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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
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:
other: Test Guideline under Japan Chemical Substance Control Law
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Lot No.: 140220
Analytical monitoring:
yes
Details on sampling:
Range Finder:
No samples were taken for analysis. A preliminary solubility trial was conducted prior to the range finder, which included prolonged stirring (24 hours), followed by filtration (Millex 0.45 um) of a 100 mg/L stock (in triplicate). This provided a mean solubility of 9.7 mg/L, which was used as
the upper concentration in the definitive test.

Definitive:
- Concentrations: 0, 0.97, 1.7, 3.1, 5.5 and 9.7 mg/L (spacing factor of 1.8).
- Frequency: Samples for analysis were taken from each concentration, control and solvent control at the start of the study (t = 0h Fresh), (t = 24h Expired), (t = 24h Fresh) and (t = 48h Expired). This provided two sets of fresh and expired samples.
- Sampling method: 0.75 mL of medium taken from the middle (from an additional sample pot) for the fresh samples at each concentration, and from a random vessel at each concentration for the expired samples.
- Sample storage conditions before analysis: Not detailed, but assumed to be analysed on the day of sampling.
Vehicle:
yes
Details on test solutions:
Preparations of test medium started with the preparation of a solvent stock solution in N,N-Dimethylformamide with the test material. Aliquots of this were then individually diluted further in DMF to provide suitable solvent stocks for each concentration. Aliquots of these stocks (0.1 mL/L) were then added individually to the test media and made to volume and stirred (magnetically) for 15 minutes. The required volume (100 mL) of test media prepared at each concentration was used as the test media and poured into individual test vessels (four per group).

An equivalent amount of solvent was added for the solvent control (vehicle) group as used in the test groups (0.1 mL/L). All prepared test solutions were clear and colourless.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia Magna
- Strain: Not detailed
- Source: National Institute for environmental Studies, Japan.
- Age at study initiation: < 24 hours old (female juvenilles)
- Feeding during test: Not fed during the test

ACCLIMATION
- Acclimation period:28 days or less (culture period)
- Acclimation conditions (same as test or not): Same as test (temperature, light, pH and dissolved oxygen concentration)
- Type and amount of food: Chlorella Vulgaris (unicellular green algae) 6mgC (Organic carbon)/2L/day
- Feeding frequency: Daily
- Health during acclimation (any mortality observed): < 20% mortality of parental daphnids 2 weeks prior to the test. No abnormalities were observed.

Test type:
semi-static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
246 mg CaCO3/L
Test temperature:
20 ± 1°C
pH:
6.0-9.0 (variation range < 1.5, not adjusted)
Dissolved oxygen:
3 mg/L or greater (not aerated)
Nominal and measured concentrations:
Nominal concentrations; 0, 0.97, 1.7, 3.1, 5.5 and 9.7 mg/L
Measured concentrations (time weighted mean); 1.00, 1.16, 3.12, 5.57 and 9.79 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: Glass vessels
- Fill volume: 100 mL
- Aeration: None
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Elendt M4, reconstituted water (including appropriate vitamins).
- Intervals of water quality measurement: Daily

OTHER TEST CONDITIONS
- Photoperiod: 16 hour light/8 hour dark
- Light intensity: Fluorescent light (800 Lux or less)

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobility at 24 and 48 hours

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8
- Range finding study: 0.097, 0.97 and 9.7 mg/L
- Test concentrations (definitive): 0, 0.97, 1.7, 3.1, 5.5 and 9.7 mg/L
- Results used to determine the conditions for the definitive study: Low Immobility observed upto limit of solubility
Reference substance (positive control):
yes
Remarks:
Potassium Dichromate
Key result
Duration:
48 h
Dose descriptor:
LC50
Effect conc.:
> 9.79 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: Greater than limit of solubility
Key result
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
9.79 mg/L
Nominal / measured:
meas. (TWA)
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
- Effect concentrations exceeding solubility of substance in test medium: Due to the low solubility of the test substance, concentration levels that might be toxic to Daphnia could not be reached. The effect concentration is greater than the limit of solubility (> 9.79 mg/L).
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- EC50: 0.58 mg/L (95% confidence limits: 0.50 - 0.67 mg/L). Within historical range.
Validity criteria fulfilled:
yes
Conclusions:
No significant immobility occured in the rangefinding test following 48 hour exposure to 0.097, 0.97 or 9.7 mg/L.
The time weighted mean exposure concentration for samples taken over the 96 hour period was 9.79 mg/L.
No immobility or abnormal behaviour was noted at any point in either control, solvent control or test vessels in the main study.
pH, dissolved oxygen and temperature were all within acceptable ranges over the course of the definitive test.
Executive summary:

Due to the very low solubility of the test substance in test medium, concentration levels that might be toxic for daphnids could not be reached. The 48h-EC50 was above the solubility limit of the test substance in test medium (> 9.79 mg/L).

Description of key information

In a 48hr acute toxicity study, Daphnia magna were exposed to the test substance at measured concentrations of 0 (control), 0 (solvent control), 1.00, 1.16, 3.12, 5.57 or 9.79 mg/L under semi-static conditions. The NOEC value, based on mortality/ sublethal effects, was 9.79 mg/L.

Key value for chemical safety assessment

Additional information

Due to the low solubility of the test substance in test medium, concentration levels that might be toxic for Daphnia could not be reached. The 48hr EC50 was above the solubility limit of the test substance in test medium (> 9.79 mg/L).

The NOEC value, based on mortality/ sublethal effects, was 9.79 mg/L.