Registration Dossier
Registration Dossier
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EC number: 234-373-8 | CAS number: 11129-15-0
Endpoint summary
Administrative data
Description of key information
Additional information
Since no data are available on calcium zirconium oxide, the aquatic toxicity of the substance is evaluated using data for zirconium dioxide (or other zirconium compounds) and calcium 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.
The results for calcium oxide were based on data obtained with calcium hydroxide. The rationale for the use of these data is that in the environment calcium oxide rapidly reacts with water, resulting in the formation of calcium hydroxide. In the tests performed with calcium hydroxide, adverse effects (mortality in fish, immobilisation in daphnids) were observed at concentrations < 100 mg/L. However, dissolution of calcium hydroxide in the test medium clearly caused a concentration-dependent increase in pH. The observed adverse effects in fish and daphnids could be ascribed to this pH increase, with initial pH being > 10 in test solutions close to the reported median effect concentrations. Since Eidam (2014, 2015) demonstrated that only a limited amount of calcium is released (in pure water) from calcium zirconium oxide, no drastic pH increase is to be expected from adding the substance to aqueous media. Therefore, taking into account all abovementioned information, calcium zirconium oxide can be concluded to be not toxic or harmful to fish.
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. Adverse effects on algal growth were also observed for calcium hydroxide. Here too, the observed effects were not direct toxic effects of the substance but indirect effects due to adherence of algal cells to precipitates formed during the test. As for zirconium dioxide, the EC50 value was > 100 mg/L, consequently, calcium hydroxide (and calcium oxide) should not be considered as harmful to algae either.
Based on all abovementioned information, calcium zirconium oxide can be concluded to be non-hazardous to aquatic organisms.
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