Zirconium acetate

Ecotoxicological Summary

Additional information

PNEC values calculated using assessment factors cannot be derived. The available acute ecotoxicity tests in fish, daphnids and algae show EC50 or LC50 values which are higher than 100 mg/L (based on added test substance). When zirconium acetate is dissolved in a buffered aqueous solution (such as a natural surface water) precipitation of zirconium as zirconium hydroxide/zirconium dioxide (pH dependent), zirconium carbonate (pH dependent), and/or zirconium phosphate will occur. In view of the extremely low water solubility of these zirconium compounds, zirconium concentrations that would be toxic for aquatic organisms will never be reached. In addition, it is commonly known that many metals form complexes with organic molecules present in water. This is also the case for zirconium. It can thus be argued that the substance will not be bioavailable to aquatic organisms.

Similarly, microorganisms in a sewage treatment plant are not expected to be exposed to zirconium (acetate), as zirconium will have been removed from the water column through hydrolysis and carbonate and/or phosphate complexation before reaching the biological treatment step. Often a pH increase step is included for metal precipitation as one of the (first) waste water treatment steps in on-site waste water treatment plants. If such as step is included the removal efficiency will be 100%. Moreover, no adverse effects have been observed in an activated sludge respiration inhibition test. Therefore no PNEC needs to be derived.

As no PNEC aquatic could be derived, no PNEC values for soil and sediment can be derived using the equilibrium partitioning method. No toxicity data are available for sediment or soil organisms, except for a short-term toxicity study to terrestrial plants, yielding only unbound NOEC values. Therefore, no PNEC values for soil and sediment can be derived applying the assessment factor either. Since zirconium acetate is not considered hazardous to the environment, no chemical safety assessment needs to be conducted and therefore no PNECs need to be derived for these compartments.

No long-term oral or dietary avian toxicity studies are available. The repeated dose toxicity study in rats (OECD 422 study with zirconium acetate) did not observe any significant adverse effects up to and including the highest tested dose (NOAEL >= 1000 mg/kg bw/day, based on anhydrous test compound). Therefore no PNEC oral can be derived. This route is considered not relevant anyway as it can be reasonably assumed that zirconium acetate will not bioaccumulate in the food chain.

Conclusion on classification

The substance does not need to be classified for environmental hazards, based on the available information for zirconium acetate, used in combination with information from read across substances. In none of the studies used to cover the aquatic toxicity endpoints, adverse effects have been observed up to and including the limit test concentration of 100 mg/L. Only for algae, growth inhibition was observed at this limit test concentration for two read across substances, however, the observed inhibition was concurrent with phosphate depletion from the test medium (through heavy complexation with zirconium), and was hence considered a phosphate deprivation effect, which is not considered relevant at a normal environmental scale. Since there were no signs of primary toxicity, the effect in algae was not considered relevant for hazard assessment or classification purposes;