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EC number: 939-967-7
CAS number: -
In the available acute ecotoxicity tests with zirconium dioxide and erbium oxide in daphnids, no adverse effects were observed on the daphnids after 48 h at a nominal initial loading rate of 100 mg/L and in a 100% v/v saturated solution, respectively. In view of the extremely low water solubility of erbium zirconium oxide, concentrations that would be toxic for aquatic organisms are not expected to be reached. Therefore, erbium zirconium oxide can be concluded to be equally non-toxic to aquatic invertebrates as zirconium dioxide and erbium oxide.
Zirconium dioxide (conclusions based on read across from zirconium basic carbonate, a reaction mass of cerium dioxide and zirconium dioxide, and zirconium dichloride oxide) was concluded not to be harmful to algae either. The observed growth inhibition effects could be clearly ascribed to phosphate depletion of the test medium through formation of strong insoluble zirconium phosphate complexes. Due to this strong complexing behaviour, which is also known for rare earth elements such as erbium, no meaningful test results can be obtained from algal growth inhibition tests. Moreover, phosphate depletion effects in small systems such as algal growth inhibition test systems are not considered to be environmentally relevant.
Finally, for fish, no adverse effects of zirconium dioxide have been observed to fish in an acute toxicity study at an initial loading rate of 100 mg/L. As erbium oxide is not classified for hazards to the aquatic environment either, it is not expected to change the unhazardous character of zirconium dioxide.
Because of these findings, further aquatic toxicity testing with erbium zirconium oxide was not considered necessary, and the behaviour and toxicity of the substance can be assumed to be similar as for zirconium dioxide and erbium oxide. No aquatic PNECs were derived for erbium zirconium oxide, because no (primary) adverse effects were observed in the available toxicity studies up to and including at the limit test concentrations / saturated solutions.
Similarly, no PNECs were derived for sediment and terrestrial organisms. No testing is needed either for these endpoints in an An VIII dossier.
Finally, no PNEC value was determined for secondary poisoning since the available mammalian studies indicate that zirconium dioxide nor erbium oxide is a hazardous substance and because there is no concern for bioaccumulation or biomagnification of zirconium or erbium in both the aquatic and terrestrial environment.
Because the substance does not need to be classified for any environmental hazard, no chemical safety assessment needs to be conducted.
As erbium zirconium oxide is very poorly soluble in water, concentrations of erbium or zirconium which are toxic to aquatic organisms will not be reached. This is confirmed based on information from acute daphnid tests with zirconium dioxide and erbium oxide as well as an acute fish test with zirconium dioxide. These individual soluble substances were not found to cause any adverse effects in the daphnids or fish up to and at the limit test dose (or in a saturated solution). Daphnid tests provide the only occasion for comparison of the toxicity of zirconium dioxide an erbium oxide in this dossier because, due to the strong complexing behaviour of zirconium and rare earth elements such as erbium with phosphates in the test medium, no meaningful results can be obtained from algal growth inhibition tests. Because neither zirconium dioxide or erbium oxide are classified for hazards to the aquatic environment, erbium zirconium oxide should not be classified for environmental hazards either, supported by the available information.
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