Registration Dossier
Registration Dossier
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EC number: 939-960-9 | CAS number: 39318-32-6
Endpoint summary
Administrative data
Description of key information
Additional information
Since no data are available on magnesium zirconium oxide, the aquatic toxicity of the substance is evaluated using data for zirconium dioxide (or other zirconium compounds) and magnesium oxide.
Zirconium dioxide was found not to be toxic or harmful to fish and aquatic invertebrates. The available reliable studies did not report any acute adverse effects (mortality in fish, immobilisation in daphnids) up to and including the limit test concentration of 100 mg/L. Adverse effects on algal growth were observed for several zirconium substances (e.g., zirconium basic carbonate, zirconium dichloride oxide, and a reaction mass of zirconium dioxide and cerium dioxide). However, phosphate monitoring during the tests indicated that the observed effects were concurrent with phosphate depletion. Therefore, the observed effects were described as being due to phosphate deprivation. No evidence has been found for direct toxic effects in algae upon exposure to zirconium compounds. Moreover, the EC50 values of all tests were > 100 mg/L, consequently, zirconium dioxide should not be considered as harmful to algae.
To demonstrate the validity of the read across assumption, i.e. that the addition of magnesium (oxide) to the crystal lattice of zirconium dioxide does not alter the unhazardous character of zirconium dioxide, data for magnesium oxide were added to the dossier for the basic toxicological endpoints acute toxicity to aquatic invertebrates and toxicity to aquatic algae (Annex VII ecotoxicological endpoints). Hereto, data from studies performed with magnesium hydroxide were used, which are considered relevant for magnesium oxide because in contact with water magnesium oxide will give rise to the formation of magnesium hydroxide. In these studies, no LC50 values < 100 mg/L were obtained, hence magnesium hydroxide and magnesium oxide should not be considered as harmful to aquatic organisms.
Consequently, taking into account all abovementioned information, magnesium zirconium oxide can be concluded to be not toxic or harmful to aquatic organisms either.
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