lambda4-cerium(4+) zirconium(4+) tetraoxidandiide

Endpoint summary

Additional information

Bioaccumulation: aquatic/sediment:

No bioaccumulation data are available on reaction mass of cerium dioxide and zirconium dioxide. The data on both constituents are thus assessed to conclude on the bioaccumulation potential.

Cerium dioxide

Regarding cerium, reliable bioaccumulation data in fish are only available on soluble salts as nitrate (Hao et al. 1996) and chloride (Yang et al. 1999). Both studies, scored as reliability 2 according to Klimisch, are considered in a weight-of-evidence approach to conclude on the bioaccumulation potential of cerium dioxide. The reasoning applied in this context is detailed hereafter. The first pre-requisite is to bring evidences that soluble and insoluble forms of a same rare earth show similar behaviour in terms of bioaccumulation in fish. In this context, a supporting study, also scored as reliability 2, is provided(Qiang et al. 1994). By comparing the results of this study with those of Yang et al. (1999), it could be concluded that soluble and insoluble forms of both yttrium and gadolinium show similar bioaccumulation behaviour.For yttrium, no bioconcentration effect was observed in Carassius auratus for the insoluble oxide form (Yang et al. 1999). For the soluble nitrate form, the BCF values measured in Cyprinus carpio ranged between 1.3 and 54 (depending on the considered organs,i.e.skeleton, muscles, gills and internal organs); suggesting no potential for bioaccumulation (Qiang et al. 1994). For gadolinium, Yang et al. (1999) did not detect any bioconcentration effect of the insoluble oxide form in Carassius auratus. And, the BCF values of the soluble nitrate form measured in Cyprinus carpio ranged between 3.5 and 105 (depending on the considered organs,i.e.skeleton, muscles, gills and internal organs); suggesting no potential for bioaccumulation (Qiang et al. 1994). Data on both rare earths thus indicated that soluble and insoluble forms behaved similarly in terms of bioaccumulation in fish. The same process could be expected for cerium. Cerium dioxide show a low water solubility (< 0.123 µg/L) and is thus less bioavailable for fish than soluble salts. Based on the evidence reported for yttrium and gadolinium, it can be expected this insoluble form of cerium (i.e.oxide) should not show any potential for bioaccumulation, as the soluble ones (i.e.chloride and nitrate).

Zirconium dioxide

A waiver was written to cover the endpoint for zirconium dioxide. 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 with (an)organic molecules in water, ZrO2 will become not-bioavailable both for aquatic and sediment-dwelling organisms. Therefore, it is not feasible to perform a bioaccumulation test in water / sediment.

Reaction mass of cerium dioxide and zirconium dioxide

Based on the data available on both constituents and due to its very low water solubility, it can be concluded that reaction mass of cerium dioxide and zirconium dioxide should not bioaccumulate. In addition, the substance can form complexes with (an) organic molecules, thus the bioavailability to aquatic organisms is low.

Bioaccumulation: terrestrial:

No bioaccumulation data are available on reaction mass of cerium dioxide and zirconium dioxide. The data on both constituents are thus assessed to conclude on the bioaccumulation potential.

Zirconium dioxide

Ferrand (2006) determined biota to soil accumulation factors for plants. In the study, transfer of Zr from soil to tomato and pea plants was studied during a 7-day exposure period in two soils (an acidic and a calcareous soil) amended with either a soluble (ZrOCl2 or Zr acetate) or an insoluble Zr compound (Zr(OH)4). Zr accumulated mainly in the roots, with Zr adsorption to the root surface being of minor relevance. Translocation to aerial parts was limited. BSAF values for roots were the highest for Zr acetate and the lowest for Zr(OH)4. They were all <= 0.1. BSAF values for aerial parts were all <= 0.005 and were also generally the highest for Zr acetate and the lowest for Zr(OH)4.

Cerium dioxide

Not mandatory REACH endpoint.

Reaction mass of cerium dioxide and zirconium dioxide

Taking into account the very low BSAF values for Zr, it can be expected that the reaction mass of zirconium dioxide and cerium dioxide will not bioaccumulate either to a significant extent in terrestrial surroundings. As the endpoint is not an obligatory REACh endpoint, no further conclusions are drawn.