Dierbium trioxide

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

4 September 2012 - 14 September 2012

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 203 (Fish, Acute Toxicity Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Water samples were taken from the control and 100 % v/v saturated solution test vessel at 0 (fresh media), 24 and 96 hours (old media) for quantitative analysis. The 0 and 24 hour samples were stored at approximately -20 °C prior to analysis.
Duplicate samples and samples at 24 (fresh media), 48 and 72 hours (old and fresh media) were taken and stored at approximately -20 °C for further analysis if necessary.

Vehicle:

no

Details on test solutions:

Due to the poor solubility of the test material, a modification of the standard method for the preparation of aqueous media was performed, exposing organisms to a saturated solution.
A saturated solution was prepared by adding 1125 mg of test material to 22.5 litres of dechlorinated tap water and stirring using a propeller stirrer at approximately 1500 rpm for 24 hours. After stirring, any undissolved test material was removed by filtration through a 0.2 µm Sartorious Sartopore filter (initial 1 litre discarded in order to pre-condition the filter) to give the 100 % v/v saturated solution.
50 mg/L was shown to be a high enough concentration to create an excess of the test material in the saturated solution.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Age at study initiation: juvenile
- Length at study initiation (mean and SD): 4.8 cm (SD = 0.2)
- Weight at study initiation (mean and SD): 1.39 g (SD = 0.32)
- Feeding during test: No
- Source: Brow Well Fisheries Limited, Hebden, Near Skipton, Yorkshire, UK

ACCLIMATION
- Acclimation period: 29 August 2012 - 9 September 2012
- Acclimation conditions (same as test or not): Yes
- Type and amount of food: Fish were fed commercial trout pellets flake food (discontinued approximately 24 hours prior to the start of the test)
- Health during acclimation (any mortality observed): There was 0 mortality in the 7 days preceding the test

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

Approximately 140 mg/L as CaCO3.

Test temperature:

14 - 15 °C

pH:

7.7 - 8.3

Dissolved oxygen:

9.4 - 10.2 mg O2/L

Nominal and measured concentrations:

Nominal concentration: 100 % v/v saturated solution.
Measured concentration: Analysis of the test preparations at 0, 24 and 96 hours showed measured test concentrations of 0.000661, 0.000568 and 0.000760 mg test material/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: 20 L glass exposure vessels
- Type: Each vessel was covered to reduce evaporation
- Aeration: Aeration was via narrow bore glass tubes
- Renewal rate of test solution: Test preparations were renewed daily to ensure that concentrations of the test material remained near nominal and to prevent the build up of nitrogenous waste products.
- No. of organisms per vessel: 7
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1. The control group was maintained under identical conditions but not exposed to the test material.
- Biomass loading rate: 0.49 g bodyweight/L (static volume)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Laboratory tap water was dechlorinated by passage through an activated carbon filter (Purite Series 500) and partly softened (Elga Nimbus 1248D Duplex Water Softener). After dechlorination and softening, the water was passed through a series of computer controlled plate heat exchangers to achieve the required temperature.

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods.

EFFECT PARAMETERS MEASURED
After 3, 6, 24, 48, 72 and 96 hours any mortalities or sub-lethal effects of exposure were determined by visual inspection of the test fish.
The water temperature, pH and dissolved oxygen concentrations were recorded daily throughout the test. The measurements at 0 hours, and after each test media renewal at 24, 48 and 72 hours, represent those of the freshly prepared test preparations while the measurements taken prior to each test media renewal, and on termination of the test after 96 hours, represent those of the used or 24 hour old test preparations.

TEST CONCENTRATIONS
- Range finding study: Yes
- Test concentrations: 100 % v/v saturated solution (3 fish)
- Results used to determine the conditions for the definitive study: Yes. No mortality occurred during the range finding study and so the definitive study was conducted using a 100 % v/v saturated solution.

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 other: % v/v saturated solution

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 other: % v/v saturated solution

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

There were no mortalities.
The results of the definitive test showed the highest test concentration resulting in 0 % mortality to be greater than or equal to 100 % v/v saturated solution, the lowest test concentration resulting in 100 % mortality to be greater than 100 % v/v saturated solution.
There were no sub-lethal effects of exposure observed.

- Observations on Test Material Solubility
Throughout the test, the test preparation was observed to be a clear colourless solution.

