Neodymium oxide

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:

3 December 2007 - 17 March 2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted to GLP in compliance with agreed protocols, with no or minor deviations from standard test guidelines and/or minor methodological deficiencies, which do not affect the quality of the relevant results.

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: triplicate samples were taken from each treatment (control and loading rate 100 mg/L) before the start of the test and at the end of the test after 48 hours.
- Sampling method: no data
- Sample storage conditions before analysis: Immediately after sampling, the samples were acidified with 10 % (v/v) nitric acid (HNO3, 65 % Suprapur, Merck) to stabilise the samples during the storage period. Then the samples were stored at room temperature in the dark.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:
The test item is a sparingly soluble substance. In order to assess its toxicity, a saturated solution was prepared and tested. The test method was based on the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures.
The test medium with the loading rate of 100 mg/L was prepared just before introduction of the daphnids (i.e., start of the test) as follows:
A dispersion of the test item was prepared in the test water by mixing 200.4 mg of test item into 2000 mL of test water using ultrasonic treatment for 15 minutes and intense stirring. No auxiliary solvent or emulsifier was used.
The dispersion was stirred by a magnetic stirrer at room temperature in the dark for 24 hours. Then, stirring was stopped and after another 24 hours the non-dissolved test item had completely settled down on the bottom of the stirring vessel. The clear equilibrated supernatant was carefully separated from the non-dissolved test item and was used as test medium. The stirring and settling periods were chosen according to the results of pre-experiments (non-GLP). In a pre-experiment, the maximum concentration of dissolved neodymium was reached after a stirring period of 24 hours. The deposition time of one day was necessary to allow a maximum amount of the test item to deposit.
- Controls: blank (test water without addition of the test item)
- Evidence of undissolved material (e.g. precipitate, surface film, etc): yes, on the bottom of the stirring vessel, but not in the final test solution

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Strain: defined by the supplier as clone 5
- Age at study initiation (mean and range, SD): the organisms used in the test were 6 - 24 hours old and were not first brood progeny
- Weight at study initiation (mean and range, SD): no data
- Length at study initiation (length definition, mean, range and SD): no data
- Method of breeding: in reconstituted water of the quality identical to the water quality used in the tests (in respect to pH, main ions, and total hardness) and under temperature and light conditions identical to those of the tests
- Feeding during test : no
- Source: Originally supplied by the University of Sheffield / UK in 1992. Since that time, the clone has been bred at the laboratory.

ACCLIMATION
- Acclimation period: no

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Hardness:

2.5 mmol/L (= 250 mg/L as CaCO3)

Test temperature:

20 °C

pH:

7.9 - 8.0

Dissolved oxygen:

8.4 - 8.6 mgO2/L

Salinity:

not applicable

Nominal and measured concentrations:

Nominal loading rate: 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type: closed to reduce the loss of water by evaporation and to avoid the entry of dust into the solutions.
- Material, size, headspace, fill volume: The test was performed in 100 mL glass beakers filled with 50 mL of test medium.
- Aeration: The test water was aerated prior to the start of the study until oxygen saturation was reached, but was not aerated during the test period.
- Type of flow-through (e.g. peristaltic or proportional diluter): none (static test)
- Renewal rate of test solution (frequency/flow rate): no renewal (static test)
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 10 mL test medium per daphnia

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted test water : analytical grade salts dissolved in purified water
- Total organic carbon: no data
- Particulate matter: no data
- Metals, pesticides, chlorine: no data
- Alkalinity: 0.8 mmol/L
- Ca/mg ratio: 4:1 (based on molarity)
- Na/K ratio: 10:1 (based on molarity)
- Conductivity: no data
- Culture medium different from test medium: no
- Intervals of water quality measurement: At the start and at the end of the test, the pH values, the dissolved oxygen concentrations and the water temperature were determined in each treatment. The appearance of the test medium was visually recorded at the start of the test and after 24 and 48 hours.

