Registration Dossier

Ecotoxicological information

Short-term toxicity to aquatic invertebrates

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
48 hours
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
other: EPA Guideline EG-1, 8/10/82
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Analytical monitoring:
yes
Details on sampling:
Samples were taken at the start and end of the exposure period.
Vehicle:
yes
Details on test solutions:
200 mg of CGA 185072 technical and 8 mg alkylphenol polyglycolether were dispersed in and made up to 200 mL with water.
Test organisms (species):
Daphnia magna
Details on test organisms:
Daphnia magna Strauss 1820
Cultures kept at the laboraotry since February 1983 under parthenogenic conditions.
Juveniles used for testing were less than 24 hours old.
Cultures were maintained in re-constituted water
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
Not applicable
Hardness:
240 mg CaCO3/L
Test temperature:
21 - 22 degrees C
pH:
7.3 - 8.3
Dissolved oxygen:
Not measured during the study
Salinity:
No applicable
Nominal and measured concentrations:
Nominal concentrations 0 (water control), 0 (vehicle control), 10, 18, 32, 58, 100 mg/L.

Measured concentrations at T0 were 9.46, 18.4, 32.4, 57.4 and 101 mg/L and at T48 were 7.94, 10.6, 27.2, 52.3, 79.6 mg/L

The results of the study were based on the nominal exposure concentrations.
Details on test conditions:
Measured environmental values were all in expected ranges.
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
act. ingr.
Basis for effect:
mobility
Details on results:
Immobility after 48 hours was 0, 5, 15, 20 and 25% in the 10, 18, 32, 58 and 100 mg/L treatments. The 48 hour EC50 was observed to be >100 mg/L.
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
The results were based on observation of the data.

Immobility after 48 hours was 0, 5, 15, 20 and 25% in the 10, 18, 32, 58 and 100 mg/L treatments. The 48 hour EC50 was observed to be >100 mg/L and the corresponding EC0 was 10 mg/L.

Validity criteria fulfilled:
yes
Conclusions:
Based on the reported information an acceptable assessment of acute toxicity to Daphnia magna was achieved.
Executive summary:

An acute toxicity with Daphnia magna was conducted in which daphnids were exposed to series of concentrations on cloquintocet-mexyl. After 48 hours immobility was 0, 5, 15, 20 and 25% in the nominal 10, 18, 32, 58 and 100 mg/L treatments. The results are based on nominal exposure concentrations.

The 48 hour EC50 was observed to be >100 mg/L and the corresponding EC0 was 10 mg/L.

Description of key information

Lowest 48-hour EC50 value >100 mg/L (nominal), water flea (EPA EG-1)


Lowest 48-hour EC50 value for the main metabolite >9.7 mg/L (nominal and mean measured), water flea (OECD TG 202)

Key value for chemical safety assessment

Additional information

In the key study (Rufli, 1988), 2 groups of 10 daphnids (Daphnia magna) were exposed to cloquintocet-mexyl at nominal concentrations of 10, 18, 32, 58 and 100 mg/L, in a static test for 48 hours. The 48-hour EC50 was >100 mg/L, the highest concentration tested. The no observed effect concentration was 18 mg/L. This GLP-compliant study was conducted to EPA guideline EG-1 and was considered to be reliable without restrictions.


In a second study (Palmer and Krueger, 1998), daphnids (Daphnia magna) were exposed to cloquintocet-mexyl at nominal concentrations of 0.063, 0.13, 0.25, 0.50 and 1.0 mg/L, in a flow-through test for 48 hours. The 48-hour EC50 for was >0.82 mg/L, the highest (measured) concentration tested. The no observed effect concentration was 0.82 mg/L. This GLP-compliant study was conducted to OECD guideline 202 and was considered to be reliable without restrictions.


Since both studies indicate that the EC50 is greater than the concentrations tested, it is proposed to select the upper of the two test concentrations as the key value for the endpoint. Therefore, for risk assessment purposes, the EC50 of >100 mg/L was used for cloquintocet-mexyl.


A study of short-term toxicity of the main metabolite of cloquintocet-mexyl to daphnids (Daphnia magna) was carried out (Putt, 1993) as a limit test. This GLP-compliant study was performed to OECD guideline 202 and is considered to be reliable without restrictions. Daphnids were exposed to a nominal concentration of 9.7 mg/L, in a semi-static system. No effects were observed at the test concentration, thus the 48-hour EC50 of the metabolite was determined to be >9.7 mg/L.


This demonstrates that cloquintocet-mexyl and its main environmental metabolite do not exhibit significant toxicity to aquatic freshwater invertebrates at or above the maximum water solubility of the substance, which is at about 0.59 mg/L at 25 °C.