ASTM WK30024

    New Test Method for Polarized Light Microscopy (PLM) Analysis of Cosmetic and Pharmaceutical Talc for Asbestos

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    Developed by Subcommittee: D22.07 | Committee D22 | Contact Staff Manager


    1. Scope

    1.1 The purpose of this test method is to determine the presence or absence (detect, non-detect) of asbestos in cosmetic and pharmaceutical talc by polarized light microscopy (PLM). Asbestos content can be estimated by (1) visual volume area estimates or (2) quantified by point count or both. This test method has a theoretical detection limit (DL) of 0.1 % on the basis of a 1300-point count. Sieving and concentration procedures by acid dissolution and ashing are provided as an option for aiding detection of asbestos at concentrations less than 0.1 %. Protocols and principles of established methods for asbestos analysis are incorporated into this test method. 1.1.1 This test method may be used for analysis of processed and unprocessed talc ore material. However, the efficacy of method and preparation procedures for processed and unprocessed talc ore have not been tested. 1.2 This test method is applicable to chrysotile (serpentine-asbestos) and amphibole asbestos encountered in talc (anthophyllite, actinolite, and tremolite). Asbestos detection and quantification by PLM may be biased by sampling, inherent sample variability, analyst variability/experience, and potential difficulty in differentiation of asbestiform from non-asbestiform amphiboles. 1.2.1 PLM analysis can be performed alone in conjunction with transmission electron microscopy (TEM) or when X-ray diffraction (XRD) analysis or both indicates the presence of serpentine or amphibole peaks or both. 1.2.2 PLM analysis alone may not be sufficient for the detection and quantification of asbestos in cosmetic and pharmaceutical talc because of resolution limits of the method. Accepted resolution limits for characterization and identification are 0.25 um for fiber width at a 5-um fiber length but may vary depending on the microscope used. Recent studies, however, indicate that a 1-um width criterion is more appropriate, particularly in differentiation of amphibole asbestos fibers from amphibole cleave fragments. Potential asbestos structures detected in cosmetic and pharmaceutical talc most likely are bundles of asbestos fibers and not individual fibers. Individual fibers in bundles may be apparent by changes in birefringence along bundle lengths, but the asbestos fiber content cannot be adequately assessed by PLM. Samples may require TEM analysis for a more complete assessment of potential asbestos fiber content if XRD indicates the presence of serpentine or amphiboles or both that may not be detected by PLM. 1.3 The values stated in SI units are to be regarded as the standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

    This standard is needed because their is no current ASTM standard for asbestos analysis of cosmetic and pharmaceutical talc by PLM. A standard ASTM PLM method for asbestos analysis of cosmetic and pharmaceutical talc is anticipated to be used by a commercial laboratories providing services to industry, internal industry laboratories, government agencies, and possibly academia.


    asbestos; talc; PLM; dispersion staining

    The title and scope are in draft form and are under development within this ASTM Committee.

    Citing ASTM Standards
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    Work Item Status

    Date Initiated:

    Technical Contact:
    Sean Fitzgerald

    Draft Under Development