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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:
24 - 26 March 1993
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Guideline and GLP compliant study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
yes
Remarks:
The test was performed in darkness. This is considered to have no effect on the outcome of the study.
Principles of method if other than guideline:
The test was performed in darkness.
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0 (control), 8.1, 27, 90, 300, 1000 mg MRD-92-428 (CT-519-92S)/L
- Sampling method: Samples were removed from each treatment on Day 0, on Day 1 due to total mortality of a treatment, i.e., 1000 mg MRD-92-428 (CT-519-92S)/L, and 2 (composite of replicates 1-4) and analysed for carbon content.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Individual treatment solutions were prepared by adding the appropriate amount of test material to laboratory dilution water in glass aspirator bottles. These solutions were mixed (< 10% vortex) on a magnetic stirrplate with teflon coated stirrbars for 1 hour. The treatments appeared clear. The WAF of each treatment solution was drawn through the outlet at the bottom of the vessel and divided into 4 replicate chambers. Test chambers were covered with glass to minimize evaporation and/or volatilization.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): No. In addition, the measured concentrations were 80% of the nominal or greater and therefore, the nominal values were used. This indicates that even at the highest dose, > 80% of the test material was in the fraction < 0.45 µm (filtration prior to analysis) and not floating at or in the surface (removal of the test solution from the bottom of the test solution preparation vessel)
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM
- Common name: Water flea
- Strain: not provided
- Source: Cultured in the Environmental Toxicology Laboratory of Exxon Biomedical Sciences, Inc.
- Age at study initiation (mean and range, SD): < 24 hours
- Method of breeding: Daphnids are kept in 1 Liter glass culture vessels with dilution water (BW2 at 20 +/- 2°C) similar in characteristics to that used during the test. Cultures of Daphnia were fed about 3.12*10^5 cells/mL of Selenastrum capriornutum and about 6 µL/mL yeast/salmon starter/cereal leaves mixture. Algae are cultured in the Environmental Toxicology Laboratory of Exxon Biomedical Sciences, Inc. using modified ASM-1 medium.
- Feeding during test: The daphnids were not fed
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
76 - 82 mg/L as CaCO3 in the dilution water
Test temperature:
19.0 to 21.0 °C
pH:
7.1 to 7.4
Dissolved oxygen:
8.5 to 9.1 mg/L
Nominal and measured concentrations:
nominal concentrations: 0 (control), 8.1, 27, 90, 300, 1000 mg MRD-92-428 (CT-519-92S)/L, corresponding to 7.78, 25.9, 86.4, 288 and 960 mg CH-SSS/L
Measured concentrations: 0 (control), 10.40, 32.31, 90.43, 295.5, and 917.2 mg a.i./L, determined by DOC analysis using a carbon content of a.i. of 48.84%
Details on test conditions:
TEST SYSTEM
- Test vessel: 30 mL glass beakers, filled with 25 mL test solution
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- Biomass loading rate: 1 daphnia/5 mL

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Laboratory dilution water, Blend Water 2 (BW2). the dilution water is aerated by circulation within the holding tank and aged for at least 24 hours before introduction to the test system.
- Total organic carbon: 1.142 mg/L as measured in a monthly water quality analysis.
- Particulate matter: NA
- Metals: below levels of concern
- Pesticides :below levels of concern
- Chlorine: MA
- Alkalinity: 30 mg/L as CaCO3
- Culture medium different from test medium: No
- Intervals of water quality measurement: start and termination of the exposure.

OTHER TEST CONDITIONS
- Photoperiod: the test was performed in darkness
- Light intensity: NA

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : EC50 at 48 hours

TEST CONCENTRATIONS
- Spacing factor for test concentrations: about 3.2
- Range finding study
- Test concentrations: control, 5, 10, 50, 100 and 1000 mg test item/L
- Results used to determine the conditions for the definitive study: Ninety percent immobilization was observed in the 1000 mg test item/L treatment during the 48 hour exposure period. No other effects were reported.
Reference substance (positive control):
no
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
439 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
other: immobilization
Remarks on result:
other: 95% C.I.: 362 - 532 mg a.i./L
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
457 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: immobilization
Remarks on result:
other: 95% C.I.: 377 - 554 mg test item/L
Details on results:
- Behavioural abnormalities: none, for immobilization see Table 3
- Other biological observations: few daphnids were trapped on the surface. This was not dose dependent.
- Mortality of control: none
- Other adverse effects control: none
- Abnormal responses: none
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none
- Effect concentrations exceeding solubility of substance in test medium: none
Reported statistics and error estimates:
The EC50 was determined using the Spearman-Karber method based on nominal concentrations.

