Yttrium oxide

Endpoint summary

Additional information

Hydrolysis:

1. Due to the insolubility of yttrium oxide, hydrolysis assay can be waived (column 2 of REACH annex VIII).

Biodegradation:

Due to the inorganic origin of yttrium oxide, biodegradation assays can be waived (column 2 of REACH annexes VII, IX and X).

Bioaccumulation:

three published data are available. The first of them was selected as a key study as generated on yttrium oxide itself (Yang et al., 1999). Furthermore, it investigated the bioaccumulation potential of this substance in fish, the preferred species as recommended in REACH Annex IX. During this microcosm experiment, no bioconcentration was detected in goldfish (Carassius auratus). A second study was selected as a supporting study as it confirms the absence of bioaccumulation in fish (Qiang et al., 1994). During this test, yttrium was applied under its trinitrate form. The BCF obtained in carp (Cyprinus carpio) ranged from 1.3 to 54. Finally, the third study, also flagged as a supporting study (Hao et al., 1996), investigated the bioconcentration of yttrium trinitrate in the algaeChlorella vulgaris, and studied whether the presence of organic ligands can impact this process. Regardless the absence or presence of ligands, low BCF values were reported (from 0.11 to 4.6). Based on these data, yttrium oxide thus presents a low potential for bioaccumulation.

 

Adsorption/desorption:

No data is available on yttrium oxide but this substance is closed to lanthanum oxide regarding the physico-chemical, toxicological and ecotoxicological properties. Indeed, both substances are high melting point solids (form: powder) of low water solubility and they does not present any classification regarding health and environmental hazards.

Read across is trust possible from lanthanum oxide for which an adsorption / desorption study has been conducted in 3 soils following the OECD 106 guideline and under GLP. Kd values were 5451 to 216905 ml/g and Kocs were 230978 to 11476472 ml/g (mean 5480283 ml/g). Depending on the prevailing environmental conditions, formation of different yttrium species may occur. Considering the adsorption of the rare earth element (i.e. yttrium) is thus a key point. For this reason, it seems also relevant to consider the data available on other yttrium compounds. In this context, three other publications tested the adsorption capacity of Y radionuclids (under carbonate and chloride form) in differents kind of soil confirmed the same behavior of absorption than GLP study on lanthanum oxide. Kd values for yttrium were assessed to be between: -46000 ml/g and 61300 ml/g for soils and around 9390 ml/g for soils from which organic matter and calcium carbonate were intentionally removed. The publication of Tao (2000) showed the adsorption capacity of lanthanids in different soils and proved that this capacity is very similar for the whole category of lanthanids and is function of chemical interaction (especially including chemical bound energy).