The Vermiculite Institute


AN OVERVIEW OF ANALYSTICAL TESTING ON
VERMICULITE FROM PALABORA, SOUTH AFRICA


I. Analytical Information

The Palabora Mining Company has conducted extensive testing of Palabora vermiculite to confirm the absence of asbestos in vermiculite from the Palabora mine. Sample collection and analyses have been performed by independent experts in the field of mineralogy and fiber assessment. Testing conducted to date has confirmed the absence of asbestos in Palabora vermiculite. This work continues on a routine basis and is a cornerstone of the Palabora quality assurance program.

  • Field studies conducted by the US. Environmental Protection Agency (EPA) at a facility located in Metuchen, New Jersey, that exfoliates Palabora vermiculite confirmed no asbestos in bulk vermiculite and air samples collected at the facility. ( EPA REPORT ON SCHUNDLER COMPANY VERMICULITE MARCH 2000

  • Institute of Occupational Medicine ("IOM"), Edinburgh, Scotland, Sampling and Analysis of Crude Vermiculite Samples for Possible Asbestiform Content (March 10, 2000). No amphibole or chrysotile fibers were detected in any of the samples of Palabora vermiculite using polarized light microscopy and dispersion staining at a detection level of 1 ppm using Health and Safety Executive MDHS 77 for asbestos in bulk materials.

  • IOM, Sampling and Analysis of Crude Vermiculite Samples for Possible Asbestiform Fiber Content (Feb. 10, 1999) No amphibole or chrysotile fibers were detected in bulk samples of commercial grade Palabora vermiculite tested by polarized light microscopy at a detection level of 1 ppm using Health and Safety Executive MDHS 77 for asbestos in bulk materials.

  • IOM, Sampling and Analysis of Vermiculite Samples for Possible Asbestiform Fiber Content (Oct 29, 1997). No amphibole or chrysotile fibers were detected in bulk samples of commercial grade Palabora vermiculite tested by polarized light microscopy at a detection level of I ppm using Health and Safety Executive MDHS 77 for asbestos in bulk materials.

  • IOM, Analysis of Crude Vermiculite Samples for Possible Asbestos Fiber Content (Feb. 26, 1996). No amphibole or chrysotile fibers were detected in bulk samples of commercial grade Palabora vermiculite tested by polarized light microscopy at a detection level of I ppm using Health and Safety Executive MDHS 77 for asbestos in bulk materials.

  • IOM, Report on Airborne Dust and Fiber Monitoring at Mandoval Coatings Ltd, Carlton-in-Lindrick, Nottinghamshire, England (Apr. 22, 1996). In all sampling locations and conditions the measured fiber concentrations were below the limit of detection for the sampling and analytical procedures (0.02-0.01f/ml).

  • Institute of Occupational Medicine ("IOM"), Edinburgh, Scotland, Analysis of Crude Vermiculite Samples for Possible Asbestiform Fiber Content, Report No. A2688 (9/12/93) and Guidance Note to Supplement Test Report No. A 2688.

    Samples representing a range of commercial grades of Palabora vermiculite were collected and analyzed by IOM with the objective of determining whether any asbestiform fibers are present. All samples of vermiculite ore and exfoliated product did not show any asbestos (amphibole or chrysotile) at low (<<0.001% by TEM) detection levels. No amphibole asbestos or chrysotile fibers were detected in any of the samples analyzed by polarized light microscopy. Chrysotile was not detected in any of the bulk materials by X-ray diffractometry.

    X-ray diffractometry indicated that digestion residues from one ore body at the mine were comprised of a mixture of hydrobiotite/mica and feldspar with little or no amphibole minerals being detected (<0. 1 %). The residues from a second ore body contained similar minerals.

    TEM analysis of digestion residues revealed mineral some mineral "fibers," i.e., particles with aspect ratios (length/diameter) greater than 3:1. These structures were mainly partially digested vermiculite/mica fragments, barite (BaSO4), calcium and potassium silicates, rutile (TiO2) and zircon (ZrSiO4). Some particles were identified that could be considered morphologically and chemically similar to amphiboles in the tremolite-actinolite composition range (calcium, iron, magnesium silicates). The lower geometric mean lengths and smaller aspect ratios of these structures distinguished them from known varieties of tremolite asbestos. Non-parallel sided blocky morphology and absence of fiber bundles further distinguished these structures as cleavage fragments that would not be properly classified as asbestiform.

  • Chatfield, Eric J. and Gregory M. Lewis, Examination of Vermiculite for the Presence of Asbestos Fibers, Ontario Research Foundation Report No. 22056-2 (October, 1979).

    Palabora vermiculite was analyzed using transmission electron microscopy (TEM), using selected area electron diffraction and energy dispersive X-ray techniques for fiber identification. The method does not involve pulverizing samples and therefore allows measurement of fiber sizes. The method is sensitive to 0.007 ppm for loose material, with a separate measurement necessary to determine whether fibers are intercalated between vermiculite layers. No asbestos fibers could be positively identified in Palabora vermiculite.

