Genetic effects of chromium tannins

Seventeen tannins used in the hide and leather industry, most of which contain mainly Cr(III) sulphates, were tested for the ability to directly induce gene mutations in Salmonella typhimurium (TA 100 strain) and chromosomal effects (sister chromatid exchanges, SCE) in cultured hamster cells (CHO line). Total chromium [Cr(III) + Cr(VI)] content and contaminating Cr(VI) were determined spectrophotometrically by reaction with diphenylcarbazide. None of the tested compounds induced gene mutations, whereas eight tannins were able to increase significantly the frequency of SCE. A contamination with Cr(VI) was detected in four compounds (from 30 up to 100 parts of Cr(VI) per 10(6) parts of compound), insufficient to be revealed by the Salmonella assay but sufficient to account for the observed SCE increase. On the other hand, the increase of SCE induced by the other four tannins could not be explained by the level of Cr(VI) contamination, and can be ascribed to other impurities present in those industrial compounds. These four tannins did not induce gene mutations in the S. typhimurium assay even when strain TA 98 was used in addition to TA 100, independently of microsomal activation. By prolonging the time of the SCE assay from 30 to 48 h in order to facilitate Cr(III) endocytosis, a significant increase of the SCE frequency was induced by an analytical-grade Cr(III) reagent (chromium chloride), absolutely uncontaminated by Cr(VI), as well as by three Cr(III) tannins, otherwise inactive in the SCE assay.