The Contamination of Lake Superior with Amphibole Gangue Minerals

Our plain-English summary of The Contamination of Lake Superior with Amphibole Gangue Minerals, by A. M. Langer, C. M. Maggiore, W. J. Nicholson, et al (1979).

The study

• Authors: A. M. Langer, C. M. Maggiore, W. J. Nicholson, A. N. Rohl, I. B. Rubin, I. J. Selikoff
• Published: Annals of the New York Academy of Sciences, pp. 549- (1979)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This 1979 laboratory study examined mineral particles from taconite (iron ore) processing by the Reserve Mining Company at Silver Bay, Minnesota, whose tailings were discharged into Lake Superior. It did not study people's health. The authors analyzed samples from the tailings, from the lake, and from tap water in municipalities drawing water from the lake, including Duluth. They used electron microscopy, electron diffraction and single-fiber chemical analysis. The tailings contained fibrous particles consistent with actinolite, cummingtonite, grunerite and hornblende. Several percent of reference nonasbestiform grunerite fibers were identical to asbestiform grunerite (amosite) in shape, structure and chemistry. In drinking water, grunerite fibers ranged from 0.6 to 2.8 times a power of ten per liter that the scanned text does not show clearly. More than half of the fibrous amphiboles in drinking water were under 1 micron long. Tap water and tailings particles were similar in composition but differed in concentration. The authors noted their counts may be conservative. They concluded that the health risk of swallowing grunerite fiber is unknown and is extrapolated from amosite data, and that the biological activity of other fibrous amphiboles warrants investigation.

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: Laboratory mineralogical analysis of tailings and water samples by microscopy, x-ray diffraction, electron diffraction and microchemical analysis, compared with mineral standards; no human health outcomes were studied
• Who was studied: Water and sediment samples from the Reserve Mining Company tailings launders at Silver Bay, Minnesota, from Lake Superior directly, and from tap water in municipalities drawing water from the lake (Table 4 lists six Duluth, Minnesota samples and a New York City tap water sample)
• Exposure: Fibrous amphibole particles from taconite tailings (gangue): cummingtonite-grunerite (grunerite's asbestiform variety is amosite), actinolite, and fragments of hornblende, present in lake water and drinking water
• Main results:
  • Tailing samples contained numerous fibrous particles with optical properties consistent with actinolite, cummingtonite, grunerite and hornblende
  • Several percent of the reference fibrous nonasbestiform grunerite fibers were identical to asbestiform grunerite (amosite) in morphology, structure and chemical composition
  • Total amphibole fiber content of drinking water ranged from about 14 to 65 times a power of ten fibers per liter, depending on sample origin (the exponent is unreadable in the scanned text)
  • Grunerite fiber in drinking water ranged from 0.6 to 2.8 times a power of ten fibers per liter (exponent unreadable in the scanned text); the authors stated that a portion of these were identical to asbestiform grunerite
  • More than half of the fibrous amphiboles in drinking water were less than 1 micron long and less than 0.2 microns wide, which made them smaller than the amosite standard
  • Tailings and Duluth water particle populations were similar in composition but differed in absolute concentrations. Tap water had less grunerite fiber than the tailings (some 7% in tailings; the tap-water figure is garbled in the scan, and the Table 4 footnote gives 4% grunerite)
  • In their discussion, the authors estimated that, at one liter of Duluth water per day, ingested fibers identical with amosite would be orders of magnitude below occupational exposure, while fibrous grunerite and actinolite combined would approach workers' exposure levels
• The authors' conclusion: The authors concluded that the health risk of directly ingesting grunerite fiber is unknown and is extrapolated from the asbestiform grunerite (amosite) data base, and that the biological activity of the other fibrous amphiboles observed is unknown and warrants investigation
• Limitations the authors state:
  • The authors stated that the fiber values may be conservative because of the constraints of their identification criteria
  • Fibers too thick or too thin to give a visible diffraction pattern were omitted from analysis
  • Not every particle could be rotated for additional diffraction patterns because of time constraints, leaving uncertainty for some 'possible' amphiboles
  • It is unknown whether the asbestos property carries down to submicroscopic fibers

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Group, Taconite, Tailings, Actinolite, Grunerite, Hornblende, Non-Asbestiform, Asbestiform.

Browse return to medical research.