Dierbium trioxide

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

17 March 2020 to 28 August 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

Testing was conducted on a soluble form of the substance as instructed by ECHA.

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Version / remarks:

2012

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.20 (Daphnia magna Reproduction Test)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Water samples were taken from the control and each test group for quantitative analysis.
- Sampling method: Samples of the freshly prepared bulk test solutions were taken on Days 0, 7, 14 and 20 and of the corresponding aged test solutions (replicates pooled) on Days 1, 8, 15 and 21.
- Sample storage conditions before analysis: With the exception of the Day 1 and Day 21 old media samples which were analysed on the day of collection, all samples were stored frozen prior to analysis. Duplicate samples were taken on each occasion and stored frozen for further analysis if necessary. All samples were bottled for analysis following filtration through 0.45 µm cellulose acetate filters (first approximate 10 mL discarded in order to pre-condition the filter).

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- The test material was found, by both visual inspection and analytical determination, to be readily soluble in test media at a concentration of 100 mg/L as erbium trinitrate pentahydrate. When left to stand overnight no visible precipitate was formed. At the request of the Sponsor a further assessment of solubility was made with chemical analysis. Because the analysed samples did not give measured concentrations within the acceptable range of 80 to 120 % of nominal, these analytical investigations were not considered further.
- A nominal amount of test material (12.5 mg) was dissolved in test water and the volume adjusted to 1 litre to give a 10 mg/L as erbium trinitrate stock solution. A series of dilutions was made from this stock solution to give the required test concentrations of 0.10, 0.18, 0.32, 0.56 and 1.0 mg/L as erbium trinitrate. The 10 mg/L stock solution and its dilutions were prepared at the beginning of the test and before each renewal period.
- The stock solution and each of the prepared concentrations were inverted several times to ensure adequate mixing and homogeneity.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- The test was carried out using 1st instar Daphnia magna derived from in-house laboratory cultures.
- Age at study initiation: less than 24 hours old
- Adult Daphnia were maintained in 150 mL glass vessels containing ISO medium (see Annex 2) in a temperature controlled room at approximately 20 C. The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Each culture was fed daily with a mixture of algal suspension (Raphidocelis subcapitata (formally known as Pseudokirchneriella subcapitata)) and GEMMA Micro 300 fish food suspension. Culture conditions ensured that reproduction was by parthenogenesis.
- Method of breeding: 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; they were not first brood progeny.
- The diet and diluent water are considered not to contain any contaminant that would affect the integrity or outcome of the study.

Test type:

semi-static

Water media type:

other: Reconstituted Water – ISO Medium

Limit test:

no

Total exposure duration:

21 d

Hardness:

252 to 278 mg/L as CaCO3

Test temperature:

20 to 22 °C

pH:

6.0 to 7.4

Dissolved oxygen:

7.9 mg/L

Nominal and measured concentrations:

0.10, 0.18, 0.32, 0.56 and 1.0 mg/L as erbium trinitrate

Details on test conditions:

TEST SYSTEM
- Test vessel: 120 mL glass vessel
- Type: closed- covered with a tight fitting plastic lid to reduce evaporation
- Material, size, headspace, fill volume: completely filled 120 mL
- Aeration: no
- Renewal rate of test solution: daily
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The reconstituted water had a pH of 6.0 ± 0.1 adjusted (if necessary) with NaOH or HCl and 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.
- Culture medium different from test medium: no
- Intervals of water quality measurement: Dissolved oxygen concentrations, pH and temperature were recorded at the start and end of the test and before and after each test media renewal. The pH and dissolved oxygen concentration were measured using a calibrated digital handheld meter whilst the temperature was measured using a calibrated digital thermometer. Measurements were made on one replicate for each test concentration. The temperature was also measured every hour in a surrogate vessel using a Testo temperature logger. The water hardness of the control and the highest surviving test concentration in the fresh and old media was measured once per week.

