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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 15 November 2015 to 22 December 2015
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)
Version / remarks:
(2004)
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Version / remarks:
(2008)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
- Solubility in water: completely miscible
- Stability in water: stable
Analytical monitoring:
yes
Details on sampling:
- Concentrations sampled: all test concentrations (and the control), at t=0 and t=48h
- Volume: 2.4 mL from the approximate centre of the test vessels
- At the end of the exposure period, the replicates were pooled at each concentration before sampling
- Sample storage conditions before analysis: in a freezer
Vehicle:
no
Details on test solutions:
The test substance was completely miscible in test medium. No correction was made for the purity/composition of the test substance. Preparation of test solutions started with the highest concentration and stock solution of 100 mg/L in the combined limit/range-finding and final test, respectively. No special treatment other than vigorous mixing (vortexing) was needed to fully dissolve the test substance in test medium at the highest concentration prepared. Lower tested concentrations were prepared by subsequent dilutions of the highest concentration and stock solution in test medium. All final solutions were clear and colourless.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Species: Daphnia magna (Crustacea, Cladocera) (Straus, 1820), at least third generation, obtained by acyclical parthenogenesis under specified breeding conditions.
- Source: In-house laboratory culture with a known history.
- Validity of batch: Daphnids originated from a healthy stock, 2nd to 5th brood, showing no signs of stress such as mortality >20%, presence of males, ephippia or discoloured animals and there was no delay in the production of the first brood.
- Characteristics: For the test selection of young daphnids with an age of < 24 hours, from parental daphnids of more than two weeks old.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
180 mg CaCO3/L
Test temperature:
19.3 - 20.6 °C
pH:
7.7 - 8.0
Dissolved oxygen:
9.4 - 9.8 mg/L
Nominal and measured concentrations:
- 1.0, 1.8, 3.2, 5.6 and 10 mg/L (nominal)
- Analysis of the samples showed that concentrations were stable and in agreement with nominal (90-100% relative to nominal)
Details on test conditions:
TEST SYSTEM
- Test vessel: 100 mL, all-glass
- Aeration: No aeration of the test solutions
- Feeding: No feeding
- No. of organisms per vessel: 5 per vessel containing 80 mL of test solution
- No. of vessels per concentration (replicates): 4
- Introduction of daphnids: Within 41 minutes after preparation of the test solutions
- No. of vessels per control (replicates): 4

TEST MEDIUM
Adjusted ISO medium. The following chemicals (analytical grade) were dissolved in tap water purified by Reverse Osmosis (RO-water, GEON Waterbehandeling, The Netherlands):
CaCl2.2H2O: 211.5 mg/L
MgSO4.7H2O: 88.8 mg/L
NaHCO3: 46.7 mg/L
KCl: 4.2 mg/L

OTHER TEST CONDITIONS
- Adjustment of pH: Not applicable
- Photoperiod: 16 hours photoperiod daily

EFFECT PARAMETERS MEASURED
The 48h-EC50 value was calculated from the weibits of the percentages of affected daphnids and the logarithms of the corresponding test item concentrations using the maximum likelihood estimation method (ToxRat Professional v 3.0.0).

RANGE-FINDING STUDY
- Test concentrations: 0.10, 1.0, 10 and 100 mg/L (nominal)
-- At 100 mg/L and control: Twenty daphnids (four replicates, 5 daphnids per vessel)
-- At 0.10, 1.0 and 10 mg/L: Ten daphnids (two replicates, 5 daphnids per vessel)
- Results used to determine the conditions for the definitive study: 100% immobility was already observed at 24 hours of exposure in the 100 mg/L group, while immobility of 100% was
further observed after 48 hours at the 10 mg/L group. No immobility was observed in the control or in any of the lower concentrations during the test period. Therefore, the expected EC50 was between nominal concentrations of 1.0 and 10 mg/L.
Reference substance (positive control):
yes
Remarks:
(sensitivity check using potassium dichromate)
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
4.1 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: Analytically confirmed nominal concentration; 95%-confidence interval: 3.4 - 4.7 mg/L
Details on results:
- At t=24h, only at 10 mg/L daphnids were immobilised (20%)
- At t=48h, daphnids were immobilized at 3.2 (40%), 5.6 (80%) and 10 mg/L (100%)
Results with reference substance (positive control):
In the latest sensitivity check, performed in the period 15 - 17 September 2015, an 48h-EC50 of 0.39 mg/L was determined. The sensitivity of the daphnia was within the range determined with the historical data collected at the testing laboratory.

Analysis of the samples taken from 1.0, 1.8, 3.2, 5.6 and 10 mg/L at the start and at the end of the final test showed that measured concentrations were stable and in agreement with nominal (90-100% relative to nominal). Based on these results, effect parameters were expressed in terms of analytically confirmed nominal concentrations.

Validity criteria fulfilled:
yes
Conclusions:
In a study performed in accordance with OECD 202 (2004) and according to GLP principles, an 48h-EC50 of 4.1 mg/L was determined for the substance, based on analytically confirmed nominal concentrations.
Executive summary:

In a study performed in accordance with OECD 202 (2004) and according to GLP principles, the acute toxicity of the substance to daphnids was investigated. A final test was performed based on the results of a preceding combined limit/range-finding test. Twenty daphnids per group (four replicates, five daphnids per replicate) were exposed to an untreated control and to nominal concentrations of 1.0, 1.8, 3.2, 5.6 and 10 mg/L prepared from a stock of 100 mg/L. The total exposure period was 48 hours and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test, from all test concentrations. Analysis of the samples showed that concentrations were stable and in agreement with nominal (90-100% relative to nominal). The study met the acceptability criteria. Under the conditions of the present study, the 48h-EC50 was 4.1 mg/L based on analytically confirmed nominal concentrations (95% confidence interval between 3.4 and 4.7 mg/L).

Description of key information

In a study performed in accordance with OECD 202 (2004) and according to GLP principles, an 48h-EC50 of 4.1 mg/L was determined for the substance, based on analytically confirmed nominal concentrations.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
4.1 mg/L

Additional information

In a study performed in accordance with OECD 202 (2004) and according to GLP principles, the acute toxicity of the substance to daphnids was investigated. A final test was performed based on the results of a preceding combined limit/range-finding test. Twenty daphnids per group (four replicates, five daphnids per replicate) were exposed to an untreated control and to nominal concentrations of 1.0, 1.8, 3.2, 5.6 and 10 mg/L prepared from a stock of 100 mg/L. The total exposure period was 48 hours and samples for analytical confirmation of exposure concentrations were taken at the start and at the end of the test, from all test concentrations. Analysis of the samples showed that concentrations were stable and in agreement with nominal (90-100% relative to nominal). The study met the acceptability criteria. Under the conditions of the present study, the 48h-EC50 was 4.1 mg/L based on analytically confirmed nominal concentrations (95% confidence interval between 3.4 and 4.7 mg/L).

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