Mesothelioma in iron ore (taconite) miners

Our plain-English summary of Mesothelioma in iron ore (taconite) miners, by D. Mirabelli (Occupational and Environmental Medicine, 2016).

The study

• Author: D. Mirabelli
• Journal: Occupational and Environmental Medicine
• Published: 2016;73(4):217-8
• Type of article: Comment
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher

In plain English

This article is a short commentary, not an original study. The author discussed a case-control study by Lambert and colleagues of mesothelioma among Minnesota iron ore miners. As described here, that study covered 68,737 miners ever employed by three companies running seven mines in the Mesabi Iron Range. It estimated exposure to elongate mineral particles (EMPs) with a job-exposure matrix, and assessed commercial asbestos exposure only qualitatively. According to the commentary, years of taconite mining and cumulative exposure to total EMPs were both associated with increased odds of mesothelioma, while years of haematite mining had no effect. The unit risk for cumulative total EMP exposure was 1.10 (95% CI 0.97 to 1.24). It was increased only for workers at mines in zones 1 and 2, not zone 4, where amphibole EMPs were present. The author noted that 23 of the 80 cases occurred among workers engaged only in haematite mining, and that confounding by commercial asbestos could not be ruled out. The author concluded that the results support a role for non-amphibole, non-asbestiform EMPs but are not yet conclusive.

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: Commentary (commissioned editorial) on a case-control study by Lambert et al.; not original research
• Who was studied: As described for the Lambert et al. study: the full working population of 68,737 iron miners, enrolled in 1982, ever employed by any of three companies that operated seven mines in the Mesabi Iron Range, Minnesota; 80 mesothelioma cases were included
• Exposure: Elongate mineral particles (EMPs), total and amphibole, estimated with a job-exposure matrix linking mines, jobs and calendar years; taconite mining and processing entail mainly non-asbestiform amphibole and non-amphibole EMPs; commercial asbestos exposure assessed only qualitatively
• Main results:
  • In the Lambert et al. study, as described here, the unit risk for cumulative exposure to total EMPs was 1.10 (95% CI 0.97 to 1.24)
  • In the Lambert et al. study, duration of taconite mining and cumulative total EMP exposure were both associated with an increased OR; duration of haematite mining had no effect
  • The unit risk was increased only among workers employed in mines in geological zones 1 and 2, not in zone 4, where amphibole EMPs were present
  • Of the 80 mesothelioma cases, 23 occurred among workers engaged only in haematite mining, where little or no exposure to non-amphibole, non-asbestiform EMPs was estimated
  • Of the 57 cases among taconite miners, 31 were employed in zone 2
  • Background from an earlier mortality study (Allen et al.), not this article: based on 30 deaths, a mesothelioma SMR of 2.77 (95% CI 1.87 to 3.96) among the 31,067 workers most likely engaged in taconite mining and refining
• The authors' conclusion: The author concluded that the zone-specific finding supports the hypothesis that non-amphibole, non-asbestiform EMPs increased mesothelioma risk among taconite workers, but that the results are not yet conclusive. The author added that, after further clarification, chiefly refinement of the exposure assessment, the findings may lead to identifying another non-asbestos mineral that causes mesothelioma, besides erionite and fluoroedenite
• Limitations the authors state:
  • Residual confounding by commercial asbestos exposure cannot be entirely ruled out, because that exposure was assessed only qualitatively
  • The only mine ever active in zone 2 was closed during the 2010–2011 measurements, so its exposure was assessed from zone 4 estimates, possibly increasing exposure misclassification
  • Inconsistency with the earlier mortality study, where zone-specific SMRs were lowest for zone 1 workers, the zone with the highest unit risk in Lambert et al.
  • The non-amphibole, non-asbestiform EMPs in the Mesabi Iron Range need better characterisation to identify a putative carcinogenic mineral

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: Mesothelioma, Taconite.

Related studies

• A case-control study of mesothelioma in Minnesota iron ore (taconite) miners — C.S. Lambert, B.H. Alexander, et al. (2016)
• Risk assessment due to environmental exposures to fibrous particulates associated with taconite ore — R. Wilson, E.E. McConnell, et al. (2008)
• The relationship between various exposure metrics for elongate mineral particles (EMP) in the taconite mining and processing industry — J. Hwang, G. Ramachandran, et al. (2014)
• An overview of the risk of lung cancer in relation to exposure to asbestos and of taconite miners — G. Berry, G.W. Gibbs (2008)
• Amphibole fibers in a taconite mine and in the lungs of the miners — B. Gylseth, T. Norseth, et al. (1981)
• The search for asbestos within the Peter Mitchell Taconite iron ore mine, near Babbitt, Minnesota — M. Ross, R.P. Nolan, et al. (2008)

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