OTHER TEST CONDITIONS
- Adjustment of pH: yes
- Photoperiod: 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods
- Light intensity: 933 to 1057 lux

EFFECT PARAMETERS MEASURED:
- On a daily basis the numbers of live and dead of the "Parental" (P1) generation, the numbers of live and dead "Filial" (F1) Daphnia and the number of discarded unhatched eggs were counted. An assessment was also made of the general condition and size of the parental daphnia as compared with the controls.
- Young daphnids were considered to be dead if no sign of movement was apparent during examination. Adult Daphnia which were unable to swim for approximately 15 seconds after gentle agitation (i.e. immobile), were considered to be dead. An immobilisation criterion for the young daphnids was considered to be inappropriate due to the large numbers of off-spring produced in the test vessels. Due to a technical oversight, no test organism observations were made on the 1.0 mg/L erbium trinitrate test group on Day 3 in error.
- At the end of the test, the length of each surviving parent animal (excluding the anal spine) was determined.

TEST CONCENTRATIONS
- Range finding study:
In the range-finding test Daphnia magna were exposed to a series of nominal concentrations of 0.10, 1.0 and 10 mg/L as erbium trinitrate. A nominal amount of test material (12.6 mg) was dissolved in test water and the volume adjusted to 1 litre to give the 10 mg/L as erbium trinitrate test concentration from which a series of dilutions was made to give further test concentrations of 1.0 and 0.10 mg/L as erbium trinitrate. The 10 mg/L test solution and its dilutions were prepared at the beginning of the range-finding test and before each renewal period. Each of the prepared concentrations were inverted several times to ensure adequate mixing and homogeneity.
In the range finding test, for each concentration a single daphnid was placed in 100 mL of the test preparation in 120 mL glass vessels which were then covered with a plastic lid to reduce evaporation. For each test and control group five replicate test vessels were prepared. The water temperature was maintained at 18 to 22 °C with a maximum deviation of ± 1 °C with a photoperiod of 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods for 10 days. The control group was maintained under identical conditions but not exposed to the test material.
The test preparations were renewed on Days 3, 5 and 7. The adult Daphnia were transferred to fresh media by wide bore pipette before the contents of each vessel were passed through a fine mesh. Young daphnids (live and dead) and any unhatched eggs were collected on the mesh and counted before being discarded. Each daphnid received approximately 5.0 to 20 µL of an algal suspension (Raphidocelis subcapitata) over the 10-Day duration and approximately 20 µL of GEMMA Micro 300 fish food suspension until Day 3. Feeding was at a level of approximately 0.1 to 0.2 mg carbon/daphnid/day, dependent on the age and size of the animals. Equal amounts of food were given to each daphnid.
A sample of each test concentration was taken for chemical analysis from the freshly prepared test media on Day 0, and from the corresponding aged media on Day 3 in order to determine the stability of the test material under test conditions. All samples were stored frozen prior to analysis. Duplicate samples were taken on each occasion and stored frozen for further analysis if required. All samples were bottled for analysis following filtration through 0.45 µm cellulose acetate filters (first approximate 10 mL discarded in order to pre-condition the filter).
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

no

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 0.35 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium

Basis for effect:

immobilisation

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 0.74 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate

Basis for effect:

immobilisation

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 0.93 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate pentahydrate

Basis for effect:

immobilisation

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.026 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.055 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.068 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate pentahydrate

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.097 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium

Basis for effect:

other: body length

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.21 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate

Basis for effect:

other: body length

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.26 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate pentahydrate

Basis for effect:

other: body length

Details on results:

