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EC number: 264-885-7
CAS number: 64417-98-7
Following the read across strategy, it is considered appropriate to cover this endpoint by data on bioaccumulation of zirconium and yttrium.For zirconium, the study of Ferrand et al.(2006) indicates that there is no potential for bioaccumulation in terrestrial organisms, the BSAF values for roots and aerial parts of terrestrial plants being all <= 0.1 and <= 0.005, respectively. For yttrium, the review by Rikken (1995) reported BSAF values for food crops in the range of 0.0014 and 0.010, whereas Markert and Li (1999) reported BSAF values for rare earth elements including yttrium in the range of 0.04 to 0.09. These BSAF values being all well below 1, it can be concluded that there is no potential for bioaccumulation of yttrium in the terrestrial environment.Because based on the low water solubility of yttrium zirconium oxide, the release of yttrium and zirconium in the environment, and hence their bioavailability, is expected to be very limited, it can be concluded that no bioaccumulation of yttrium or zirconium from yttrium zirconium oxide is to be expected in the terrestrial environment.
1. Information on zirconium
In the study of Ferrand et al. (2006), transfer of zirconium from soil
to tomato and pea plants was studied during a 7-day exposure period in
two soils (an acidic and a calcareous soil) amended with either a
soluble (zirconium dichloride oxide or zirconium acetate) or an
insoluble zirconium compound (Zr(OH)4). Zirconium accumulated mainly in
the roots, with zirconium adsorption to the root surface being of minor
relevance. Translocation to aerial parts was limited. BSAF values for
roots were the highest for zirconium acetate and the lowest for Zr(OH)4.
They were all <= 0.1. BSAF values for aerial parts were all <=
0.005 and were also generally the highest for zirconium acetate and the
lowest for Zr(OH)4. These values are however all below 1, indicating
that zirconium has no potential for bioaccumulation in terrestrial
2. Information on yttrium
Because rare earth elements are being used as fertiliser to promote
plant growth for certain types of crops in certain regions, a
substantial amount of literature is available on the transfer of rare
earths to plants in the terrestrial environment. Only a limited amount
of data is included in this endpoint summary, however, this amount of
information is considered sufficient for drawing conclusions on this
Rikken (1995) summarized literature data on the accumulation of rare
earth metals in plants, as a part of the investigation of data on the
transfer of rare earths in the chain artificial fertilizers - soil -
crops - livestock and man. The data for concentration of yttrium in
different vegetables and feeding stuffs and the soil were collected and
biota-to-soil accumulation factors (BSAFs) were calculated.
The concentration and accumulation of rare earths in plants differed as
a consequence of plant and soil properties (e.g., species, Ca-content).
The concentrations of rare earth elements in plants (dry weight) were in
general low: < 0.2 mg/kg dw for root and leaf vegetables, < 0.05 mg/kg
dw in most fruits and < 1 mg/kg dw in herbs/grasses. BSAFs for rare
earth elements are usually within a range of 0.0001 to 0.001 for feed
crops and 0.0001 to 0.01 for food crops. For yttrium specifically, BSAFs
were in a range of 0.0014 - 0.010 for food crops. No data were reported
for feed crops.
Further, Tyler (2004) reviewed the information about rare earth elements
in soil and plant systems and arrived at the conclusion that
concentrations of rare earths in plants are usually very low compared to
their total concentration in soils. For example, BSAFs in forest plants
of NW Germany were reported to be as low as 0.04 - 0.09 (Markert and Li,
Generally, the reviewed data indicated a low accumulation potential of
yttrium and rare earth elements in general. Therefore, it can be assumed
that there is no risk for accumulation in the terrestrial/sediment food
Rikken, M.G.J., 1995. De accumulatie van zeldzamen aardmetalen.
RIVM Rijksinstituut voor volksgesondheid en milieu, Bilthoven.Report
nr. 601014 013.
Markert, B., De Li, Z., 1991. Natural background concentrations of rare
earth elements in a forest ecosystem. Science of the Total Environment
103: 27 -35.
Tyler, G., 2004. Rare earth elements in soil and plant systems. A
review. Plant and Soil 267: 191 -206.
3. Conclusion on yttrium zirconium oxide
Based on the available data on terrestrial bioaccumulation of zirconium
and yttrium, and taking into account the low water solubility of yttrium
zirconium oxide and hence the expected low bioavailability of zirconium
and yttrium in the environment, it can be concluded that there is no
potential for terrestrial bioaccumulation of yttrium or zirconium.
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