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Sediment toxicity

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Description of key information

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.

Even though soluble chromium (III) substances may have some potential for toxicity to sediment organisms, effects of the poorly soluble chromium (III) oxide are highly unlikely. Regarding its potential for aquatic toxicity, chromium (III) oxide does not classify as “harmful”, “toxic or very toxic to aquatic life” or “may cause long lasting harmful effects to aquatic life”. Chromium (III) oxide is also not expected to be an unclassified hazard to the aquatic environment in accordance with ECHA guidance on IR & CSA, Part B: Hazard Assessment (V. 2.1, December 2011). Based on the lack of a potential for toxicity to aquatic organisms and/or bioaccumulation and its behaviour (poor solubility) in sediments, chromium (III) oxide is expected to have a low potential for toxicity in sediments.

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Additional information

The potential of chromium (III) oxide for toxicity to sediment-dwelling organisms is low based on available sediment toxicity data of soluble chromium substnaces. Furthermore, the acute and chronic aquatic hazard potential of chromium (III) oxide is low as summarized in section 6.1 "Cr2O3_Aquatic tooxicity'.

The potential for bioaccumulation of chromium (III) oxide in aquatic environments is low based on its poor solubility in environmental media and the low BAFs available for chromium. In aquatic environments, a significant fraction of the total chromium is associated with the solid phase (e.g., bound to particulate phase, precipitation of insoluble inorganic complexes). In sediment, trivalent chromium will be converted rapidly to insoluble Cr(III)-species and therefore has a low mobility in this compartment. Furthermore, adsorption data indicate that chromium (III) species are strongly adsorbed to suspended matter and sediment. Since the solubility of chromium (III) oxide is low, a low mobility can be expected in aquatic systems. Monitoring data for chromium background concentrations in sediments are provided by the FOREGS Geochemical Baseline Mapping Programme, which offers high quality, multi-purpose homogeneous environmental geochemical baseline data for Europe. The median (range) for chromium content of European stream sediments is 63.0 mg/kg (< 3.0 - 3320 mg/kg) indicating that chromium is naturally abundant in sediments.

In accordance with ECHA guidance on IR & CSA, Part B: Hazard Assessment (V. 2.1, December 2011), „For substances which are classified as harmful, toxic or very toxic to aquatic life (i.e. H412, H411, H410 and H400), an aquatic PNEC can be derived. In these circumstances there are unclassified hazards to the sediment and soil compartments because toxicity to aquatic organisms is used as an indicator of concern for sediment and soil organisms, and a screening risk characterisation is undertaken using the equilibration partitioning method (EPM) to derive PNECs for sediment and soil. Hence quantitative exposure assessment, i.e. derivation of PECs, is mandatory for the water, sediment and soil environmental compartments.

Substances with the only environmental classification as ‘May cause long lasting harmful effects to aquatic life’ (i.e. H413) have been established as persistent in the aquatic environment and potentially bioaccumulative on the basis of test or other data. There are also potential hazards for these substances for the sediment and soil compartments, because these substances are potentially bioaccumulative in all organisms and are also potentially persistent in sediment and soil. Hence exposure assessment is mandatory for the water, sediment and soil environmental compartments, which may be quantitative or qualitative as appropriate. PBT and vPvB substances have been established as persistent and bioaccumulative (and the former also as toxic) in the environment as a whole. Hence qualitative exposure assessment is mandatory for the water, sediment and soil environmental compartments...

If there are ecotoxicity data showing effects in aquatic organisms, but the substance is not classified as dangerous for the aquatic environment, an aquatic PNEC can nevertheless be derived thus indicating a hazard to the aquatic environment. In these circumstances there are also unclassified hazards to the sediment and soil compartments because toxicity to aquatic organisms is used as an indicator of concern for sediment and soil organisms and a screening risk characterisation is undertaken using the equilibration partitioning method (EPM) to derive PNECs for sediment and soil.“

Regarding its potential for aquatic toxicity, chromium (III) oxide does not classify as “harmful”, “toxic or very toxic to aquatic life” or “may cause long lasting harmful effects to aquatic life”. Chromium (III) oxide is also not expected to be an unclassified hazard to the aquatic environment. Based on the lack of a potential for toxicity to aquatic (sediment) organisms and/or bioaccumulation and its behaviour (poor solubility) in sediments, chromium (III) oxide is also not considered an unclassified hazard to sediment organisms.