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Bioaccumulation: aquatic / sediment

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Endpoint:
bioaccumulation in aquatic species: fish
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
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 analogy with lanthanum nitrate. The available data is adequate for classification and labeling purposes and PBT assessment is not required for inorganic substances so no further testing is required.
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non GLP study conducted to a non guideline method and read-across from an analogous substance. Literature paper considered inherently reliable.
Reason / purpose for cross-reference:
other: Target
Qualifier:
no guideline followed
Principles of method if other than guideline:
Bioconcentration and elimination of five light rare earth elements were investigated in carp (Cyprinus carpio L.).
Bioconcentration experiments were carried out over a 43-day period. Two additional aquariums each containing 10 fish served as controls and were also used for analysis of the background levels of the substance in carp.
Fish were sacrificed at time intervals from each of the test groups. The sample fish were rinsed with distilled water and the surfaces of the fish bodies were dried. Careful dissection was made to divide the fish into various tissue categories. Skeleton, muscle, gills and internal organs were removed into 50 ml beakers respectively.
After weighing samples were digested with HNO3-HClO4 mixtures and evaporated to near dryness. The residues were dissolved in 80 ml of 0.8 mol/L HCl and transferred to 8x200 mm columns packed with 1x8 strong cation exchanges (Dowex 50-X8). Then 90 ml of 1.75 mol/L HNO3 followed with 70 ml 1.2 mol/L HCl were added to each column. Test substance adsorbed by resins were finally eluted by 140 ml of 4.0 mol/L HCl. The elutes were evaporated to ca. 1 mL, then transferred to 10 mL volumetric flasks, and made up with distilled water. The resultant solutions were subsequently used for analysis by ICP-AES.
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
La(NO3)3.nH2O
Vehicle:
no
Details on preparation of test solutions, spiked fish food or sediment:
Tap water was purified and dechlorinated through a purifier mainly consisting of filter papers and activated carbon. The obtained water was used as the diluent employed in all testing.
Test organisms (species):
Cyprinus carpio
Details on test organisms:
All fish were first year juveniles
Average length = 7.0 cm
Average weight = 3.7 g
Route of exposure:
aqueous
Test type:
semi-static
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
43 d
Total depuration duration:
8 d
Test temperature:
11 to 14°C
pH:
6.4 to 7.4
Dissolved oxygen:
> 7.0 mg/L
Details on test conditions:
Bioconcentration

Two glass aquariums with 60 litre capacity were used as containers for duplicate experiments. The fish were divided into two groups of 60. Each group of fish was placed into an aquarium containing 30 litres of water. Stock solutions were added, with stirring. The final concentration of the element in the test aquariums was 0.30 Cw mg/L.

The test water was well aerated and water temperature was maintained at 11 - 14°C by a temperature controller. Water pH was modified to 6.0 with HNO3 and NaOH in order to minimise possible precipitation ion exchange and adsorption.

A volume of 20 litres of test solution in each aquarium was renewed every other day.

Fish were fed on dry food prior to each renewal.

Bioconcentration experiments were carried out over a 43-day period. Two additional aquariums each containing 10 fish served as controls and were also used for analysis of the background levels of the substance in carp.

Fish were sacrificed at time intervals from each of the test groups. The sample fish were rinsed with distilled water and the surfaces of the fish bodies were dried. Careful dissection was made to divide the fish into various tissue categories. Skeleton, muscle, gills and internal organs were removed into 50 ml beakers respectively.

Elimination

When equilibrium was reached 30 fish of each test aquarium were placed in non-contaminated water renewed three times a week to monitor elimination according to the same experimental protocols as during the bioconcentration study.
Nominal and measured concentrations:
Concentrations were based on nominal values only.
Details on estimation of bioconcentration:
After weighing samples were digested with HNO3-HClO4 mixtures and evaporated to near dryness. The residues were dissolved in 80 ml of 0.8 mol/L HCl and transferred to 8x200 mm columns packed with 1x8 strong cation exchanges (Dowex 50-X8). Then 90 ml of 1.75 mol/L HNO3 followed with 70 ml 1.2 mol/L HCl were added to each column. Test substance adsorbed by resins were finally eluted by 140 ml of 4.0 mol/L HCl. The elutes were evaporated to ca. 1 mL, then transferred to 10 mL volumetric flasks, and made up with distilled water. The resultant solutions were subsequently used for analysis by ICP-AES.
Type:
BCF
Value:
0.8 L/kg
Basis:
organ w.w.
Remarks:
Muscle
Remarks on result:
other: Day 43
Type:
BCF
Value:
3.66 L/kg
Basis:
organ w.w.
Remarks:
Skeleton
Remarks on result:
other: Day 43
Type:
BCF
Value:
13.5 L/kg
Basis:
organ w.w.
Remarks:
Gills
Remarks on result:
other: Day 43
Type:
BCF
Value:
602 L/kg
Basis:
organ w.w.
Remarks:
Internal organs
Remarks on result:
other: Day 43
Type:
BCF
Value:
828 L/kg
Basis:
organ w.w.
Remarks:
Internal Organs
Remarks on result:
other: Day 29
Details on results:
Bioconcentration Factors L/kg wet weight
Tissue 3d 8d 15d 29d 36d 43d
Muscle 0.60 0.56 0.50 1.20 0.27 0.83
Skeleton 0.40 0.56 0.70 1.23 0.96 3.66
Gills 3.86 12.8 4.99 12.6 13.8 13.5
Internal organ 130 167 399 828 45.2 602

At the end of the 43-day exposure period equilibrium was considered to have been reached.

