heptan-2-yl [(5-chloroquinolin-8-yl)oxy]acetate

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

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 211 (Daphnia magna Reproduction Test)

Principles of method if other than guideline:

According to OECD guideline No. 211 and OPPTS Test Guideline 850.1300

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

yes

Details on test solutions:

N,N-dimethylformamide (DMF) was used for the preparation of the application solutions. DMF concentration in the test solutions: 100 uL DMF per litre test water.

Test organisms (species):

Daphnia magna

Details on test organisms:

females of a clone of the species Daphnia magna Straus.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Post exposure observation period:

no

Hardness:

2.5 mmol/L (= 250 mg/L) as CaCO3

Test temperature:

19 - 21 °C

pH:

7.6 - 7.9

Dissolved oxygen:

>= 8.2 mg/L

Nominal and measured concentrations:

nominal: 37.5, 75, 150, 300, 600 µg/L
measured: 25.9, 54, 98, 202, 437 µg/L (time weighted mean concentration)

Reference substance (positive control):

no

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 437 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 437 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

mortality

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

>= 437 µg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth

Validity criteria fulfilled:

yes

Conclusions:

No significant effect was determined on the survival, reproduction rate and body length of the daphnids up to and including the highest test concentration. Therefore the 21-day no observed effect concentration (NOEC) value for cloquintocet-mexyl was 437 µg/L (nominal 600 µg/L).

Executive summary:

The effects of cloquintocet-mexyl on the survival, body length and reproduction of Daphnia magna were investigated in a semi-static test over 21 days conducted under GLP to OECD TG 211. The nominal test concentrations were 37.5, 75, 150, 300 and 600 µg/L, and the time-weighted average measured concentrations were between 65 and 73% of nominal concentrations. All effect concentrations were therefore based on the measured concentrations. No significant toxic effects of the test item on the survival or on the mean reproduction rate of parental daphnids was determined up to and including the highest test concentration of 437 µg/L (nominal 600 µg/L) over the period of 21 days. In addition, no significant effects on the mean length, nor any visible abnormalities, were observed in the daphnids at the highest test concentration. Therefore, the highest concentration of cloquintocet-mexyl tested without toxic effects after an exposure period of 21 days (21-day NOEC) was at least 437 µg/L.

Description of key information

21-day NOEC >0.437 mg/L (mean measured), water flea (OECD TG 211)

21 -day NOEC for the main metabolite = 32 mg/L (nominal), water flea (OECD TG 211)

Additional information

Two studies on the long-term toxicity of cloquintocet-mexyl to aquatic invertebrates are available. These studies were conducted to GLP and OECD TG 211.

A reliable 21-day semi-static reproduction test with Daphnia magna was performed by Bätscher (2003). Cloquintocet-mexyl had no toxic effects on survival, reproduction, and on the growth of Daphnia magna at concentrations up to 0.437 mg/L (mean measured concentration for nominal test concentration of 0.6 mg/L). Therefore the 21-day NOEC was >0.437 mg/L in this study.

A second study by Vial (1990) investigated the toxicity of cloquintocet-mexyl to Daphnia magna according to OECD TG 202, Part 2 (1984). The 21-day reproduction NOEC was reported as 0.002 mg /L. However, due to methodological deficiencies in the preparation of test solutions and issues with inhomogeneous distribution of test material in the media, this study is considered as non-reliable and will not be used in the hazard characterisation.

The study by Bätscher (2003) used Dimethylformamide (DMF) as a solvent (max. 0.1 mL/L medium), which is acceptable according to OECD TG 23 for testing of difficult substances. In the study by Vial (1990), a stock solution was prepared 3x/week by making up 10 mg test substance to 1L with test water, but the study report does not indicate how this was achieved (e.g. intensive stirring, ultrasonication).

Since the nominal test concentrations were close to the water solubility limit of cloquintocet-mexyl (0.6 mg/L) in both tests, it can be assumed that the substance was more homogeneously distributed in the study of Bätscher (2003) where solvent was used to prepare the test media. A statement in the Vial (1990) report that “the Day 14 (in freshly renewed medium) recoveries were too high, probably due to heterogenicity of the distribution of the test substance in the test vessels”, appears to support this view. Further evidence is provided by the study results. In the Bätscher (2003) test no or little mortalities of adult daphnids were found across the whole concentration range. By contrast, Vial (1990) reported that mortality increased (only from day 8 onwards) on a variable basis between the concentrations and large changes from one day to the next were observed. It is suggested that this was a result of the inhomogeneous distribution of the test substance, perhaps even the availability of small particles which were taken up by the daphnids (which are filter-feeders) resulting in these “over-night”/acute events of toxicity. This makes the test results unreliable.

A reliable study on the survival and reproduction of Daphnia magna was conducted to OECD TG 211 with the main environmental metabolite of cloquintocet-mexyl (Hertl 1997). This study was GLP compliant and is considered to be reliable without restrictions. Based on nominal test item concentrations, the 21-day NOEC of the metabolite was 32 mg/L.

This demonstrates that cloquintocet-mexyl has more severe long-term effects on aquatic freshwater invertebrates than its main environmental metabolite.