Rapporteur's Report Session 2: characterization of fibrous minerals

Our plain-English summary of Rapporteur's Report Session 2: characterization of fibrous minerals, by A.M. Langer (Regulatory Toxicology and Pharmacology, 2008).

The study

• Author: A.M. Langer
• Journal: Regulatory Toxicology and Pharmacology
• Published: 2008;52(1 Suppl):S73-4
• Read it: PubMed · Publisher

In plain English

This was a rapporteur's report, not an original study. The author summarized papers from a conference session on fibrous minerals in taconite iron ore from Minnesota's Mesabi Range. Ross, Nolan and Nord sampled the Peter Mitchell Taconite Iron Ore Mine. Some sites had fiber bundles of grunerite, ferroactinolite and ferrian sepiolite, which made up much less than one percent of the ore body, but these authors concluded that no asbestos of any type was found in the mine pit. Axten and Foster reported actinolite, tremolite and grunerite particles in the air around the Silver Bay processing facility, and these decreased over time. They said that changing methods meant samples from different periods could not be directly compared. Zanko, Niles and Oreskovich found no amphibole minerals in coarse tailings from the western Mesabi Range. They said some crushed amphibole fragments from the eastern range were morphologically difficult to distinguish from asbestiform fibers, and they raised concern about quartz. Citing the Minnesota Department of Health, the author noted twenty-five confirmed mesotheliomas among Cloquet ceiling-tile workers, at a plant where amosite and chrysotile were used. The author said the papers raised questions about what analysts actually measure.

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: Rapporteur's report summarizing papers presented in a conference session (no original data collected by the author)
• Who was studied: Papers on taconite iron ore, tailings, and air and water samples from the Mesabi Range, Minnesota, including the Peter Mitchell mine near Babbitt and the Silver Bay processing facility
• Exposure: Amphibole minerals in taconite ore (cummingtonite, grunerite, actinolite and variants), and whether they are asbestiform or cleavage fragments; also crystalline silica (quartz)
• Main results:
  • Ross and colleagues (Peter Mitchell mine): some sampled sites contained mineral fiber bundles of grunerite, ferroactinolite and ferrian sepiolite, but they concluded no asbestos of any type was found in the mine pit
  • Ross and colleagues: these fibrous minerals made up very much less than one percent of the ore body mass
  • Axten and Foster: actinolite, tremolite and grunerite particles in the air in and around the Silver Bay facility steadily decreased in concentration over time
  • Axten and Foster: fiber levels in Lake Superior waters declined to values seen in the natural runoff of rivers entering the lake
  • Zanko and colleagues: no amphibole minerals were found in five groups of coarse tailings samples from the western Mesabi Range
  • Zanko and colleagues: in the Eastern Mesabi, amphiboles crushed to form fragments, some of which were morphologically difficult to distinguish from asbestiform fibers
  • Author's note citing the Minnesota Department of Health (2007): twenty-five mesotheliomas confirmed, and three more suspected, among workers at the Cloquet ceiling-tile plant. The plant used more than 3100 tons of amosite in 1958 to 1964 and almost 6800 tons of chrysotile in 1965 to 1974
• The authors' conclusion: The author concluded that the papers raised critical issues: whether it is known with certainty what the analyst is measuring, whether asbestos was accurately distinguished from cleavage fragments, and whether risk calculations reflect what is actually known
• Limitations the authors state:
  • Axten and Foster: because sampling and analysis methods changed over time, samples from one period could not be directly compared with those from another
  • Axten and Foster: distinguishing asbestos fibers from elongate cleavage fragments was not part of the assays when environmental studies began in the 1970s
  • Wilson and colleagues' risk calculation assumed that the amphiboles in the air samples have the same carcinogenic potency as asbestos minerals

Related studies

• Rapporteur's Report Session 6: risk assessment of asbestos and other fibrous mineral particulates — R.P. Nolan, A.M. Langer (2008)
• 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)
• Comprehensive assessment of exposures to elongate mineral particles in the taconite mining industry — J. Hwang, G. Ramachandran, et al. (2013)
• The search for asbestos within the Peter Mitchell Taconite iron ore mine, near Babbitt, Minnesota — M. Ross, R.P. Nolan, et al. (2008)
• The origins of public concern with taconite and human health: Reserve Mining and the asbestos case — M.E. Berndt, W.C. Brice (2008)

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