- Physico-Chemical Measurements
Temperature was maintained at 14 to 15 °C throughout the test, while there were no treatment related differences for oxygen concentration or pH.
The oxygen concentration in one of the test vessels was observed to have an air saturation value (ASV) in excess of 100 %. This was considered to be due to the presence of microscopic air bubbles in the media super-saturating the diluent and was considered not to have had an impact on the outcome or integrity of the test as no adverse effects were observed in the control group.

- Verification of Test Concentrations
Analysis of the test preparations at 0, 24 and 96 hours showed measured test concentrations of 0.000578, 0.000497 and 0.000664 mg/L as erbium (equivalent to 0.000661, 0.000568 and 0.000760 mg/L of test material), respectively, were obtained and it was therefore considered justifiable to estimate the LC50 values in terms of the nominal test concentration only.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study, the 96 hour LC50 was greater than 100 % v/v saturated solution. The No Observed Effect Concentration was superior or equal to 100 % v/v saturated solution.

Executive summary:

The acute toxicity potential of the test material to Oncorhynchus mykiss was investigated in accordance with the standardised guidelines OECD 203 and EU Method C.1.

In a limit test, seven fish were exposed to an aqueous solution of the test material at a single concentration of 100 % v/v saturated solution for a period of 96 hours at a temperature of 14 to 15 °C under semi-static test conditions.

The number of mortalities, and any sub-lethal effects of exposure, in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours.

No mortality or sub-lethal effects were seen throughout the duration of the exposure.

Under the conditions of this study, the 96 hour LC50 was greater than 100 % v/v saturated solution. The No Observed Effect Concentration was superior or equal to 100 % v/v saturated solution.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 April 2020 to 21 September 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Version / remarks:

2019

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- The concentration and stability of the test material in the test preparations were verified by chemical analysis of the freshly prepared test media at 0 and 72 hours, and of the corresponding old or expired test media at 24 and 96 hours i.e. 2 complete sets of the 4 renewal periods.
- 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:

Preliminary Assessment of Solubility
- The test material was found, by visual inspection, 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. This analytical investigation confirms that the test material was completely soluble in test media to a nominal concentration of 100 mg/L as erbium trinitrate pentahydrate.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Source: Brow Well Fisheries Limited, Hebden, near Skipton, Yorkshire, UK (maintained in-house since 22 July 2020)
- Age at study initiation: juvenile
- Length: the fish had a mean standard length of 6.6 cm (standard deviation = 0.48) at the end of the definitive test.
- Weight: the fish had a mean body weight of 2.4 g (standard deviation = 0.57) at the end of the definitive test.
- Maintenance of the brood fish: Fish were maintained in a glass tank at a loading rate not exceeding 0.8 g body weight per litre.

ACCLIMATION
- Acclimation period: Fish were acclimatised to test conditions from 7 September 2020 to 17 September 2020.
- The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. The water temperature was controlled at approximately 13 to 14 °C with a dissolved oxygen content of greater than or equal to 9.2 mg O2/L. These parameters were recorded daily.
- Type and amount of food during acclimation: The stock fish were fed commercial trout pellets which was discontinued approximately 25 hours prior to the start of the definitive test.
- Health during acclimation: There were no mortalities in the 7 days prior to the start of the test.

Test type:

semi-static

Water media type:

other: reconstituted water (ISO medium)

Limit test:

no

Total exposure duration:

96 h

Test temperature:

13 to 15 °C

pH:

6.0 to 6.1 in the fresh solutions and from 5.9 to 6.7 in the old solutions

Dissolved oxygen:

over 7.5 mg/L

Nominal and measured concentrations:

Nominal: 0.0625, 0.125, 0.25, 0.50 and 1.0 mg/L as erbium trinitrate
Geometric mean measured: 0.051, 0.11, 0.23, 0.46 and 0.90 mg/L as erbium trinitrate, 0.024, 0.051, 0.11, 0.22 and 0.43 mg/L as erbium, and 0.064, 0.14, 0.29, 0.58 and 1.1 mg/L as erbium trinitrate pentahydrate

Details on test conditions:

TEST SYSTEM
- Test vessel: 25 litre glass exposure vessels
- Type: The test vessels were covered to reduce evaporation.
- Material, size, headspace, fill volume: 20 litres
- Aeration: The test vessels were aerated via narrow bore glass tubes.
- Renewal rate of test solution (frequency/flow rate): A semi-static test regime was employed in the test involving a daily renewal of the test preparations to prevent the build up of nitrogenous waste products and to maintain the dissolved test material concentrations. Fish were transferred from the old or expired media to the freshly prepared test media every 24 hours by net and bucket.
- No. of organisms per vessel: 7
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- Biomass loading rate: 0.84 g body weight/litre (static volume)

