Dipraseodymium trioxide

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:

27 March 2017 to 21 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)

Analytical monitoring:

yes

Details on sampling:

- Samples were taken from the control and the 100 % v/v saturated solution test group from the freshly prepared bulk test preparation at 0 hours and from the old or expired pooled replicates at 48 hours for quantitative analysis.
- All samples were stored frozen prior to analysis.
- Duplicate samples were taken and stored frozen for further analysis if necessary.

Vehicle:

yes

Remarks:

test water

Details on test solutions:

PRELIMINARY MEDIA PREPARATION TRIAL
- 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 OECD. Therefore a media preparation trial was conducted in order to determine the solubility of the test material under test conditions.
- The variable nature of the results from the preparation trial suggested that no method of preparation was suitable at effectively removing all of the undissolved material from the media. In addition, as there was no increase in dissolved test material when extending the stirring period beyond 24 hours, the test material was prepared as a saturated solution at an initial loading rate of 100 mg/L, stirred via propeller stirrer for 24 hours prior to the removal of any undissolved test material by filtration through a 0.2 µm Sartorius Sartopore filter (first approximate 2 litres discarded in order to pre-condition the filter) to give a nominal concentration of approximately 0.098 mg/L.

PREPARATION AND APPLICATION OF TEST SOLUTION:
A nominal amount of test material (1100 mg) was dispersed in 11 liters of test water with the aid of propeller stirring at approximately 1500 rpm for 24 hours. After 24 hours the stirring was stopped and any undissolved test material was removed by filtration through a 0.2 μm Sartorius Sartopore filter (first approximate 2 liters discarded in order to pre-condition the filter) to give a 100% v/v saturated solution.
The prepared concentration was inverted several times to ensure adequate mixing and homogeneity.

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:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

250 mg/L as CaCO3

Test temperature:

17 to 23°C

pH:

7.8 ± 0.2

Dissolved oxygen:

Approximately air-saturation value

Nominal and measured concentrations:

Nominal: 100 % (v/v)
Measured: 0 hrs: 0.111 mg/ L and 48 hrs: 0.0716 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 150 mL glass beakers
- Type: The test vessels were covered to reduce evaporation
- Material, size, headspace, fill volume: 100 mL of test preparation
- 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 was recorded daily, pH and dissolved oxygen concentrations were recorded at the start and termination of the test. 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 (1100 mg) was dispersed in 11 litres of test water with the aid of propeller stirring at approximately 1500 rpm for 24 hours. After 24 hours the stirring was stopped and any undissolved test material was removed by filtration through a 0.2 µm Sartorius Sartopore filter (first approximate 2 liters discarded in order to pre-condition the filter) 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 two replicates were employed for each control and test group, each containing 5 daphnids. The vessels was maintained in a temperature controlled room maintaining the water temperature at 18 to 22°C with a maximum deviation of ±1°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 150 mL test and control vessel contained 100 mL of test media and was covered to reduce evaporation. After 24 and 48 hours the number of immobilised daphnids were recorded. The control group was maintained under identical conditions but not exposed to the test material.

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:

48 h

Dose descriptor:

EC50

Effect conc.:

> 0.089 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOEC

Effect conc.:

0.089 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

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. Sub lethal effects were observed in the 0.10, 1.0 and 10% v/v saturated solution test concentrations, however, as no effects were observed in the 100% v/v saturated solution test concentration, 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.
- Chemical analysis of the freshly prepared 100% v/v saturated solution test preparation at 0 hours showed a measured praseodymium concentration of 0.061 mg/L (equivalent to 0.071 mg/L of test material). There was no significant change in the measured concentrations at 48 hours indicating that the test material was stable under test conditions.

DEFINITIVE TEST
- Verification of Test Concentrations: Chemical analysis of the 100% v/v saturated solution test preparation at 0-hours showed that a measured test concentration of 0.095 mg/L as praseodymium (equivalent to 0.11 mg/L as test material). Analysis of the test preparation at 48 hours showed that a measured concentration of 0.061 mg/L as praseodymium (equivalent to 0.072 mg/L as test material) was obtained and hence it was considered appropriate to calculate the results based on the geometric mean measured test concentration in order to give a “worst case” analysis of the data. The geometric mean measured concentration was determined to be 0.076 mg/L as praseodymium (equivalent to 0.089 mg/L as test material).
- Immobilisation Data: There was no immobilisation in 20 daphnids exposed to a test concentration of 100% v/v saturated solution for a period of 48 hours. Exposure of Daphnia magna to the test material gave EC50 values based on the geometric mean measured test concentration of greater than 0.076 mg/L as praseodymium (equivalent to 0.089 mg/L as test material). The No Observed Effect Concentration was 0.076 mg/L as praseodymium (equivalent to 0.089 mg/L as test material).
- Sub-Lethal Effects: A sub-lethal effect of exposure was observed in the control at 48 hours. This response was trapping at the surface.
- Validation Criteria: The test was considered to be valid given that no more than 10% 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 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 607 to 667 Lux.
- Observations on Test Item 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 0.089 mg/L. The No Observed Effect Concentration was 0.089 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 0.098 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 22°C under static test conditions. The test material solution was prepared by stirring an excess (100 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 filtration (0.2 µm Sartorius Sartopore filter, first approximately 2 litres discarded in order to pre-condition the filter) to produce a 100% v/v saturated solution of the test material.

Chemical analysis of the 100% v/v saturated solution test preparation at 0 hours showed that a measured test concentration of 0.095 mg/L as praseodymium (equivalent to 0.11 mg/L as test material). Analysis of the test preparation at 48 hours showed that a measured concentration of 0.061 mg/L as praseodymium (equivalent to 0.072 mg/L as test material) was obtained and hence it was considered appropriate to calculate the results based on the geometric mean measured test concentration in order to give a “worst case” analysis of the data. The geometric mean measured concentration was determined to be 0.076 mg/L as praseodymium (equivalent to 0.089 mg/L as test material).

This study showed that there were no toxic effects at saturation, as there was no immobilisation in 20 daphnids exposed to a test concentration of 100 % v/v saturated solution for a period of 48 hours. The test was considered to be valid.

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 0.089 mg/L. The No Observed Effect Concentration was 0.089 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 0.089 mg/L. The No Observed Effect Concentration was 0.089 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.089 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 0.098 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 22°C under static test conditions. The test material solution was prepared by stirring an excess (100 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 filtration (0.2 µm Sartorius Sartopore filter, first approximately 2 litres discarded in order to pre-condition the filter) to produce a 100% v/v saturated solution of the test material.

Chemical analysis of the 100% v/v saturated solution test preparation at 0 hours showed that a measured test concentration of 0.095 mg/L as praseodymium (equivalent to 0.11 mg/L as test material). Analysis of the test preparation at 48 hours showed that a measured concentration of 0.061 mg/L as praseodymium (equivalent to 0.072 mg/L as test material) was obtained and hence it was considered appropriate to calculate the results based on the geometric mean measured test concentration in order to give a “worst case” analysis of the data. The geometric mean measured concentration was determined to be 0.076 mg/L as praseodymium (equivalent to 0.089 mg/L as test material).

This study showed that there were no toxic effects at saturation, as there was no immobilisation in 20 daphnids exposed to a test concentration of 100% v/v saturated solution for a period of 48 hours. The test was considered to be valid.

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 0.089 mg/L. The No Observed Effect Concentration was 0.089 mg/L.