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Ecotoxicological information

Short-term toxicity to fish

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short-term toxicity to fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
96 hours
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
according to guideline
OECD Guideline 203 (Fish, Acute Toxicity Test)
Fish size 45 to 52 mm (mean 49 mm)
GLP compliance:
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable
Analytical monitoring:
Details on sampling:
Samples were taken at the start (0 hours) and end (96 hours) of the exposure period.
Details on test solutions:
3.2 g of CGA 185072 and 400 mg alkylphenol-polyglykol-ether were mixed with and made up to 1000 mL with water. A fresh stock solution was prepared every 24 hours.
Test organisms (species):
Ictalurus punctatus
Details on test organisms:
Obtained from a commercial hatchery (Osage Catfish, Missouri, USA. Fish were acclimated for 19 days prior to tesing.
Test type:
Water media type:
Limit test:
Total exposure duration:
96 h
Post exposure observation period:
Not applicable
166 mg CaCO3/L
Test temperature:
22 degrees C
7.9 - 8.2
Dissolved oxygen:
77 to 102% of ASV
Not applicable
Nominal and measured concentrations:
Nominal test concentrations were 0 (control), 0 (vehicle control) 1.8, 3.2, 5.8, 10, 18 and 32 mg/L.

Measured test concentrations after 96 hours were 0.85, 1.6, 3.3, 6.2, 9.9 and 26 mg/L.
Details on test conditions:
Test conditions were appropriate for the species tested.
Reference substance (positive control):
96 h
Dose descriptor:
Effect conc.:
14 mg/L
Nominal / measured:
meas. (not specified)
Conc. based on:
act. ingr.
Basis for effect:
mortality (fish)
Remarks on result:
other: 6.7 - 170 mg/L
Results with reference substance (positive control):
Not applicable
Reported statistics and error estimates:
The LC50 values were calcuated according to Berkson, JASA 48 (1953), pages 569 - 599

LC-values were graphically determined on gausso-logarithmic probability paper.
Sublethal observations / clinical signs:

There were no mortalities in either control group. After 96 hours mortality was 0, 20, 30, 20, 50 and 60% in the 0.85, 1.6, 3.3, 6.2, 9.9 and 26 mg/L treatments. Sub-lethal effects were seen in all of the test treatments except 0.85 mg/L, the LC0 was therefore 0.85 mg/L. The 96 hour LC50 was calculated to be 14 mg/L (based on measured concentrations at the end of the study).

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

An acute toxicity with channel catfish (Ictalurus punctatus) was conducted in which fish were exposed to series of concentrations on cloquintocet-mexyl. After 96 hours mortality was 0, 20, 30, 20, 50and 60% in the 0.85, 1.6, 3.2, 6.2, 9.9 and 26 mg/L measured treatments.

The 96 hour LC50 for cloquintocet-mexyl to channel catfish was determined to be 14 mg/L, with the LC0 observed to be 0.85 mg/L.

Description of key information

Lowest 96-h LC50 = 14 mg/L in channel catfish (OECD TG 203)

Lowest 96-h LC50 for the main metabolite = 82.6 mg/L in bluegill sunfish (OECD TG 203)

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
14 mg/L

Additional information

Five acute toxicity tests with four freshwater species were conducted. The fish were exposed to 5 or 6 concentrations at a temperature of 12-14 °C (rainbow trout) or 22-23 °C (bluegill, carp, and catfish). The pH values were between 7.8 and 8.5 in all five studies. The results are summarized in the table below and are expressed as initial measured and mean measured concentrations (Rufli 1988, Rufli 1988b, Rufli 1988c, Rufli 1989). The 96-h LC50 of cloquintocet-mexyl in fish ranged from 14 to >133 mg/L, depending on the species.

In a second short-term toxicity study (Palmer and Krueger, 1998) with rainbow trout (Oncorhynchus mykiss), fish were exposed to cloquintocet-mexyl at nominal concentrations of 0.045, 0.097, 0.19, 0.38 and 0.97 mg/L, in a flow-through test for 96 hours. The 96-hour LC50 value was >0.97 mg/L, the highest (measured) concentration tested. The no observed effect concentration was 0.97 mg/L.

In addition, the prolonged short-term toxicity of cloquintocet-mexyl to rainbow trout (Oncorhynchus mykiss) was investigated (Grade, 1992) according to OECD guideline 204. The study was GLP compliant and is considered to be reliable without restriction. The overall 21-day NOEC of cloquintocet-mexyl to juvenile fish under flow-through conditions was 0.004 mg/L (nominal), based on change in a calculated condition index. The overall 21-day LOEC and LC50 endpoints were 0.016 and 0.51 mg/L (nominal), respectively.

Four studies conducted to GLP and OECD TG 203 investigated the short-term toxicity of the main environmental metabolite of cloquintocet-mexyl (i.e. [(5-chloroquinolin-8-yl)oxy]acetic acid) to fish (Grade 1992a, Grade 1992b, Grade 1992c and Grade 1992d). The lowest LC50 and NOEC values were obtained for Bluegill sunfish (Lepomis macrochirus), with 82.6 mg/L and 8.3 mg/L respectively.

This demonstrates that cloquintocet-mexyl is anticipated to have a higher acute toxicity to fish than its major environmental metabolite.