Risk factors for malignant mesothelioma in people with no known exposure to asbestos

Our plain-English summary of Risk factors for malignant mesothelioma in people with no known exposure to asbestos, by B. Musk, L. Gordon, H. Alfonso, et al (American Journal of Industrial Medicine, 2017).

The study

• Authors: B. Musk, L. Gordon, H. Alfonso, A. Reid, N. Olsen, R. Mina, P. Franklin, S. Peters, F. Brims, J. Hui, N. de Klerk
• Journal: American Journal of Industrial Medicine
• Published: 2017;60(5):432-436
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Objectives: Malignant mesothelioma (MM) is a rare and generally fatal cancer, usually caused by asbestos, although about 5-10% of cases report no asbestos exposure. This study aimed to identify sources whereby people in Western Australia (WA) may be unknowingly exposed to asbestos or to other exposures which may cause MM.

Methods: Cases with no known asbestos exposure were selected from the WA Mesothelioma Register (WAMR). Matched controls were selected from hospital patients admitted for conditions unrelated to asbestos. Occupational histories were coded by an industrial hygienist. Data were analyzed using conditional logistic regression.

Results: Thirty-eight MM participants and 134 controls were recruited. Risk of MM was increased (OR = 3.1, 95%CI 1.0-9.6) after no known, but likely, exposure to asbestos at work.

Conclusions: Because of its extensive use, few people in WA have never been exposed to asbestos. Unrecognized exposure may cause most MM cases initially regarded as "no exposure." Am. J. Ind. Med. 60:432-436, 2017. © 2017 Wiley Periodicals, Inc.

© 2017 Wiley Periodicals, Inc.

In plain English

This matched case-control study in Western Australia sought unrecognized asbestos or other exposures in people with malignant mesothelioma and no known asbestos exposure. On the state mesothelioma register, 38 of 519 cases (7.3%) had such histories. Over 9 years, 38 cases and 134 hospital controls with conditions unrelated to asbestos (65 with other cancers, 69 with general medical conditions) were interviewed about their histories. An industrial hygienist, unaware of diagnoses, coded exposures to 47 substances. Among cases compared with controls, likely asbestos exposure at work was linked to a significantly raised risk (odds ratio 3.1, 95% confidence interval 1.0 to 9.6). Any asbestos exposure gave an odds ratio of 1.8 (0.8 to 4.2), which was not statistically significant. Parents' work exposure to asbestos was more common among cases. An "other chemicals" group had the largest estimate, which the authors judged probably due to chance. The authors concluded that most such cases likely occur, at a very low rate, among many people who had small amounts of asbestos exposure. They noted that interviewers would have been aware of diagnoses, particularly of non-cancer controls.

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: matched case-control study
• Who was studied: Malignant mesothelioma cases from the Western Australia Mesothelioma Register whose histories showed no known asbestos exposure (38 of 519 cases, 7.3%). Controls were hospital patients with conditions unrelated to asbestos, matched for age, sex, postcode and year of admission. Over 9 years, 38 cases, 65 controls with other cancers and 69 medical controls were recruited.
• Exposure: Occupational and environmental exposures from lifetime job and residence histories, including those of family members living with participants. An industrial hygienist coded the histories into 47 substances in 10 groups, including asbestos, radiation, organic dusts, mineral dusts, synthetic mineral fibre, metals and other chemicals. The questionnaire avoided direct reference to asbestos.
• Main results:
  • Among cases compared with controls, the relative risk of malignant mesothelioma was significantly elevated after any likely asbestos exposure at work (probable or definite, intensity slight or greater): odds ratio 3.1, 95% CI 1.0 to 9.6.
  • The overall effect of any asbestos exposure was raised but not statistically significant (odds ratio 1.8, 95% CI 0.8 to 4.2).
  • Occupational exposure to asbestos in parents was more common among cases than controls, using the same criteria.
  • The "other chemicals" group had the largest estimated relative risk of the major exposure groups, but no more specific exposure could be identified. The authors considered this probably due to chance.
  • Radiation exposure gave an estimate of zero relative risk: 12 controls were exposed and no cases were exposed.
  • Eligible cases without asbestos exposure were far fewer than anticipated.
• The authors' conclusion: The authors concluded that most malignant mesothelioma cases in Western Australians with "no known" asbestos exposure likely occur, at a very low rate, among large numbers of people who actually had small amounts of asbestos exposure. They also concluded that this is consistent with there being no threshold for the disease and no other cause of mesothelioma in Western Australia.
• Limitations the authors state:
  • Interviewers, though not the industrial hygienist, would have been aware of patients' diagnoses, particularly for non-cancer controls. The authors state that regular supervision should have prevented more detailed questioning of mesothelioma patients.
  • The extent to which background exposure to asbestos contributed to the cases' mesothelioma could not be determined.
  • All five cases and five of the six controls with "other chemicals" exposure were exposed in industrial settings, where unrecognized asbestos exposure could also have occurred.

Topics

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

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Asbestos Exposure, Mesothelioma.

Related studies

• Incidence of malignant mesothelioma in Aboriginal people in Western Australia — P. Franklin, A. Reid, et al. (2016)
• A Bayesian approach to assess interaction between known risk factors: the risk of lung cancer from exposure to asbestos and smoking — D. Wraith, K. Mengersen (2008)
• Are children more vulnerable to mesothelioma than adults? A comparison of mesothelioma risk among children and adults exposed non-occupationally to blue asbestos at Wittenoom — A. Reid, P. Franklin, et al. (2018)
• Asbestos and smoking as risk factors for idiopathic retroperitoneal fibrosis: a case-control study — M. Goldoni, S. Bonini, et al. (2014)
• Effects of asbestos and smoking on gas diffusion in people exposed to crocidolite — H.S. Alfonso, L. Fritschi, et al. (2005)
• Ultra-low-dose chest computer tomography screening of an asbestos-exposed population in Western Australia — F.J. Brims, C.P. Murray, et al. (2015)

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