    No amphibole asbestos was detected, either intercalated within the flakes or in the associated fine dust. Detection limits were 0.8 ppm for intercalated amphibole and 0.007 ppm for dust.

    No chrysotile asbestos could be detected in Palabora vermiculite. The appearance of detached vermiculite fragments, in the form of rolled-up scrolls, could be morphologically misleading; but compositions and electron diffraction patterns confirmed these structures were not asbestos.

    Fiber measurements by phase contrast microscopy (PCM) optical technique alone could be misleading. Confirmation by TEM is necessary to distinguish vermiculite scrolls and cleavage fragments from objects identified as "fibers" by PCM alone.

    TEM analysis of air monitoring samples taken at an exfoliation plant revealed no detectable amphibole fibers (>5um)/ml at detection levels of 0.024 and 0.047 f/ml.

II. Assessment of Palabora Vermiculite Carcinogenicity/ Tumerigenicity

Studies confirm the absence of carcinogenic/tumorigenic potential for Palabora vermiculite. Workers mining and processing Palabora vermiculite in South Africa were shown not to be at an increased risk for pneumoconiosis, lung function impairment, or increased respiratory symptoms in a study of 172 workers in 1989, when compared to a non-vermiculite exposed comparison group.

  • Hessel, P.A. and G.K. Sluis-Cremer, X-ray findings, lung function, and respiratory symptoms in black South African vermiculite workers, Am. J. of Ind. Med 1989; 45:630-634.

  • Swensson, Ake, Experimental Investigations on the Fibro-Genetic Effects of the Mica Mineral Vermiculite, Arbetarskyddverketo (Industrial Medicine Section of The Worker Protection Directorate's Labor-Medicine Division and the King Gustav V Research Institute), Stockholm, Sweden (1975).

    Vermiculite from Palabora, South Africa, was ground to particles < 5.0 u diameter and applied to female Sprague-Dewey rats at 1 ml suspension containing 40 mg vermiculite by single intratracheal injection. The particles produced an initial cellular reaction, and the slight new formation of connective tissue fibriles. The progressive tendency was very insignificant or non-existent. The reaction was somewhat more pronounced than that to titanium dioxide, which is regarded as being inert. It was much less pronounced, and fundamentally different with regard to progression, than reaction to quartz particles. In this experiment, therefore, it was found that the vermiculite only had an insignificant fibrogenic tendency.

  • Hunter, B. and C. Thomson, Evaluation of the tumorigenic potential of vermiculite by intrapleural injection in rats, British Journal of Industrial Medicine, Vol. 30, p. 167-173 (1973).

    The tumorigenic potential of Palabora vermiculite was compared to Rhodesian chrysotile by intrapleural injection in rats. Mesothelioma developed in 48% of the rats treated with asbestos. No tumors were associated with the vermiculite injections. It is considered possible that the lack of carcinogenic potential of vermiculite is directly related to the ability of the animals to restrict the material within stable granulomata.

III. Analytical Information on Vermiculite and Fibers

  • Chatfield, E.J. and J.M. Lewis, Development and Application of an Analytical Technique for Measurement of Asbestos Fibers in Vermiculite, Scanning Electron Microscopy (1980).

    Fiber-like scrolls of material which is morphologically similar to chrysotile may be misidentified as asbestos; examination of these structures using energy dispersive X-ray analysis confirms these scrolls could not be classified as asbestos.

  • Wylie, A.G., Discriminating Amphibole Cleavage Fragments from Asbestos: Rationale and Methodology, NIOSH VIIth International Pneumoconioses Conferecne (1988)

    In describing mineral samples for biological experiments, hand specimen descriptions, locations, chemical composition, microscopic properties and comprehensive dimensional data should be provided. If these data are available, the differences between cleavage fragments and asbestos fibers are obvious. ... It is essential if we are to understand what properties of minerals make them carcinogenic, fibrogenic or benign that comprehensive data be published for all minerals used in biological experiments.

  • Kohyama, N. ,Airborne Asbestos Levels in Non-Occupational Environments in Japan.

    Airborne asbestos fibers (chrysotile) were found in almost all air samples collected in non-occupational environments in Japan, with a geometric mean of 18 f/l (0.3 ng/m3). Chrysotile fibers were also found in air samples from a small isolated island in the Pacific Ocean as well as ice samples from ten thousand years ago in Antarctica. These observations suggest that chrysotile fibers have been liberated both by industrial activities and natural weathering, and have circulated the earth.

The Vermiculite Institute
c/o The Schundler Company P.O. Box 513 Metuchen, New Jersey 08840
(ph)732-287-2244 (fax) 732-287-4185
www.schundler.com
mailto:info@schundler.com

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