Zirconium oxide, hafnium and ytterbium doped

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: simulation testing on ultimate degradation in surface water

Data waiving:

study technically not feasible

Justification for data waiving:

the study does not need to be conducted because the substance is highly insoluble in water

Transformation products:

no

Reference 2

Endpoint:

biodegradation in water: sediment simulation testing

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because direct and indirect exposure of sediment is unlikely

Transformation products:

no

Description of key information

According to REACH Annex IX, column 2, item 9.2.1.2, "Further degradation testing shall be proposed by the registrant if the chemical safety assessment according to Annex I indicates the need to investigate further the degradation of the substance." Furthermore, waiving may be considered "if the substance is highly insoluble in water". As "zirconium oxide, hafnium and ytterbium doped" is highly insoluble in water (see IUCLID section 4.8), the REACH endpoint requirement 9 .2.1.2 is waived.

REACH Annex IX, column 2, item 9.2.1.4, foresees waiving if "the substance is readily biodegradable". However, for an inorganic substance for which the chemical assessment is based on the elemental concentration (i.e. pooling all inorganic speciation forms), biotic degradation in the environment is an irrelevant process. Biotic processes may alter the speciation form of an element, but it will not eliminate the element from the environment by degradation or transformation processes. This elemental-based assessment (i.e. pooling all speciation forms) can be considered as a worst-case assumption for risk assessment. Most importantly, simulation tests of biological degradation are technically not feasible with " zirconium oxide, hafnium and ytterbium doped". According to REACH Annex XI, point 2, the guidance given in the test methods referred to in Article 13(3), more specifically on the technical limitations of a specific method, shall always be respected. The test guidelines relevant for biological degradation in surface water and/or water-sediment systems are OECD 308 and 309 (and their counterparts in EU Regulation 440/2008). The applicability of these test methods is explicitly restricted to organic chemicals. Therefore, as an inorganic compound, "zirconium oxide, hafnium and ytterbium doped" falls outside the technical feasibility domain of biological degradation testing.

Apart from that, waiving is possible in line with REACH Annex IX, column 2, item 9.2.1.4, if a direct or indirect exposure of the sediment compartment can be excluded. Based on the information on identified uses, direct exposure of sediment to zirconium oxide, hafnium and ytterbium doped is excluded. 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. Due to the extremely low water solubility of ytterbium(III), the substance is not expected to be released from sewage treatment plants (STPs) to receiving waters to a significant extent. Undissolved particles are expected to be removed in the sedimentation tank of the STP. Thus, indirect exposure of sediments is not expected.