Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Hydrolysis

Hydrolysis is not considered to be a relevant process determining the environmental fate of yttrium zirconium oxide. Due the limited water solubility of the substance, it is anticipated that the substance predominantly remains an insoluble mass in the environment and only to a limited extent hydrolysis processes will occur.

Biodegradation

Due to its inorganic nature, biodegradation is not a relevant process determining the environmental fate of yttrium zirconium oxide and therefore no studies need to be performed.

Bioaccumulation

Due to its limited water solubility, the substance is not expected to give rise to substantial levels of bioavailable yttrium or zirconium in the aquatic or terrestrial environment. Any bioavailable yttrium or zirconium may be taken up by organisms, however, bioaccumulation potential has been demonstrated to be limited for both elements. For zirconium, reliable data on bioaccumulation in the aquatic environment are available only for algae and cyanobacteria. The highest BCF value was 0.064 L/kg ww, indicating no potential for bioaccumulation. For yttrium, reliable data are available for aquatic plants, aquatic invertebrates, and fish. BCF/BAF values were 992.7, 27.36 to 1482.6, and 1.3 to 54 L/kg ww, respectively. As for other rare earth elements, bioaccumulation was observed to decrease when ascending the food chain. The key BAF value for fish was 4.65 L/kg ww, indicating a very low potential for bioaccumulation in the aquatic environment. For the terrestrial environment, based on available data for both zirconium and yttrium, it can be concluded that there is no potential for bioaccumulation, as all reported BSAF values were well below 1.

Transport and distribution

Based on available data, both yttrium and zirconium can be concluded to strongly adsorb to particulate matter, adsorption being however somewhat less pronounced in soil compared to sediment and suspended matter. Log Kp values for zirconium were 5.0, 5.47 and 4.13 for suspended matter, sediment and soil, respectively. For yttrium, log Kp values of 4.78 and 3.59 were obtained for sediment and soil, respectively. No data were available for suspended matter. However, due to the limited water solubility of yttrium zirconium oxide, only minor amounts of yttrium and zirconium are expected to be available for adsorption processes and hence adsorption is not considered to be a major process determining the environmental fate of the substance. It is anticipated that the majority of the substance remains an insoluble mass in the environment.