Chromium (III) oxide

Toxicity to terrestrial arthropods

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. Chromium (III) oxide can be considered environmentally and biologically inert during short- and long-term exposure. 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.

Applying the EPM (and a Log Kp (soilds-water in soil) of 3.9 as determined by EPA, 2005), the lowest NOEC, i.e. the 28 d NOEC of 560 mg Cr/kg soil dw could be converted into a porewater concentration of 0.07 mg/L chromium, a concentration that is at least 7000-fold above the dissolved chromium concentration of < 0.01 microg/L as determined after 28 d in the T/D test (Hedberg and Wallinder, 2012). Thus, based on reported effect concentrations of soluble chromium (III) substances and the poor solubility of chromium (III) oxide, bioavailability and subsequently the potential for toxicity to soil arthropods is low.

Based on its behaviour (poor solubility and bioavailability) in soils and the corresponding lack of a potential for bioaccumulation and for toxicity to aquatic and terrestrial organisms (summarized in Section 6.3 “Cr2O3_ Terrestrial Toxicity”), chromium (III) oxide is expected to have a low potential for toxicity to soil arthropods.