[Carcinogenic and mutagenic activity of chrysotile, processed with iron chloride (III)].

This work is devoted to the study of the role of iron ions in the carcinogenic and mutagenic activity of chrysotile. For this aim natural chrysotile was treated with ferric chloride (III), washed, crushed and intratracheally introduced into Wistar rats. When administered to rats intact chrysotile induced mesotheliomas in 27,9 + 4,6% of cases, and chrysotile modified with ferric chloride - in 1,3 +/- 1,3%. Mutagenicity of the same samples was studied in the micronucleus test when administered intraperitoneally to mice Fl (CBA x S57Bl6). Polychromatic erythrocytes in the bone marrow were investigated 24 hours after intraperitoneal administration. The frequency of polychromatic erythrocytes with micronuclei was decreased from 7,4 +/- 0,18 by 1000 due to the action of chrysotile, from 2,8 +/- 0,42 for 1000 after the introduction of a modified sample. It is hypothesized that the ferric chloride modifies the surface of asbestos fibers that reduces the induction of free radicals which are the primary cause of and carcinogenic effects of chrysotile.

Effects of nanodispersed iron on the morphofunctional parameters of the blood system.

The effects of nanodispersed iron forms on the morphology and function of the blood system were studied. Maghemite and lepidocrocite caused a leukocytic shift towards segmented neutrophil forms, reduction of lymphocyte rigidity, and stimulated their compactization. In addition, the counts of small hyperchromatic erythrocytes with high rigidity increased in the blood flow. The results indicated that a single dose of nanodispersed iron-containing drugs improved the blood respiratory function and its microrheology.

[Experimental rationale for carcinogenic risk of asbestos cement industry and its products].

During intraperitoneal administration of dispersiveness-comparable chrysotile or asbestos cement fibers to rats (20 mg thrice), mesotheliomas were found in 45.1 and 7.7% of cases respectively. Asbestos cement dust induced tumors in 2.5% of cases, which is of biological importance. Cement or freeze asbestos destruction cement dust failed to cause tumors. The latter were not detected in a control group receiving physiological saline. Asbestos cement fibers and fascicles are covered by a cement matrix. Fiber amorphization gradually occurs. In lung tissue, there may be destruction of the cement coat of fascicles and release of native chrysotile fibers that are carcinogenic.

[On decreasing carcinogenic activity of calcified chrysotile fibers].

When chrysotile fibers treated with Portland cement, Mg was partially substituted by Ca, therefore monolayer of Ca(OH)2 was formed as a cover, and that changed acidity force, number of active centers and biological activity (absent mutageneity, generation of active oxygen forms by macrophages was characterized by lower maximum and longer time to background level vs. native chrysotile).

[Characterization of the biological properties of acid-treated chrysotile-asbestos fibers].

Boiling of chrysotile of the textile brand PRZh1-50 in concentrated hydrochloric acid for 10, 15, and 20 minutes gave rise to three chrysotile-asbestos samples. The content of MgO decreased from to 24, 19, and 9%, respectively. As compared with the baseline values, the number and force of positively charged electrical centers were less in the samples containing 24 and 19% MgO and more in the sample having 9% MgO; the negatively charged centers were present in the former two samples and absent in the third one. When the samples were intrapleurally administered to rats, their hemolytic activity, induction of active oxygen radicals, mutagenic activity (micronuclear test using murine bone marrow cells), and the frequency of mesotheliomas were less in the treated samples than in the baseline ones; but there were no differences between the treated samples. Thus, the altered physicochemical properties of the fibrillar surface of asbestos diminished its biological aggressiveness; however, increased treatment rates failed to lead to its further decrease. There was no relationship of the biological properties to the number and force of electric charges of the surface.

[The electric properties of fiber surface and the toxicity of asbestos]. / Elektricheskie svoistva poverkhnosti volokon i toksichnosti asbesta.

Thermal treatment, autoclaving and their combination yielded 3 samples of chrysotile-asbestos. With these, as compared with parent Type PRZh-1-50 Bazhenov chrysotile, the structure of fibers deteriorated and the number of negative discharges increased in the first two samples; the superficial structure substantially increased and the number of positive centers greatly decreased in the third sample. The ratio of positive to negative centers was less in all treated samples than that in the parent one, it decreased particularly during combined treatment. In this sample, hemolytic and mutagenic activity and cytotoxicity were substantially decreased; carcinogenic activity was greatly decreased (by 4 times) (as shown by the pleural mesothelioma indication test during intrapleural administration to rats). Thermal treatment and autoclaving insignificantly lowered the hemolytic activity and mutagenicity; carcinogenicity of these samples was much less (by 2.3 and 2 times) than that of parent chrysotile.

[Carcinogenic activity of synthetic chrysotile asbestos with various fiber sizes and chemical composition]. / Kantserogennaia aktivnost' sinteticheskikh khrizatil-asbestov s razlichnymi razmerami volokon i khimicheskim sostavom.

Synthetic Mg-chrysotiles (analogous to natural ones by chemical composition) with fine short, thick short and fine long fibres under intrapleural injections (20 mg thrice) induced mesotheliomas in noninbred rats in 3.3, 0 and 12% of rats, respectively. Ni- and Co-chrysotiles with fine and short fibres caused such tumours in 7.6 and 30.2%, Co-chrysotile with plate-like fibres induced tumours in 26.8%. The role of chemical structure and particle sizes have been discussed.