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Environmental fate & pathways

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The solubility of chromium (III) oxide in environmental media is low. In a short-term transformation/dissolution test with a loading of 100 mg/L, a dissolved Cr concentration of 0.11 microg/L Cr was determined at pH 6 after 7 days whereas dissolved Cr concentrations were below the LOD (< 1 microg/L) at pH 8. Transformation/dissolution at a loading of 1 mg/L resulted in dissolved chromium concentrations below the LOD (< 0.01 microg/L) at pH 6 after 7 days and 28 days. Furthermore, chromium (VI) could not be detected during the test (< 0.01 microg/L) (Hedberg and Wallinder, 2012). Thus, 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 environmental toxicity, or the lack thereof.

Proprietary studies are not available for chromium (III) oxide. The fate 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. Data are available on aquatic and terrestrial bioaccumulation and adsorption of chromium (III). For a documentation and justification of the read-across approach, please refer to the separate document attached to section 13, namely Read Across Assessment Report for chromium (III) oxide.

Chromium (III) oxide does not oxidize in laboratory tests but is rather sorbed by various soil components, including organic matter and iron oxides and unavailable for oxidation. Since the solubility of chromium (III) oxide is low, a low mobility can be expected in aquatic and terrestrial systems. Accordingly, the potential for bioaccumulation of chromium (III) oxide in aquatic and terrestrial environments is low based on its poor solubility in environmental media and the low BAFs available for soluble chromium (III) substances.

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