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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:
2001-06-11 to 2001-06-26
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Version / remarks:
1984
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Version / remarks:
1989
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: At the start of the test samples of about 15 mL were taken from the test vessels with the diluted WAF and the control, just before the distribution of the solutions over the four batches and adding the test animals. At the end of the test the solutions from the four batches were combined and mixed and 15 mL samples from the undiluted WAF and the control were used for analysis.
- Sample storage conditions before analysis: Samples were stored in a refrigerator until analyses.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION:
The test solution was a Water Accommodated Fraction (WAF) prepared from 1.01 g test substance in 2 liters of DSW. THis solution was slowly stirred for approximately 48 hours, then transferred into a seperation funnel and left at test temperature for phase separation. After approximately 3 hours, when phase separation was complete, the aqueous phase was withdrawn and used to prepare the following dilutions: 1:16 - 1:8 - 1:4 -1:2 and the undiluted WAF
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: water fleas
- Source: Akzo Nobel Chemicals Research, Arnhem, Dept. CGS-ENV
- Age at study initiation: less than 24 hours
- Feeding during test: no feeding


Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
approximately 12°dH
Test temperature:
19.3 to 21 °C
pH:
7.5 to 8.1 (at the start)
8.0 to 8.1 (at the end)
Dissolved oxygen:
8.5 to 8.6 (at the start)
8.9 to 9.0 (at the end)
Nominal and measured concentrations:
- nominal concentrations: 0.1906, 0.3813, 0.7625, 1.525, 3.05 mg/L
- measured concentrations: The results show that the undiluted WAF contains 3.05 mg/L test item at the beginning of the test and below the detection limit (1.64 mg/L) at the end of the test, which is less than 80 % of the initial concentration. These results show that the test substance is probably not stable under test conditions.
Details on test conditions:
TEST SYSTEM
- Test vessel: 400 mL glass beakers containing approximately 250 mL of the test solution
- Type: closed
- Aeration: no
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dutch Standard water
- Intervals of water quality measurement: The dissolved oxygen and pH of all test concentrations and controls were measured at the beginning and at the end of the test. The temperature was measured continuously in an additional test vessel filled with deionized water and kept under identical conditions as the actual test vessels.

OTHER TEST CONDITIONS
- Photoperiod: 16 hours per day provided by fluorescent tubes


EFFECT PARAMETERS MEASURED : The daphnias were exposed to the chosen concentrations of the test substance as described below and immobility and sub-lethal effects were recorded at approximately 24 and 48 hours.

Reference substance (positive control):
no
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
0.79 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 0.68 and 0.93 mg/L
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
1.16 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
0.381 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
LOEC
Effect conc.:
0.763 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC100
Effect conc.:
1.525 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
Sublethal effects were not observed in the concentrations where no immobility was observed.
Reported statistics and error estimates:
The EC50 was calculated with the computer program TOXCALC version 5.0 according to Standard Operation Procedure L2, using the trimmed Spearman-Kärber method. The concentration as measured in the WAF at the beginning of the test was used to calculate the concentrations of the dilutions. The concentrations causing zero and 100 % immobility were derived directly from the test observations.
Validity criteria fulfilled:
yes
Conclusions:
The EC50 (48 h) of tert-butyl peroxyneodecanoate was calculated to be 0.79 mg/L with 95% confidence limits of 0.68 and 0.93 mg/L.
The highest concentration causing no immobility (no observed effect concentration, NOEC) after 48 hours amounted to 0.38 mg/L, whereas 0.76 mg(L was the lowest tested concentration (LOEC, 48 h) at which significant immobility was observed as compared to the control. The EC100 was 1.53 mg/L, which was observed after 48 hours.
Executive summary:

The acute toxicity of the Water Accommodated Fraction (WAF) of tert-butyl peroxyneodecanoate to Daphnia magna (water flea) was tested under static conditions for 48 hours in accordance with OECD guideline no. 202 and EU method C.2. The test item is immiscible with water and therefore a WAF was prepared. The following dilutions of the WAF were tested: 1:16 - 1:8 - 1:4 - 1:2 and the undiluted WAF. Chemical analyses of the control and WAF were performed and showed that the test substance is probably unstable under test conditions. At beginning of the test a concentration of 3.05 mg/L was measured. At the end of the test a concentration below 1.64 mg/L was measured. The concentration at the beginning of the test was used for calculation of the effect concentrations.

The EC50 (48 h) was calculated to be 0.79 mg/L with 95% confidence limits of 0.68 and 0.93 mg/L.

The highest concentration causing no immobility (no observed effect concentration, NOEC) after 48 hours amounted to 0.38 mg/L, whereas 0.76 mg/L was the lowest tested concentration (LOEC, 48 h) at which significant immobility was observed as compared to the control. The EC100 was 1.53 mg/L, which was observed after 48 hours.

Sublethal effects were not observed in the test concentrations where no immobility was observed.

Description of key information

The acute toxicity to invertebrates was assessed according to OECD guideline 202 and EU-method C.2. In this 48-hour acute toxicity test with daphnia, the EC50 value was 0.79 mg/L (nominal concentration). The no-observed-effect concentration (NOEC) was 0.381 mg/L (nominal concentration).

 

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
0.79 mg/L
EC50/LC50 for marine water invertebrates:
0.381 mg/L

Additional information

The acute toxicity of the Water Accommodated Fraction (WAF) of tert-butyl peroxyneodecanoate to Daphnia magna (water flea) was tested under static conditions for 48 hours in accordance with OECD guideline no. 202 and EU method C.2. The test item is immiscible with water and therefore a WAF was prepared. The following dilutions of the WAF were tested: 1:16 - 1:8 - 1:4 - 1:2 and the undiluted WAF. Chemical analyses of the control and WAF were performed and showed that the test substance is probably unstable under test conditions. At beginning of the test a concentration of 3.05 mg/L was measured. At the end of the test a concentration below 1.64 mg/L was measured. The concentration at the beginning of the test was used for calculation of the effect concentrations. The EC50 (48 h) was calculated to be 0.79 mg/L with 95% confidence limits of 0.68 and 0.93 mg/L. The highest concentration causing no immobility (no observed effect concentration, NOEC) after 48 hours amounted to 0.38 mg/L, whereas 0.76 mg/L was the lowest tested concentration (LOEC, 48 h) at which significant immobility was observed as compared to the control. The EC100 was 1.53 mg/L, which was observed after 48 hours. Sublethal effects were not observed in the test concentrations where no immobility was observed.

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