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EC number: 264-885-7
CAS number: 64417-98-7
Only results for yttrium are shown here.
Table 1: Background values of yttrium in Cyprinus carpio
Y concentration (µg/g wet weight)
Content of yttrium in the dry fish food was under the detection limit.
Table 2: Bioaccumulation in Cyprinus carpio exposed to 0.5 mg/L yttrium
Following the read across strategy, it is considered appropriate to cover this endpoint by data on bioconcentration/bioaccumulation of zirconium and yttrium.For zirconium, only one study is available: the study of Garnham et al. (1993), yielding a maximum BCF value of 0.064 L/kg ww for bioconcentration of zirconium (added as zirconium dichloride oxide, but quickly hydrolysed to zirconium dioxide and/or hydroxide) in cyanobacteria and microalgae. These results indicate that zirconium has no potential for bioconcentration/bioaccumulation.For yttrium three studies are available, reporting on bioconcentration/bioaccumulation of yttrium in aquatic plants (Yang et al., 1999), aquatic invertebrates (Yang et al., 1999; Stronkhorst and Yland, 1998), and fish (Yang et al., 1999; Tu et al., 1994). Overall, the obtained BCF/BAF values were 992.7 L/kg ww for aquatic plants, 27.36 to 1482.6 L/kg ww for aquatic invertebrates, and 1.3 to 54 L/kg ww for fish. A key BAF value of 4.65 L/kg ww is calculated for fish. As for otherare earth elements, yttrium bioaccumulation seems to decrease when ascending the food chain. Therefore, the bioaccumulation potential of yttrium can be concluded to be low.Due to the low water solubility of yttrium zirconium oxide as well as the individual substances yttrium oxide and zirconium dioxide, yttrium and zirconium bioavailability in the aquatic environment, after introduction of yttrium zirconium oxide, is expected to be very low. Consequently, based on the results on bioconcentration/bioaccumulation of yttrium and zirconium, no substantial bioconcentration/bioaccumulation is to be expected.
1. Information on zirconium
The accumulation of zirconium by cyanobacteria and microalgae was
characterized by Garnham et al. (1993). In this study the organisms were
exposed to solutions of zirconium dichloride oxide. Actual exposure
however was rather to zirconium dioxide, since zirconium dichloride
oxide hydrolyses rapidly in aqueous solutions at environmentally
relevant pH, resulting in the precipitation of zirconium as zirconium
dioxide or hydroxide. In all cyanobacterial and microalgal species
examined, accumulation consisted of a single rapid energy-independent
phase ("biosorption"). No energy-dependent accumulation was observed.
Biosorption of zirconium was concentration-dependent, followed a
Freundlich adsorption isotherm, and was dependent on pH, showing
decreasing accumulation with decreasing pH. Zirconium desorption from
micro-algae and cyanobacteria was increased by increasing external
cation concentrations or by decreasing the pH of the desorption agent.
Overall, biosorption/bioaccumulation was very limited. BCF values
between 0.0525 and 0.64 L/kg dw were obtained. Assuming 90% water
content in the organisms, the highest value can be recalculated to a BCF
of 0.064 L/kg ww. Since no bioconcentration/bioaccumulation data are
available for zirconium for other groups of organisms, this BCF can be
considered as the key BCF for zirconium.
2. Information on yttrium
Published data are
available reporting on the bioaccumulation potential of yttrium.
Yang et al. (1999)
studied the potential for bioaccumulation of rare earth elements in
different species (duckweed, daphnids, shellfish and goldfish) in a
static laboratory experiment using aquatic microcosms. In this microcosm
study, goldfish, shellfish, daphnids and duckweed were exposed for up to
16 days to a single concentration of yttrium (added as yttrium oxide,
together with other rare earth compounds). Yttrium analysis in samples
taken after 16 days of exposure yielded BCF/BAF values of ca. 2.5,
27.36, 430.5, and 992.7 L/kg ww for goldfish, shellfish, daphnids, and
The laboratory study of Tu et al. (1994) reported BCF values for muscle,
skeleton, gills, and internal organs of carp (Cyprinus carpio) after 45
days of exposure to yttrium trinitrate. Maximum BCF values found during
the 45-day exposure period for muscle tissue, skeleton, gills, and
internal organs were 1.3, 3.8, 8.0 and 54 L/kg ww, respectively. The BCF
values for internal organs were the highest but are not considered as a
good indication of the bioconcentration potential of yttrium, since the
alimentary tract reflects the normal transit of the substance. Anyhow,
the results of this study, together with those of the microcosm study of
Yang et al. (1999), indicates that yttrium has an extremely low
bioaccumulation potential in fish.
Sneller et al. (2000) discussed the study of Stronkhorst and Yland
(1998), which calculated BAF values for amphipods (Corophium volutator)
taken from a harbour in the Netherlands. The BAF value from this study
reported by Sneller et al. (2000) for yttrium was 7413 L/kg dw
(corresponding to 1482.6 L/kg ww, assuming 20% dw).
From the available studies, BCF/BAF values for aquatic plants, aquatic
invertebrates and fish were 992.7 L/kg ww, between 27.36 and 1482.6 L/kg
ww, and between 1.3 and 54 L/kg ww, respectively. As for other rare
earth elements, bioconcentration/bioaccumulation in fish seems to be
substantially lower than in organisms at a lower level in the food
chain. The fact that goldfish in a microcosm study (in which they could
feed on other organisms present in the microcosm) did not bioaccumulate
yttrium (estimated BAF value of 2.5 L/kg ww), indicates that any
bioconcentration/bioaccumulation is levelled out when ascending the food
chain. Clearly, yttrium has a very limited potential to bioaccumulate
through the food chain and it definitely does not biomagnify. In case
exposure assessments need to be performed, a value is needed that can be
used for calculating exposure levels in prey via the generic scenario
for secondary poisoning starting in the aquatic food chain, as well as
for calculating exposure levels for exposure of man via the environment.
An average (arithmetic mean) BAF of 4.65 L/kg ww for fish was therefore
calculated based on the results of the two available studies. Before
calculating the overall mean, a study-specific mean (geometric mean) was
calculated for the study of Tu et al. (1994). All data were included,
i.e. also data for internal organs. Therefore, the average BAF of 4.65
L/kg ww can be considered as a worst case value.
3. Conclusion on yttrium zirconium oxide
Based on the low water solubility of yttrium zirconium oxide as well as
the individual components of the solid solution (zirconium dioxide and
yttrium oxide), the bioavailability of yttrium and zirconium from
yttrium zirconium oxide is anticipated to be extremely low in the
aquatic environment. Any bioavailable yttrium or zirconium is not
expected to bioaccumulate/biomagnify throughout the aquatic food chain
to a significant extent, based on the available data on
bioconcentration/bioaccumulation of zirconium and yttrium (see above).
Based on these studies, it can be concluded that there is no concern for
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