One interesting study is called, “Generation of hydroxyl radical by crocidolite asbestos is proportional to surface” by Andrew J. Ghio, Jing Zhang and Claude A. Piantadosi Division of Allergy, Critical Care, and Respiratory Medicine, Department of Medicine, Box 3177, Duke University Medical Center, Durham, North Carolina 27710, U.S.A. Archives of Biochemistry and Biophysics - Volume 298, Issue 2, 1 November 1992, Pages 646-650. Here is an excerpt: “Abstract - Differences among fibrous silicates to effect injury in biological systems have been postulated to reflect oxidant generation by structural iron within the crystal lattice of amphiboles. Iron is also coordinated to the surface of all silicates in concentrations which depend on the density of acidic functional groups. We tested the hypothesis that oxidant generation by crocidolite is proportional to surface-complexed iron rather than variance in the lattice concentrations of this transition metal. Surface iron was quantified after its reduction to Fe2+ and chelation by citrate. Thiobarbituric acid (TBA) reactive products and dihydroxybenzoic acid products of salicylate were employed as indices of nonspecific oxidant and hydroxyl radical generation, respectively. Surface iron, TBA reactive products, and dihydroxybenzoic acid products all diminished after pretreatment of crocidolite with the metal chelator deferoxamine in concentrations varying from 0 to 250 m . Inclusion of deferoxamine in the reaction mixture provided similar results of diminishing both TBA reactive products and dihydroxybenzoic acid generation. We conclude that oxidant generation by crocidolite is proportional to surface concentrations of iron which can be chelated using deferoxamine. The design of synthetic fibers without health effects after exposure will likely necessitate decreasing the number of surface acidic functional groups to diminish the capacity to complex iron (i.e., minimize the percentage SiO2).”
Another interesting study is called, “Structural imperfection and morphology of crocidolite (blue asbestos)” by M. Alario Franco, J. L. Hutchison, D. A. Jefferson & J. M. Thomas - Nature 266, 520 - 521 (07 April 1977). Here is an excerpt: “ELECTRON microscopic studies of fibrous materials, including a range of chain silicates1 6, synthetic polymers7 and carbon fibres8, have almost exclusively involved examination of the structural characteristics visible when the fibre axis is perpendicular to the electron beam. It is extremely difficult to prepare ultra-thin sections of fibrous samples such that this axis is parallel to the beam; and yet it is in this projection that the greatest insights into structural and morphological irregularities are likely to be achieved, a fact well illustrated by the high-resolution studies of Yada9 on chrysotile asbestos which, being less brittle than crocidolite and other amphiboles, was amenable to the normal techniques of ultra-microtomy. We present here preliminary results of a successful axial study of crocidolite (blue asbestos), the fibrous form of the amphibole mineral riebeckite (idealised formula Na2Fe5(Si4O11)2(OH)2, space group C2/m, a = 0.973, b = 1.806, c = 0.533 nm, = 103.3°). The electron micrographs reveal several novel features.”
Another interesting study is called, “Asbestos Tissue Burden Study on Human Malignant Mesothelioma” by Yasunosuke Suzuki and Steven R. Yuen - Department of Community and Preventive Medicine, Mount Sinai School of Medicine - INDUSTRIAL HEALTH Vol.39 , No.2(2001)pp.150-160. Here is an excerpt: “Abstract: Asbestos fibers in the lung and mesothelial tissues (mesotheliomatous tissue and hyaline plaque) taken from 151 human malignant mesothelioma cases were identified and characterized by high resolution analytical electron microscopy. Asbestos fibers were present in almost all of the lung tissue as well as in the mesothelial tissue. The most common asbestos types seen in the lung were an admixture of chrysotile with amphiboles followed by amphiboles alone and chrysotile alone. The majority of asbestos types seen in the mesothelial tissues were chrysotile alone, followed by chrysotile plus amphibole and amphibole alone. A disproportion of asbestos types between the lung and mesothelial tissues was frequently observed. The most common pattern of the disproportion was chrysotile plus amphibole(s) in the lung and chrysotile only in the mesothelial tissues, followed by amphibole(s) in the lung and chrysotile only in the mesothelial tissues. Such a disproportion was considered to have been caused by chrysotile fiber's strong capacity to translocate from the lung to mesothelial tissues. The number of asbestos fibers in the lung was 456.4 × 106 fibers/dry gram in maximum, 0.08 × 106 fibers/dry gram in minimum and 105 × 106 fibers/dry gram on average; in the mesothelial tissues it was 240.0 × 106 fibers/dry gram in maximum, 0.03 × 106 fibers/dry gram in minimum and 49.84 × 106 fibers/dry gram on average. These numbers were greater than those seen in the general population. The majority of asbestos fibers detected in the lung and mesothelial tissues were shorter than 5 ¼m in length. Asbestos fibers fit to Stanton's hypothetical dimensions (e8.0 ¼m in length and d0.25 ¼m in diameter) were only 4.0%, since the majority of these fibers were shorter.
By: Monty J. Wrobleski
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