Characterization of Lone Pine, California, tremolite asbestos and preparation of research material

Our plain-English summary of Characterization of Lone Pine, California, tremolite asbestos and preparation of research material, by M. Harper, B. Van Gosen, O.S. Crankshaw, et al (The Annals of Occupational Hygiene, 2015).

The study

• Authors: M. Harper, B. Van Gosen, O.S. Crankshaw, S.S. Doorn, T.J. Ennis, S.E. Harrison
• Journal: The Annals of Occupational Hygiene
• Published: 2015;59(1):91-103
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Well-characterized amphibole asbestos mineral samples are required for use as analytical standards and in future research projects. Currently, the National Institute for Standards and Technology Standard Reference Material samples of asbestos are listed as 'Discontinued'. The National Institute for Occupational Safety and Health (NIOSH) has a goal under the Asbestos Roadmap of locating and characterizing research materials for future use. Where an initial characterization analysis determines that a collected material is appropriate for use as a research material in terms of composition and asbestiform habit, sufficient amounts of the material will be collected to make it publicly available. An abandoned mine near Lone Pine, California, contains a vein of tremolite asbestos, which was the probable source of a reference material that has been available for the past 17 years from the Health and Safety Laboratory (HSL) in the UK. Newly collected fibrous vein material from this mine was analyzed at Research Triangle Institute (RTI International) with some additional analysis by the US Geological Survey's Denver Microbeam Laboratory. The analysis at RTI International included: (i) polarized light microscopy (PLM) with a determination of principal optical properties; (ii) X-ray diffraction; (iii) transmission electron microscopy, including energy dispersive X-ray spectroscopy and selected-area electron diffraction; and (iv) spindle stage analysis using PLM to determine whether individual fibers and bundles of the samples were polycrystalline or single-crystal cleavage fragments. The overall findings of the study indicated that the material is tremolite asbestos with characteristics substantially similar to the earlier distributed HSL reference material. A larger quantity of material was prepared by sorting, acid-washing and mixing for sub-division into vials of ~10g each. These vials have been transferred from NIOSH to RTI International, from where they can be obtained on request.

Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2014.

In plain English

This laboratory study examined tremolite asbestos collected from inside a vein in an abandoned mine near Lone Pine, California. The mine was the probable source of a tremolite asbestos reference sample supplied by the UK Health and Safety Laboratory (HSL). The study looked at the mineral itself, not at people or health effects. A 17.6 g sample was examined with polarized light microscopy, X-ray diffraction, transmission electron microscopy with chemical and diffraction analysis, and spindle stage microscopy. These methods identified the material as tremolite, and small amounts of calcite were also found. Its chemistry was consistent with the HSL reference, and its iron content was very low (about 0.5%). The median length-to-width ratio of particles seen under the light microscope was 48:1. The authors concluded that about 90% of fibers were asbestiform, meaning bundles of fine fibrils. A larger batch was cut, acid-washed to remove calcite, and packed into 487 vials of 9.5 to 10.5 g each. The authors noted that nobody had checked whether the bulk material matched the tested sample, or whether the vials matched each other.

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 mineral characterization study (light microscopy, X-ray diffraction, electron microscopy, spindle stage analysis) with preparation of a research material
• Who was studied: Tremolite asbestos from a vein inside an abandoned mine (the McIlroy property) near Lone Pine, Inyo County, California. A 17.6 g initial sample was split into five subsamples, and about 7.7 kg of raw bulk material was later processed.
• Exposure: Not a human exposure study. The material studied was tremolite asbestos taken only from the vein inside the mine.
• Main results:
  • X-ray diffraction showed that the fibers in the Lone Pine samples had tremolite crystal structures.
  • Minor calcite was detected in all replicate X-ray diffraction scans of the Lone Pine material.
  • Under polarized light microscopy, the optical properties of the Lone Pine fibers were consistent with tremolite asbestos.
  • The median aspect ratio of particles examined by light microscopy in the Lone Pine material was 48:1.
  • Chemical analysis (EDS) of the Lone Pine material was consistent with tremolite and with the HSL tremolite asbestos reference.
  • The iron content of the Lone Pine tremolite was very low, about 0.5%.
  • Aspect ratios and spindle stage results indicated that about 90% of fibers were polyfilamentous fibrillar crystals (asbestiform).
  • The bulk material was acid-washed to remove calcite and packed into 487 vials holding 9.5 to 10.5 g each.
• The authors' conclusion: The authors concluded that all methods agreed the Lone Pine material is tremolite, and that about 90% of fibers are asbestiform.
• Limitations the authors state:
  • No one checked whether the bulk material in the vials had the same properties as the initial tested sample, or whether the vials matched each other.
  • The electron diffraction (SAED) patterns were measured by hand and are less precise than the X-ray diffraction measurements.

Topics

Medical terms in this study, explained in our Lexicon: Tremolite, Amphibole Asbestos, NIOSH, Asbestiform, Polarized Light Microscopy (PLM), X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), energy dispersive X-ray spectroscopy (EDS).

Related studies

• "Rinse and trickle": a protocol for TEM preparation and investigation of inorganic fibers from biological material — R. Vigliaturo, S. Capella, et al. (2016)
• Pulmonary fibrosis in workers exposed to non-asbestiform tremolite asbestos minerals — H.Y. Yang, R.H. Shie, et al. (2013)
• Characterization and assessment of the potential toxicity/pathogenicity of fibrous glaucophane — D. Di Giuseppe, M. Harper, et al. (2019)
• Acid leaching studies of chrysotile asbestos from mines in the Coalinga region of California and from Quebec and British Columbia — A. Morgan (1997)
• Preparation and characteristics of a calcium magnesium silicate (bredigite) bioactive ceramic — C. Wu, J. Chang, et al. (2005)
• Evaluation of the presence of asbestos in cosmetic talcum products — J.S. Pierce, A.S. Riordan, et al. (2017)

Browse more research in The Annals of Occupational Hygiene, or return to medical research.