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Long-term toxicity to aquatic invertebrates

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The rate and extent to which chromium (III) oxide produces soluble (bio)available ionic and other chromium-bearing species in environmental media is limited. Further, the poor solubility of chromium (III) oxide is expected to determine its behaviour and fate in the environment, and subsequently its potential for ecotoxicity. Proprietary studies are not available for chromium (III) oxide. However, the fate and toxicity of chromium (III) oxide in the environment is evaluated by assessing the fate of its ecotoxicologically relevant moiety, the chromium (III) ion, and read-across to data available for other chromium (III) substances is applied.

In accordance with ECHA’s Guidance on IR & CSA, Appendix R.7.13-2 (2008),the poorly soluble substance chromium (III) oxide is evaluated by comparing the dissolved chromium (III) ion level resulting from the T/Dp at a loading rate of 1 mg/L after 28 d with the lowest chronic effect concentration as determined for the (soluble) chromium (III) ion.The lowest reliable chronic effect concentration determined for the (soluble) chromium (III) ion is a 21 d NOEC of 0.7 mg Cr(III)/L observed in a chronic toxicity test for the effect of chromium (III) chloride on the reproduction of Daphnia magna (Kühn et al., 1989).Dissolved chromium concentrations of <0.01 µg/L in the T/Dp after 28 days at pH 6 (i.e. the pH that maximizes the dissolution) are significantly lower than the lowest chronic effect concentration derived for aquatic invertebrates (i.e. NOEC of 0.7 mg Cr/L). Hence, chromium (III) oxide is not sufficiently soluble in environmental media to cause chronic toxicity to aquatic invertebrates at the level of the lowest chronic effect concentration (expressed as NOEC).

For further information on the applied read-across approach and the evaluation of the poorly soluble substance chromium (III) oxide, please refer to the section "Cr2O3_Aquatic toxicity".

Based on the poor solubility of chromium (III) oxide in environmental media, long-term toxicity to aquatic invertebrates is not expected.

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