Yttrium zirconium oxide

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

no hazard identified

Marine water

Hazard assessment conclusion:

no data: aquatic toxicity unlikely

STP

Hazard assessment conclusion:

no data: aquatic toxicity unlikely

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

No aquatic PNEC values were derived for yttrium zirconium oxide. No adverse effects were observed in the available toxicity studies (fish and aquatic invertebrates) with zirconium dioxide and yttrium oxide at the limit test concentrations. Algal growth inhibition tests with other zirconium compounds revealed adverse effects on growth which were however concurrent with phosphate depletion. Phosphate complexation by both zirconium and rare earth elements represents a technical difficulty in algal growth inhibition tests which cannot be overcome. Either the zirconium/rare earth or the phosphate will be depleted from the test medium, depending on which of both is in excess of the other. Therefore, no meaningful results can be obtained in algal growth inhibitions tests with zirconium or rare earth compounds. The phosphate deprivation effect is a secondary effect and is not considered environmentally relevant since it may only occur at a very small local scale, such as at point discharges. Taking all this in account, yttrium zirconium oxide can be considered non-hazardous to aquatic organisms, as is the case for zirconium dioxide and yttrium oxide too.

Because the substance does not need to be classified for any environmental hazard, no chemical safety assessment needs to be conducted. Therefore, and taking into account the results of the aquatic toxicity tests included in this dossier, it is not considered necessary to perform toxicity tests with sediment or terrestrial organisms. As for aquatic organisms, the substance is not considered to be hazardous to sediment or terrestrial organisms. This is supported by the results of a short-term study (using zirconium hydroxide, zirconium acetate, and zirconium dichloride oxide) in terrestrial plants, which did not reveal any adverse effects up to the highest doses tested. Therefore no PNEC values were determined for sediment and terrestrial organisms either.

Finally, no PNEC value was determined for secondary poisoning since the available mammalian studies indicate that zirconium dioxide nor yttrium oxide is a hazardous substance and because there is no concern for bioaccumulation or biomagnificiation of zirconium or yttrium in both the aquatic and terrestrial environment.

Conclusion on classification

As yttrium zirconium oxide has a limited water solubility, concentrations of yttrium or zirconium which are toxic to aquatic organisms are anticipated not to be reached. This is supported by information from acute fish and daphnid tests with zirconium dioxide and yttrium oxide. These individual substances were not found to cause any adverse effects in daphnids and fish up to the limit test concentrations, and are hence not classified for any environmental hazard. Based on these fish and daphnid tests it is concluded that yttrium zirconium oxide is not to be classified for environmental hazards either. Data from algal growth inhibition tests are not considered for classification purposes since the strong complexation of zirconium and rare earth elements such as yttrium with phosphates in the test medium confuses the results of these tests. The adverse effects on algal growth observed in such tests are due to phosphate deprivation and are not a direct toxic effect of zirconium or the rare earth itself.