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Supporting information is available in the form of results from a study in which the bioconcentration of the rare earth elements lanthanum, gadolinium and yttrium was investigated in carp (Cyprinus carpio) during a 45-day semi-static experiment (Qiang, 1994). In groups A, B, C, carps were exposed to stock solutions containing individual rare earths tested as their nitrates at final concentrations of 0.5 mg/L La, Gd or Y. In group D, carps were exposed to a mixed solution of the three rare earths containing 0.5 mg/L of each element. Controls were tested in parallel. Fish were sacrificed at time intervals and skeleton, muscles, gills and internal organs were dissected. Rare earth concentrations in fish tissues and water were determined using ICP-AES.

The bioaccumulation values (differences between the background concentration in unspiked fish tissue and the concentration in spiked tissue) in various tissues of carp, both in individual and mixed rare earth groups, increased with time. At the end of the 45 -day exposure period, the equilibrium was reached or approached. The bioaccumulation values for individual element solutions (Groups A,B,C) and those for mixed rare earth solution (Group D) did not differ significantly; indicating that among the three rare earths studied, neither synergistic nor antagonistic effect played a part in the bioaccumulation process.

After 45 days, the BCF values reported for the different rare earth were the followings:

* Lanthanum: Muscles: BCF = 3.2, Skeleton: BCF = 6.1, Gill: BCF = 18, Internal organs: BCF = 91.

* Gadolinium: Muscles: BCF = 3.5, Skeleton: BCF = 5, Gill: BCF = 14, Internal organs: BCF = 105.

* Yttrium: Muscles: BCF = 1.3, Skeleton: BCF = 3.8, Gill: BCF = 8, Internal organs: BCF = 54.

As a result, none of the studied rare earth elements show any potential for bioaccumulation.