RANGE-FINDING TEST
-No immobilisation was observed at the test concentration of 0.10 mg/L erbium trinitrate, however, immobilisation was observed at both 1.0 and 10 mg/L erbium trinitrate (20 and 100 % respectively). Sub lethal effects of exposure were observed at 10 mg/L erbium trinitrate. These responses were parental daphnids being observed to be both smaller and paler than the control daphnids. The mean numbers of young produced per surviving adult were comparable in the control and 0.10 mg/L erbium trinitrate test group (40.8 and 40.6, respectively), whereas it was reduced at 1.0 mg/L erbium trinitrate (24.75).
-Based on this information test concentrations of 0.10, 0.18, 0.32, 0.56 and 1.0 mg/L erbium trinitrate were selected for the definitive test.
-Chemical analysis of the test preparations on Day 0 showed measured test concentrations to range from 0.058 to 7.8 mg/L as erbium trinitrate (58% to 78% of nominal), equivalent to 0.028 to 3.7 mg/L as erbium, and 0.073 to 9.8 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the corresponding aged preparations on Day 3 showed measured test concentrations to range from 0.033 to 5.6 mg/L as erbium trinitrate (7% to 56% of nominal); equivalent to 0.016 to 2.6 mg/L as erbium, and 0.041 to 7.0 mg/L as erbium trinitrate pentahydrate respectively. Given the failure to obtain near nominal concentrations in the Day 0 preparations, and the inconsistent pattern in decline in measured concentrations of the corresponding aged preparations it was considered appropriate to analyse the duplicate samples which had been stored frozen.
-Analysis of the duplicate Day 0 test samples showed measured test concentrations to range from 0.065 to 7.7 mg/L as erbium trinitrate (61% to 77% of nominal), equivalent to 0.031 to 3.6 mg/L as erbium, and 0.081 to 9.6 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the duplicate Day 3 test samples showed measured test concentrations to range from 0.031 to 5.4 mg/L as erbium trinitrate (5% to 54% of nominal); equivalent to 0.014 to 2.6 mg/L as erbium, and 0.038 to 6.8 mg/L as erbium trinitrate pentahydrate respectively. These results confirmed that those obtained from the initial analysis were correct. Given the decline in measured test concentrations in the aged preparations over 3 days, it was decided to run the definitive test with a daily renewal of the test preparations.

DEFINITIVE TEST

- Verification of Test Concentrations:
Analysis of the freshly prepared test solutions on Days 0, 7, 14 and 20 showed measured test concentrations to range from 0.079 to 0.88 mg/L as erbium trinitrate (79 to 93 % of nominal), equivalent to 0.037 to 0.41 mg/L as erbium, and 0.099 to 1.1 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the corresponding aged preparations on Days 1, 8, 15 and 21 showed measured test concentrations to range from less than the limit of quantification (LOQ) of the analytical method employed, determined to be 0.041 mg/L as erbium trinitrate to 0.69 mg/L as erbium trinitrate (12 to 69 % of nominal), equivalent to less than the LOQ, determined to be 0.019 mg/L as erbium to 0.33 mg/L as erbium, and less than the LOQ, determined to be 0.050 mg/L as erbium trinitrate pentahydrate to 0.86 mg/L as erbium trinitrate pentahydrate respectively.
Given the decline in measured test concentrations in the aged preparations, and also the slight variability in the measured test concentrations obtained from the freshly prepared test samples within each period of media renewal it was considered appropriate to calculate the results based on the geometric mean measured test concentrations which were determined to be 0.055, 0.11, 0.21, 0.37 and 0.74 mg/L as erbium trinitrate, 0.026, 0.050, 0.097, 0.17 and 0.35 mg/L as erbium, and 0.068, 0.13, 0.26, 0.46 and 0.93 mg/L as erbium trinitrate pentahydrate respectively.

- Validation Criteria
The following validation criteria were achieved during the test:
Control mortality: 20 % (required: ≤ 20 %)
Mean number of live young per surviving adult (control group): 118 (required: ≥ 60 after 21 days)
Coefficient of variation for control group: 11 % (required: ≤ 25 %)
No ephippia produced: 0 (required: 0)
Dissolved oxygen: ≥7.9 mg O2/L (required: > 3 mg O2/L)
pH (control group): 6.1 to 7.4, variation 1.3 (required: 6 to 9, variation ≤ 1.5)

- Lethal Effects on the Parental Generation (P1)
Mortality (20 % immobilisation) was observed in the control, 0.11 and 0.74 mg/L mean measured erbium trinitrate test groups. No mortalities occurred at 0.055, 0.21 and 0.37 mg/L erbium trinitrate. Statistical analysis of the mortality data showed that the mortalities observed in all test groups were not significantly different (P≥0.05) when compared to the control group.
ECx, NOEC and LOEC values (immobilisation) based on the geometric mean measured test concentrations were determined by visual inspection of the data or by Fisher’s Exact Binomial Test with Bonferroni Correction and Qualitative Trend Analysis by Contrasts.

