Lutetium oxide

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:

21 November 2016 to 8 May 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

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:

Lutetium oxide

EC Number:

234-764-3

EC Name:

Lutetium oxide

Cas Number:

12032-20-1

Molecular formula:

Lu2O3

IUPAC Name:

Lutetium oxide

Test material form:

solid: particulate/powder

Details on test material:

- Name of test material (as cited in study report): dilutetium trioxide
- Physical state/Appearance: white solid
- Further information confidential.

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

- Sampling method:
* Samples were taken in triplicate.
* 0 h: samples taken from the control and each test group (bulk test preparation)
* 48 h: samples taken from the control and the 100% v/v saturated solution (pooled replicates), and additionally from the extra samples run alongside the test for the 1.0 and 10% v/v saturated solutions
- Sample storage conditions before analysis: All samples were stored frozen prior to analysis.

Test solutions

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Due to the insolubility of the test item in test water, a saturated solution method of preparation was considered most appropriate.
- Stirring experiment: A nominal amount of test item (500 mg) was dispersed in 5 liters of test water with the aid of vigorous magnetic stirring for 96 hours. After 3, 24 and 96 hours, the pH of the media was checked and a sample taken for chemical analysis after filtration through a 0.2 μm Gelman Acrocap filter (initial 100 mL discarded).
- The results obtained from the stirring experiment indicated that a 96-h stirring period was optimal to ensure solution equilibrium.
- The actual test solutions were 1.0, 10 and 100% v/v saturated solutions. The 100% v/v saturated solution was prepared as described for the stirring experiment (96 h stirring, 0.2-µm filtered). The 1.0 and 10% v/v saturated solutions were then prepared through serial dilution of the 100% v/v saturated solution.

Test organisms

Test organisms (species):

Daphnia magna

Details on test organisms:

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

ACCLIMATION
- Method of breeding: Clone has been bred at Harlan 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: green algae Desmodesmus subspicatus and Tetramin flake food suspension
- Feeding frequency: daily
- Gravid adults were isolated the day before initiation of the test such that the young daphnids produced overnight were less than 24 h old.
- 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:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Test conditions

Hardness:

250 mg CaCO3/L

Test temperature:

21-22 °C

pH:

t=0h: 7.7-7.9
t=48h: 7.6-7.9

Dissolved oxygen:

t=0h: 7.4-8.5 mg/L
t=48h: 8.9-9.0 mg/L

Salinity:

not applicable

Conductivity:

not applicable

Nominal and measured concentrations:

Analytically determined concentrations in samples taken during the combined range finder limit test (control, 100% v/v saturated solution) were as follows:
0 h: 48 h: Mean measured concentrations were < LOQ and 0.48 mg Lu/L (i.e. < LOQ, 0.54 mg Lu2O3/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): covered with glass plates to reduce the loss of water by evaporation and to avoid the entry of dust into the solutions
- Aeration: prior to the start of the study until oxygen saturation was reached but not during the study
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4 (100% v/v saturated solution), 1 (1.0 and 10% v/v saturated solution)
- 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 was recorded daily, dissolved oxygen and pH were recorded at the start and termination of the test

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: a 16-hour light to 8-hour dark cycle with a 20-minute transition period (simulation of dusk and dawn)
- Light intensity: between 574 to 590 Lux.

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

TEST CONCENTRATIONS
- Range finding study: yes (the study consisted of a combined range finder limit test)
- Test concentrations: control, 1.0, 10, 100% v/v of a saturated solution with nominal loading rate of 100 mg/L
- Results used to determine the conditions for the definitive study: no, no further study performed

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: % v/v of a saturated solution with nominal loading rate of 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

No immobilisation was observed in any of the test solutions.
The 48-h EC50 was therefore > 100% v/v of a saturated solution with nominal loading rate 100 mg/L.
The mean measured dissolved Lu concentration in the 100% v/v saturated solution was 0.48 mg/L (equivalent to 0.54 mg/L test item).
No sub-lethal effects were observed throughout the test.
Note that this dissolved concentration may have been slightly overestimated because the laboratory acidified the samples before filtration, consequently the measured Lu concentration might include some redissolved precipitated Lu

Results with reference substance (positive control):

- Results with reference substance valid: yes
- 24-h EC50: 1.3 mg/L
- 48-h EC50: 1.2 mg/L

Reported statistics and error estimates:

No statistics applied.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The acute toxicity of dilutetium trioxide to Daphnia magna was investigated in accordance with OECD guideline 202 and GLP. A combined range finder limit test was performed, in which no significant adverse effects were observed up to and including the highest concentration tested (i.e., a 100% v/v saturated solution with nominal loading rate 100 mg/L). The 48-h EC50 was therefore > 100% v/v of a saturated solution with nominal loading rate 100 mg/L. The mean measured dissolved Lu concentration in this saturated solution was 0.48 mg Lu/L (corresponding to 0.54 mg/L test item). Note that this concentration may have been overestimated because acidification was by accident done before filtration, consequently, the measurement may include some redissolved precipitated Lu.