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.
- Reconstituted Water – ISO Medium: CaCl2.2H2O: 294 mg/L, MgSO4.7H2O: 123 mg/L, NaHCO3: 65 mg/L and KCl: 5.8 mg/L.
- Culture medium different from test medium: no
- Intervals of water quality measurement: The water temperature, pH and dissolved oxygen concentrations were recorded daily throughout the test. The measurements at 0 hours, and after each test media renewal at 24, 48 and 72 hours, represent those of the freshly prepared test preparations while the measurements taken prior to each test media renewal, and on termination of the test after 96 hours, represent those of the used or the 24-hour old test preparations. The pH and dissolved oxygen concentration were measured using a calibrated digital handheld meter whilst the temperature was measured using a calibrated digital thermometer.

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods

EFFECT PARAMETERS MEASURED
- Any mortalities and sub-lethal effects of exposure were recorded at 1, 3, 6, 24, 30, 48, 52, 72, 77 and 96 hours after the start of exposure. The criteria of death were taken to be the absence of both respiratory movement and response to physical stimulation.

TEST CONCENTRATIONS
- Range finding study :
The test concentrations to be used in the definitive test were determined by a preliminary range-finding test. In the range-finding test fish were exposed to a series of nominal test concentrations of 1.0, 10 and 100 mg/L as erbium trinitrate. The test material was dissolved directly in test water. A nominal amount of test material (2772 mg erbium trinitrate pentahydrate) was dissolved in test water and the volume adjusted to 22 litres to give the 100 mg/L as erbium trinitrate test concentration from which a series of dilutions was made to give the remaining test concentrations of 10 and 1.0 mg/L. The 100 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 stirred with a flat bladed stirrer for approximately 1 minute to ensure adequate mixing and homogeneity.
In the range-finding test three fish were placed in each test and control vessel and maintained in a temperature controlled room at approximately 13 to 15 °C with a photoperiod of 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods for a period of 96 hours under semi-static test conditions with a 24-hour test medium renewal period. Each 25 to 30 litre test and control vessel contained 20 litres of test media and was covered to reduce evaporation. After 1, 3, 6, 24, 29, 48, 52, 72, 74 and 96 hours any mortalities or sub-lethal effects of exposure were determined by visual inspection of the test fish. The control group was maintained under identical conditions but not exposed to the test material. Fish were transferred from the old or expired media to the freshly prepared test media every 24 hours by net and bucket. A sample of each test concentration was taken for chemical analysis at 0 and 24 hours in order to determine the stability of the test material under test conditions. All 0-hour samples were stored frozen prior to analysis alongside the 24-hour test samples. 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: Based on the results of the range-finding test the following test concentrations were assigned to the definitive test: 0.0625, 0.125, 0.25, 0.50 and 1.0 mg/L as erbium trinitrate.

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

0.13 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium

Basis for effect:

mortality (fish)

Remarks on result:

other: 95 % Confidence Limits: 0.068 – 0.25 mg/L

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

0.26 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate

Basis for effect:

mortality (fish)

Remarks on result:

other: 95 % Confidence Limits: 0.14 – 0.52 mg/L

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

0.33 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate pentahydrate

Basis for effect:

mortality (fish)

Remarks on result:

other: 95 % Confidence Limits: 0.18 – 0.65 mg/L

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.051 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium

Basis for effect:

mortality (fish)

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.11 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate

Basis for effect:

mortality (fish)

Key result

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.14 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

other: Erbium trinitrate pentahydrate

Basis for effect:

mortality (fish)

Details on results:

RANGE-FINDING TEST
- There were no sub-lethal effects of exposure during the range-finding test.
- The results showed no mortalities in the control group. Whilst two mortalities (67 % mortality) were observed in the 1.0 mg/L erbium trinitrate test group, 100 % mortality was observed in both the 10 and 100 mg/L erbium trinitrate test groups.
- Chemical analysis of the freshly prepared test solutions at 0 hours showed measured test concentrations to range from 0.93 to 93 mg/L as erbium trinitrate (92 to 99 % of nominal), equivalent to 0.44 to 44 mg/L as erbium, and 1.2 to 116 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the corresponding aged preparations at 24 hours showed measured test concentrations to range from 0.84 to 90 mg/L as erbium trinitrate (84 to 94 % of nominal), equivalent to 0.40 to 43 mg/L as erbium, and 1.1 to 113 mg/L as erbium trinitrate pentahydrate respectively.

