Registration Dossier

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

The adsorption of Yb(III) on silica and aluminium is strongly dependent on pH. While adsorption at acidic pH values in negligible, Kd values at the pH range of ca. 6.6 to 8 range between 2,300 and 12,000. As the test substance zirconium oxide, hafnium, ytterbium doped is highly insoluble and only insignificant amounts of Yb are released (see section 4.8 of the present dossier) no study on hydrolysis was conducted. Due to its poor solubility the test substance is not expected to be found in the water phase.

Regarding biodegradation in water, sediment and soil, all endpoints were waived as the substance is both highly insoluble and inorganic and thus biodegradation testing is technically not feasible.

In general, the concept of bioaccumulation is limited regarding application on metals due to different reasons, e.g. active elimination processes, different metal specification due to different environmental conditions. BCF and BAF for Yb varied significantly in aquatic organisms in reviewed studies. No tendency of biomagnification in fish was found. Thus, a key BCF factor could not be derived.

Additional information

Adsorption/Desorption conclusions are based on read-across from Yb(III). Conclusions on bioaccumulation are based on a review-report on bioaccumulation of metals including Yb(III) (read-across). The findings are supported by data on Zirconium.

Due to the low water solubility of the metal components contained in the test substance (zirconium oxide, hafnium and ytterbium doped), a full transformation/dissolution protocol was carried out to study the potential release of these metals to the environment. After 7 and 28 days (nominal loading of 100 mg/L, pH 8), only ytterbium(III) was found in solution with a maximum concentration of 0.069 µg/L. Zirconium and hafnium were both below the detection limit of 0.07 and 0.02 µg/L, respectively. Therefore, information on ytterbium(III) is relevant for the assessment of environmental fate properties of zirconium oxide, hafnium and ytterbium doped and adsorption studies with ytterbium are used in a read-across approach to fulfil the REACH requirements for endpoints 9.3.1 “Adsorption/desorption screening” and 9.3.2 "Bioaccumulation in aquatic species".