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Ecotoxicological information

Toxicity to soil macroorganisms except arthropods

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Reference
Endpoint:
toxicity to soil macroorganisms except arthropods: short-term
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
Guideline:
OECD Guideline 207 (Earthworm, Acute Toxicity Tests)
Principles of method if other than guideline:
OECD guideline 207 (1984)
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
no
Details on preparation and application of test substrate:
A stock mixture was prepared by premixing weighed amounts of the substance with 200 g fine quartz sand.
Test organisms (species):
Eisenia fetida
Animal group:
annelids
Details on test organisms:
TEST ORGANISM
- Common name: earthworm
- Source: P. Ehret, Ostermundigen, Switzerland
- Age at test initiation (mean and range, SD): adult (>2 months of age), mature with clitellum
- Weight at test initiation (mean and range, SD): 300 to 355 mg in dose groups, 315 mg in control group

ACCLIMATION
- Acclimation period: earthworms arriving from the supplier were kept for three days in original soil
- Acclimation conditions (same as test or not): 24 hours conditioning in artificial soil
Study type:
laboratory study
Substrate type:
artificial soil
Limit test:
no
Total exposure duration:
14 d
Remarks:
Soil was prepared in accordance to OECD TG 207
Post exposure observation period:
no
Test temperature:
20 °C
pH:
start: 5.7 - 6.0
Moisture:
start: 39 - 40 % of dry weight of soil
end: 35 - 37 % of dry weight of soil
Details on test conditions:
exposure: beakers of 1 L filled with 750 g soil (wet weight), covered with perforated plastic film
continuous illumination, 400-800 Lux cold white fluorescent light
soil: according to OECD guideline 207
40 worms per concentration and control (10 worms per test container)
age: adult (> 2 months of age), mature with clitellum
adaptation: 24 h conditioning in artificial soil
feeding: none
Nominal and measured concentrations:
blank control
60, 130, 250, 500, 1000 mg/kg (nominal)
Reference substance (positive control):
no
Key result
Duration:
14 d
Dose descriptor:
LC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mortality
Details on results:
mortalities:
control: 3% (7 d), 3% (14 d)
60 mg/kg: 3% (7d), 3% (14d)
130 mg/kg: 5% (7d), 5% (14d)
250 mg/kg: 0% (7d), 5% (14d)
500 mg/kg: 3% (7d), 10% (14d)
1000 mg/kg: 3% (7d), 13% (14d)
Validity criteria fulfilled:
yes
Conclusions:
The 14-day LC50 for cloquintocet-mexyl to earthworms was >1000 mg/kg dry weight (nominal concentration).
Executive summary:

A study on acute toxicity of cloquintocet-mexyl to the earthworn (Eisenia foetida) was conducted under GLP to OECD TG 207. Earthworms were exposed to nominal concentrations of test item of 60, 130, 250, 500 and 1000 mg/kg dry weight of soil over a period of 14 days. The mortality of test organisms was observed over the study period. The highest number of mortalities was observed at the highest test concentration of 1000 mg/kg, where 5 out of 40 earthworms (13%) perished. Consequently, the 14-day LC50 value in this study was greater than 1000 mg/kg dry weight (nominal concentration).

Description of key information

14-day LC50 >1000 mg/kg soil (dry weight), earthworm, (OECD TG 207, Rufli 1989)
14-day LC50 of metabolite >1000 mg/kg soil (dry weight), earthworm (OECD TG 207, Kleiner 1999)

Key value for chemical safety assessment

Additional information

Rufli (1989) investigated the toxicity of cloquintocet-mexyl to earthworms (Eisenia foetida) in a GLP compliant study performed according to OECD TG 207. The highest number of mortalities was observed at the highest test concentration of 1000 mg/kg soil (dry weight), where 5 out of 40 earthworms (13%) perished. Based on this, the 14-day LC50 was greater than 1000 mg/kg soil dry weight (nominal concentration).

The acute toxicity of the main environmental metabolite of cloquintocet-mexyl to earthworms (Eisenia foetida) was tested under GLP to OECD TG 207 (Kleiner 1999). No effects were seen at the nominal test concentration of 1000 mg test item/kg soil dry weight. Therefore, the NOEC is determined to be 1000 mg test item/kg soil dry weight.

The LC50 of >1000 mg/kg reported by Rufli (1989) for cloquintocet-mexyl has been selected for the chemical safety assessment.