Aerodigestive and gastrointestinal tract cancers and exposure to crocidolite (blue asbestos): incidence and mortality among former crocidolite workers

Our plain-English summary of Aerodigestive and gastrointestinal tract cancers and exposure to crocidolite (blue asbestos): incidence and mortality among former crocidolite workers, by A. Reid, G. Ambrosini, N. de Klerk, et al (International Journal of Cancer, 2004).

The study

• Authors: A. Reid, G. Ambrosini, N. de Klerk, L. Fritschi, B. Musk
• Journal: International Journal of Cancer
• Published: 2004;111(5):757-61
• Cited by: 31 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The objective of this article was to assess the association between the incidence and mortality from aerodigestive cancers and exposure to crocidolite (blue asbestos). Our study is a cohort study of former workers of the now-defunct crocidolite mining and milling operation at Wittenoom, Western Australia, who have been followed up since 1979 and on whom asbestos exposure and smoking information was known. Standardised mortality and incidence rates were used to compare former workers with the Western Australian male population. Cases were matched with up to 10 randomly assigned controls, and conditional logistic regression was used to examine the relationship between asbestos exposure, smoking status and cancer incidence. There were 129 incident cases from all cancers of interest and 57 deaths. Former workers had a significantly higher risk of mortality from upper aerodigestive cancers than the Western Australian male population. The incidence of upper and lower aerodigestive cancers was higher in the Wittenoom cohort but not significantly so. Cumulative exposure to asbestos did not appear to be associated with the incidence of stomach cancer, colorectal cancer or upper aerodigestive cancers. Smoking status was strongly associated with the incidence of upper aerodigestive cancers, with current smokers experiencing the greatest risk. Our study with longer and more complete follow-up, smoking information and a stronger study design does not show an association between cumulative asbestos exposure and stomach cancer or other gastrointestinal cancers. The excess mortality from upper aerodigestive cancers seen in this cohort of former asbestos workers compared to the Western Australian male population does not appear to be associated with exposure to crocidolite.

Copyright 2004 Wiley-Liss, Inc.

In plain English

This study followed men who worked at the crocidolite (blue asbestos) mine and mill at Wittenoom, Western Australia, from 1943 to 1966. The authors compared rates of upper aerodigestive cancers (lip, mouth, tongue, pharynx, larynx, maxillary sinus) and oesophageal, stomach and colorectal cancers with those of Western Australian men. In a subset with smoking information (45% of the workforce), men with stomach, colorectal or upper aerodigestive cancers were compared with matched controls. The whole cohort had 37 deaths from upper aerodigestive cancers against 15 expected. In the subset, cumulative crocidolite exposure showed no association with upper aerodigestive cancers (odds ratio 1.02, 95% CI .85 to 1.22) or colorectal cancer (.97, .84 to 1.12). For stomach cancer it was 1.38 (.99 to 1.92), falling to 1.28 (0.94 to 1.76) adjusted for place of birth. Current smokers, compared with never smokers, had an odds ratio of 8.31 (1.04 to 66.2) for upper aerodigestive cancers. The authors concluded that excess upper aerodigestive cancer deaths did not appear to be associated with crocidolite exposure. They noted the results could not be generalised to the whole workforce.

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 study of former workers. They were compared with the Western Australian male population using standardised incidence and mortality rates. A nested case-control analysis matched cases with up to 10 controls and used conditional logistic regression, separately for stomach cancer, colorectal cancer and upper aerodigestive cancers.
• Who was studied: Former workers of the Australian Blue Asbestos crocidolite mining and milling operation at Wittenoom, Western Australia, employed 1943 to 1966 (6,908 workers in total). The case-control analysis used the subset traced from 1979 who answered smoking questionnaires (45% of the original workforce). Analyses were restricted to men. Deaths were followed to September 2000 and cancer registrations to between 1997 and 1999, depending on the state.
• Exposure: Crocidolite only, with no other forms of asbestos. Each worker's cumulative exposure (fibre per ml-years) was estimated from 1966 airborne fibre measurements and employment records. Smoking status (never, past, current) came from questionnaires.
• Main results:
  • Whole cohort, compared with Western Australian men: 37 deaths from upper aerodigestive cancers against 15 expected (standardised mortality ratio 251, 95% CI 182 to 346), about twice that expected.
  • Whole cohort: incidence of upper aerodigestive cancers was higher than expected (71 observed against 45 expected; SIR 158, 95% CI 126 to 200), particularly cancers of the pharynx (SIR 188, 115 to 307) and larynx (SIR 182, 116 to 285).
  • Whole cohort: mortality from lower aerodigestive cancers (oesophagus, stomach, colon and rectum) was not significantly higher than in Western Australian men.
  • Smoking data subset: incidence of upper aerodigestive cancers (SIR 132, 95% CI 96 to 180) and of lower aerodigestive cancers was higher than in Western Australian men, but not significantly.
  • Stomach cancer (19 cases, 158 controls): the odds ratio for cumulative crocidolite exposure was 1.38 (95% CI .99 to 1.92, p .057).
  • Stomach cancer: adding place of birth to the model reduced the odds ratio for cumulative exposure to 1.28 (95% CI 0.94 to 1.76).
  • Upper aerodigestive cancers (39 cases, 326 controls): no association was found with cumulative crocidolite exposure (odds ratio 1.02, 95% CI .85 to 1.22).
  • Upper aerodigestive cancers, compared with never smokers: current smokers had an odds ratio of 8.31 (95% CI 1.04 to 66.2) and past smokers 4.84 (.63 to 37.5).
  • Colon and rectum cancer (58 cases, 466 controls): neither cumulative crocidolite exposure (odds ratio .97, 95% CI .84 to 1.12) nor smoking status was associated.
• The authors' conclusion: The authors concluded that the excess mortality from upper aerodigestive cancers did not appear to be associated with crocidolite exposure. They also concluded that their study did not show an association between cumulative asbestos exposure and stomach cancer or other gastrointestinal cancers.
• Limitations the authors state:
  • The exposure analysis used a subset (45% of the original workforce) that differed from the whole cohort, for example with fewer foreign-born and very short-term workers. The authors said the results cannot be generalised to all former Wittenoom workers.
  • Smoking status was taken from each man's most recent questionnaire, so it may not reflect his status at the time he was designated a case or control.
  • Controls were restricted to Western Australian residents, which could under-represent particular ethnic subgroups.
  • Information on alcohol intake had been collected only recently. The authors suggested that heavy drinking may have contributed to the high mortality from these cancers.

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, Lung cancer.

Medical terms in this study, explained in our Lexicon: Crocidolite, Cohort Study, Wittenoom, Asbestos Exposure, Incidence, Cumulative Exposure, Stomach Cancer, Colorectal Cancer.

Related studies

• Mortality of former crocidolite (blue asbestos) miners and millers at Wittenoom — A.W. Musk, N.H. de Klerk, 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)
• Age and sex differences in malignant mesothelioma after residential exposure to blue asbestos (crocidolite) — A. Reid, G. Berry, et al. (2007)
• Cancer incidence among women and girls environmentally and occupationally exposed to blue asbestos at Wittenoom, Western Australia — A. Reid, J. Heyworth, et al. (2008)
• 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)

Browse more research in International Journal of Cancer, or return to medical research.