Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Hydrolysis

Zirconium acetate is a metallorganic compound. The organic acetate part is readily biodegradable, and therefore, for that part of the molecule, the hydrolysis study can be waived according to column 2 of Annex VIII.

Biodegradation

For the inorganic part of the molecule no biodegradation testing is required (Column 2 of REACH Annex VII and IX). For the organic part (acetate) no further biodegradation testing is required (simulation tests in water, sediment, and soil) because the substance is readily biodegradable (Column 2 of REACH Annex IX).

Bioaccumulation

Under environmental conditions it is expected that instantaneous hydrolysis of zirconium acetate will occur with the formation of zirconium dioxide. Zirconium dioxide has an extremely low water solubility and will precipitate out of the solution.

Due to its extremely low water solubility, the substance will not reach high concentrations in the water, so bioaccumulation in aquatic organisms can be regarded as negligible. Furthermore, due to complexation to organic matter, zirconium dioxide will become unavailable both for aquatic and sediment-dwelling organisms. Based on experimental data available for algae and cyanobacteria zirconium has no potential to bioconcentrate/bioaccumulate in the aquatic foodchain. Experimental data for terrestrial plants (experiments conducted with zirconium dichloride oxide, zirconium acetate, and zirconium hydroxide, i.e., two 'water soluble' and one 'insoluble' zirconium compound) confirm that neither for the terrestrial foodchain there is a concern for bioaccumulation.

Transport and distribution

Adsorption of zirconium compounds (as such) to particles of suspended matter, sediment, or soil, is not expected to occur. It is rather the zirconium cation (or potentially other cationic zirconium species) that will adsorb to particulate matter. Therefore, the assessment of the potential for adsorption and the derivation of adsorption coefficients is element-based (not substance-based). Based on the derived Kp values, zirconium can be concluded to strongly adsorb to particulate matter. Therefore, its environmental distribution will be mainly to sediment and soil, depending on the emission pathway under consideration. For adsorption to occur however, zirconium has to end up in the aqueous phase of the environmental compartment under consideration (water column, or pore water in sediment/soil).