Praseodymium 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:

2013-03-03 - 2013-03-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2014

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Praseodymium trinitrate

EC Number:

233-796-5

EC Name:

Praseodymium trinitrate

Cas Number:

10361-80-5

Molecular formula:

HNO3.1/3Pr

IUPAC Name:

praseodymium trinitrate

Test material form:

solid: crystalline

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Concentrations of dissolved Pr were determined in at least one of the triplicate samples from each treatment per sampling time.
- Sampling method: Triplicate samples were taken from each treatment at the start and end of each test medium renewal period (after filtration through a membrane filter, Whatman, Type NC45, pore size 0.45 µm).
- Sample storage conditions before analysis: All samples are stored at room temperature in the dark after sampling until analysis.

Test solutions

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Due to the low solubility of the test item in test water, a dispersion with the loading rate of 132 mg/L (corresponding to 100 mg/L anhydrous praseodymium trinitrate) was prepared at the start of the test and before each test medium renewal by dispersing 131.8 mg of the test item (dosing range: 131.7–131.8 mg) in 1000 mL of test water. This preparation was supported by ultrasonic treatment for 15 minutes. The pH of the dispersion was adjusted to 6.0 using 1 M hydrochloric acid solution, followed by intense stirring on a magnetic stirrer over 3 hours in the dark, to dissolve a maximum amount of the test item in the dispersion. No auxiliary solvent or emulsifier was used.

The stirring period of 3 hours was confirmed in a stirring experiment. In this experiment, stirring times of 3, 24 and 96 hours were tested in parallel, and the maximum concentration of dissolved elemental praseodymium was analytically measured after 3 hours of stirring. After the 3-hour stirring period, the dispersion of the test item was filtered through a membrane filter (Schleicher & Schuell, Type NC45, pore size 0.45 µm). The undiluted filtrate was used as the highest concentrated test medium and as a stock solution for preparation of the test media with lower test concentrations. For this preparation, the filtrate was serially diluted with test water. The test media were prepared just before the start of the test (= addition of daphnids) and before each test medium renewal.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain: Straus
- Source: University of Sheffield / UK in 1992
- Age at study initiation (mean and range, SD): 6-24 hours (not a first brood progeny)
- Feeding during test: no
- Method of breeding: clone has been bred at Harlan Laboratories in reconstituted water of the quality identical to the water quality used in the test

ACCLIMATION
- Type and amount of food: green algae Desmodesmus subspicatus CHODAT, Strain No. 86.81 SAG, supplied by the Collection of Algal Cultures or a mixture of this algal suspension and a commercial fish diet
- Feeding frequency: daphnids are generally fed three times a week
- Health during acclimation (any mortality observed): good. No mortalities observed

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:

20 - 21°C

pH:

New test media:
0 h = 5.9-6.2
24 h = 5.9-6.3
Old test media:
24 h = 6.7-6.8
48 h = 6.5-6.9

Dissolved oxygen:

8.3 - 8.6 mg/L

Salinity:

not applicable

Nominal and measured concentrations:

Analytically determined concentrations of dissolved praseodymium in the test media (control, dilutions 1:16, 1:8, 1:4, 1:2, and the undiluted filtrate) were as follows:
Day 0, 0 h (start of experiment) = < LOQ, 0.494, 1.01, 2.07, 4.12, and 8.33 mg Pr/L (i.e. < LOQ, 1.15, 2.35, 4.81, 9.55 and 19.3 mg Pr(NO3)3/L)
Day 1, 24 h (end of 1st renewal period) = < LOQ,0.199, 0.650, 0.661, 1.16, and 4.81 mg Pr/L (i.e.< LOQ, 0.462, 1.51, 1.53, 2.68 and 11.2 mg Pr(NO3)3/L)
Day 1, 0 h (start of 2nd renewal period) = < LOQ,0.236,1.36,2.48,2.80, and 7.88 mg Pr/L (i.e.< LOQ,0.548,3.16,5.76,6.50 and 18.28 mg Pr(NO3)3/L)
Day 2, 24 h (end of 2nd renewal period) = 0.00775/0.00823, 0.132, 0.209,0.366, 1.56 and 8.48 mg Pr/L (i.e 0.0180/0.0191,0.306,0.485,0.849,3.61 and 19.7 mg Pr(NO3)3/L).
Over the test medium renewal periods of 24 h, the concentrations of dissolved Pr decreased (recovery 15 to 107% of initially measured concentrations, on average 23 to 82%). The concentrations found in the control samples at Day 2, 24 hours although higher than the LOQ were considered to be slight contamination or just a higher background reading on this particular day and insignificant in real practical terms. The concentration in the treatment with the undiluted filtrate was slightly higher at ‘Day 2 – 24h’ than at ‘Day 1 – 0h’. It was not possible to explain this slight increase over the second renewal period with the available information. As the mortality was high in this treatment (i.e. 95 %), it is expected this slight increase in concentration had no significant consequence on the biological results.Biological results were based on mean measured concentrations calculated as the arithmetic mean of the two geometric means determined for dissolved Pr measured at the start and end of each test medium renewal period.Mean measured concentrations were as follows (not mentioning the control, for which dissolved Pr was < LOQ):0.25,0.67,1.1,2.1, 7.3 mg Pr/L (i.e. 0.57,1.6,2.5, 5 and 17 mg Pr(NO3)3/L)

