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Ecotoxicological information

Short-term toxicity to fish

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Endpoint:
short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
23.01.03 - 17.06.03
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
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:
Test solutions were prepared daily.
Verification of the test item concentrations was carried out after 0 and 24 h for batch 1.
For batches 2, 3 and 4 test item concentrations were verified after 0 h only.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Prepared daily. 10 g/L solution in desalted water, which then served as a stock solution.
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): Test solutions at 90 and 150 mg/L were yellow coloured and brown flocculations were observed at the bottom of the test vessels. Test solutions at 260 – 800 mg/L were brown coloured and completely clear.
Test organisms (species):
Cyprinus carpio
Details on test organisms:
TEST ORGANISM

- Source: Di Mamma, Brakel, Netherlands
- Length at study initiation (length definition, mean, range and SD): 3 cm (mean)

HOLDING CONDITIONS

- Holding conditions: Fish held in 200 or 300 L tanks containing dechlorinated drinking water at 20°C + 2°C with continuous flow
- Type and amount of food during acclimation: Fed approximately 2% of body weight
- Feeding frequency during acclimation: Daily
- Health during acclimation (any mortality observed): Quarantined for 14 days prior to test without any treatment. Fish showed a normal behaviour pattern and were free from visible diseases.

FEEDING DURING TEST

- Feeding during test: None
Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
96 h
Hardness:
14° dH
Test temperature:
20.2°C (mean)
19.8 - 20.7°C
pH:
3.0 - 7.7. Discrepancy of the pH from desired value (pH 8+ 1) is an effect of the product in water
Dissolved oxygen:
97 - 101 % saturation
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal 90, 150, 260, 460 and 800 mg/L.
Measured (batch 1, 0 hour): 45, 129, 263, 448 and 756 mg/L (the value corresponding to nominal 90 mg/L was out of range and not regarded as valid)
Measured (batch 1, 24 hours); 90, 148, 266, 476 and 840 mg/L
Measured (batch 2, 0 hour, 90 mg/L nominal): 95 mg/L
Measured (batch 3, 0 hour, 90 mg/L nominal): 90 mg/L
Measured (batch 4, 0 hour, 90 mg/L nominal): 101 mg/L
As the measured concentrations at 24 hours did not deviate by more than 20% from nominal, nominal concentrations were used for the reporting of results.
Details on test conditions:
TEST SYSTEM

- Test vessel: 20 L tanks
- Aeration: Continuous
- Renewal rate of test solution (frequency/flow rate): Renewal every 24 hours
- No. of organisms per vessel: 10, each at ~0.4 g
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 1
- No. of vessels per vehicle control (replicates): Not relevant

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Synthetic freshwater
- Ca/mg ratio: 4:1

OTHER TEST CONDITIONS

- Adjustment of pH: None. The test solutions at 460 and 800 mg/L were not used due to low pH, for animal welfare reasons
- Photoperiod: 16h light 8 h dark

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Mortality

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.7
Reference substance (positive control):
not specified
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
116 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Remarks on result:
other:
Remarks:
Range: 90 - 150 mg/L
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
41.4 mg/L
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality (fish)
Remarks on result:
other: LC50 based on rhodium concentration calculated from the data in the report based on a rhodium concentration of 35.7%
Details on results:
It was concluded that the test substance was present over the whole test duration and therefore the results were calculating using the nomnal concentrations.
Validity criteria fulfilled:
yes
Remarks:
control mortality did not exceed 10% at the end of the test; DO concentration was > 60 % of the air saturation value at the temperature used; the concentration of the test item was maintained throughout the test (> 80% of the nominal concentration).
Conclusions:
The 96h LC50 of Rhodium (III) nitrate hydrate is 116 mg/L.
Executive summary:

Enste-Diefenbach (2003) is a GLP compliant study and followed a standard guideline. However, pH values were outside the desired limit for this test and the two highest test concentrations were not used due to the very low pH. There was some evidence of undissolved test material in the 90 and 150 mg/L test solutions but the higher test concentrations were clear. No mortality was observed at 90 mg/L, and 100 % mortality was observed in the 150 and 260 mg/L test solutions. The LC50 value was therefore determined graphically. The 96h LC50 of Rhodium (III) nitrate hydrate is 116 mg/L.

 

This study followed a standard test guideline but there were restrictions in the study design therefore it is assigned a Klimisch score of 2 (reliable with restrictions).

Endpoint:
short-term toxicity to fish
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH


1. HYPOTHESIS FOR THE ANALOGUE APPROACH

Read across between metal compounds should take into account the oxidation state of the metal and the contribution of any potential toxicity due to the ligands. Both diammonium sodium hexakis(nitrito-N)rhodate and rhodium trinitrate (hydrate) are in the same oxidation state (Rh(III)). Both substances are also soluble and therefore likely to be available in the aquatic environment. Although there are differences in the ligands between the source and target substances, toxicity is considered to be attributed to rhodium(III), with the ligands not considered to contribute significantly to the toxicity of either substance.

There is some evidence from other precious metals that substances in which the metallic centre is coordinated with chloro ligands exhibit greater toxicity than substances with other types of ligands.

Toxicity to Daphnia and algae have been assessed for both substances in order to test the hypothesis that read across between the two substances is appropriate. Read across from rhodium trinitrate (hydrate) to diammonium sodium hexakis(nitrito-N)rhodate is then proposed for the acute toxicity to fish endpoint.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

Source: Rhodium trinitrate (hydrate)
Target: Diammonium sodium hexakis(nitrito-N)rhodate

3. ANALOGUE APPROACH JUSTIFICATION

The read across hypothesis for fulfilling REACH data requirements is based on the source and target substances both containing rhodium in the same oxidation state, being available in the environment and having ligands that do not contribute additional toxicity. Available physico-chemical and ecotoxicity data for the two substances has been assessed in order to verify if the read across approach is acceptable.

