Neodymium(3+) acetate

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

30 January 2017 to 27 April 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

2004

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Room temperature in the dark over silica gel

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 100% v/v
- Sampling method: Samples were taken from the control and the 100 % v/v saturated solution test group from the bulk test preparation at 0 and 24 hours hours and from the pooled replicates at 24 and 48 hours for quantitative analysis.
- Sample storage conditions before analysis: All samples were stored frozen prior to analysis.

Vehicle:

yes

Remarks:

Test Water

Details on test solutions:

- Preliminary solubility work conducted indicated that the test material was practically insoluble in water using traditional methods of preparation e.g. ultrasonication and high shear mixing.
Based on this information the test material was categorised as being a ‘difficult substance’ as defined by the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (OECD 2000). Therefore a media preparation trial was conducted in order to determine the solubility of the test material under test conditions.
- Based on the media preparation trial the test material was prepared using a saturated solution method of preparation at an initial loading rate of 50 mg/L, stirred for a period of 48 hours prior to the removal of any undissolved test material by centrifugation at 40000 g for 30 minutes to give a nominal test concentration of approximately 4.1 mg/L.

- Test water:
Reconstituted Water – ISO Medium containing: 294 mg/L CaCl2.2H2O, 123 mg/L MgSO4.7H2O, 65 mg/L NaHCO3 and 5.8 mg/L KCl. The reconstituted water had a pH of 7.8 ± 0.2 adjusted (if necessary) with NaOH or HCl and was aerated until the dissolved oxygen concentration was approximately air-saturation value. The reconstituted water had an approximate theoretical total hardness of 250 mg/L as CaCO3.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Age: Gravid adults were isolated the day before initiation of the test, such that the young daphnids produced overnight were less than 24 hours old. These young were removed from the cultures and used for testing.
- Feeding during test: no

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

250 mg/L as CaCO3

Test temperature:

19 to 22°C

pH:

7.0 to 7.8

Dissolved oxygen:

7.4 to 9.0 mg O2/L

Nominal and measured concentrations:

Nominal: 100% (v/v)
Measured: 0 hrs: 6.69 mg/ L (fresh), 24 hrs: 4.17 mg/L (old) and 3.86 mg/L (fresh), 48 hrs: 2.64 mg/L (old)

Details on test conditions:

TEST SYSTEM
- Test vessel: 150 mL glass jars
- Type: The test vessels were covered to reduce evaporation
- Material, size, headspace, fill volume: 100 mL of test preparation
- Renewal of test solution: after 24 hours the test concentrations were freshly prepared and the daphnids transferred by wide bore pipette from the 24-hour old test media into the fresh test media.
- 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 containing: 294 mg/L CaCl2.2H2O, 123 mg/L MgSO4.7H2O, 65 mg/L NaHCO3 and 5.8 mg/L KCl. The reconstituted water was aerated until the dissolved oxygen concentration was approximately air-saturation value. The reconstituted water had an approximate theoretical total hardness of 250 mg/L as CaCO3.
- Water quality assessments: The water temperature, pH and dissolved oxygen concentrations were recorded daily throughout the test. The measurements at 0 hours and after the test media renewal at 24 hours represent those of the freshly prepared test preparations while the measurements taken prior to the test media renewal, and on termination of the test after 48 hours, represent those of the used or 24-hour old test preparations. The pH and dissolved oxygen concentration were measured using a Hach Flexi handheld meter whilst the temperature was measured using a Hanna Instruments HI 93510 digital thermometer. The light intensity during the light period was measured using an ATP Instrumentation Lux meter. The appearance of the test media was recorded daily.