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Photoperiod: A 16 hour light to 8 hour dark cycle with a 30 minute transition period was used.
- Light intensity: between approximately 490 and 650 Lux

EFFECT PARAMETERS MEASURED
The daphnids were observed for immobility after 24 and 48 hours of exposure (daphnids not being able to swim within 15 seconds after gentle agitation of the test beaker were considered to be immobilized).
The NOELR and EL0 were determined directly from the raw data.
The EL50 and the EL100 could not be determined due to the absence of a toxic effect of the test item in this test.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not relevant (limit test)
- Range finding study: yes
- Test concentrations of the range finding study: no data
- Results used to determine the conditions for the definitive study: no mortality at the undiluted loading rate.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Details on results:

APPEARANCE OF THE TEST MEDIUM
No remarkable observations were made concerning the appearance of the test medium. The test medium was a clear solution throughout the whole test duration.

ANALYTICAL MONITORING
In the analysed test medium samples from the start of the test the measured neodymium concentration was 0.55 mg/L. During the test period of 48 hours, the neodymium concentration decreased to 0.13 mg/L. The mean measured neodymium concentration (calculated as geometric mean between the measurement at test start and test end) was 0.26 mg/L, corresponding to a neodymium oxide concentration of 0.31 mg/L. The solubility limit reached during this test was thus different from that obtained during the water solubility test (see IUCLID section 4.8). Such contrasting results could be explained by the different water media used in the water solubility test and ecotoxicological studies (media containing analytical grade salts).

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Mortality: no data
- 48 h EC50: 0.53 mg/L (acceptance range: 0.53 - 1.1 mg/L) (potassium dichromate)

Reported statistics and error estimates:

None as no adverse effect was observed

 Table 1 Effect of the Test Material on the Mobility of Daphnia magna

Loading Rate (mg/L)	Mean Measured Test Material Concentration (mg/L)	No. of Daphnids Tested	Immobilised Daphnids after 24 hours		Immobilised Daphnids after 48 hours
			Number	%	Number	%
Control	-	20	0	0	0	0
100	0.31	20	0	0	0	0

Validity criteria fulfilled:

yes

Conclusions:

The test material had no acute toxic effects on Daphnia magna up to its solubility limit in the test water at the loading rate of 100 mg/L under the present test conditions. The 48 hour EL50 and NOELR were thus > 100 mg/L and ≥100 mg/L, respectively.
The mean measured concentration of the test item in the solution was determined to be 0.31 mg/L, therefore the NOEL was ≥0.31 mg/L.

Executive summary:

The acute toxicity of the test material to Daphnia magna was determined in a 48 hour static test in accordance with the standardised guidelines OECD 202 and EU Method C.2.

Daphnids were exposed to the test chemical at a nominal loading rate of 100 mgL for 48 hours.

In the control and the test solution (loading rate of 100 mg/L), no immobilised test organisms were observed during the period of 48 hours. The 48 hour EL50 and NOELR were thus > 100 mg/L and ≥100 mg/L, respectively. The mean measured concentration of the test item in the solution was determined to be 0.31 mg/L, therefore the NOEL was ≥0.31 mg/L.

Description of key information

The 48 hour EL50 and NOELR were > 100 mg/L and ≥100 mg/L, respectively. The mean measured concentration of the test item in the solution was determined to be 0.31 mg/L, therefore the NOEL was ≥0.31 mg/L.

Additional information

The key study was conducted in line with GLP and the standardised guidelines OECD 202 and EU Method C.2. It was assigned a reliability score of 1 in accordance with the criteria detailed by Klimisch (1997).

The acute toxicity of the test material to Daphnia magna was determined in a 48 hour static test.

Daphnids were exposed to the test chemical at a nominal loading rate of 100 mgL for 48 hours.

In the control and the test solution (loading rate of 100 mg/L), no immobilised test organisms were observed during the period of 48 hours. The 48 hour EL50 and NOELR were thus > 100 mg/L and ≥100 mg/L, respectively. The mean measured concentration of the test item in the solution was determined to be 0.31 mg/L, therefore the NOEL was ≥0.31 mg/L.