Details on test conditions:

TEST SYSTEM
- Test vessel: 100-mL glass beakers filled with 50 mL of test medium
- Type (delete if not applicable): open
- 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 test water according to ISO 6341
- Ca/mg ratio: 4:1
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Adjustment of pH: 1) adjustment of dispersion to pH 6.0 after the 3-h stirring period using 1 M NaOH, 2) adjustment of test medium (for dilution of the filtrate) to pH 6.0 using 1 M HCl
- Photoperiod: A 16-hour light to 8-hour dark cycle with a 30-minute transition period
- Light intensity: Light intensity during the light period was approximately between 390 and 560 Lux.

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

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2 (spacing factor for serial dilutions)
- Range finding study: No

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.:

0.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

dissolved

Remarks:

praseodymium

Basis for effect:

mobility

Remarks on result:

other: 95%CL: 0.51-1.4 mg/L

Effect concentrations 2

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

2 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: praseodymium trinitrate, anhydrous

Basis for effect:

mobility

Remarks on result:

other: 95% CL: 1.2-3.3 mg/L

Details on results:

48-hour EC0 and NOEC of dissolved praseodymium was 0.25 mg/L (corresponding to 0.57 mg/L when expressed in anhydrous praseodymium trinitrate)
48-hour EC100 of dissolved praseodymium was > 7.3 mg /L (corresponding to > 17 mg/L when expressed in anhydrous praseodymium trinitrate)

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50/LC50: 48-hour EC50: 0.94 mg/L L (within the internal historical range: 48-hour EC50 from 2000 to 2012: 0.43-1.1 mg/L)

Reported statistics and error estimates:

NOEC, EC0 and EC100 were determined directly from the raw data.
24-h EC50 could not be calculated due to absence of toxicity and was therefore also determined directly from the raw data.
48-h EC50 and 95% confidence limits were calculated using Weibull Analysis with linear weighted regression.
The two lowest treatments were excluded from the statistical evaluation, as they did not contribute to the dose-response relationship.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The test item had acute toxic effects on Daphnia magna. The 48-hour EC50 was calculated to be 0.9 mg/L of dissolved praseodymium with 95% confidence limits of 0.51 and 1.4 mg/L (corresponding to 2.0 mg/L of anhydrous praseodymium trinitrate with 95% confidence limits of 1.2 and 3.3 mg/L).Based on this value, praseodymium trinitrate should be considered as toxic to aquatic invertebrates.

Executive summary:

The acute toxicity of praseodymium trinitrate to Daphnia magna was determined in a 48-hour semi-static test according to the OECD guideline 202 and in compliance with the principles of Good Laboratory Practice. Juvenile daphnids were exposed to a control treatment and the test chemical at various concentrations (a dispersion with the loading rate of 132 mg/L (corresponding to 100 mg/L of anhydrous praseodymium trinitrate) was used as stock solution for test media preparation; the undiluted filtrate and dilutions 1:2, 1:4, 1:8 and 1:16 of this undiluted filtrate were used as test media). Organisms were observed after 24 and 48 hours for immobility.

After 48 hours of exposure, no immobilized test organisms were recorded in the control and up to and including the mean measured concentration of 0.25 mg/L of dissolved praseodymium, corresponding to 0.57 mg/L of anhydrous praseodymium trinitrate. At the mean measured concentration of 2.1 and 7.3 mg/L of dissolved praseodymium (corresponding to 5.0 and 17 mg/L of anhydrous praseodymium trinitrate), 65% and 95% of the daphnids were found to be immobile, respectively. The 48-h EC50 was determined to be 0.9 mg/L for dissolved praseodymium and 2.0 mg/L for anhydrous praseodymium trinitrate; meaning this substance is toxic to aquatic invertebrates.