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The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

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Short-term toxicity to fish:

The 96-hr acute toxicity of zirconium dioxide to Brachydanio rerio was studied under static conditions, according to OECD Guideline 203. Fish were exposed to control and test chemical at nominal concentration of 100 mg /L. Mortality/immobilization were observed daily. No mortality was observed during the test, neither in the control nor in the group exposed to the test item. The 96 hour LL50 and NOELR were thus > 100 mg/L zirconium dioxide, equivalent to >74 mg Zr/L.


Short-term toxicity to aquatic invertebrates:

The acute toxicity of zirconium dioxide to Daphnia magna was studied under static conditions according to EU method C2. Daphnids were exposed to control and test chemical at an initial loading rate of 100 mg/L for 48 hours. Mortality and immobilization were observed after 24 and 48 hours. No significant immobilization was observed with the loading rate of 100 mg/L zirconium dioxide, equivalent to >74 mg Zr/L. The 48h-NOEC and 48h-EC50 were thus superior to this value.


Long-term toxicity to fish and aquatic invertebrates:

Zr ions released in the aquatic environments will form ZrO2 and precipitate. In view of the lack of effects in the available acute aquatic toxicity tests for ZrO2, its extremely low water solubility and its tendency to form complexes with (an)organic molecules in water (and thus to become non-bioavailable), there is no need to investigate further the effects on aquatic organisms. Based on this justification, these endpoints are waived.


Toxicity to aquatic algae and cyanobacteria:

In absence of study on zirconium dioxide itself an analogue substance containing 30% zirconium dioxide was used. In a 72 -hour toxicity study, the cultures of green algal species Scenedesmus subspicatus were exposed to the reaction mass of cerium dioxide and zirconium dioxide at the loading rates of 0.32, 1.0, 3.2, 10, 32 and 100 mg/L under static conditions in accordance with the EU Commission Directive 92/69/EEC, C.3 (1992), and OECD Guideline 201 (2006). The NOELR, the LOELR and EL50 values based on the growth rate were 32 mg/L, 100 mg/L and > 100 mg/L, respectively. The observed growth inhibitory effects were attributed to phosphate depletion. This was supported by another study where Chlorella vulgaris cells were exposed to ZrOCl2, which is known to hydrolyse into ZrO2 especially at neutral pH. Growth inhibition was caused by phosphate precipitation. No direct toxic effects to algae are to be expected by insoluble zirconium compounds such as ZrO2.


Toxicity to microorganisms:

Ionic zirconium (Zr4+) at relevant pH conditions (pH 7 - 8) of aquatic and terrestrial environments will rapidly transform to zirconium-oxide and -hydroxide complexes, precipitate and not be bioavailable to aquatic organism. Microorganisms in the STP will not be exposed to Zr, as it will either be removed in the primary settling tank before reaching the microorganisms, or it will not be bioavailable due to complexation. Testing is waived because the study does not need to be conducted if the substance is highly insoluble in water.

A standard activated sludge respiration inhibition study was still performed with zirconium acetate. No statistically significant toxic effects were observed at all test concentrations employed. The 3-h EC50 and NOEC were determined to be >1000 mg/L and ≥1000 mg/L anhydrous zirconium acetate, respectively, equivalent to >530 mg/L and ≥530 mg/L zirconium.