DEFINITIVE TEST
Verification of Test Concentrations:
- Analysis of the freshly prepared test solutions at 0 and 72 hours showed measured test concentrations to range from 0.051 to 0.94 mg/L as erbium trinitrate (82 to 100 % of nominal), equivalent to 0.024 to 0.44 mg/L as erbium, and 0.064 to 1.2 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the corresponding aged preparations at 24 and 96 hours showed measured test concentrations to range from 0.047 to 0.91 mg/L as erbium trinitrate (75 to 96 % of nominal), equivalent to 0.022 to 0.43 mg/L as erbium, and 0.059 to 1.1 mg/L as erbium trinitrate pentahydrate respectively.
- Given the slight decline in measured test concentrations in the aged preparations it was considered justifiable to calculate the results based on the geometric mean measured test concentrations which were determined to be 0.051, 0.11, 0.23, 0.46 and 0.90 mg/L as erbium trinitrate, 0.024, 0.051, 0.11, 0.22 and 0.43 mg/L as erbium, and 0.064, 0.14, 0.29, 0.58 and 1.1 mg/L as erbium trinitrate pentahydrate respectively.

Mortality Data
- The NOEC after 96 hours exposure was determined to be 0.051 mg/L as erbium, 0.11 mg/L as erbium trinitrate and 0.14 mg/L as erbium trinitrate pentahydrate. The LOEC was considered to be 0.11 mg/L as erbium, 0.23 mg/L as erbium trinitrate and 0.29 mg/L as erbium trinitrate pentahydrate.

Sub-Lethal Effects
- After approximately 25 hours exposure a single fish in the 0.0625 mg/L erbium trinitrate test group was found to be moribund, as was a single fish in the 0.25 mg/L erbium trinitrate test group after approximately 96 hours exposure. Due to animal welfare implications (the Animals (Scientific Procedures) Act 1986 Amendment Regulations 2012) these fish were killed and classed as mortalities for the following observational time point.

Validity Criteria
- The test was considered to be valid given that none of the control fish died during the test and that the oxygen concentration at the end of the test was equal to or greater than 60 % of ASV (6.1 mg O2/L at 15 °C) in the control and test vessels. Analytical measurements were also conducted during the test.

Water Quality Criteria
- Temperature was maintained at approximately 13 to 15 °C throughout the test, while there were no treatment related differences for oxygen concentration or pH. Oxygen concentration was maintained over 7.5 mg/L throughout the test. pH varied from 6.0 to 6.1 in the fresh solutions and from 5.9 to 6.7 in the old solutions.

Observations on Test Material Solubility
- The control and test material preparations were observed to be clear colourless solutions throughout the test.

Sublethal observations / clinical signs:

Cumulative Mortality Data in the DefinitiveTest

Nominal Concentration (mg/L as erbium trinitrate)	Cumulative Mortality (Initial Population = 7)										Mortality (%)
	1 Hour	3 Hours	6 Hours	24 Hours	30 Hours	48 Hours	52 Hours	72 Hours	77 Hours	96 Hours
Control	0	0	0	0	0	0	0	0	0	0	0
0.0625	0	0	0	0	1	1	1	1	1	1	14
0.125	0	0	0	0	0	0	0	0	0	0	0
0.25	0	0	0	0	0	0	0	2	2	4	57
0.50	0	0	0	0	0	0	2	3	5	5	71
1.0	0	0	0	0	0	1	2	5	5	6	86

Summary of Results

96-Hour Endpoint	Erbium (mg/L)	Erbium trinitrate (mg/L)	Erbium trinitrate pentahydrate (mg/L)
LC50*	0.13	0.26	0.33
95% Confidence Limits	0.068 – 0.25	0.14 – 0.52	0.18 – 0.65
No Observed Effect Concentration (NOEC)	0.051	0.11	0.14
Lowest Observed Effect Concentration (LOEC)	0.11	0.23	0.29

