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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
17 October 2016 to 24 May 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reference:
Composition 0
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Test material information:
Composition 1
Analytical monitoring:
yes
Details on sampling:
- Sampling method: Samples were taken in triplicate. Samples were taken at 0 hours from the control and each test group from the bulk test preparation. Samples taken after 48 hours from the control and the 100% v/v saturated solution were taken from pooled replicates. Additionally, samples were taken after 48 h from the extra samples run alongside the test for the 1.0 and 10% v/v saturated solution test groups.
- Sample storage conditions before analysis: All samples were stored frozen prior to analysis.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Due to the insolubility of the test item in test water, a saturated solution method of preparation was considered most appropriate.
- Stirring experiment: A nominal amount of test item (1024.5 mg) was dispersed in 5 liters of test water with the aid of vigorous magnetic stirring for 96 hours to give a nominal concentration of 100 mg/L anhydrous gadolinium oxalate. After 3, 24 and 96 hours, the pH of the media was checked and adjusted to approximately pH 7.5-7.8 and a sample taken for chemical analysis after filtration through a 0.2 μm Gelman Acrocap filter (initial 100 mL discarded).
- The results obtained from the stirring experiment indicated that a 3-h stirring period was the most appropriate.
- The actual test solutions were 1.0, 10 and 100% v/v saturated solutions. The 100% v/v saturated solution was prepared as described for the stirring experiment (3 h stirring, 0.2-µm filtered). The 1.0 and 10% v/v saturated solutions were then prepared through serial dilution of the 100% v/v saturated solution.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Scientific name: Daphnia magna
- Strain: Straus
- Common name: Water flea
- Source: in-house laboratory cultures
- Age at study initiation (mean and range, SD): < 24 hours (not a first brood progeny)
- Feeding during test: no

ACCLIMATION
- Method of breeding: Clone has been bred at Harlan Laboratories in Elendt M7 medium in a temperature controlled room maintaining water temperature at 18-22°C.
- Lighting cycle: 16 h light + 8 h dark, 20-min dawn and dusk transition periods
- Type and amount of food: green algae Desmodesmus subspicatus and Tetramin flake food suspension
- Feeding frequency: daily
- Gravid adults were isolated the day before initiation of the test such that the young daphnids produced overnight were less than 24 h.
- Diet and diluent water are considered not to contain any contaminant that would affect the integrity or outcome of the study.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Hardness:
250 mg CaCO3/L
Test temperature:
20-22 °C
pH:
t=0h: 7.8-8.0
t=48h: 7.7-7.8
Dissolved oxygen:
t=0h: 7.3-7.4 mg/L
t=48h: 8.6-8.7 mg/L
Salinity:
not applicable
Nominal and measured concentrations:
Analytically determined concentrations in samples taken during the combined range finder limit test (control, 1.0, 10, 100% v/v saturated solution) were as follows:
0 h: 48 h: 0.00388 (0.00414*), 0.0193, 0.0175, 2.06 (0.962*) mg anhydrous gadolinium oxalate/L (i.e. 0.00211 (0.00225*), 0.0105, 0.0951, 1.12 (0.523*) mg Gd/L, and
* Duplicate sample. Samples considered to have been mixed up during initial analysis. The highest measured concentration is considered to correspond to the 0 h concentration. No impact considered.

Note that acidification of the samples was done before filtration, implying that the measured concentrations represent not true dissolved concentrations, and might have included some redissolved precipitated gadolinium.
Details on test conditions:
TEST SYSTEM
- Test vessel: 150-mL glass beakers filled with 100 mL of test medium
- Type (delete if not applicable): covered with glass plates to reduce the loss of water by evaporation and to avoid the entry of dust into the solutions
- Aeration: prior to the start of the study until oxygen saturation was reached but not during the study
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4 (100% v/v saturated solution), 1 (1.0 and 10% v/v saturated solution)
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted water (ISO medium), 294 mg/L CaCl2.2H2O, 123 mg/L MgSO4.7H2O, 65 mg/L NaHCO3, 5.8 mg/L KCl.
- Culture medium different from test medium: yes (culture medium Elendt M7)
- Intervals of water quality measurement: water temperature was recorded daily, dissolved oxygen and pH were recorded at the start and termination of the test

OTHER TEST CONDITIONS
- Adjustment of pH: The reconstituted water had a pH of 7.8 ± 0.2 adjusted (if necessary) with NaOH or HCl.
- Photoperiod: a 16-hour light to 8-hour dark cycle with a 20-minute transition period (simulation of dusk and dawn)
- Light intensity: between 385 to 545 Lux.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): immobilisation, daily

TEST CONCENTRATIONS
- Range finding study: yes (the study consisted of a combined range finder limit test)
- Test concentrations: control, 1.0, 10, 100% v/v of a saturated solution with nominal loading rate of 100 mg/L
- Results used to determine the conditions for the definitive study: no, no further study performed
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
100 other: % v/v of a saturated solution with nominal loading rate of 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
No significant immobilisation was observed in any of the test solutions.
The 48-h EC50 was therefore > 100% v/v of a saturated solution with nominal loading rate 100 mg/L.
After 48 h, only 1 daphnid in one replicate in the 100% v/v saturated solution was immobilised.
The mean measured dissolved Gd concentration in the 100% v/v saturated solution was 0.745 mg/L (equivalent to 2.8 mg/L anhydrous gadolinium oxalate). Note that this dissolved concentration may have been overestimated because the laboratory acidified the samples before filtration, consequently the measured Gd concentration might include some redissolved precipitated Gd.
No sub-lethal effects were observed throughout the test.
Results with reference substance (positive control):
- Results with reference substance valid? yes
- 24-h EC50: 0.83 mg/L
- 48-h EC50: 0.64 mg/L
Reported statistics and error estimates:
No statistics applied.
Validity criteria fulfilled:
yes
Conclusions:
The acute toxicity of gadolinium oxalate to Daphnia magna was investigated in accordance with OECD guideline 202 and GLP. A combined range finder limit test was performed, in which no significant adverse effects were observed up to and including at the highest concentration tested (i.e., a 100% v/v saturated solution with nominal loading rate 100 mg/L). The 48-h EC50 was therefore > 100% v/v of a saturated solution with nominal loading rate 100 mg/L. The mean measured dissolved Gd concentration in this saturated solution was 0.745 mg Gd/L (corresponding to 2.8 mg/L anhydrous gadolinium oxalate). Note that this concentration may have been overestimated because acidification was by accident done before filtration, consequently, the measurement may include some redissolved precipitated Gd.

Description of key information

The acute toxicity of gadolinium oxalate to Daphnia magna was investigated in accordance with OECD guideline 202 and GLP (Ablitt, 2017, Klimisch 1). A combined range finder limit test was performed, in which no significant adverse effects were observed up to and including at the highest concentration tested (i.e., a 100% v/v saturated solution with nominal loading rate 100 mg/L). The 48-h EC50 was therefore > 100% v/v of a saturated solution with nominal loading rate 100 mg/L. The mean measured dissolved Gd concentration in this saturated solution was 0.745 mg Gd/L (corresponding to 2.8 mg/L anhydrous gadolinium oxalate).

Key value for chemical safety assessment

Additional information