Article DetailsMeasuring Asbestos Structures and the Impact on Mesothelioma Development |
| Date Added: April 20, 2010 08:57:44 AM |
| Author: Monty Wrobleski |
| Category: Health |
| Asbestos exposure can lead to lung tumor development. There have been many inhalation studies which analyze variables such as length, wideth and complexity of asbestos fibers. One interesting study on point is called, “The Sizes, Shapes, and Mineralogy of Asbestos Structures that Induce Lung Tumors or Mesothelioma in AF/HAN Rats Following Inhalation” by D. Wayne Herman, Kenny S. Crump, Eric J. Chatfield, John M.G. Davis and Alan D. Jones - ICF Kaiser Engineers, Oakland, California, ICF Kaiser Engineers, Ruston, Louisiana, Chatfield Technical Consulting Limited, Mississauga, Ontario, Canada, Institute of Occupational Medicine, Edinburgh, United Kingdom - Volume 15 Issue 2, Pages 181 – 195 Published 29 May 2006. Here is an excerpt: “Data from inhalation studies in which AF/HAN rats were exposed to nine different types of asbestos dusts (in 13 separate experiments) are employed in a statistical analysis to determine if a measure of asbestos exposure (expressed as concentrations of structures with defined sizes, shapes and mineralogy) can be identified that satisfactorily predicts the observed lung tumor or mesothelioma incidence in the experiments. Due to limitations in the characterization of asbestos structures in the original studies, new exposure measures were developed from samples of the original dusts that were re-generated and analyzed by transmission electron microscopy using a direct transfer technique. This analysis provided detailed information on the mineralogy (i.e., chrysotile, amosite, crocidolite or tremolite), type (i.e., fiber, bundle, cluster, or matrix), size (length and width) and complexity (i.e., number of identifiable components of a cluster or matrix) of each individual structure. No univariate measure of exposure was found to provide an adequate description of the lung tumor responses observed among the inhalation studies, although the measure most highly correlated with tumor incidence is the concentration of structures >20 µm in length. Multivariate measures of exposure were identified that do adequately describe the lung tumor responses. Structures contributing to lung tumor risk appear to be long (>5 µm) thin (0.4 µm) fibers and bundles, with a possible contribution by long and very thick (>5 µm) complex clusters and matrices. Potency appears to increase with increasing length, with structures longer than 40 um being about 500 times more potent than structures between 5 and 40 um in length. Structures <5 µm in length do not appear to make any contribution to lung tumor risk. This analysis did not find a difference in the potency of chrysotile and amphibole toward the induction of lung tumors. However, mineralogy appears to be important in the induction of mesothelioma with chrysotile being less potent than amphibole.” Another interesting article regarding asbestos is called, “Iron mobilization from asbestos by chelators and ascorbic acid.” By Lund LG, Aust AE - Arch Biochem Biophys. 1990 Apr;278(1):61-4. - Department of Chemistry and Biochemistry, Utah State University, Logan 84322-0300. Here is an excerpt: “The ability of chelators and ascorbic acid to mobilize iron from crocidolite, amosite, medium- and short-fiber chrysotile, and tremolite was investigated. Ferrozine, a strong Fe(II) chelator, mobilized Fe(II) from crocidolite (6.6 nmol/mg asbestos/h) and amosite (0.4 nmol/mg/h) in 50 mM NaCl, pH 7.5. Inclusion of ascorbate increased these rates to 11.4 and 4.9 nmol/mg/h, respectively. Ferrozine mobilized Fe(II) from medium-fiber chrysotile (0.6 nmol/mg/h) only in the presence of ascorbate. Citrate and ADP mobilized iron (ferrous and/or ferric) from crocidolite at rates of 4.2 and 0.3 nmol/mg/h, respectively, which increased to 4.8 and 1.0 nmol/mg/h in the presence of ascorbate. Since ascorbate alone mobilized iron from crocidolite (0.5 nmol/mg/h), the increase appeared to result from additional chelation by ascorbate. Citrate also mobilized iron from amosite (1.4 nmol/mg/h) and medium-fiber chrysotile (1.6 nmol/mg/h). Mobilization of iron from asbestos appeared to be a function not only of the chelator, but also of the surface area, crystalline structure, and iron content of the asbestos. These results suggest that iron can be mobilized from asbestos in the cell by low-molecular-weight chelators. If this occurs, it may have deleterious effects since this could result in deregulation of normal iron metabolism by proteins within the cell resulting in iron-catalyzed oxidation of biomolecules.” If you found any of these excerpts interesting, please read the studies in their entirety. We all owe a debt of gratitude to the people examining these important issues. Monty Wrobleski is the author of this article on Asbestos Exposure. Find more information about Navy Asbestos Claims here. |