Measured water solubility data shows that both substances are soluble (0.76 g L-1 for diammonium sodium hexakis(nitrito-N)rhodate and 1170 g L-1 for rhodium trinitrate (hydrate)). In the available ecotoxicity tests conducted with diammonium sodium hexakis(nitrito-N)rhodate measured concentrations were within 80% of nominal at test start and remained stable throughout the tests. In the acute fish study conducted with rhodium trinitrate (hydrate) measured concentrations at test start were also within 80% of nominal (apart from one sample which was significantly higher than nominal and therefore disregarded) and measured concentrations at the end of the 24-hour renewal period were also within 80% of nominal. Both substances are therefore considered to be available in the aquatic environment.

The inorganic ligands are not expected to impact on the toxicity of either substance. However, this was assessed by comparing test data for other acute ecotoxicity endpoints (Daphnia and algae). An acute Daphnia study was completed for diammonium sodium hexakis(nitrito-N)rhodate (Simon 2014). Based on the Daphnia data, the EC50 for diammonium sodium hexakis(nitrito-N)rhodate is lower than that for rhodium trinitrate (when expressed as concentrations of rhodium), although the confidence intervals of the two values overlap. There were also potential pH issues with the rhodium trinitrate Daphnia study and the EC50 reported may be lower than expected based on the test item toxicity alone. Read-across from rhodium trinitrate for the other ecotoxicity endpoints was thus uncertain based on the Daphnia data, and an algal growth inhibition study with diammonium sodium hexakis(nitrito-N)rhodate was conducted (Wenzel 2015).

The results of the algal studies for the two substances were compared and were very similar. As the algal results for the two substances were similar this supports the hypothesis that the ligands do not contribute significantly to the toxicity of either test item, and toxicity can mainly be attributed to rhodium(III). It is therefore considered appropriate to read across the result from rhodium trinitrate (hydrate) for the toxicity to fish endpoint. There is some variability between the results for the two substances, particularly with the Daphnia results, but as fish are not the most sensitive trophic level (LC50 41.4 mg Rh L-1 for fish compared to ErC50 of >0.32 mg Rh L-1 and EbC50 of 0.31 mg Rh L-1 for algae) read across is considered to be appropriate for this endpoint as any potentially small difference in results between the two substances would not lead to a difference in environmental classification, which will be assigned based on the algal results.

Daphnia and algal results are similar for the two substances, and therefore the inorganic ligands are not considered to contribute significantly to the toxicity of either substance. Although there is some variability in the available ecotoxicity results, as algae are the most sensitive trophic level and will drive classification, it is considered to be appropriate to read across the acute toxicity to fish data in order to reduce the need for additional vertebrate testing. Acute toxicity to Daphnia and algal toxicity endpoints will be completed with data on the substance itself.

4. DATA MATRIX

Please see attached Read Across Justification Report.
Reason / purpose for cross-reference:
read-across source
Reference substance (positive control):
not specified
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
116 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality (fish)
Remarks on result:
other:
Remarks:
Range: 90 - 150 mg/L
Duration:
96 h
Dose descriptor:
LC50
Effect conc.:
41.4 mg/L
Nominal / measured:
nominal
Conc. based on:
element
Basis for effect:
mortality (fish)
Remarks on result:
other: LC50 based on rhodium concentration calculated from the data in the report based on a rhodium concentration of 35.7%
Conclusions:
The 96h LC50 of Rhodium (III) nitrate hydrate is 116 mg/L.
Executive summary:

Enste-Diefenbach (2003) is a GLP compliant study and followed a standard guideline. However, pH values were outside the desired limit for this test and the two highest test concentrations were not used due to the very low pH. There was some evidence of undissolved test material in the 90 and 150 mg/L test solutions but the higher test concentrations were clear. No mortality was observed at 90 mg/L, and 100 % mortality was observed in the 150 and 260 mg/L test solutions. The LC50 value was therefore determined graphically. The 96h LC50 of Rhodium (III) nitrate hydrate is 116 mg/L.

 

This study followed a standard test guideline but there were restrictions in the study design therefore it is assigned a Klimisch score of 2 (reliable with restrictions).

Description of key information

The 96 hour LC50 value, read across from rhodium trinitrate (hydrate) is 41.4 mg Rh L-1.

Key value for chemical safety assessment

Additional information

Acute toxicity to fish data are read across from rhodium trinitrate (hydrate). Read across is considered to be appropriate for the acute fish endpoint as although there are differences in the ligands between the two substances, any toxicity is attributed to rhodium and both diammonium sodium hexakis(nitrito-N)rhodate and rhodium trinitrate (hydrate) are in the same oxidation state (Rh(III)). Although there is some variability in the Daphnia results between the two substances, as Daphnia and algal results are similar for the two substances, and as algae are the most sensitive trophic level and will drive classification, it is considered appropriate to read across data for acute toxicity to fish from another rhodium(III) substance, rhodium trinitrate (hydrate).

Enste-Diefenbach (2003) is a GLP compliant study and followed a standard guideline. However, pH values were outside the desired limit for this test and the two highest test concentrations were not used due to the very low pH. There was some evidence of undissolved test material in the 90 and 150 mg L-1 test solutions but the higher test concentrations were clear. No mortality was observed at 90 mg L-1, and 100 % mortality was observed in the 150 and 260 mg L-1 test solutions. The LC50 value was therefore determined graphically. The 96h LC50 of Rhodium (III) nitrate hydrate is 116 mg L-1 (41.4 mg Rh L-1). This study followed a standard test guideline but there were restrictions in the study design therefore it is assigned a Klimisch score of 2 (reliable with restrictions).