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Bioaccumulation: aquatic / sediment

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Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study fully describes the experimental conditions and the results however it is not conducted in accordance with a standard test method or to GLP.
Qualifier:
no guideline followed
Principles of method if other than guideline:
During this study, only an uptake phase was carried out.
GLP compliance:
no
Radiolabelling:
no
Details on sampling:
- Sampling intervals/frequency for test organisms: Based on the table of results presented in the publication, fish were sampled after 5, 10, 17, 24, 31, 38 and 45 days of exposure.

- Sampling intervals/frequency for test medium samples: No data.

- Sample storage conditions before analysis: No data.

- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods): After being sacrificed, the sampled fish were rinsed with distilled water and the surface of the fish bodies were dried. Dissection was made to divide the fish into various tissue categories: skeleton, muscles, gills, internal organs, which were removed into respective 25-mL tall-form beakers. These samples were digested with HNO3-HClO4 mixture and evaporated to near dryness. The residue were dissolved in 80 mL of 0.8 mol/L HCl and transferred to 8 x 200 mm columns packed with 1 x 8 strong cation exchangers (Dowex 50-X8). K, Na, Li, Bi, Mo, W, Cd, Pt, Au and Hg in the solutions were not adsorbed by the resins and washed away with the solutions. Then 90 mL of 1.75 mol/L HNO3 was added to each column to elute Ba and Sr, folloed by 70 mL of 1.2 mol/L HCl to elute Fe, Al, Ca, Mg, Mn and Ti. These previous procedures allowed to separate the rare earth elements from the major element matrices. If not, analytical difficulties may arise due to the low contents and bad distributions of the rare earth elements in the organisms as compared with major elements as Ca, Mg, Na and K. The rare earth elements adsorbed on the resins were finally eluted by 140 mL of 4 mol/L HCl. The eluates were evaporated to about 1 mL, transferred to 10-mL volumetric flasks, and made up to volume with distilled water. The resultant solutions were subsequently used for analysis by ICP-AES.

- Sampling of fish food: Some of the dry fish food was dissolved in HNO3 and its rare earth elements contents were determined by ICP-AES.
Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The La, Gd, and Y stock solutions were added dropwise to the diluent water with stirring either separately in the group A, B, C, respectively, or in interaction in the group D.
- Controls: Two additional aquaria were tested in parallel.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): No data.
Test organisms (species):
Cyprinus carpio
Details on test organisms:
TEST ORGANISM
- Common name: carp.
- Age at study initiation: first-year juveniles.
- Length at study initiation: 5.5 to 7.3 cm (average = 6.4 cm).
- Weight at study initiation: 4.2 to 8.7 g (average = 6.2 g).
- Feeding during test: Fish were fed on dry food every other day one hour prior to each renewal.
No further data.

ACCLIMATION
- Acclimation period: 10 days.
- Acclimation conditions: same as test.
- Health during acclimation: The mortality rate was less than 5 %.
No further data.
Route of exposure:
aqueous
Test type:
semi-static
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
45 d
Total depuration duration:
0 d
Hardness:
53 - 60 mg/L as CaO
Test temperature:
11 - 14 °C
pH:
Water pH was modified to 6 intermittently with HNO3 in order to minimize possible precipitation ion exchange and adsorption of the rare earth elements.
Dissolved oxygen:
> 7 mg/L
TOC:
No data
Salinity:
Not applicable
Details on test conditions:
TEST SYSTEM
- Test vessel:
* Type (open / closed): No data
* Material, size, headspace, fill volume: Glass aquaria with a 20-L capacity filled with 15 L of the diluent water.
- Aeration: The test water was well aerated.
- Type of flow-through: not a flow-through, but a semi-static test.
- Renewal rate of test solution (frequency/flow rate): A volume of 10 L of test solution in each aquarium was renewed every other day.
- No. of organisms per vessel: 20 fish in the groups A,B,C,D exposed to rare earth elements, 10 fish in control groups.
- No. of vessels per concentration (replicates): 2.
- No. of vessels per control replicates): 2.
- Biomass loading rate: 8.27 g/L in the groups A,B,C,D. 4.13 g/L in the control groups supposing that the water volume was the same as in the exposed groups.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap water purified and dechlorinated through a water purifier mainly consisting of filter papers and activated carbon.
- Particulate matter: No data.
- Metals, Pesticides: No data.
- Chlorine: 7 - 8.5 mg/L.
- Alkalinity: No data.
- Ca/mg ratio: No data.
- Conductance: 170 mOhms/cm
- Holding medium different from test medium: The same water was used as the diluent employed in all testing.
- Intervals of water quality measurement: No data.
- Intervals of test medium replacement: A volume of 10 L of test solution in each aquarium was renewed every other day.

