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Bioaccumulation: aquatic / sediment

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Description of key information

No bioaccumulation data are available on dierbium trioxide but literature data provide information on the soluble nitrate salts of lanthanum, gadolinium and yttrium. BCF values of 1.3-105 were recorded after 29-45days in; muscles, skeleton, gills and internal organs.Therefore these compounds show no bioccumulation potential and, since dierbium trioxide is insoluble in  water, it is expected that it will be less bioavailable than the soluble salts tested.

Key value for chemical safety assessment

Additional information

In accordance with section 1 of REACH Annex XI (testing does not appear scientifically necessary), the bioaccumulation study (required in section 9.3.2.) does not need to be conducted as the substance can be predicted not to be bioaccumulative based on an analogy with the heavy rare earth compound, yttrium nitrate. The available data are adequate for classification and labelling purposes and PBT assessment is not required for inorganic substances so no further testing is required.


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.