Registration Dossier

Diss Factsheets

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Hydrolysis

Hydrolysis is not considered to be a relevant process determining the environmental fate of magnesium zirconium oxide. Due the limited water solubility of the substance, it is anticipated that the substance predominantly remains an insoluble mass in the environment and only to a limited extent hydrolysis processes will occur.

Biodegradation

Due to its inorganic nature, biodegradation is not a relevant process determining the environmental fate of magnesium zirconium oxide and therefore no studies need to be performed.

Bioaccumulation

Due to its low water solubility, limited amounts of zirconium and magnesium are expected to be released from magnesium zirconium oxide in the aquatic or terrestrial environment. Released zirconium and magnesium will be subject to speciation and distribution processes, among which bioaccumulation is not considered to be very important:

- For zirconium, reliable data on bioaccumulation in the aquatic environment are available only for algae and cyanobacteria. The highest BCF value was 0.064 L/kg ww, indicating no potential for bioaccumulation in aquatic organisms. Similarly, the available data for terrestrial plants yielded BSAF values well below 1, allowing to conclude that there is no potential for bioaccumulation of zirconium in terrestrial organisms either.

- For magnesium, bioaccumulation is not considered relevant as it is an essential element and organisms actively regulate their inner magnesium levels. The results from a study on magnesium accumulation in a terrestrial plant, added to this dossier, are in line with this conclusion, as BSAF values clearly increased with decreasing magnesium content of the soil.

Transport and distribution

The assessment of the potential for adsorption and the derivation of adsorption coefficients is also element-based (not substance-based). For adsorption to occur, magnesium and zirconium have to end up in the aqueous phase of the environmental compartment under consideration (water column, or pore water in sediment/soil).

Based on the available data, zirconium can be concluded to strongly adsorb to particulate matter, adsorption being however somewhat less pronounced in soil compared to sediment and suspended matter. Log Kp values for zirconium were 5.0, 5.47 and 4.13 for suspended matter, sediment, and soil, respectively. The environmental distribution of zirconium will be mainly to sediment and soil, depending on the emission pathway under consideration.

For magnesium, an indicative log Kp value of < 1.2 was obtained for soil. This values indicate much less strong adsorption than zirconium to particulate matter. Magnesium is rather exchangeable in a soil-pore water system, as could be expected for an element that is essential to plants. No data for sediment-water and suspended matter-water have been included in the dossier.