- Sub-lethal Effects on the Parental Generation (P1)
Visual assessment of the parental daphnids in the control group showed a single adult daphnid to be pale with reduced mobility the day prior to its death (Day 13). Assessment of the 0.11 mg/L erbium trinitrate test group showed there to be no effects on size or colour with the exception of replicate R3 which was observed to be either pale or pale and small prior to its death on Day 10. In the 0.37 mg/L erbium trinitrate test group a single adult daphnid was observed to be small between Days 6 and 9. This was considered not to be test material related given that the effect was transient and only occurred in a single replicate. In the 0.74 mg/L erbium trinitrate test group, two of the parental daphnids surviving to the end of the test were observed to be small. Again, this effect was considered not to be test material related given that the effect was transient.
No sublethal effects were observed in either the 0.055 or 0.21 mg/L erbium trinitrate test groups throughout the duration of the test.
After 21 days the length of each surviving adult (excluding the anal spine) was determined. Statistical analysis of the results showed that there were no significant differences (P≥ 0.05) between the control and the 0.055, 0.11 and 0.21 mg/L erbium trinitrate test groups; however, a significant difference (P<0.05) was determined between the control and the 0.37 and 0.74 mg/L erbium trinitrate test groups in terms of length of the daphnids after 21 days exposure to the test material. In these groups the length was reduced by 8.2 and 5.3 % respectively, as compared to the control group. ECx, NOEC and LOEC values (body length) based on the geometric mean measured test concentrations were calculated by the 3-Parameter Normal Cumulative Distribution Function or Williams Multiple Sequential t-test incorporating Shapiro Wilk's test on normal distribution, Trend Analysis by Contrasts and Levene’s test on variance homogeneity.

- Effects on Reproduction
After 21 days there were no statistically significant differences (P≥0.05) between the control and the 0.055 mg/L erbium trinitrate test group in terms of the number of live young produced per adult, however, a significant difference (P<0.05) was determined between the control and the 0.11, 0.21, 0.37 and 0.74 mg/L erbium trinitrate test groups in terms of number of live young produced per adult after 21 days exposure to the test material. In these four test groups the numbers of live young produced per adult were reduced by 17.7, 27.8, 36.3 and 37.8 % respectively as compared to the control group.
ECx, NOEC and LOEC values (reproduction) based on the geometric mean measured test concentrations were determined by Probit analysis using Linear maximum Likelihood Regression or Williams Multiple Sequential t-test Procedure incorporating Shapiro Wilk's test on normal distribution, Trend Analysis by Contrasts and Levene’s test on variance homogeneity

- Effects on the Filial Generation (F1)
Information on the effects of the test material on the F1 generation is limited, since, by study design, the young are removed soon after liberation from the brood pouch. However, an assessment made at each media renewal showed the "filial" daphnids produced by the 0.055, 0.11 and 0.21 mg/L erbium trinitrate test groups were in the same general condition as the young produced by the controls over the duration of the test. The young produced in a small number of replicates by the 0.37 mg/L erbium trinitrate test group were observed to be pale and/or small when compared to the control young on Days 13, 14, 20 and 21, whilst some pale young were observed in the 0.74 mg/L erbium trinitrate test group on Days 14 and 17. The presence of some aborted eggs was noted in a single control replicate on Day 21.
Young were first produced in the control, 0.21, 0.37 and 0.74 mg/L erbium trinitrate test groups on Day 9, and in the 0.055 and 0.11 mg/L erbium trinitrate test groups on Day 10.
Numbers of unhatched eggs and dead young were low in all control and treatment groups surviving to maturation.

- Water Quality Criteria
Temperature was maintained at approximately 20 to 22 °C throughout the test, while there were no treatment related differences for oxygen concentration or pH. Oxygen concentrations were maintained over 7.9 mg/L throughout the test. The pH varied from 6.0 to 6.9 in the fresh solutions and from 6.1 to 7.4 in the old solutions.
The water hardness was observed to be in the range 252 to 278 mg/L as CaCO3 in the control and the highest surviving test group throughout the test.
Throughout the test the light intensity was observed to be in the range 933 to 1057 lux.
The water temperature was also recorded in the control vessel every hour using a Testo temperature logger and was maintained at approximately 20 to 22 °C throughout the test.