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: 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods
- Light intensity: (between 200 and 1200 Lux)

RANGE-FINDING STUDY
- Test concentrations: 0.10, 1.0, 10 and 100% v/v saturated solution.
- A nominal amount of test material (550 mg) was dispersed in 11 litres of test water with the aid of propeller stirring at approximately 1500 rpm for 48 hours. After 24 hours the stirring was stopped and any undissolved test material was removed by centrifugation at 40000 g for 30 minutes to give a 100% v/v saturated solution. A series of dilutions was made from this saturated solution to give further test concentrations of 0.10, 1.0 and 10% v/v saturated solution. Each prepared concentration was inverted several times to ensure adequate mixing and homogeneity.
- In the range-finding test 10 daphnids were placed in each test and control vessel and maintained in a temperature controlled room maintaining the water temperature at 18 to 22°C with a photoperiod of 16 hours light and 8 hours darkness for a period of 48 hours with 20 minute dawn and dusk transition periods. Each 250 mL test and control vessel contained 200 mL of test media and was covered to reduce evaporation. After 24 and 48 hours the number of immobilised daphnids were recorded.
- Results used to determine the conditions for the definitive study: Yes, Based on the results of the range-finding test a "limit test" was conducted at a concentration of 100% v/v saturated solution to confirm that at highest attainable test concentration no immobilisation or adverse reactions to exposure were observed.

ASSESSMENTS
- Test organism observations: Any immobilisation or adverse reactions to exposure were recorded at 24 and 48 hours after the start of exposure. The criterion of effect used was that daphnia were considered to be immobilised if they were unable to swim within 15 seconds after gentle agitation.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 4.2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 4.2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

RANGE FINDING TEST
No immobilisation was observed at the test concentrations of 0.10, 1.0, 10 and 100% v/v saturated solution. A single daphnid was observed to be trapped at the surface in the 1.0 and 10% v/v saturated solutions, however, this was considered to be due to natural causes and as such was considered not to have had an impact on the outcome of the test.
Based on this information, a single test concentration of four replicates, of 100% v/v saturated solution was selected for the definitive test. This experimental design conforms to a "Limit test" to confirm that at highest attainable test concentration, no immobilisation or adverse reactions to exposure were observed.
Chemical analysis of the 100% v/v saturated solution test preparation at 0 hours showed that a measured concentration of 3.2 mg/L was obtained. Analysis at 48 hours showed that a measured concentration of 2.1 mg/L was obtained, indicating that the test material was unstable under test conditions.

DEFINITIVE TEST
- Verification of Test Concentrations:
Chemical analysis of the freshly prepared test preparations at 0 and 24 hours showed measured test concentrations to range from 3.4 to 6.7 mg/L. Analysis of the old or expired test preparations at 48 hours showed measured test concentrations had declined, to between 2.6 and 4.2 mg/L (62 to 68% of the fresh measured test concentrations) and hence it was considered appropriate to calculate the results based on the geometric mean measured test concentrations in order to give a “worst case” analysis of the data. The geometric mean measured test concentration was determined to be 4.2 mg/L.
- Immobilisation Data:
There was no significant immobilization in 20 daphnids exposed to a test concentration of 100% v/v saturated solution for a period of 48 hours. A single immobilized daphnia was observed in the 100% v/v saturated solution test group, however, given that less than 10% immobilization was observed, this was considered not to have had an impact in the outcome of the test. The No Observed Effect Concentration after 24 and 48 hours exposure was 4.2 mg/L.
-Sub-Lethal Effects:
No sub-lethal effects of exposure were observed throughout the test.

-Validation Criteria:
The test was considered to be valid given that none of the control daphnids showed immobilisation or other signs of disease or stress and that the oxygen concentration at the end of the test was equal to or greater than 3 mg/L in the control and test vessels.
-Water Quality Criteria:
Temperature was maintained at 19°C to 22°C throughout the test, while there were no treatment related differences for oxygen concentration or pH. Throughout the test the light intensity was observed to be in the range 504 to 563 Lux.
- Observations on Test Material Solubility:
At the start and throughout the test all control and test solutions were observed to be clear colourless solutions.

Results with reference substance (positive control):

-The 48h-EC50 for the positive control was 0.64 mg/L, the NOEC was 0.56 mg/L. The results from the positive control with potassium dichromate were within the normal range for this reference material.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the study, the acute toxicity of the test material to the freshwater invertebrate Daphnia magna has been investigated and based on the geometric mean measured test concentration gave a 48-hour EC50 value of greater than 4.2 mg/L. The No Observed Effect Concentration was 4.2 mg/L.

