Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

1. Information on zirconium dioxide (CAS# 1314-23-4)

No reliable data were available for the endpoints toxicity to soil macroorganisms except arthropods, toxicity to terrestrial arthropods and toxicity to soil microorganisms. These endpoints are waived based on following justification: as zirconium dioxide is not classified and consequently no exposure assessment needs to be done, there is currently no reason that triggers the performance of a soil macroorganisms study. Furthermore, a plant growth study with both insoluble and soluble zirconium compounds did not show any adverse effects.

Toxicity to terrestrial plants:

As no reliable studies were available on zirconium dioxide, read-across data from supporting substances were evaluated to support data waiving for this endpoint.

Ferrand (2006) performed a plant growth study with zirconium oxychloride according to EPA OPPTS guideline 850.4230. In this study, tomato and pea seedlings (ca. 21 days old) were exposed for 7 days to two different soils contaminated with either a soluble zirconium compound (ZrOCl2 or zirconium acetate) or an insoluble zirconium compound (Zr(OH)4). In none of the experiments adverse effects were observed on root or shoot fresh weight of the plants. Unbound NOEC values were obtained for all experiments. The lowest unbound NOEC was >= 264 mg Zr/kg dw for the calcareous soil (164 mg Zr/kg background) amended with 100 mg Zr/kg ZrOCl2 or zirconium acetate. The highest unbound NOEC was >= 703.4 mg Zr/kg dw for the acidic soil (417.4 mg Zr/kg background) amended with 286 mg Zr/kg Zr(OH)4. Because ZrO2 is also a highly insoluble zirconium compound and background zirconium in soils is also assumed to be present as insoluble zirconium compounds such as zirconium dioxide and ZrSiO4, the unbound NOECs for the experiments with Zr(OH)4 are more relevant for zirconium dioxide.

Toxicity to birds:

No reliable data are available for this endpoint. Testing is waived based on following justification: as zirconium dioxide is not classified and consequently no exposure assessment needs to be done, there is currently no reason that triggers the performance of a toxicity study in birds. Furthermore, as the bioaccumulation potential of zirconium dioxide is extremely low, members higher in the food chain are considered not relevant for further examination.

2. Information on erbium oxide (CAS# 12061-16-4)

At this point in time it is not deemed necessary to add data on erbium oxide to the dossier. This conclusion is based on the similarly low toxicity of erbium oxide and zirconium dioxide to aquatic organisms as well as on the fact that the terrestrial endpoints can be waived for both zirconium dioxide and erbium oxide based on the fact that these substances are not classified and hence no exposure assessment is required. Therefore there is no trigger for terrestrial toxicity testing.

3. Conclusion on erbium zirconium oxide

It is expected that the substance will have a similar terrestrial ecotoxicity profile as the read-across substance zirconium dioxide. Further, there is no trigger for terrestrial toxicity testing anyway because erbium zirconium oxide is not classified and therefore no chemical safety assessment needs to be performed.