TOXICITY IN-VITRO OF SOME SILICON CARBIDES AND SILICON NITRIDES - WHISKERS AND POWDERS

The objectives of this work were to investigate the toxicity of silico n carbide whiskers and powders and silicon nitride whiskers and powder s and to compare their toxicity with the toxicity of crocidolite. The effects studied were inhibition of the cloning efficiency of V79 cells , formation of DNA strand breaks by means of a nick translation assay, formation of oxygen radicals in three different assays, and the abili ty to stimulate neutrophils to produce hydroxyl radicals. All material s showed concentration-dependent inhibition of the cloning efficiency of V79 cells. The inhibition by the most toxic whiskers was in the sam e order of magnitude as that of crocidolite. Milled whiskers and powde rs were less toxic than the whiskers. There was a high DNA breaking po tential for crocidolite and four of the silicon carbide whiskers and a rather low one for the other materials. Formation of hydroxyl radical s was found for crocidolite and one of the silicon carbide whiskers. I n the neutrophil activation test, there was a great variation in the d ifferent materials' abilities to activate neutrophils. There was also a good correlation between chemiluminescence and H2O2 formation. The h ighest activation was found in neutrophils exposed to two of the silic on carbide whiskers and one milled whisker The conclusion of the inves tigation is that some of the ceramic materials studied had damaging bi ological effects comparable to or greater than those of crocidolite. T he results from the investigation clearly imply that caution is needed in the introduction of new ceramic fiber materials, so that the corre ct precautions and protective devices are used in order to avoid harm to the personnel handling the material. (C) 1997 Wiley-Liss, Inc.