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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:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 850.1010 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
Duplicate samples were collected from the batches of test solution prepared for each treatment and control group at the beginning of the test, prior to distributing the test solutions between the replicates. Duplicate water samples were also collected from two of the four replicate test chambers at the end of the test at 48 hours (± 1 hour) to measure concentrations of test substance. The samples were collected from the batch solutions and at mid-depth from the test chambers. All samples were collected directly into a glass liquid scintillation vials. One sample from each test group was processed immediately for analysis, and the second sample for each group was stored and refrigerated as a backup for possible future analysis.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
The highest concentration test solution was prepared by mixing a calculated amount of test substance in 2 L of UV sterilized dilution water at a nominal concentration of 120 mg a.s./L. The test solution was adjusted to 100% active ingredient during preparation, based on the test substance purity (98.5%), and also served as the primary stock solution for preparing the remaining test solutions. The 120 mg a.s./L test solutions was sonicated for 60 minutes and stirred on a stir plate for 60 minutes. The 120 mg a.s./L was clear and bright yellow-green in color after stirring, and was continually stirred during preparation of remaining test concentrations. Aliquots of the 120 mg a.s./L test solution were proportionally diluted with dilution water to prepare four additional test solutions at nominal concentrations of 7.5, 15, 30 and 60 mg a.s./L. The test solutions were stirred on a stir plate for 60 minutes, and ranged in appearance from clear and colorless to clear and greenish yellow in color, increasing in intensity with increasing concentration. After mixing, 250 mL of solution was placed in each of four replicate test chambers per treatment group. The negative control solution was dilution water only. No precipitate was noted in any of the test substance treatment solutions, and the physical appearance of the test solutions at termination was the same as that observed at test initiation.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Daphnia
- Strain/clone: Daphnia magna
- Source: In house culture
- Age of neonates: less than 24 hours old
- Feeding during test: Not fed
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
1.5, 24 and 48 hours (±1 hour)
Hardness:
136 mg/L (as CaCO3)
Test temperature:
19.7 to 20.8°C
pH:
8.1 to 8.5
Dissolved oxygen:
≥7.4 mg/L (≥82% of saturation)
Conductivity:
352 μS/cm
Nominal and measured concentrations:
Nominal: 7.5, 15, 30, 60 and 120 mg a.s./L
Measured: 7.4, 15, 29, 60 and 122 mg a.s./L
Details on test conditions:
TEST SYSTEM
- Test vessel: 250-mL glass beaker containing 200 mL of test solution (6.5-cm test solution depth)
- Aeration: No
- Type of flow-through: Static
- No. of organisms per vessel: 5
- No. of vessels per concentration: Four
- No. of vessels per control: Four

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The water used for culturing and testing was freshwater obtained from a well approximately 40 meters deep located on the test facility site. The well water was passed through a sand filter to remove particles greater than approximately 25 μm, and pumped into a 37800-L storage tank where the water was aerated with spray nozzles. Prior to use, the water was filtered to 0.45 μm and passed through an ultraviolet sterilizer to remove fine particles and microorganisms.
- Alkalinity: 174 to 180 mg/L (as CaCO3)
- Conductivity: 284 – 364 μS/cm
- Culture medium different from test medium: No

OTHER TEST CONDITIONS
- Adjustment of pH: 8.1 to 8.5
- Photoperiod:16 hours of light and 8 hours of darkness including 30 min transitional period preceding and following the 16-hr light interval.
- Light intensity: 472 lux at initiation

EFFECT PARAMETERS MEASURED: Immobility and behavioral observations were made at approximately 1.5 hours, and at 24 and 48 hours (± 1 hour) following initiation of exposure.

VEHICLE CONTROL PERFORMED: yes
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 122 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
other: Immobility
Duration:
48 h
Dose descriptor:
EC0
Effect conc.:
29 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
other: Immobility
Duration:
48 h
Dose descriptor:
EC100
Effect conc.:
> 122 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
act. ingr.
Basis for effect:
other: Immobility
Reported statistics and error estimates:
There was less than 50% immobility for daphnids in any of the test substance treatment groups during the test, which precluded the statistical calculation of EC50 values at 24 and 48 hours. Therefore, the EC50 values were estimated to be greater than the highest concentration tested.
Validity criteria fulfilled:
yes
Conclusions:
48Hr- EC50 (Daphnia Magna): >122 mg a.s./L (Immobility)
Executive summary:

The study was conducted according to guidelines, OECD 202 and US EPA OPPTS 850.1010 to determine 48 hour static acute toxicity in Daphnia magna.

Treatments consisted of a dilution water control and five nominal concentrations of 7.5, 15, 30, 60 and 120 mg active substance (a.s.)/L (equivalent to 7.4, 15, 29, 60 and 122 active substance (a.s.)/L, based on mean, measured test substance concentrations). Five daphnids were used per replicate with four replicates per test concentration and control.

Immobility and behavioral observations were made at approximately 1.5 hours, and at 24 and 48 hours (± 1 hour) following initiation of exposure.

The 48-hour EC50, based on mean measured concentrations and immobility data, was determined to be greater than 122 mg a.s./L. The highest mean measured test concentration causing no immobility at test end was 29 mg a.s./L. The lowest mean measured test concentration causing 100% immobility at test end was greater than 122 mg a.s./L.

Description of key information

48 -hr EC50 (Daphnia magna) > 122 mg/L; OECD 202;Reliability = 1

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
122 mg/L

Additional information

Acute aquatic invertebrate tests were conducted in two freshwater species. In daphnia magna, the 48-hour EC50 was > 122 mg/L.