Reaction mass of cerium phosphate and lanthanum phosphate and terbium phosphate

Bioaccumulation: aquatic / sediment

Description of key information

By analogy, reaction mass of lanthanum phosphate and cerium phosphate and terbium phosphate should not show any potential for bioaccumulation.

Additional information

Reaction mass of lanthanum phosphate and cerium phosphate and terbium phosphate has not been tested for its bioaccumulation potential. As a result, information on the constituents should be addressed.

 

Reliable bioaccumulation data in fish are only available on soluble salts of cerium and lanthanum, as nitrates and chlorides (Hao et al., 1996; Qiang et al., 1994; Yang et al., 1999). By contrast, no information was found on insoluble compounds of these rare earth, as phosphates or oxides. Thus, the studies on the soluble salts, scored as reliability 2 according to Klimisch, have to be considered in a weight-of-evidence approach to conclude on the bioaccumulation potential of lanthanum phosphate and cerium phosphate. A first pre-requisite to this approach is to bring evidences that within the family of the rare earth compounds, soluble and insoluble forms of a same element show similar behaviour in terms of bioaccumulation in fish. Yttrium and gadolinium were chosen to demonstrate this assumption as these rare earth present bioaccumulation data for both soluble and insoluble compounds. By comparing the results of Qiang et al. (1994) with those of Yang et al. (1999), it could be concluded that soluble and insoluble forms of both yttrium and gadolinium show similar bioaccumulation behavior:

- For yttrium, no bioconcentration effect was indeed 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 8 (depending on the considered organs, i.e. skeleton, muscles, gills); 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 14 (depending on the considered organs, i.e. skeleton, muscles, gills); 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 and lanthanum. The data on the soluble forms reveal no potential for bioaccumulation:

- For lanthanum, three studies are available on the nitrate salt. Yang et al. (1999) observed no bioconcentration at all. Qiang et al. (1994) and Hao et al. (1996) reported BCF_Lavalues ranging from 0.83 to 18 (depending on the considered organs, i.e. skeleton, muscles, gills).

- For cerium, studies are available on nitrate and chloride salts. Yang et al. (1999) observed no bioconcentration at all using cerium trichloride. Hao et al. (1996) reported BCF_Cevalues ranging from 0.22 to 12.8 (depending on the considered organs, i.e. skeleton, muscles, gills) using cerium trinitrate.

Based on the evidence reported for yttrium and gadolinium that a same bioaccumulation behavior is expected for soluble and insoluble forms within the rare earth family, it can be expected the insoluble forms of cerium and lanthanum (i.e. phosphate) present in the reaction mass should not show any potential for bioaccumulation.

 

Less information are available on terbium. However, a study of environmental monitoring (Suzuki et al., 1975), scored as reliability 2, dealing with both terbium and cerium also showed these elements do not show any potential for bioaccumulation in the tested seawater organisms.

 

By analogy with its constituents, a similar conclusion can be expected for the reaction mass which is also characterized by a low water solubility (2.06 µg/L).