*Calculated by Probit analysis using linear max. likelihood regression

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of this study, the exposure of rainbow trout (Oncorhynchus mykiss) to the test material gave the following results based on the geometric mean measured test concentrations:
LC50: 0.13 mg/L Erbium (95 % Confidence Limits: 0.068 – 0.25 mg/L), 0.26 mg/L Erbium trinitrate (95 % Confidence Limits: 0.14 – 0.52 mg/L) and 0.33 mg/L Erbium trinitrate pentahydrate (95 % Confidence Limits: 0.18 – 0.65 mg/L).
No Observed Effect Concentration (NOEC): 0.051 mg/L Erbium, 0.11 mg/L Erbium trinitrate and 0.14 mg/L Erbium trinitrate pentahydrate.
Lowest Observed Effect Concentration (LOEC): 0.11 mg/L Erbium, 0.23 mg/L Erbium trinitrate and 0.29 mg/L Erbium trinitrate pentahydrate.

Executive summary:

The acute toxicity of the test material to fish was investigated in accordance with the standardised guidelines OECD 203 and EU Method C1, under GLP conditions.

The study was performed to assess the acute toxicity of the test material to rainbow trout (Oncorhynchus mykiss). Following a preliminary range-finding test, fish were exposed, in groups of seven, to aqueous solutions of the test material over a range of nominal concentrations of 0.0625, 0.125, 0.25, 0.50 and 1.0 mg/L as anhydrous erbium trinitrate for a period of 96 hours at a temperature of approximately 13 to 15 °C under semi-static test conditions with a 24-hour test medium renewal period. In order to maximise the dissolved concentrations of the test material, fish were exposed in test media adjusted to pH 6.0. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 1, 3, 6, 24, 30, 48, 52, 72, 77 and 96 hours after the start of exposure.

Analysis of the freshly prepared test solutions at 0 and 72 hours showed measured test concentrations to range from 0.051 to 0.94 mg/L as erbium trinitrate (82 to 100 % of nominal), equivalent to 0.024 to 0.44 mg/L as erbium, and 0.064 to 1.2 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the corresponding aged preparations at 24 and 96 hours showed measured test concentrations to range from 0.047 to 0.91 mg/L as erbium trinitrate (75 to 96 % of nominal), equivalent to 0.022 to 0.43 mg/L as erbium, and 0.059 to 1.1 mg/L as erbium trinitrate pentahydrate respectively. Given the slight decline in measured test concentrations in the aged preparations it was considered justifiable to calculate the results based on the geometric mean measured test concentrations which were determined to be 0.051, 0.11, 0.23, 0.46 and 0.90 mg/L as erbium trinitrate, 0.024, 0.051, 0.11, 0.22 and 0.43 mg/L as erbium, and 0.064, 0.14, 0.29, 0.58 and 1.1 mg/L as erbium trinitrate pentahydrate respectively.

Under the conditions of this study, the exposure of rainbow trout (Oncorhynchus mykiss) to the test material gave the following results based on the geometric mean measured test concentrations:

LC50: 0.13 mg/L Erbium (95 % Confidence Limits: 0.068 – 0.25 mg/L), 0.26 mg/L Erbium trinitrate (95 % Confidence Limits: 0.14 – 0.52 mg/L) and 0.33 mg/L Erbium trinitrate pentahydrate (95 % Confidence Limits: 0.18 – 0.65 mg/L).

No Observed Effect Concentration (NOEC): 0.051 mg/L Erbium, 0.11 mg/L Erbium trinitrate and 0.14 mg/L Erbium trinitrate pentahydrate.

Lowest Observed Effect Concentration (LOEC): 0.11 mg/L Erbium, 0.23 mg/L Erbium trinitrate and 0.29 mg/L Erbium trinitrate pentahydrate.

Description of key information

Two acute toxicity to fish studies have been conducted.

Study 1: Harlan, 2013 (study conducted on Dierbium trioxide)

The 96 hour LC50 was greater than 100 % v/v saturated solution.

The No Observed Effect Concentration was superior or equal to 100 % v/v saturated solution.

This study was conducted on the registered substance but it is now acknowledged that ecotoxicity of most poorly soluble metal compounds

is best assessed using data generated on the soluble metal ion and comparing this to data obtained in a transformation dissolution study. This

is the approach that was subsequently agreed by ECHA to use for the chronic Daphnia and fish studies. The results of this earlier study are therefore provided as supporting information only.