Table 1   Dissolved oxygen, pH and temperature in the test solutions

Nominal concentration of MRD-92-428 (CT-519-92S)

[mg/L]

0 hours

48 hours

Dissolved oxygen

[mg/L]

pH

Temperature

[°C]

Dissolved oxygen

[mg/L]

pH

Temperature

[°C]

0

9.4

7.3

20.9

8.5

7.3

19.0

8.1

9.2

7.4

20.9

8.6

7.4

19.2

27

9.2

7.4

21.0

8.5

7.4

19.6

90

9.2

7.4

21.0

8.5

7.4

19.5

300

9.2

7.4

21.0

8.5

7.4

19.2

1000

9.2

7.4

21.0

9.1*

7.1*

20.0*

 

* Since 100% immobilization was observed after 24 hours, these values were determined at the 24 hour observation interval.

 Table 2: Results of the dose verification analysis

Nominal concentrations

Measured concentrations*

[mg test item/L]

[mg a.i./L]

Day 0

Day 2

mean

% of nominal a.i./L

Control

0

-

-

8.1

7.78

10

10.85

10.40

133.8

27

25.92

32.59

32.03

32.31

124.7

90

86.4

94.14

86.72

90.43

104.7

300

288

291.7

299.3

295.5

102.6

1000

960

967.8

866.6**

917.2

95.5

*calculated from DOC measurements using a carbon content of a.i. of 48.84 %.

** measured after 24 hours due to 100% immobilization

 

 Table 3: Immobilization

     

Nominal concentrations

Immobilization [%]

[mg test item/L]

[mg a.i./L]

Day 1

Day 2

Control

0

0

0

8.1

7.78

0*

0

27

25.92

0

0*

90

86.4

0

0*

300

288

0

15*

1000

960

100

100

*One of the non-immobilized daphnids was floating on the surface.

Note: in the control and at nominal test concentrations of 7.78 to 288 mg a.i./L all daphnids were normal throughout the exposure period. 

 

Validity criteria fulfilled:
yes
Conclusions:
48-hour-EC50 to daphnids: 439 mg a.i./L.
Executive summary:

The acute toxicity of MRD-92 -428 (CT-519 -925) - which contains 95 -97% a.i. - to Daphnia magna was determined in a static test under GLP. The test was performed similar to EEC C.2 and OECD 202. The test was started with a control and nominal concentrations of 8.1, 27, 90, 300, 1000 mg MRD-92-428 (CT-519-92S)/L, corresponding to 7.78, 25.9, 86.4, 288 and 960 mg a.i./L assuming an average content of a.i. of 96%. The concentrations were analyzed by DOC analyses using a carbon content of CH-SSS of 48.84%. The mean measured concentrations were 0 (control), 10.40, 32.31, 90.43, 295.5, and 917.2 mg a.i./L for nominal concentrations of 7.78, 25.9, 86.4, 288 and 960 mg a.i./L All values were > 80 % and hence results were based on nominal concentrations. For each test concentration and the control, 4 replicates with 5 daphinds each were set up in 30 mL vessels filled with 25 mL test solution. The test was performed in darkness. After 48 hours of exposure, 0, 0, 0, 0, 15 and 100 % of the daphnids were immobilized at 0 (control),7.78, 25.9, 86.4, 288 and 960 mg a.i./L. The corresponding 48 h EC50 value is 439 mg a.i./L.

This study is considered to be acceptable for the risk assessment.

Description of key information

48 h EC50: 439 mg a.i./L

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
439 mg/L

Additional information

For this endpoint one Klimisch 1 study is availabe (Cytec Tarigia, 1993).

The acute toxicity of MRD-92 -428 (CT-519 -925) - which contains 95 -97% a.i. (calculations were performed with the average concentration of 96%)- to Daphnia magna was determined in a static test under GLP. The test was performed similar to EEC C.2 and OECD 202. The test was started with a control and nominal concentrations of 8.1, 27, 90, 300, 1000 mg MRD-92-428 (CT-519-92S)/L, corresponding to 7.78, 25.9, 86.4, 288 and 960 mg a.i./L. The concentrations were analyzed by DOC analyses using a carbon content of a.i. of 48.84%. The mean measured concentrations were 0 (control), 10.40, 32.31, 90.43, 295.5, and 917.2 mg a.i./L for nominal concentrations of 7.78, 25.9, 86.4, 288 and 960 mg a.i./L All values were > 80 % and hence results were based on nominal concentrations. For each test concentration and the control, 4 replicates with 5 daphinds each were set up in 30 mL vessels filled with 25 mL test solution. The test was performed in darkness. After 48 hours of exposure, 0, 0, 0, 0, 15 and 100 % of the daphnids were immobilized at 0 (control),7.78, 25.9, 86.4, 288 and 960 mg a.i./L. The corresponding 48 h EC50 value is 439 mg a.i./L.

This study is considered to be acceptable for the risk assessment.