murray, A.B. Musk
• Journal: Australian and New Zealand Journal of Public Health
• Published: 2016;40(4):383-7
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: To describe the incidence of malignant mesothelioma (MM) in Aboriginal people in Western Australia (WA) and determine the main routes of exposure to asbestos in this population.

Methods: All MM cases in Western Australia, as well as the primary source of asbestos exposure, are recorded in the WA Mesothelioma Register. Aboriginal cases up to the end of 2013 were extracted from the register and compared with non-Aboriginal cases with respect to the primary means/source of exposure. Age-standardised incidence rates for each decade from 1980 were calculated for both Aboriginals and non-Aboriginals. Age-standardised mortality rates were calculated for the period 1994-2008 and compared with international rates.

Results: There were 39 cases (77% male) of MM among WA Aboriginal people. Twenty-six (67%) were a direct result of the mining of crocidolite at Wittenoom and the subsequent contamination of the surrounding lands. Of the non-Aboriginal MM cases (n = 2070, 86.3% male), fewer than 25% can be attributed to Wittenoom. Aboriginals had consistently higher 10-year incidence rates than non-Aboriginals and, when compared to world populations, the highest mortality rate internationally.

Conclusion: When incidence rates in Aboriginal people are compared with non-Aboriginal people, the Wittenoom mining operation has had a disproportionate effect on MM incidence in the local Aboriginal population.

© 2016 Public Health Association of Australia.

In plain English

This study used the Western Australia Mesothelioma Register to describe malignant mesothelioma in Aboriginal people in Western Australia up to the end of 2013 and to compare them with non-Aboriginal cases. Of 2,124 registered cases, 39 were Aboriginal and 2,070 were non-Aboriginal. Twenty-six of the 39 Aboriginal cases were linked to the Wittenoom crocidolite (blue asbestos) mining operations: five mine and mill workers, 12 transport workers, five residents and four visitors. Non-occupational exposure was more common among Aboriginal cases (28.0% v 13.9%). Aboriginal cases were significantly younger at diagnosis and at first exposure. Aboriginal people had higher age-standardised incidence rates in most decades from 1980, but not in 1990 to 1999. The authors noted that the small numbers made comparisons vary. For 1994 to 2008, the Aboriginal mortality rate (4.11 per 100,000) was the highest of the populations compared, more than double the United Kingdom's 1.78. The authors concluded that blue asbestos mining at Wittenoom was the major contributor to the high rate in Aboriginal people. They noted that some cases may have been missed and that Aboriginality may have been misrecorded.

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: Register-based descriptive study comparing Aboriginal and non-Aboriginal mesothelioma cases, with age-standardised incidence rates by decade and age-standardised mortality rates compared with international rates
• Who was studied: All 2,124 malignant mesothelioma cases in the WA Mesothelioma Register up to the end of 2013: 2,070 non-Aboriginal, 39 Aboriginal and 15 of unknown racial status
• Exposure: Asbestos exposure as classified by the Register committee, with a focus on crocidolite (blue asbestos) mined and milled at Wittenoom from 1943 to 1966. This included mining and milling work, transport of raw asbestos, living in Wittenoom and visiting Wittenoom.
• Main results:
  • Twenty-six of the 39 Aboriginal cases were directly related to the Wittenoom mining operations: five mine and mill workers, 12 transport workers, five Wittenoom residents and four Wittenoom visitors.
  • For Aboriginal cases, 74% of occupational and 82% of non-occupational cases were associated with the Wittenoom mining operations. The figures for non-Aboriginal cases were 22% and 31%.
  • Non-occupational exposures made up a larger share of Aboriginal cases than of non-Aboriginal cases (28.0% v 13.9%, p=0.02).
  • Asbestos transport accounted for a larger share of Aboriginal cases than of non-Aboriginal cases (30.7% v 4.7%).
  • Building and construction was the most common occupational exposure for non-Aboriginal cases (17.7%) but accounted for 7.7% of Aboriginal cases.
  • Aboriginal cases were significantly younger than non-Aboriginal cases at diagnosis (median 57.9 v 69.0 years) and at first exposure (median 16.0 v 21.0 years).
  • Women made up a larger share of Aboriginal cases than of non-Aboriginal cases (23.0 v 13.7%). This difference was not statistically significant.
  • Of the 39 Aboriginal cases, 36 were pleural and three were peritoneal, a similar proportion to the non-Aboriginal group.
  • Aboriginal people had higher age-standardised incidence rates in most decades. Examples per 100,000 (persons) were 6.16 v 4.24 in 2010 to 2013 and 4.09 v 2.32 in 1980 to 1989. In 1990 to 1999 the Aboriginal rate was lower (3.66 v 3.92).
  • For 1994 to 2008, the age-standardised mortality rate was 4.11 per 100,000 for WA Aboriginal people and 2.74 for WA non-Aboriginal people. This was the highest of the populations compared, more than double the UK's 1.78; Australia's rate was 1.65.
  • In a sensitivity analysis assuming the Aboriginal population was under-counted by 15%, the 1994 to 2008 Aboriginal mortality rate was 3.6 per 100,000. This was still higher than the other international rates.
• The authors' conclusion: The authors concluded that blue asbestos mining at Wittenoom was the major contributor to the high mesothelioma incidence in WA Aboriginal people. They added that further cases may develop because of past exposure and ongoing access to contaminated land.
• Limitations the authors state:
  • Some Aboriginal cases may not have been recorded because many Aboriginal people live in remote areas with limited access to medical facilities.
  • People exposed in WA who left the state and were diagnosed elsewhere would be missed.
  • Rates may be inaccurate because Aboriginality may be under- or over-reported in census data.
  • The recorded Aboriginality of cases may not always have been accurate.
  • The exposure assigned by the committee may not reflect all sources, and the authors could not be certain that it was the actual cause of each case.
  • Because there were few Aboriginal cases, differences between the groups varied considerably over the decades.
  • The younger age at first exposure for Aboriginal women was based on information for five cases only.

Topics

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

Medical terms in this study, explained in our Lexicon: Mesothelioma, Asbestos Exposure, Incidence, Crocidolite, Wittenoom.

Related studies

• 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)
• Cancer incidence among women and girls environmentally and occupationally exposed to blue asbestos at Wittenoom, Western Australia — A. Reid, J. Heyworth, et al. (2008)
• Autoimmune antibodies and asbestos exposure: Evidence from Wittenoom, Western Australia — A. Reid, P. Franklin, et al. (2018)
• Plasma vitamin concentrations and incidence of mesothelioma and lung cancer in individuals exposed to crocidolite at Wittenoom, Western Australia — H.S. Alfonso, L. Fritschi, et al. (2006)
• Pattern of malignant mesothelioma incidence and occupational exposure to asbestos in Western Australia — A.W. Musk, N. Olsen, et al. (2015)
• Familial aggregation of malignant mesothelioma in former workers and residents of Wittenoom, Western Australia — N. de Klerk, H. Alfonso, et al. (2013)

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