Zirconium oxide, hafnium and ytterbium doped

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Remarks:

see review report on bioaccumulation

Adequacy of study:

key study

Justification for type of information:

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 endpoint 9.3.2 “Bioaccumulation in aquatic species”.

Reason / purpose for cross-reference:

read-across source

Type:

BAF

Value:

>= 0.02 - <= 230 000 dimensionless

Remarks on result:

other: Fish in 6 studies, in 4 studies no Yb detectable in fish tissue

Type:

BAF

Value:

>= 0.041 - <= 200 000 dimensionless

Remarks on result:

other: Aquatic invertebrates in 6 studies

Type:

BCF

Value:

>= 0.57 - < 16 000 dimensionless

Remarks on result:

other: aquatic plants in 8 studies

Validity criteria fulfilled:

not applicable

Conclusions:

The authors of the bioaccumulation review conclude that lanthanides are unlikely to biomagnify in higher tier organisms in the environment.

Executive summary:

The bibliographic review “Aquatic Bioaccumulation of Lanthanides, Yttrium and Zirconium” assessed 59 publications. 18 studies dealt with ytterbium which belongs to the group of lanthanides. For multiple reasons, ECHA's concept of bioaccumulation applies for organic compounds, but has its limitations for inorganic compounds such as the Ytterbium.

The BCF/BAF values for Ytterbium ranged from 0.57 to 1.6E4 for aquatic plants (8 studies calculated BCF values for aquatic plants) and 0.041 to 2E5 for aquatic invertebrates (6 studies calculated BAF values for aquatic invertebrates). For fish, 4 studies could not detect Yb in the fish tissues and thus no BAF values were calculated. In 6 studies, BAF values ranged from not calculable due to no detectable concentration, 0.02 to 2.3E5 for fish.

The review authors argued that both surface adsorption and very low concentrations in water may explain high BCF for lanthanides and associated metals. Moreover, detoxification by storage in e.g. granules or specific organs (in case of fish) were reported for different lanthanides. The influence of environmental conditions on uptake of the metals was demonstrated for ytterbium. No biomagnification is expected for Yb along the food chain.

This information is used in a read-across approach in the assessment of the target substance. 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 ecotoxicological studies with ytterbium are thus used in a read-across approach.

Description of key information

On basis of a review report on bioaccumulation on different rare earth metals including Ytterbium, it was shown that the concept of bioaccumulation does not apply for 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. No tendency of biomagnification in fish was found.

Additional information

Supporting information showed that the BCF values for ytterbium and zirconium compounds computed by the US EPA were around 4. The overall variation of BCF values in the supporting information back the key information: the concept of bioaccumulation is difficult to apply to the target substance.

Endpoint conclusions are based on read-across from Yb and Zr. Due to the low water solubility of the metal components contained in the 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 the bioaccumulation potential of zirconium oxide, hafnium and ytterbium doped and the review report on rare earth metals including ytterbium and additional supporting information on zirconium are used in a read-across approach to fulfil the REACH requirements for bioaccumulation.