[Impact of modification of the fiber surface of chrysotile on its biological activity]

Samples of commercial chrysotile-asbestos and asbestos cement, which were equal in number, were prepared. The content of fibers, up to 80 microm in length, was 87.4 and 85.0% in the first and second samples, respectively. Chemical analysis confirmed that there were cement components onto the surface of fibrils in the second sample. Onto the surface of native asbestos fibers, there were considerable distribution bands of active centers in the range of pH values of 5, 6.4, and 7.3; their largest number was at pH 6.4. Asbestos cement fibers had a band at pH 7.3, i.e. there was displacement towards the neutral region. Thus, their capacity for oxidative processes is likely to be lower than that in the fibers from the first sample. The mutagenic activity of the commercial chrysotile, examined in the micronucleus test, was substantially higher (p < 0.01) than that in the asbestos cement sample wherein it did not differ from that seen in the control experiment (saline solution). Mutagenicity was not found in cement and asbestos cement dust (2-3% of fibers) either. It is probable that the absence of mutagenicity in the cement-coated asbestos fibers may be attributable to a considerable reduction in their potencies for the formation of active radicals (oxygen, lipid peroxidation, and others).