Reaction mass of cerium dioxide and lanthanum oxide and lanthanum fluoride

Bioaccumulation: aquatic / sediment

Description of key information

By analogy, reaction mass of cerium dioxide and lanthanum oxide and lanthanum fluoride should not show any potential for bioaccumulation.  

Additional information

Reaction mass of cerium dioxide and lanthanum oxide and lanthanum fluoride 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). These 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, lanthanum oxide and lanthanum fluoride. 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, the result of Qiang et al. (1994) is very helpful. 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 and lanthanum. Cerium dioxide, lanthanum oxide and lanthanum fluoride show low water solubilities (< 0.123 µg/L, 69.6 µg/L and 0.65 to 14.91 mg/L, respectively) and are thus less bioavailable for fish than soluble salts. Based on the evidence reported for yttrium and gadolinium, it can be expected these insoluble forms of cerium and lanthanum (i.e. oxides and fluoride) should not show any potential for bioaccumulation, as the soluble ones (i.e. chloride and nitrate). By analogy with its constituents, a similar conclusion can be expected for the reaction mass which is also characterized by a low water solubility (2.23 µg/L).