Asbestos And Iron On Crocidolite Hav Limited Redox Activity

One interesting study is called, Mobilization of iron from crocidolite asbestos by certain chelators results in enhanced crocidolite-dependent oxygen consumption - Archives of Biochemistry and Biophysics Volume 287, Issue 1, 15 May 1991, Pages 91-96 by
Loren G. Lund and Ann E. Aust. Here is an excerpt: Abstract - The reactivity of iron on crocidolite asbestos with dioxygen was determined and compared with iron mobilized from crocidolite. Ferrozine, a strong Fe(II) chelator, was used to demonstrate that iron on crocidolite was redox active. More Fe(II) was mobilized from crocidolite (1 mg/ml) by ferrozine anaerobically (11.2 nmol/mg crocidolite/h) than aerobically (6.6 nmol/mg/h) in 50 m NaCl, pH 7.5, suggesting that Fe(II) on crocidolite reacts with O2 upon aqueous suspension. However, suspension of crocidolite in 50 m NaCl, pH 7.5, did not result in a measurable amount of O2 consumption. The addition of reducing agents (1 m ) increased the amount of Fe(II) on crocidolite, and addition of ascorbate resulted in 0.4 nmol O2 consumed/mg crocidolite/min. Therefore, iron on crocidolite had limited redox activity in the presence of ascorbate. However, mobilization of iron from crocidolite increased its redox activity. Citrate, nitrilotriacetate (NTA), or EDTA (1 m ) mobilized 79, 32, or 58 iron, respectively, in preincubations up to 76 h, and increased O2 consumption upon addition of ascorbate to 2.8, 7.6, or 22.0 nmol O2 consumed/mg/min, respectively. This activity depended only upon the presence of a component(s) mobilized from crocidolite by the chelators. Pretreatment of crocidolite with the iron chelator desferrioxamine B (10 m ) inhibited O2 consumption. The results of the present study suggest that iron on or in crocidolite is responsible for the redox activity of crocidolite, but that mobilization of iron by chelators such as citrate, NTA, or EDTA greatly enhances its redox activity. Thus, iron mobilization from crocidolite in vivo by low-molecular-weight chelators may lead to the increased production of reactive oxygen species which may damage biomolecules, such as DNA.

Another interesting study is called, Roentgenographic lung changes, asbestosis and mortality in a Belgian asbestos-cement factory. By Lacquet LM, van der Linden L, Lepoutre J. - IARC Sci Publ. 1980;(30):783-93. Here is an excerpt: Abstract - Annual chest radiographs, work history and mortality of 1,973 workers in an asbestos-cement factory were correlated with age and with duration and level of dust exposure. Degree of radiographic lung change was significantly related to fibre-years of exposure in the case of small lung opacities, pleural adhesions and pleural thickening. For 29 cases of asbestosis diagnosed between 1963 and 1977, a highly significant dose-response relationship was found. In comparison with national mortality rates, there was an excess of deaths due to cancer of the gastrointestinal tract, although there was no relationship to fibre-years.

Another study is called, Malignant mesothelioma associated with low pulmonary tissue asbestos burdens: a light and scanning electron microscopic analysis of 18 cases. By Srebro SH, Roggli VL, Samsa GP. Department of Pathology, Durham Veterans' Administration, North Carolina, USA. Mod Pathol. 1995 Aug;8(6):614-21. Here is an excerpt: Abstract - Most malignant mesothelioma cases are associated with pulmonary asbestos body (AB) counts significantly greater than those of the general population. However, the question remains whether malignant mesothelioma cases associated with "normal" AB counts (i.e., indistinguishable from the general population) represent background incidence levels or are, actually, asbestos related. We performed AB counts (by light microscopy) and mineral fiber analysis (by scanning electron microscopy) in 18 mesothelioma cases with AB counts within our normal range (0 to 20 AB/G wet lung) and in 19 "control" cases. Our study demonstrated that approximately one-third (6 of 18) of the mesothelioma cases have asbestos fiber burdens greater than 95% of the control levels. These results suggest that these six mesothelioma cases may be asbestos related despite AB counts similar to those of the general population. An asbestos etiology was suggested in three additional cases, but too few amphibole fibers were identified in these cases to be certain of a value above background. The remaining nine cases showed no evidence of an asbestos etiology. Electron microscopic analysis of pulmonary mineral fibers may be required to differentiate asbestos-related mesotheliomas from non-asbestos-related cases when AB counts are within the range of background values.

Another study is called, Presence of fibers in the urine of a baboon gavaged with chrysotile asbestos - Environmental Research - Volume 20, Issue 2, December 1979, Pages 335-340 by William H. Hallenbecka and Kusum J. Patel-Mandlika. Here is an excerpt: Abstract - Preliminary evidence is presented which indicates that chrysotile asbestos fibers can be recovered in the urine of a baboon which had been gavaged with chrysotile. This result supports the contention that ingested asbestos fibers can penetrate the gastrointestinal tract of man.

If you found any of these excerpts interesting, please read the studies in their entirety. We all owe a debt of gratitude to these fine researchers.

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