Fiber contamination of vermiculites: a potential occupational and environmental health hazard

Our plain-English summary of Fiber contamination of vermiculites: a potential occupational and environmental health hazard, by F. Moatamed, J.E. Lockey, W.T. Parry (Environmental Research, 1986).

The study

• Authors: F. Moatamed, J.E. Lockey, W.T. Parry
• Journal: Environmental Research
• Published: 1986;41(1):207-18
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000425).

Abstract

Vermiculite ores from Montana, Virginia, and South Africa have been analyzed for the presence of amphibole contamination. Fibrous actinolite was found in unexpanded Montana vermiculite ore at a maximum concentration of 2.0%. The fibers persisted in the expanded ore at a maximum concentration of 0.6%. Actinolite was also found in the Virginia vermiculite ore but at a lower concentration and mostly as cleavage fragments with low length-to-width ratios. South African ore contained rare anthophyllite fibers also with low length-to-width ratios. Vermiculite ores have the potential for amphibole contamination and can represent potential health hazards without proper occupational and environmental control measures.

In plain English

This was a laboratory analysis of vermiculite ore samples. The authors examined unexpanded (raw) and expanded vermiculite from Libby, Montana (grades No. 2 and 3), Virginia and South Africa, using light microscopy, x-ray diffraction and electron microscopy. The highest amphibole content was 2%, in unexpanded Libby No. 2 ore. Unexpanded South African ore contained 0.4% and unexpanded Virginia ore 1.3%. Fibers persisted in expanded Libby ore at up to 0.6%. The Libby No. 2 amphibole was mostly fibrous actinolite with some anthophyllite, with fibers up to 40 micrometres long. Virginia actinolite occurred mostly as cleavage fragments with low length-to-width ratios. Unexpanded South African ore was essentially fiber free, and its rare fibers were mostly anthophyllite. No chrysotile was found in any ore. The authors concluded that fibrous actinolite in raw and expanded Libby ore represents a potential health hazard unless proper environmental and respiratory protection is used. They noted that the health implications of short cleavage fragments are not well defined.

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 vermiculite ore samples (no human subjects), using polarized light microscopy, x-ray diffraction, scanning electron microscopy and analytical scanning-transmission electron microscopy
• Who was studied: Unexpanded and expanded vermiculite ore samples. Libby, Montana ore (grade Nos. 2 and 3) was obtained in 1981 from a Salt Lake City expander facility that used only Libby ore. Virginia and South Africa ores (grade No. 4) were also obtained in 1981.
• Exposure: Amphibole contamination (actinolite, tremolite, ferro-actinolite, anthophyllite) of unexpanded and expanded vermiculite ore. Chrysotile was also looked for. No human exposure was measured.
• Main results:
  • Amphibole by bulk weight: 2% in unexpanded Libby No. 2 ore (the highest), 0.4% in unexpanded South Africa ore, and 1.3% in unexpanded Virginia ore
  • In expanded Libby ore, fibers persisted at a maximum concentration of 0.6%
  • The amphibole in Libby No. 2 ore was identified as mostly actinolite with some anthophyllite
  • Fibers in unexpanded Libby No. 2 ore measured up to 40 micrometres long and 0.2 to 5 micrometres in diameter
  • The Libby actinolite was fibrous, with length-to-width ratios greater than 10 to 1
  • Under transmission electron microscopy, fibers were frequent in Libby No. 2 and No. 3 samples and infrequent in Virginia and South Africa samples. Among randomly selected fibers (Table 2), 10 of 10 were actinolite in both unexpanded and expanded Libby No. 2. In Libby No. 3, 9 of 10 were actinolite in each form, with 1 of 10 tremolite (unexpanded) and 1 of 10 ferro-actinolite (expanded).
  • Virginia actinolite formed mostly cleavage fragments with low length-to-width ratios, and few fibers were found in expanded Virginia ore
  • Unexpanded South Africa ore was essentially fiber free, and its rare fibers were mostly anthophyllite with low length-to-width ratios
  • In South Africa ore, x-ray diffraction detected 0.4% fibrous amphibole in the unexpanded form and none in the expanded form
  • No chrysotile fibers were found in any of the vermiculite ores
• The authors' conclusion: The authors concluded that fibrous actinolite in raw and expanded (Libby) vermiculite represents a potential health hazard to humans unless proper environmental and respiratory protection is used
• Limitations the authors state:
  • Light microscopy identifies only large amphibole fragments. Other techniques are needed to look for submicroscopic respirable fibers.
  • The health implications of actinolite cleavage fragments with short length-to-width ratios (as in the Virginia ore) are not well defined
  • The line between actinolite and tremolite is based only on iron content. The authors describe it as arbitrary and say it may have no biological significance.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Libby vermiculite mine, Montana
• Virginia Vermiculite Co. mine, Virginia

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: vermiculite, Amphibole Group, Actinolite, Cleavage Fragment, Anthophyllite.

Related studies

• Health of vermiculite miners exposed to trace amounts of fibrous tremolite — J.C. McDonald, A.D. McDonald, et al. (1988)
• Pulmonary changes after exposure to vermiculite contaminated with fibrous tremolite — J.E. Lockey, S.M. Brooks, et al. (1984)
• An evaluation of potential occupational exposure to asbestiform amphiboles near a former vermiculite mine — J.F. Hart, T.M. Spear, et al. (2009)
• Cohort study of mortality of vermiculite miners exposed to tremolite — J.C. McDonald, A.D. McDonald, et al. (1986)
• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part II. Mortality — H.E. Amandus, R. Wheeler (1987)
• The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part I. Exposure estimates — H.E. Amandus, R. Wheeler, et al. (1987)

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