Study 2: Covance, 2021 (study conducted on Erbium trinitrate pentahydrate)

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

LC50 = 0.13 mg/L as Erbium. This equates to LC50 = 0.149 mg/L as Dierbium Trioxide.

No Observed Effect Concentration (NOEC) = 0.051 mg/L as Erbium. This equates to NOEC = 0.058 mg/L as Dierbium Trioxide

This second study was conducted to allow determination of an acute ERV, to be used for risk assessment and

classification and labelling purposes. The results of this study are considered to be key. Since the study was conducted on

Erbium trinitrate pentahydrate the results have been converted by a molecular weight calculation to give values relevant for the registered substance.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

LC50

Remarks:

Converted for Dierbium Trioxide

Effect concentration:

0.149 mg/L

Additional information

Harlan (2013)

The acute toxicity of the test material to Oncorhynchus mykiss was investigated in accordance with the standardised guidelines OECD 203 and EU Method C.1 under GLP conditions. It was assigned a reliability score of 1 in accordance with the criteria set forth in Klimisch (1997).

In a limit test, seven fish were exposed to an aqueous solution of the test material at a single concentration of 100 % v/v saturated solution for a period of 96 hours at a temperature of 14 to 15 °C under semi-static test conditions. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours. No mortality or sub-lethal effects were seen throughout the duration of the exposure.

Under the conditions of this study, the 96 hour LC50 was greater than 100 % v/v saturated solution. The No Observed Effect Concentration was superior or equal to 100 % v/v saturated solution.

Covance (2021)

The acute toxicity of the test material to fish was investigated in accordance with the standardised guidelines OECD 203 and EU Method C1, under GLP conditions. The study was assigned a reliability score of 1 in accordance with the criteria set forth in Klimisch (1997).

The study was performed to assess the acute toxicity of the test material to rainbow trout (Oncorhynchus mykiss). Following a preliminary range-finding test, fish were exposed, in groups of seven, to aqueous solutions of the test material over a range of nominal concentrations of 0.0625, 0.125, 0.25, 0.50 and 1.0 mg/L as anhydrous erbium trinitrate for a period of 96 hours at a temperature of approximately 13 to 15 °C under semi-static test conditions with a 24-hour test medium renewal period. In order to maximise the dissolved concentrations of the test material, fish were exposed in test media adjusted to pH 6.0. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 1, 3, 6, 24, 30, 48, 52, 72, 77 and 96 hours after the start of exposure.

Analysis of the freshly prepared test solutions at 0 and 72 hours showed measured test concentrations to range from 0.051 to 0.94 mg/L as erbium trinitrate (82 to 100 % of nominal), equivalent to 0.024 to 0.44 mg/L as erbium, and 0.064 to 1.2 mg/L as erbium trinitrate pentahydrate respectively. Analysis of the corresponding aged preparations at 24 and 96 hours showed measured test concentrations to range from 0.047 to 0.91 mg/L as erbium trinitrate (75 to 96 % of nominal), equivalent to 0.022 to 0.43 mg/L as erbium, and 0.059 to 1.1 mg/L as erbium trinitrate pentahydrate respectively. Given the slight decline in measured test concentrations in the aged preparations it was considered justifiable to calculate the results based on the geometric mean measured test concentrations which were determined to be 0.051, 0.11, 0.23, 0.46 and 0.90 mg/L as erbium trinitrate, 0.024, 0.051, 0.11, 0.22 and 0.43 mg/L as erbium, and 0.064, 0.14, 0.29, 0.58 and 1.1 mg/L as erbium trinitrate pentahydrate respectively.

Under the conditions of this study, the exposure of rainbow trout (Oncorhynchus mykiss) to the test material gave the following results based on the geometric mean measured test concentrations:

LC50: 0.13 mg/L Erbium (95 % Confidence Limits: 0.068 – 0.25 mg/L), 0.26 mg/L Erbium trinitrate (95 % Confidence Limits: 0.14 – 0.52 mg/L) and 0.33 mg/L Erbium trinitrate pentahydrate (95 % Confidence Limits: 0.18 – 0.65 mg/L).

No Observed Effect Concentration (NOEC): 0.051 mg/L Erbium, 0.11 mg/L Erbium trinitrate and 0.14 mg/L Erbium trinitrate pentahydrate.

Lowest Observed Effect Concentration (LOEC): 0.11 mg/L Erbium, 0.23 mg/L Erbium trinitrate and 0.29 mg/L Erbium trinitrate pentahydrate.