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Description of key information

Based on the available evidence, cerium can be concluded not to accumulate in the terrestrial foodchain, since BSAF values for plants and invertebrates are typically below 1.

Key value for chemical safety assessment

Additional information

Because rare earth elements are being used as fertiliser to promote plant growth for certain types of crops in certain regions, a substantial amount of literature is available on the transfer of cerium and other rare earths to plants in the terrestrial environment. Only a limited amount of data is included in this dossier, however, this amount of information is considered sufficient for drawing conclusions on this endpoint.

Rikken (1995) summarized literature data on the accumulation of rare earth metals in plants, as a part of the investigation of data on the transfer of rare earths in the chain artificial fertilizers - soil - crops - livestock and man. The data for concentration of cerium in different vegetables and feeding stuffs and the soil were collected and biota-to-soil accumulation factors (BSAFs) were calculated.

The concentration and accumulation of rare earths in plants differed as a consequence of plant and soil properties (e.g., species, Ca-content). The concentrations of rare earth elements in plants (dry weight) were in general low: < 0.2 mg/kg dw for root and leaf vegetables, < 0.05 mg/kg dw in most fruits and < 1 mg/kg dw in herbs/grasses. BSAFs for rare earth elements are usually within a range of 0.0001 to 0.001 for feed crops and 0.0001 to 0.01 for food crops. For cerium specifically, BSAFs were in a range of < 0.00003 - 0.194 for food crops and 0.00001 - 0.088 for feed crops.

Furthermore, Tyler (2004) reviewed the information about rare earth elements in soil and plant systems and arrived at the conclusion that concentrations of rare earths in plants are usually very low compared to their total concentration in soils. For example, BSAFs in forest plants of NW Germany were reported to be as low as 0.04 - 0.09.

Next to information on transfer of cerium from soil to plants, some information can be added on transfer of cerium from sediment to sediment-dwelling organisms or higher aquatic plants rooted in sediment. As an example, Moermond et al. (2001, see endpoint 5.3.1) reported BSAF values from 0.037 to 0.139 for the amphipod Corophium volutator based on samples from the field as well as from a laboratorium study (dry weight based). This study indicates that cerium has a low potential for bioaccumulation through transfer from solid phases to organisms living in contact with the solid phase under consideration. Finally, Marcussen et al. (2008, see endpoint 5.3.1) analysed cerium concentrations in sediment and water spinach (rooted in the sediment) of several locations in a lake in Cambodia receiving waste water. Based on the obtained results, BSAF values could be calculated ranging from 0.0013 and 0.0059 (wet weight based). This study also confirms the low bioaccumulation potential of cerium from sediment to organisms living in close contact with the sediment.

Generally, the reviewed data indicated a low accumulation potential of cerium and rare earth elements in general. Therefore, it can be assumed that there is no risk for accumulation in the terrestrial/sediment food chain.

Specific references:

Rikken, M.G.J., 1995. De accumulatie van zeldzamen aardmetalen. RIVM Rijksinstituut voor volksgesondheid en milieu, Bilthoven. Report nr. 601014 013.

Tyler, G., 2004. Rare earth elements in soil and plant systems. A review. Plant and Soil 267: 191-206.