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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From January 13, 2016 to January 30, 2017
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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
Specific details on test material used for the study:
Batch no.: CH 192955/01
Purity/composition: 88.88%
Appearance: clear yellow liquid
Analytical monitoring:
yes
Remarks:
UPLC/MS
Details on sampling:
- Samples (2 mL) were taken from all test concentrations and the control at the start and at the end of the test. At the end of the exposure period, the replicates were pooled at each concentration before sampling.
- In addition, the glass wool containing undissolved residue was kept for possible analysis.
Vehicle:
no
Details on test solutions:
Preparation of test solutions started with a loading rate of 113 mg/L applying a two-day period of magnetic stirring after which the resulting mixture was allowed to stabilize overnight. Subsequently, the saturated solution (SS) was siphoned off over glass wool and used as the highest test concentration. Lower test concentrations were prepared by subsequent dilutions of the SS in test medium. All final test solutions were clear and colourless at the start of the test.
Test organisms (species):
Daphnia magna
Details on test organisms:
Species: Daphnia magna (Crustacea, Cladocera) (Straus, 1820), at least third generation, obtained by a cyclical parthenogenesis under specified breeding conditions
Source: In-house laboratory culture with a known history
Characteristics: For the test selection of young daphnids with an age of < 24 h, from parental daphnids of more than two weeks old
Start of each batch: With newborn daphnids, i.e. less than 3 d old, by placing about 250 of them into 5 L of medium in an all-glass culture vessel
Maximum age of the cultures: 4 weeks
Renewal of the cultures: After 7 d of cultivation half of the medium twice a week
Temperature of medium: 18-22°C
Feeding: Daily, a suspension of fresh water algae
Medium: M7, as prescribed by Dr. Elendt-Schneider
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
180 mg/L expressed as CaCO3
Test temperature:
18-22°C
pH:
7.9 - 8.1
Dissolved oxygen:
8.6 - 11.0 mg/L
Salinity:
-
Conductivity:
-
Nominal and measured concentrations:
- Test substance: Solutions containing 1.0, 10 and 100% of the SS prepared at 113 mg/L.
- Controls: Test medium without the test substance or other additives.
Details on test conditions:
Test duration: 48 h
Test type: Static
Test vessels: 100 mL, all-glass
Medium: Adjusted ISO medium
Number of daphnids: 20 each for the control and the highest test concentration, 10 for each intermediate test concentration
Loading: 5 per vessel containing 80 mL of test solution
Light: 16 h photoperiod daily
Feeding: No feeding
Aeration: No aeration of the test solutions.
Introduction of daphnids: Within 29 min after preparation of the test solutions

Combined limit/range-finding test:
A combined limit/range-finding test was performed. Twenty daphnids per group (5 per replicate, quadruplicate) were exposed to an untreated control and to the undiluted SS prepared at 113 mg/L, in a limit test. In addition ten daphnids per group (5 per replicate, duplicate) were exposed to 1.0 and 10% of the SS in the combined range-finding test. The total exposure period was 48 h and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test.

Measurements and recordings:
Immobility (including mortality): At 24 and 48 h
pH and dissolved oxygen: At the beginning and at the end of the test, for the highest concentration and the control.
Temperature of medium: Continuously in a temperature-controlled vessel, beginning at the start of the test.
Reference substance (positive control):
yes
Remarks:
potassium dichromate (K2Cr2O7)
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 2.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat.
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
EL50
Effect conc.:
> 113 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
- From 24 h of exposure onwards, a floating layer was observed on the surfaces of the two highest test concentrations. At the end of the test, the highest test concentration had furthermore become hazy.
- No significant immobility was observed in the control and the lowest concentration tested, while 20 and 25% of the daphnids exposed to 10 and 100% SS were immobilized, respectively, at the end of the test. The 48 h EC50 was beyond the range tested, i.e. exceeded 2.6 mg/L being the average concentration of test substance in a solution prepared at a loading rate of 113 mg/L.
- At the highest test concentration, undissolved test substance was observed attached to the surface of exposed, mobile daphnids, which caused them to stick together upon touching each other. However, the affected individuals were still able to detach again without external influence and consequently judged to be mobile.
Results with reference substance (positive control):
Daphnids were exposed for a maximum of 48 h to potasium dichromate (K2Cr2O7) concentrations of 0.10, 0.18, 0.32, 0.56, 1.0 and 1.8 mg/L and to a control. Twenty daphnids were exposed per concentration.The actual responses in this test were within the ranges of the expected responses at the different concentrations, i.e. the 48 h EC50 was within the expected range of 0.28 to 0.9 mg/L.
- The 24h-EC50 was 0.91 mg/L with a 95% confidence interval ranging from 0.77 to 1.1 mg/L.
- The 48h-EC50 was 0.58 mg/L with a 95% confidence interval ranging from 0.49 to 0.67 mg/L.
Validity criteria fulfilled:
yes
Conclusions:
Under the study conditions, the 48 h EC50 of the test substance was determined to be greater than 2.6 mg/L (measured average concentration) or the loading rate of 113 mg/L (Augusiak, 2017).
Executive summary:

A study was conducted to determine the short-term toxicity of the test substance to aquatic invertebrates according to OECD Guideline 202 and EU Method C.2, in compliance with GLP. A combined limit/range-finding test was performed. Twenty daphnids per group (5 per replicate) were exposed to an untreated control and to the undiluted saturated solution (SS) prepared at a loading rate of 113 mg/L, in the limit test. In addition, ten daphnids per group (5 per replicate) were exposed to 1.0 and 10% of the SS in the combined range-finding test. A positive control (potassium dichromate) was also included in the experiment. The total exposure period was 48 h and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test. Samples taken from the highest test concentration were analysed by UPLC/MS. Based on the analytical results, the average concentration in the undiluted SS was calculated to be 2.6 mg/L. The mobility of the animals was assessed after 24 and 48 h. No significant immobility was observed in the control and the lowest tested concentration, while 20 and 25% of the daphnids exposed to 10 and 100% SS were immobilized, respectively. The positive control substance produced results within th expected range. Overall, the study met the acceptability criteria prescribed by the study plan and was considered valid. Under the study conditions, the 48 h EC50 of the test substance to Daphnia magna was determined to be greater than 2.6 mg/L (measured average concentration) or the loading rate of 113 mg/L (Augusiak, 2017).

Description of key information

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
2.6 mg/L

Additional information

A study was conducted to determine the short-term toxicity of the test substance to aquatic invertebrates according to OECD Guideline 202 and EU Method C.2, in compliance with GLP. A combined limit/range-finding test was performed. Twenty daphnids per group (5 per replicate) were exposed to an untreated control and to the undiluted saturated solution (SS) prepared at a loading rate of 113 mg/L, in the limit test. In addition, ten daphnids per group (5 per replicate) were exposed to 1.0 and 10% of the SS in the combined range-finding test. A positive control (potassium dichromate) was also included in the experiment. The total exposure period was 48 h and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test. Samples taken from the highest test concentration were analysed by UPLC/MS. Based on the analytical results, the average concentration in the undiluted SS was calculated to be 2.6 mg/L. The mobility of the animals was assessed after 24 and 48 h. No significant immobility was observed in the control and the lowest tested concentration, while 20 and 25% of the daphnids exposed to 10 and 100% SS were immobilized, respectively. The positive control substance produced results within th expected range. Overall, the study met the acceptability criteria prescribed by the study plan and was considered valid. Under the study conditions, the 48 h EC50 of the test substance to Daphnia magna was determined to be greater than 2.6 mg/L (measured average concentration) or the loading rate of 113 mg/L (Augusiak, 2017).

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