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Environmental fate & pathways

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Additional information

Micrometric cerium dioxide


Due to the high insolubility of cerium dioxide, hydrolysis assay can be waived (column 2 of REACH Annex VIII).


Due to the inorganic nature of cerium dioxide, biodegradation studies can be waived (Column 2 of REACH Annex VII).


A weight-of-evidence approach was carried out to assess the bioaccumulation potential of cerium dioxide. Data on soluble cerium salts, and evidences showing that soluble and insoluble forms of a same rare earth present similar bioaccumulation properties, were used to conclude that cerium dioxide should not show any potential for bioaccumulation.


Adsorption/desorption tests allow to determine a distribution coefficient, which is the ratio of equilibrium concentrations of a dissolved substance in a two-phase system consisting of a sorbent (typically soil or sewage sludge) and an aqueous phase. Hence, suitable methods must be available to determine the substance concentration in both phases. In a first step, the HPLC method (OECD 121, EU C19) may be used as a screening. However, such a method is not suitable for inorganic compounds as cerium dioxide. Batch equilibrium method (OECD 106, EU C18) may be considered in a more definitive step. Here again, this method is hardly applicable to cerium dioxide. Indeed, this substance is highly insoluble. In an attempt to perform an adsorption/desorption test on cerium dioxide, a preliminary experiment dealing with water solubility was performed. And the cerium concentration was below the limit of detection. Furthermore, in the water solubility experiment (RCC study 17425, 2007), the cerium concentration could not be quantified, as below the limit of quantification. The water solubility of cerium dioxide was thus calculated based on the quantification limit. In the adsorption-desorption test, using batch equilibrium method, it is expected that the cerium concentration in the aqueous phase could not be quantified. As a result, a data waiving is proposed for this test, due to the absence of an analytical method sufficiently precise to quantify this highly insoluble compound.

Nanometric cerium dioxide


Due to the inorganic nature of nanoparticulate cerium dioxide, biodegradation is not applicable.


A study of reliability 2 according to Klimisch is available and concludes that nanometric cerium dioxide does not show any potential for bioaccumulation.

Aggregation and sedimentation in natural aqueous media:

A study of reliability 2 according to Klimisch is available and investigates the electrophoretic mobility, the state of aggregation and the rate of sedimentation of cerium dioxide nanoparticles in different aqueous media associated with seawater, lagoon, river and groundwater. It appears that the nanoparticles were more stable in stormwater, mesocosm water and treated effluent which are generally low in ionic strength and medium to high in TOC content. The aggregation was faster, resulting in greater deposition, in lagoon water and seawater which showed high ionic strength and low to medium TOC content. The situation is intermediate in groundwater and river water.

No further data on environmental fate and pathways of cerium dioxide nanoparticles.