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The genotoxic and carcinogenic activity of chromium derives from Cr(VI), which in physiological solutions exist as chromate-anion. 

- The numerous studies on Cr(VI) -compounds have given the evidence that chromium(VI) is genotoxic.

- There exist some positive data on experimental germ cell mutagenicity, but not on zinc tetraoxychromate (the substance has not been tested). These data are not considered to have significant effect on classification due to low bioavailability.

Chromium-induced DNA damage is thought to be the primary mechanism of chromate genotoxicity and mutagenicity, but it is only clearly observed at doses that are also capable of producing cell death. Recently, data has been presented to the EPA’s Cancer Assessment Review Committee (CARC) to support mutagenicity as the initiating step in Cr(VI) -induced carcinogenesis (McCarroll et al 2010). Structural genetic lesions produced by Cr(VI) include DNA adducts, DNA-strand breaks, DNA–protein crosslinks, oxidized bases, abasic sites, and DNA inter- and intrastrand crosslinks.      


Short description of key information:
There are no in vitro or in vivo genotoxicity studies of zinc tetraoxychromate. However, in vitro tests of zinc potassium chromate are positive.
The numerous studies on Cr(VI) -compounds have given the evidence that chromium(VI) is genotoxic.

The numerous studies on Cr(VI) -compounds have given the evidence that chromium(VI) is genotoxic.

Endpoint Conclusion: Adverse effect observed (positive)

Justification for classification or non-classification

The genotoxicity tests of another moderately soluble chromate, zinc potassium chromate, and the genotoxicity of chromate anion in general, lead to the conclusion that there are good evidence that zinc tetraoxychromate should be classified as genotoxic –Muta 2 according to CLP system.

No additional studies on genotoxicity/mutagenicity are needed.