Physicochemical characterization of cryogenically ground, size separated, fibrogenic particles

Our plain-English summary of Physicochemical characterization of cryogenically ground, size separated, fibrogenic particles, by P.S. Thorne, E.N. Lightfoot, R.M. Albrecht (Environmental Research, 1985).

The study

• Authors: P.S. Thorne, E.N. Lightfoot, R.M. Albrecht
• Journal: Environmental Research
• Published: 1985;36(1):89-110
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

A method for cryogenically grinding and separating (by size) fibrogenic minerals in the 1-micron size range is described and verified for chrysotile asbestos, quartz, forsterite (an olivine), and tantalum with a battery of analytical tests. Through use of energy dispersive X-ray spectroscopy, neutron activation analysis, X-ray photoelectron spectroscopy, and X-ray diffraction analysis it is shown that the grinding and separation procedure described does not alter the mineral composition, preserves the trace element composition, maintains the surface composition, and preserves the crystalline structure. Further, investigation of electrokinetic properties of these dusts by electrophoretic quasielastic light scattering is described. The small size dispersity of these samples facilitates use of this technique for the determination of the apparent electrokinetic charge and estimations of surface charge density at ionic strengths below physiological. It is suggested that analyses of the type described here be an integral part of studies of the fibrogenic, immunologic, or toxicologic properties of such minerals. This work has been performed in conjunction with the authors' studies of the effects of these particulates on macrophage ultrastructure and immunologic function in vitro.

In plain English

This was a laboratory methods study, not a study of people, animals, or disease. The authors described grinding minerals into particles about 1 micrometer in size in an impact grinder immersed in liquid nitrogen, then sorting them by size by settling and filtering. They tested it on chrysotile asbestos from San Benito County, California, and on quartz, forsterite (an olivine) and tantalum. Under the electron microscope (50 particles each), the ground chrysotile fibers averaged 1.00 micrometers long and 0.07 micrometers wide. The authors' text said treated chrysotile had 11% more chromium and iron and 21% more manganese and nickel than untreated chrysotile, but their table's manganese (678 to 858 ppm) and nickel (1914 to 2425 ppm) values imply about 27%. The authors said that grinding did not significantly alter composition. Chrysotile's surface had silicon and magnesium oxides in the same proportions as the fiber interior. Its X-ray diffraction matched a reference chrysotile. The authors concluded that the technique preserves particle composition and structure. They stated that their charge measurements cannot yet be reliably extrapolated to conditions in the body.

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 methods study: grinding, size separation and physicochemical characterization of mineral particles
• Who was studied: Mineral particle samples, not people: chrysotile asbestos, quartz, forsterite and tantalum, with polystyrene latex beads as a calibration control. 50 particles were measured per size analysis. The work was done at the University of Wisconsin, Madison, and the article was accepted in 1984.
• Exposure: No human exposure was studied. Chrysotile from San Benito County, California (Calidria Division, Union Carbide) and the other minerals were cryogenically ground in an impact grinder immersed in liquid nitrogen, then size-separated by sedimentation and filtration.
• Main results:
  • Ground chrysotile fibers measured by scanning electron microscopy (N = 50, mean and standard deviation): largest dimension 1.00 plus or minus 0.44 micrometers, smallest dimension 0.07 plus or minus 0.02 micrometers, aspect ratio 13.8 plus or minus 5.1.
  • By energy dispersive X-ray spectroscopy, the major oxides in the chrysotile were SiO2 (55%), MgO (43%) and FeO (2%), expressed as normalized weight percent.
  • The authors' text states that, by neutron activation analysis, treated chrysotile had 11% more chromium and iron and 21% more manganese and nickel than untreated chrysotile. The article's Table 4 values for manganese (678 to 858 ppm) and nickel (1914 to 2425 ppm) correspond to increases of about 27%, not 21%.
  • Across the test particles, the authors reported that cryogenic grinding did not significantly alter composition.
  • X-ray photoelectron spectroscopy showed that the surface of the ground chrysotile had silicon and magnesium oxides in the same proportions as the bulk of the fibers.
  • X-ray diffraction data for the ground chrysotile corresponded to a reference monoclinic chrysotile sample.
• The authors' conclusion: The authors concluded that the grinding and separation technique preserves both the composition and the structure of the particles and fibers.
• Limitations the authors state:
  • The electrokinetic (surface charge) results cannot yet be reliably extrapolated to physiological conditions.
  • The method could not readily determine the sign (positive or negative) of the particles' electrophoretic mobility.
  • Producing large quantities of dust by this method would take considerable time.
  • Relative element concentrations varied slightly among particles of the same species.

Mines named here

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

• Santa Rita mine, Joaquin Ridge near Coalinga, California

All asbestos mines

Topics

Medical terms in this study, explained in our Lexicon: Fibrogenic, Chrysotile, Forsterite, Olivine, energy dispersive X-ray spectroscopy (EDS), X-Ray Diffraction (XRD), Crystalline, Macrophage.

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• Characterization of talc and associated minerals — D.H. Hamer, F.R. Rolle, et al. (1976)
• Chronic inhalation toxicity of size-separated glass fibers in Fischer 344 rats — T.W. Hesterberg, W.C. Miiller, et al. (1993)
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