Observations on Test Item Solubility
At the start and throughout the test all control and test solutions were observed to be clear colourless solutions.

Summary of Results

Endpoint		Geometric Mean Measured Concentration [95% Confidence Limits]
		Erbium (mg/L)	Erbium trinitrate (mg/L)	Erbium trinitrate pentahydrate (mg/L)
Immobilization[1]	EC10	>0.35	>0.74	>0.93
	EC20	>0.35	>0.74	>0.93
	EC50	>0.35	>0.74	>0.93
	NOEC	≥0.35	≥0.74	≥0.93
	LOEC	Not determined	Not determined	Not determined
Reproduction[2]	EC10	0.019 [0.003 – 0.038]	0.041 [0.006 – 0.083]	0.049 [0.007 – 0.10]
	EC20	0.061 [0.024 – 0.093]	0.13 [0.053 – 0.20]	0.16 [0.064 – 0.25]
	EC50	0.59^4 [0.33 – 2.7]	1.2^4 [0.69 – 5.6]	1.6^4 [0.87 – 7.2]
	NOEC	0.026	0.055	0.068
	LOEC	0.050	0.11	0.13
Body Length[3]	EC10	>0.35	>0.74	>0.93
	EC20	>0.35	>0.74	>0.93
	EC50	>0.35	>0.74	>0.93
	NOEC	0.097	0.21	0.26
	LOEC	0.17	0.37	0.46

[1]Calculated by Fisher’s Exact Binomial Test with Bonferroni Correction and Qualitative Trend Analysis by Contrasts or determined by visual inspection of the data.

[2]Calculated by Williams Multiple Sequential t-test incorporating Shapiro‑Wilk's test on normal distribution, Trend Analysis by Contrasts and Levene’s test on variance homogeneity or Probit analysis using Linear maximum Likelihood Regression.

[3]Calculated by Williams Multiple Sequential t-test incorporating Shapiro‑Wilk's test on normal distribution, Trend Analysis by Contrasts and Levene’s test on variance homogeneity or 3-Parameter Normal Cumulative Distribution Function.

⁴Value determined by extrapolation as at the maximum test concentration employed, only a 38% reduction in the number of young produced was observed when compared to the control.

 

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study, exposure of daphnia magna to the test material gave the following results:
Immobilisation: EC50: Erbium >0.35 mg/L, Erbium trinitrate >0.74 mg/L and Erbium trinitrate pentahydrate >0.93 mg/L. NOEC: Erbium ≥0.35 mg/L, Erbium trinitrate ≥0.74 mg/L and Erbium trinitrate pentahydrate ≥0.93 mg/L.
Reproduction: EC50: Erbium 0.59 mg/L (0.33-2.7 mg/L), Erbium trinitrate 1.2 mg/L (0.69-5.6 mg/L) and Erbium trinitrate pentahydrate 1.6 mg/L (0.87-7.2 mg/L). NOEC: Erbium 0.026 mg/L, Erbium trinitrate 0.055 mg/L and Erbium trinitrate pentahydrate 0.068 mg/L.
Body length: EC50: Erbium >0.35 mg/L, Erbium trinitrate >0.74 mg/L and Erbium trinitrate pentahydrate >0.93 mg/L. NOEC: Erbium 0.097 mg/L, Erbium trinitrate 0.21 mg/L and Erbium trinitrate pentahydrate 0.26 mg/L.

Executive summary:

The chronic toxicity of the test material to Daphnia magna was investigated in accordance with the standardised guidelines OECD 211 and EU Method C.20, under GLP conditions.

Based on the results of a preliminary range finding test, Daphnia magna were exposed (10 replicates of a single daphnid per group) to solutions of the test material at nominal concentrations of 0.10, 0.18, 0.32, 0.56 and 1.0 mg/L as erbium trinitrate for a period of 21 days. Test solutions were renewed daily. In order to maximize the dissolved concentrations of the test material, daphnids were exposed in test media adjusted to pH 6.0. The numbers of live and dead adult Daphnia and young daphnids (live and dead) were determined daily. The Daphnia were fed daily with a mixture of algal suspension. On Days 0 to 3 the Daphnia were also fed GEMMA Micro 300 fish food suspension.