The elimination process of the test substance in gills, muscle and skeleton can be divided into two periods; a fast elimination period following a slower loss period. During an 8-day elimination experiment the elimination rate slowed and equilibrium was reached. The elimination pattern suggests that light rare earth elements that bioconcentrate in fish tissues may exist in two forms: one is unbound (accounting for 50-70% of total concentrations found in tissues) and the other which is tightly bound in the tissue.

The elimination process of rare earth elements in internal organs can also be divided into two periods. In the first period concentrations increased and reached a maximum at the end of the second day. In the second period the concentrations began to decrease and the kinetics of elimination can be described by the one-compartment model as follows:

C(t) = C(i) e-kt

where
C(i) = the maximum concentration in the internal organs
k = the biological elimination rate constant

A first-order process has been demonstrated during the second period of elimination in internal organs. An increasing period before elimination can be explained by the transportation of the rare earth elements from gills, muscle and skeleton to internal organs. When equilibrium was not reached the rate of elimination in gills, muscle and skeleton was faster than in internal organs.

Validity criteria fulfilled:
not applicable
Conclusions:
The study shows that some bioaccumulation of light rare earth elements can occur but that elimination processes reduce the bioaccumulation factors over a period of time.
The highest BCF value observed during the study for lanthanum was 828 in internal organs after 29 days and this reduced to 602 by the end of the study at 43 days.
The REACH criteria for PBT and vPvB as stated in Annex XIII give cut-off BCF values of 2000 and 5000 respectively and it is therefore considered reasonable to assume that lanthanum trihydroxide should not be considered to meet either of these criteria on the basis of the available data.
Executive summary:

Literature data exists on the bioaccumulation of soluble salts of light rare earth elements. Data on lanthanum nitrate can be used to provide an estimate of the bioaccumulation potential of lanthanum trihydroxide.

The study shows that some bioaccumulation of light rare earth elements can occur but that elimination processes reduce the bioaccumulation factors over a period of time.

The highest BCF value observed during the study for lanthanum was 828 in internal organs after 29 days and this reduced to 602 by the end of the study at 43 days.

The REACH criteria for PBT and vPvB as stated in Annex XIII give cut-off BCF values of 2000 and 5000 respectively and it is therefore considered reasonable to assume that lanthanum trihydroxide should not be considered to meet either of these criteria on the basis of the available data on an analogous substance.

Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
weight of evidence
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. Gills tissues retained the second highest concentration, suggesting that the gill is one of the main site of rare earth deposition in carp. By contrast, accumulation by muscles was minimal.

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. 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.

Description of key 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 analogy with lanthanum nitrate. The available data is adequate for classification and labelling purposes and PBT assessment is not required for inorganic substances so no further testing is deemed to be required.

No bioaccumulation data are available on lanthanum trihydroxide but literature data provide information on the soluble salt lanthanum nitrate. BCF values of 1.2-13.8 were recorded after 29-45 days in; muscles skeleton and gills. Higher BCF values of 91-828 were recorded in internal organs. In all tissues equilibrium was reached or approached within the time period. Elimination in internal organs was shown to occur with a half life of 7 days.  Lanthanum nitrate is therefore eliminated from fish and does not significantly bioaccumulate.  Being much less water soluble it is expected that lanthanum trihydroxide will be less bioavailable than the soluble salt 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 analogy with lanthanum nitrate. The available data is adequate for classification and labelling purposes and PBT assessment is not required for inorganic substances so no further testing is deemed to be required.

No bioaccumulation data are available on lanthanum trihydroxide but literature data provide information on the soluble salt lanthanum nitrate. BCF values of 1.2-13.8 were recorded after 29-45 days in; muscles skeleton and gills. Higher BCF values of 91-828 were recorded in internal organs. In all tissues equilibrium was reached or approached within the time period. Elimination in internal organs was shown to occur with a half life of 7 days. Lanthanum nitrate is therefore eliminated from fish and does not significantly bioaccumulate. The REACH criteria for PBT and vPvB as stated in Annex XIII give cut-off BCF values of 2000 and 5000 respectively and it is therefore considered reasonable to assume that lanthanum trihydroxide should not be considered to meet either of these criteria on the basis of the available data on an analogous substance. Furthermore being of very low water solublity it is expected to be less bioavailable than the soluble salt tested.