OTHER TEST CONDITIONS
- Adjustment of pH: Water pH was modified to 6 intermittently with HNO3 in order to minimize possible precipitation ion exchange and adsorption of the rare earth elements.
- Photoperiod: No data
- Light intensity: No data.

RANGE-FINDING / PRELIMINARY STUDY
No data.
Nominal and measured concentrations:
Groups A, B, C: The three rare earths are tested separately with a final concentration of 0.5 mg/L.
Group D: The three rare earths are tested in interaction and the mixed solution contained a final concentration of 0.5 mg/L of each element.
Reference substance (positive control):
no
Details on estimation of bioconcentration:
BASIS INFORMATION
- Measured/calculated logPow: Not applicable to inorganic substances.
No further data.

BASIS FOR CALCULATION OF BCF
The maximum BCF was calculated by dividing the maximum concentration of a rare earth element in certain tissue of carp by the nominated concentration of the same element in the test water.
Type:
BCF
Value:
3.2 - 91
Time of plateau:
45 d
Calculation basis:
other: At the end of the 45 days, the equilibrium was reached or approached
Remarks on result:
other: Muscles: BCF = 3.2, Skeleton: BCF = 6.1, Gill: BCF = 18, Internal organs: BCF = 91
Remarks:
Conc.in environment / dose:[La] = 0.5 mg/L
Type:
BCF
Value:
3.5 - 105
Time of plateau:
45 d
Calculation basis:
other: after 45 days, the equilibrium was reached or approached
Remarks on result:
other: Muscles: BCF = 3.5, Skeleton: BCF = 5, Gill: BCF = 14, Internal organs: BCF = 105
Remarks:
Conc.in environment / dose:[Gd] = 0.5 mg/L
Type:
BCF
Value:
1.3 - 54
Time of plateau:
45 d
Calculation basis:
other: After 45 days, the equilibrium was reached or approached
Remarks on result:
other: Muscles: BCF = 1.3, Skeleton: BCF = 3.8, Gill: BCF = 8, Internal organs: BCF = 54
Remarks:
Conc.in environment / dose:[Y] = 0.5 mg/L
Details on results:
There was no mortality of fish during the 45-day exposure period.

Rare earth concentration in fish food:

Contents of the rare earth elements in the dry fish food were all under the detection limits. This result gave the assurance that the bioaccumulation process was not partly due to food-derived rare earth elements.

Bioaccumulation in carp:

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 pattern of accumulation for all the elements were similar, suggesting that carp accumulated the three rare earths at a comparable rate. The bioaccumulation values for individual element solutions (Groups A,B,C) and those for mixed rare earth solution (Group D) were in good agreement, with no significant difference; indicating that among the three rare earths studied, neither synergistic nor antagonistic effect played a part in the bioaccumulation process.

Bioconcentration factors:

The internal organs had much larger BCF than the other tissues. This was expected considering that the alimentary tract reflects normal transit of the substance. For this reason, this observation cannot be considered as an indication of bioaccumulation.

Validity criteria fulfilled:
not specified
Conclusions:
Lanthanum nitrate, gadolinium nitrate and yttrium nitrate do not show any potential for bioaccumulation in carp.
Executive summary:

The bioconcentration of the rare earth elements lanthanum, gadolinium and yttrium was studied 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 show any potential for bioaccumulation.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
supporting study
Reason / purpose for cross-reference:
read-across source
Type:
BCF
Value:
3.2 - 91
Time of plateau:
45 d
Calculation basis:
other: At the end of the 45 days, the equilibrium was reached or approached
Remarks on result:
other: Muscles: BCF = 3.2, Skeleton: BCF = 6.1, Gill: BCF = 18, Internal organs: BCF = 91
Remarks:
Conc.in environment / dose:[La] = 0.5 mg/L
Type:
BCF
Value:
3.5 - 105
Time of plateau:
45 d
Calculation basis:
other: after 45 days, the equilibrium was reached or approached
Remarks on result:
other: Muscles: BCF = 3.5, Skeleton: BCF = 5, Gill: BCF = 14, Internal organs: BCF = 105
Remarks:
Conc.in environment / dose:[Gd] = 0.5 mg/L
Type:
BCF
Value:
1.3 - 54
Time of plateau:
45 d
Calculation basis:
other: After 45 days, the equilibrium was reached or approached
Remarks on result:
other: Muscles: BCF = 1.3, Skeleton: BCF = 3.8, Gill: BCF = 8, Internal organs: BCF = 54
Remarks:
Conc.in environment / dose:[Y] = 0.5 mg/L

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

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.