Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Biodegradation

Due to its inorganic nature, biodegradation studies on erbium zirconium oxide can be waived (REACH Annex VII, 9.2.1.1 column 2).

Bioaccumulation

Due to the extremely low water solubility of erbium zirconium oxide, erbium and zirconium will not reach high concentrations in the water column, so bioaccumulation in aquatic organisms can be regarded as negligible. This is supported by experimental data available for algae and cyanobacteria (read across from zirconium dichloride oxide, a 'water soluble' zirconium compound which is rapidly transformed to the insoluble zirconium dioxide at environmentally relevant pH levels). These data confirm that zirconium has no potential to bioconcentrate/bioaccumulate in the aquatic foodchain. Experimental data for terrestrial plants (experiments conducted with zirconium dichloride oxide, zirconium acetate, and zirconium hydroxide, i.e., two 'water soluble' and one 'insoluble' zirconium compound) confirm that neither for the terrestrial foodchain there is a concern for bioaccumulation. No individual data on erbium are included in the dossier, as this is not considered necessary (no required endpoints for an Annex VII dossier and similar behaviour expected as for zirconium).

Transport and distribution

Here too, because erbium zirconium oxide is an extremely insoluble compound, only an extremely limited amount of erbium and zirconium is expected to end up in the solution of the environmental compartment under consideration (water column, sediment pore water or soil pore water). Therefore adsorption to particulate matter is not considered a very important process in the environmental distribution of this substance. Experimental and field data on zirconium indicate that zirconium strongly adsorbs to particulate matter. A similar behaviour can be expected for erbium (no individual data added to the dossier as this is an endpoint not required for an Annex VII dossier). It can be concluded that, if released from erbium zirconium oxide, the environmental distribution of both elements will be mainly to sediment and soil, depending on the emission pathway under consideration.