Praseodymium trichloride

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:

24 April 2017 - 19 June 2017

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)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

trichloropraseodymium; heptahydrate

Cas Number:

10025-90-8

Molecular formula:

PrCl3.7H2O

IUPAC Name:

trichloropraseodymium; heptahydrate

Test material form:

solid: particulate/powder

Details on test material:

- Name of the test material (as in the report): praseodymium trichloride heptahydrate
- Physical state: solid
- Appearance: green crystalline powder
- Further information on test material 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.
- Sample storage conditions before analysis: Samples were taken on the day of analysis. Duplicate samples were stored frozen until analysis (if required).

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Preliminary stirring experiment: Due to the pH dependent solubility of the test item in the test water as well as its pH lowering capacity, a preliminary stirring experiment was performed to determine the optimal stirring time for reaching solution equilibrium and the optimal procedure for test solution preparation. 755 mg of test item was dispersed in 5 L of pH 6.0 test water with the aid of vigorous magnetic stirring for 96 h. After 3, 24 and 96 h the stirring was stopped and the pH checked and adjusted if necessary. After the pH check any undissolved test item was removed by filtration through a 0.2 µm Gelman Acrocap filter (first approximate 100 mL discarded in order to pre-condition the filter) to give a 100% v/v saturated solution. A sample was taken after each stirring period for immediate preparation and chemical analysis. This preliminary experimented indicated that the highest dissolved concentration was already observed after 3 h and therefore 3 h was used as equilibration period in the main experiment.
- The 100% v/v saturated solution for the main test was prepared in the same way as described above, applying a stirring period of 3 h. A series of dilutions was made from the saturated solution to give test concentrations of 0.32, 1.0, 3.2, 10 and 32% of the v/v saturated solution.

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): juveniles < 24 hours old
- Feeding during test: no

ACCLIMATION
- Method of breeding: clone has been bred at Envigo 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: a mixture of algal suspension (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:

21-22°C

pH:

New test media:
0 h = 5.8-6.2
24 h = 5.9-6.3
Old test media:
24 h = 6.5-7.4
48 h = 6.5.-7.3

Dissolved oxygen:

New test media: 6.6-9.2 mg/L
Old test media: 8.6-8.8 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: Control + 0.32, 1.0, 3.2, 10 and 32% v/v of a saturated solution with nominal loading rate of 100 mg/L (as anhydrous PrCl3).
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):
Although measurements in fresh media confirm correct dosing, analysis of samples and duplicate samples in the old test media of the 0.32 and 1.0% dilutions suggest that these test solutions have been switched during the test. Therefore, the values were switched back for calculation of geometric mean measured test concentrations. The results for the duplicate samples were not used in this calculation, as they confirmed the measurements in the original samples.

Geometric Mean Measured Test Concentration as praseodymium (mg/L) = Geometric Mean Measured Test Concentration as praseodymium tricholride (mg/L) = Geometric Mean Measured Test Concentration as Test Item (mg/L) =

Details on test conditions:

TEST SYSTEM
- Test vessel: 150-mL glass beakers filled with 100 mL of test medium
- Type (delete if not applicable): open, covered to reduce evaporation
- Aeration: The test water was aerated prior to the start of the study. No aeration during the study.
- 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 perparation 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 421 and 537 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 (anhydrous praseodymium trichloride)
- Results used to determine the conditions for the definitive study: yes: after 48 hours, 6/10 daphnids were immobilised in the 10% v/v dilution and 10/10 daphnids were immobilised in the 100% v/v saturated solution itself

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.:

1.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

element (dissolved fraction)

Basis for effect:

mobility

Remarks on result:

other: 95% CL: 0.99-1.9 mg/L

Effect concentrations 2

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

2.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Remarks:

expressed as anhydrous praseodymium trichloride

Basis for effect:

mobility

Details on results:

Other effect concentrations:
24-h EC50 = 4.1 mg Pr/L (7.1 mg PrCl3/L)
48-h NOEC = 0.16 mg Pr/L (0.28 mg PrCl3/L)
48-h LOEC = 1.0 mg Pr/L (1.8 mg PrCl3/L)

Sub-lethal effects (pale in colour, reduced mobility, trapping at the surface):
- After 48 h in the 0.32 v/v dilution, 2 (out of 5) daphnids were trapped at the surface in both replicate 1 and 2, whereas all other daphnids in the different replicates were normal in appearance.
- After 24 h in the 10% v/v dilution, respectively 3, 1, 2 and 4 (out of 5) daphnids had reduced mobility in the different replicates, whereas all other daphnids in the different replicates were immobilised.
- After 48 h in the 10% v/v dilution, 1 (out of 5) daphnid had reduced mobility in replicate 1, whereas all other daphnids in the different replicates were immobilised.
- After 48 h in the 32% v/v dilution, 1 (out of 5) daphnid had reduced mobility and pale colour in replicate 1, whereas all other daphnids in the different replicates were immobilised.

Results with reference substance (positive control):

- Results with reference substance valid? yes
- 24-h EC50: 0.83 mg/L (95% CI: 0.70-0.98 mg/L)
- 48-h EC50: 0.64 mg/L (95% CI not possible to determine)
- The results from the positive control with potassium dichromate were within the normal range for this reference item.

Reported statistics and error estimates:

The EC50 values and associated confidence limits at 24 and 48 h and the slope of the response curve and its standard error were calculated by Probit analysis using Linear Maximum-Likelihood regression. The LOEC and NOEC at 24 and 48 h were calculated using the Step-Down Cochran Armitage Test. 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 praseodymium trichloride 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 Pr concentrations was determined to be 1.4 mg/L (corresponding to 2.4 mg/L of anhydrous praseodymium trichloride).