Executive summary:

The potential toxicity of the test material to Daphnia magna was determined in accordance with the standardised guidelines OECD 202 and EU Method C.2 under GLP conditions, using an acute immobilisation test.

Preliminary solubility work conducted indicated that it was not possible to obtain a testable solution of the test material using traditional methods of preparation e.g. ultrasonication and high shear mixing. A preliminary media preparation trial indicated that a dissolved test material concentration of approximately 4.1 mg/L was obtained from a saturated solution method of preparation indicating this to be the limit of water solubility of this material under test conditions.

Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to an aqueous solution of the test material at a concentration of 100% v/v saturated solution for 48 hours at a temperature of 19 to 22°C under static test conditions. The test material solution was prepared by stirring an excess (50 mg/L) of test material in test water using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test material was removed by centrifugation at 40000 g for 30 minutes to produce a 100% v/v saturated solution of the test material.

Chemical analysis of the freshly prepared test preparations at 0 and 24 hours showed measured test concentrations to range from 3.9 to 6.7 mg/L. Analysis of the old or expired test preparations at 48 hours showed measured test concentrations had declined, to between 2.6 and 4.2 mg/L (62 to 68% of the fresh measured test concentrations) and hence it was considered appropriate to calculate the results based on the geometric mean measured test concentrations in order to give a “worst case” analysis of the data. This study showed that there were no toxic effects at saturation. All validity criteria were met.

Under the conditions of the study, the acute toxicity of the test material to the freshwater invertebrate Daphnia magnahas been investigated and based on the geometric mean measured test concentration gave a 48 -hour EC₅₀value of greater than 4.2 mg/L. The No Observed Effect Concentration was 4.2 mg/L.

Description of key information

Under the conditions of the study, the acute toxicity of the test material to the freshwater invertebrate Daphnia magna has been investigated and based on the geometric mean measured test concentration gave a 48-hour EC50 value of greater than 4.2 mg/L. The No Observed Effect Concentration was 4.2 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

4.2 mg/L

Additional information

The potential toxicity of the test material to Daphnia magna was determined in accordance with the standardised guidelines OECD 202 and EU Method C.2 under GLP conditions, using an acute immobilisation test. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Preliminary solubility work conducted indicated that it was not possible to obtain a testable solution of the test material using traditional methods of preparation e.g. ultrasonication and high shear mixing. A preliminary media preparation trial indicated that a dissolved test material concentration of approximately 4.1 mg/L was obtained from a saturated solution method of preparation indicating this to be the limit of water solubility of this material under test conditions.

Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to an aqueous solution of the test material at a concentration of 100% v/v saturated solution for 48 hours at a temperature of 19 to 22°C under static test conditions. The test material solution was prepared by stirring an excess (50 mg/L) of test material in test water using a propeller stirrer at approximately 1500 rpm for 24 hours. After the stirring period any undissolved test material was removed by centrifugation at 40000 g for 30 minutes to produce a 100 % v/v saturated solution of the test material.

Chemical analysis of the freshly prepared test preparations at 0 and 24 hours showed measured test concentrations to range from 3.9 to 6.7 mg/L. Analysis of the old or expired test preparations at 48 hours showed measured test concentrations had declined, to between 2.6 and 4.2 mg/L (62 to 68% of the fresh measured test concentrations) and hence it was considered appropriate to calculate the results based on the geometric mean measured test concentrations in order to give a “worst case” analysis of the data. This study showed that there were no toxic effects at saturation. All validity criteria were met.

Under the conditions of the study, the acute toxicity of the test material to the freshwater invertebrate Daphnia magna has been investigated and based on the geometric mean measured test concentration gave a 48-hour EC50 value of greater than 4.2 mg/L. The No Observed Effect Concentration was 4.2 mg/L.