Analysis of the freshly prepared test solutions on Days 0, 7, 14 and 20 showed measured test concentrations to range from 0.079 to 0.88 mg/L as erbium trinitrate (79 to 93 % of nominal), equivalent to 0.037 to 0.41 mg/L as erbium, and 0.099 to 1.1 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the corresponding aged preparations on Days 1, 8, 15 and 21 showed measured test concentrations to range from less than the limit of quantification (LOQ) of the analytical method employed, determined to be 0.041 mg/L as erbium trinitrate, to 0.69 mg/L as erbium trinitrate (12 to 69 % of nominal), equivalent to less than the LOQ, determined to be 0.019 mg/L as erbium, to 0.33 mg/L as erbium, and less than the LOQ, determined to be 0.050 mg/L as erbium trinitrate pentahydrate, to 0.86 mg/L as erbium trinitrate pentahydrate respectively. Given the decline in measured test concentrations in the aged preparations, and also the slight variability in the measured test concentrations obtained from the freshly prepared test samples within each period of media renewal it was considered appropriate to calculate the results based on the geometric mean measured test concentrations which were determined to be 0.055, 0.11, 0.21, 0.37 and 0.74 mg/L as erbium trinitrate, 0.026, 0.050, 0.097, 0.17 and 0.35 mg/L as erbium, and 0.068, 0.13, 0.26, 0.46 and 0.93 mg/L as erbium trinitrate pentahydrate respectively.

Under the conditions of this study, exposure of daphnia magna to the test material gave the following results:

Immobilisation: EC50: Erbium >0.35 mg/L, Erbium trinitrate >0.74 mg/L and Erbium trinitrate pentahydrate >0.93 mg/L. NOEC: Erbium ≥0.35 mg/L, Erbium trinitrate ≥0.74 mg/L and Erbium trinitrate pentahydrate ≥0.93 mg/L.

Reproduction: EC50: Erbium 0.59mg/L (0.33-2.7 mg/L), Erbium trinitrate 1.2 mg/L (0.69-5.6 mg/L) and Erbium trinitrate pentahydrate 1.6 mg/L (0.87-7.2 mg/L). NOEC: Erbium 0.026mg/L, Erbium trinitrate 0.055mg/L and Erbium trinitrate pentahydrate 0.068mg/L.

Body length: EC50: Erbium >0.35 mg/L, Erbium trinitrate >0.74 mg/L and Erbium trinitrate pentahydrate >0.93 mg/L. NOEC: Erbium 0.097mg/L, Erbium trinitrate 0.21mg/L and Erbium trinitrate pentahydrate 0.26 mg/L.

Key results for safety assessment and classification and labelling are as follows:

EC10 = 0.019 mg/L as Erbium. This equates to EC10 = 0.022 mg/L as Dierbium Trioxide.

No Observed Effect Concentration (NOEC) = 0.026 mg/L as Erbium. This equates to NOEC = 0.030 mg/l as Dierbium Trioxide.

Description of key information

Under the conditions of this study, exposure of daphnia magna to the test material gave the following results:

Immobilisation: EC50: Erbium >0.35 mg/L, Erbium trinitrate >0.74 mg/L and Erbium trinitrate pentahydrate >0.93 mg/L. NOEC: Erbium ≥0.35 mg/L, Erbium trinitrate ≥0.74 mg/L and Erbium trinitrate pentahydrate ≥0.93 mg/L.

Reproduction: EC50: Erbium 0.59mg/L (0.33-2.7 mg/L), Erbium trinitrate 1.2 mg/L (0.69-5.6 mg/L) and Erbium trinitrate pentahydrate 1.6 mg/L (0.87-7.2 mg/L). NOEC: Erbium 0.026mg/L, Erbium trinitrate 0.055mg/L and Erbium trinitrate pentahydrate 0.068mg/L.

Body length: EC50: Erbium >0.35 mg/L, Erbium trinitrate >0.74 mg/L and Erbium trinitrate pentahydrate >0.93 mg/L. NOEC: Erbium 0.097mg/L, Erbium trinitrate 0.21mg/L and Erbium trinitrate pentahydrate 0.26 mg/L.

