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Two Ames mutagenicity tests in S. typhimurium TA100 are available that were done with and without S9 metabolic activation at concentrations of 0.2 -1.6 and 10 -500 µg/plate, respectively. Neither test followed a specific guideline. The former test proofed positive even at these very low concentrations of 0.2 -1.6 µg/plate, the latter was negative on account of a coating that reduced the availability of the toxicophore chromium(VI). Two sister chromatide exchange assays, one conducted similar to the OECD guideline 479 protocol, were positive in chinese hamster ovary cells at concentrations of 0.1 or 5 -150 µg/mL. Exposure of the same cell line in chromosomal aberration tests (one similar to the OECD guideline 479 protocol) did not lead to an increase in chromosomal aberrations at concentrations of 5 µg/L -5 mg/L. An in vivo mincronucleus test that was conducted at concentrations of 15, 50 and 2x 100 mg/kg bw with intraperitoneal administration of chrome yellow in comparison with soluble chromates was negative. The soluble compounds (zinc potassium chromate, zinc tetroxy chromate and sodium dichromate) were all tested positive at concentrations up to 50 mg/kg bw.


Short description of key information:
Several in vitro studies addressing Ames-mutagenicity, sister chromatid exchange and chromosomal aberration are available. Most of them do not follow a guideline but all give a positive result if there were done with uncoated material in the presence of a metabolizing system. Additionally, an in vivo micronucleus test is available with intraperitoneal adminstration of 25, 50 and 100 mg/kg bw of the test material that proofed negative.

Endpoint Conclusion:

Justification for classification or non-classification

Although most in vitro genotoxicty tests were positive, a genotoxic potential could not be verified in vivo. Therefore, a classification is not warranted.

However, the negative results in the micronucleus test of the test substance, which presented a very low water solubility (1%; as opposed to 6-8% for zinc potassium chromate or to 2380 g/l for sodium dichromate), are likely not reliable, because the treatment with the chemical did not show evidence for absorption and transport to the bone marrow, as evidenced by a lack of reduction in PCEs frequency. Thus, although the in vivo genetic toxicity test gave negative, chromium and its compounds, particularly chromium(VI), may cause chromosomal effects, indicating carcinogenic potential because interactions with DNA have been linked with the mechanism of carcinogenicity.