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Ecotoxicological information

Toxicity to aquatic plants other than algae

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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 thus evaluated by comparing the dissolved chromium (III) ion level resulting from the T/Dp at a loading rate of 1 mg/L after 7 and 28 d with the lowest acute or chronic effect concentration, respectively, as determined for the (soluble) chromium (III) ion.The lowest acute effect concentration is a 31 d EC50 of 9.9 mg Cr(III)/L observed for the effects of chromium (III) on the root dry weight of Myriophyllum spicatum (Stanley, 1974). The lowest chronic effect concentration determined for the (soluble) chromium (III) ion is a 32 d NOEC of 0.27 mg Cr(III)/L observed in a growth inhibition test for the effects of chromium (III) nitrate on the growth rate of Salvinia herzogii (Maine et al., 2004).Dissolved chromium concentrations of <0.01 µg/L in the T/Dp after 7 and 28 days at pH 6 (i.e. the pH that maximizes the dissolution) are significantly lower than the lowest acute effect concentration derived for aquatic plants (i.e. EC50 of 9.9 mg Cr(III)/L) and the lowest chronic effect concentration derived for aquatic plants (i.e. NOEC of 0.27 mg Cr(III)/L). Hence, chromium (III) oxide is not sufficiently soluble in environmental media to cause acute or chronic toxicity to aquatic plants at the level of the lowest acute and chronic effect concentration (expressed as the EC50/NOEC, respectively).

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, toxicity to aquatic plants is not expected.

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