Key results for safety assessment and classification and labelling are as follows:

EC10 = 0.019 mg/L as Erbium. This equates to EC10 = 0.022 mg/L as Dierbium Trioxide.

No Observed Effect Concentration (NOEC) = 0.026 mg/L as Erbium. This equates to NOEC = 0.030 mg/l as Dierbium Trioxide.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

LC10

Remarks:

Converted for Dierbium Trioxide.

Effect concentration:

0.022 mg/L

Fresh water invertebrates

Dose descriptor:

NOEC

Remarks:

Converted for Dierbium Trioxide.

Effect concentration:

0.03 mg/L

Additional information

The chronic toxicity of the test material to Daphnia magna was investigated in accordance with the standardised guidelines OECD 211 and EU Method C.20, under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria set forth by Klimisch et al. (1997).

Based on the results of a preliminary range finding test, Daphnia magna were exposed (10 replicates of a single daphnid per group) to solutions of the test material at nominal concentrations of 0.10, 0.18, 0.32, 0.56 and 1.0 mg/L as erbium trinitrate for a period of 21 days. Test solutions were renewed daily. In order to maximize the dissolved concentrations of the test material, daphnids were exposed in test media adjusted to pH 6.0. The numbers of live and dead adult Daphnia and young daphnids (live and dead) were determined daily. The Daphnia were fed daily with a mixture of algal suspension. On Days 0 to 3 the Daphnia were also fed GEMMA Micro 300 fish food suspension.

Analysis of the freshly prepared test solutions on Days 0, 7, 14 and 20 showed measured test concentrations to range from 0.079 to 0.88 mg/L as erbium trinitrate (79 to 93 % of nominal), equivalent to 0.037 to 0.41 mg/L as erbium, and 0.099 to 1.1 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the corresponding aged preparations on Days 1, 8, 15 and 21 showed measured test concentrations to range from less than the limit of quantification (LOQ) of the analytical method employed, determined to be 0.041 mg/L as erbium trinitrate, to 0.69 mg/L as erbium trinitrate (12 to 69 % of nominal), equivalent to less than the LOQ, determined to be 0.019 mg/L as erbium, to 0.33 mg/L as erbium, and less than the LOQ, determined to be 0.050 mg/L as erbium trinitrate pentahydrate, to 0.86 mg/L as erbium trinitrate pentahydrate respectively. Given the decline in measured test concentrations in the aged preparations, and also the slight variability in the measured test concentrations obtained from the freshly prepared test samples within each period of media renewal it was considered appropriate to calculate the results based on the geometric mean measured test concentrations which were determined to be 0.055, 0.11, 0.21, 0.37 and 0.74 mg/L as erbium trinitrate, 0.026, 0.050, 0.097, 0.17 and 0.35 mg/L as erbium, and 0.068, 0.13, 0.26, 0.46 and 0.93 mg/L as erbium trinitrate pentahydrate respectively.

Under the conditions of this study, exposure of daphnia magna to the test material gave the following results:

Immobilisation: EC50: Erbium >0.35 mg/L, Erbium trinitrate >0.74 mg/L and Erbium trinitrate pentahydrate >0.93 mg/L. NOEC: Erbium ≥0.35 mg/L, Erbium trinitrate ≥0.74 mg/L and Erbium trinitrate pentahydrate ≥0.93 mg/L.

Reproduction: EC50: Erbium 0.59mg/L (0.33-2.7 mg/L), Erbium trinitrate 1.2 mg/L (0.69-5.6 mg/L) and Erbium trinitrate pentahydrate 1.6 mg/L (0.87-7.2 mg/L). NOEC: Erbium 0.026mg/L, Erbium trinitrate 0.055mg/L and Erbium trinitrate pentahydrate 0.068mg/L.

Body length: EC50: Erbium >0.35 mg/L, Erbium trinitrate >0.74 mg/L and Erbium trinitrate pentahydrate >0.93 mg/L. NOEC: Erbium 0.097mg/L, Erbium trinitrate 0.21mg/L and Erbium trinitrate pentahydrate 0.26 mg/L.