Cytotoxic, mutagenic and clastogenic effects of industrial chromium compounds

Ten Cr(III) compounds, used in the leather tanning industry, and a Cr(III) compound, containing chromite and used as a pigment, were tested for cytotoxicity (inhibition of growth and survival of cultured hamster cells), mutagenicity (point mutations in S. typhimurium) and clastogenic activity (chromosomal aberrations and sister chromatid exchanges in hamster cells). Reference Cr compounds were potassium dichromate as Cr(VI), and chromium chloride and two different preparations of chromium nitrate as Cr(III). A contamination with Cr(VI) was detected in some of the Cr(III) tannins, chromite and one chromium nitrate. Cr(III) compounds were cytotoxic at concentrations of Cr(III) 100-500 times higher than Cr(VI), but contaminated Cr(III) compounds showed a significant cytotoxicity. Reference Cr(VI) but not Cr(III) was mutagenic: of the contaminated compounds only chromite and chromium nitrate, which contained higher levels of Cr(VI), were found to be mutagenic. The frequency of sister chromatid exchanges was significantly increased only by Cr(VI) and the more contaminated Cr(III) compounds. However, an increase of chromosomal aberrations was produced also by reference Cr(III) salts and the weakly contaminated industrial Cr(III) compounds. These results confirm the view that the active mutagenic agent in intact cell systems is Cr(VI), but indicate that industrial Cr(III) compounds cannot be considered genetically inert, as they can be contaminated by Cr(VI) and induce chromosomal aberrations.