Gadolinium trinitrate

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2016-09-26 to 2017-04-07

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Gadolinium trinitrate

EC Number:

233-437-2

EC Name:

Gadolinium trinitrate

Cas Number:

10168-81-7

Molecular formula:

Gd(NO3)3

IUPAC Name:

gadolinium trinitrate

Test material form:

solid: crystalline

Details on test material:

- Name of test material (as cited in the report): gadolinium trinitrate
- CAS = 19598-90-4 (i.e. the hexahydrate form Gd(NO3)3.6H2O). According to Annex V, point 6 of the REACH regulation (CE) No. 1907/2006, this form will be covered by the registration of the anhydrous form (CAS number: 10168-81-7).
- Physical state: crystalline solid
- Further information on test item is confidential

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Sampling method: Samples were taken from the control and each surviving test group from the freshly prepared bulk test preparation at 0 and 24 hours and from the old or expired pooled replicates at 24 and 48 hours for quantitative analysis. Duplicate samples were taken and stored frozen for further analysis if necessary.

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- The test solutions for use in the definitive test were prepared through serial dilution of a 100% v/v saturated solution. The 100% v/v saturated solution was prepared by stirring (with the aid of propeller stirring) a nominal amount of test item (1100 mg) in 11 L of test water at approximately 1500 rpm for 24 h. The nominal concentration of anhydrous Gd(NO3)3 was hence 76.5 mg/L (corresponding to 100 mg test item/L, i.e. hydrated gadolinium trinitrate). Given the low solubility of the test item at the test pH, the correction for water content was considered to be unnecessary as an excess of test item was being stirred in the media. After 24 h of stirring, the solution was filtered (0.2 µm Gelman Acrocap filter, first 100 mL discarded) to remove any undissolved material. No pH adjustments were done.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Scientific name: Daphnia magna
- Common name: Water flea
- Source: in-house laboratory culture
- Age at study initiation (mean and range, SD): < 24 hours (not a first brood progeny)
- Feeding during test: no

ACCLIMATION
- Method of breeding: 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 in order to guarantee that the young daphnids they produced overnight were less than 24 hours old for use in the test.
- Diet and diluent water are considered not to contain any contaminant that would affect the integrity or outcome of the study.

Study design

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test conditions

Hardness:

250 mg CaCO3/L

Test temperature:

21 °C

pH:

t=0h (fresh medium): 6.6-7.7
t=24h (old medium): 7.0-8.0
t=24h (fresh medium): 7.2-7.7
t=48h (old medium): 7.7-7.9

Dissolved oxygen:

8.3-9.3 mg O2/L

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: Control + 10, 18, 32, 56 and 100% of the SS

Measured concentrations (mg/L) at t=0h (fresh): Measured concentrations (mg/L) at t=24h (old): Measured concentrations (mg/L) at t=24h (fresh): Measured concentrations (mg/L) at t=48h (old):
Geometric mean test concentrations (mg/L): Geometric mean test concentrations (mg/L):

Details on test conditions:

TEST SYSTEM
- Test vessel: 150-mL glass beakers filled with 100 mL of test medium
- Aeration: prior to the start of the study until oxygen saturation was reached but not during the study
- Renewal rate of test solution (frequency/flow rate): semi-static test with a 24-h renewal
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- 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, pH and dissolved oxygen content were measured at the beginning of the test in the fresh media, after 24 hours in the old and fresh media and at the end of the test in the old media

OTHER TEST CONDITIONS
- Adjustment of pH: The reconstituted water had a pH of 7.8 ± 0.2 (adjusted (if necessary) with NaOH or HCl). No pH adjustment was done after addition of the test item during the preparation of a saturated solution for use in the definitive test.
- Photoperiod: a 16-hour light to 8-hour dark cycle with a 20-minute transition period (simulation of dusk and dawn)
- Light intensity: between 528 to 565 Lux.

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

TEST CONCENTRATIONS
- Range finding study: yes
- Test concentrations: control, 0.1, 1.0, 10, 100% v/v of a saturated solution with nominal loading rate of 100 mg/L (gadolinium trinitrate hexahydrate)
- Measured concentrations in the 10% dilution and the 100% SS (mg/L) at t=0h: 1.25, 12.9 mg Gd/L
- Measured concentrations in the 10% dilution and the 100% SS (mg/L) at t=48h: 0.75, 5.69 mg Gd/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

1.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element (dissolved fraction)

Basis for effect:

mobility

Remarks on result:

other: 95% CL = 1.1-1.9 mg Gd/L

Effect concentrations 2

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

2.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Remarks:

expressed as: anhydrous gadolinium trinitrate

Basis for effect:

mobility

Remarks on result:

other: 95% CL = 2.4-4.0 mg Gd(NO3)3/L

Details on results:

Sub-lethal effects:
Sub-lethal effects of exposure were observed in the 18, 32 and 56% dilutions of the 100% v/v saturated solution. These responses were reduced movement and trapping at the surface.

Other effect concentrations:
24-h EC50 = 2.1 mg Gd/L (4.6 mg Gd(NO3)3/L)
48-h NOEC = 0.81 mg Gd/L (1.8 mg Gd(NO3)3/L)
48-h LOEC = 1.4 mg Gd/L (3.1 mg Gd(NO3)3/L)

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
These results were within the normal range observed for this reference item within the testing laboratory and confirmed the suitability of the test system.

Reported statistics and error estimates:

The EC50 values and associated confidence limits at 24 and 48 hours and the slope of the response curve and its standard error were calculated by Probit analysis using Linear Maximum-Likelihood regression. The Lowest Observed Effect Concentration and the No Observed Effect Concentration at 24 and 48 hours were calculated using Step-down Cochran Armitage Procedure. All results were calculated using the ToxRat Professional computer software package (TOXRAT).

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The acute toxicity of gadolinium trinitrate to Daphnia magna was investigated in accordance with OECD guideline 202 and conform GLP requirements. The 48-h EC50 based on geometric mean measured dissolved Gd concentrations was determined to be 1.3 mg Gd/L (corresponding to 2.9 mg/L anhydrous test item).