Methyl (R)-2-(4-(3-chloro-5-trifluoromethyl-2-pyridyloxy)phenoxy)propionate

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:

other: OECD Guideline for Testing of Chemicals No 202, Daphnia sp., Acute Immobilisation Test and Reproduction Test

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Haloxyfop-R methyl ester (XRD-535)
Lot #: RMM 2055
Purity: 96.4%

Analytical monitoring:

yes

Details on sampling:

Samples for analysis of the ester and acid hydrolysis product of the test substance were taken on six occasions during the 21 day exposure period. Three sets of new test solutions and three sets of 24 h old solutions were sampled during the test.

Vehicle:

yes

Remarks:

Acetone

Details on test solutions:

A solvent stock solution was prepared by addition of test substance to acetone. The nominal concentration of the solvent stock was 60 mg/mL. This solvent stock solution, prepared once each week of the test was used to prepare an aqueous test solution by direct addition to dilution water. The stock solution was stored between 0 and 5°C. The aqueous test solution was prepared daily for the duration of the test and stirred on a magnetic stirrer for approximately one hour before use. The nominal concentration of the aqueous test solution was 6 mg/L. From this aqueous test solution a series of dilutions was prepared using dilution water to provide the following nominal concentrations of test substance: 0.06, 0.2, 0.6 and 2.0 mg/L.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea
- Strain/clone: Daphnia magna
- Age at study initiation: <24 h
- Source: Shell Research Ltd., Sittingbourne, UK.

Feeding during test
- Food type: Concentrated suspension of Chlorella vulgaris at approximately 500000 cells/mL. A yeast suspension was also added daily as a dietary supplement.
- Amount: 0.2 mL (50 mg/L suspension) per culture per day.
- Frequency: Daily

ACCLIMATION
- Acclimation period: 8 days
- Feed: Suspension of Chlorella vulgaris and yeast

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Test temperature:

19.0 to 21.8°C

pH:

7.4-8.6

Dissolved oxygen:

86-109% air saturated value

Nominal and measured concentrations:

Nominal: Water and solvent controls, 0.06, 0.2, 0.6, 2.0 and 6.0 mg/L
Measured: Water and solvent controls, 0.049, 0.157, 0.509, 1.48, 4.59 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 600 mL glass beakers
- Type: Closed
- Material, size, headspace, fill volume: 600 mL glass beakers containing 400 mL of test medium
- Renewal rate of test solution (frequency/flow rate): Test media was changed daily
- No. of organisms per vessel: 40
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): 4
- Loading rate: 1 daphnid per 40 mL test medium

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The water used for the culturing and testing of D. magna is a reconstituted freshwater prepared by mixing treated mains water and a proprietary mineral water in the ratio 1:1. The treated mains dilution water is the laboratory mains supply.
- Metals: Fe (<10 µg/L), Pb (<5 µg/L), Cu (<10 µg/L)
- Pesticides: DDT, Dieldrin, Endrin, Aldrin: <0.002 to <0.1 µg/L
- Chloride: 33.5 mg/L Cl
- Alkalinity: 160 mg/L HCO3
- Conductivity: 413 µS/cm

OTHER TEST CONDITIONS
- Photoperiod: 16 h photoperiod

EFFECT PARAMETERS MEASURED: At 24 h intervals the adult D. magna were observed for immobility, the presence of eggs in the brood pouch and mortality and the survivors transferred to fresh test media. D. magna were considered to be immobile if, when the contents of the test vessel were briefly swirled they did not swim during a 15 second period of observation. Any dead Daphnia were recorded. After the adult D. magna had been transferred to fresh test media any juvenile Daphnia produced (live or dead) in the previous 24 h were counted and discarded.

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

1.13 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: mean no. of juveniles per adult

Remarks on result:

other: 95% CL: 0.983-1.30 mg/L

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.509 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

reproduction

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

0.509 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

other: adult survival

Details on results:

Gravid D. magna were observed in the control and solvent control vessels and at 0.049, 0.157, 0.509 and 1.48 mg/L on day six. On day seven the majority of adult D. magna in all test and control vessels with the exception of the highest concentration group were gravid. There were no gravid adults in the media at the highest concentration of 4.59 mg/L. By day eight all adult D. magna were gravid with the exception of one small adult in the control group, one small adult at 0.049 mg/L and one adult in each of the four replicate vessels at 4.59 mg/L.
The first juveniles were produced on day nine in the control and solvent control media and at 0.049 and 0.509 mg/L. A few of the juveniles produced in the control and at 0.049 and 0.509 mg/L were dead on the bottom of the test vessels. All of the juveniles produced at 1.48 mg/L were dead.
On day 10 juveniles were produced in all of the test groups with the exception of the 4.59 mg/L group. Low numbers of dead juveniles were produced in the control, solvent control, 0.157 and 0.509 mg/L media. 13 live juveniles were produced at 1.48 mg/L, 91 dead juveniles were also present.
By day 11 live juveniles had been produced in all test vessels with the exception of one vessel at 1.48 mg/L and all of the test vessels at 4.59 mg/L. Low numbers of dead juveniles were observed in one control and one solvent control vessel and in all of the 0.509, three of the 1.48 and all of the 4.59 mg/L test vessels respectively.
On day 12 low numbers of dead juveniles were observed in one control, one solvent control and at 0.049, 0.157, 0.509, 1.48 and 4.59 mg/L respectively.
From day 13 onwards dead and immobile Daphnia were observed only in the 1.48 and 4.59 mg/L test vessels.
No live juveniles were produced in any of the 4.59 mg/L test vessels during the study.
Adult D. magna mortality was below 10% for both control groups, 0.049, 0.157 and 0.509 mg/L groups. For 1.48 and 4.59 mg/L groups it was 26 and 35% respectively.
At the end of the study all surviving adult D. magna were weighed (wet weight) and measured. There were significant differences in adult length between the solvent. control group and the control (p <0.001) and the 4.59 mg/L group (p <0.001), which was significantly smaller. There were significant differences in wet weight between the solvent control and the control group (p <0.001). There were also significant differences between the solvent control group and the 1.48 mg/L (p <0.001) and 4.59 mg/L (p <0.01) treatments which were all significantly smaller.

Validity criteria fulfilled:

yes

Conclusions:

21-day NOEC (D. magna): 0.509 mg/L (reproduction and adult survival)

Executive summary:

A Daphnia magna reproduction study was performed with test substance. The 21-day reproduction study was performed under semi-static conditions with daily renewal of test solutions. The study was carried out in accordance with the OECD Guideline for Testing of Chemicals No 202, Daphnia sp., Acute Immobilisation Test and Reproduction Test.

The following nominal concentrations of test substance were prepared in dilution water: 0.06, 0.2, 0.6, 2.0 and 6.0 mg/L. Both a solvent control (dilution water and acetone) and a control (dilution water only) treatment were included. There were four replicate test vessels per treatment, each vessel containing a nominal ten D. magna aged less than 24 hours at the start of the test.

A concentrated stock solution of test substance in acetone was prepared weekly, the stock solution was stored between 0 and 5°C. Fresh test solutions were prepared daily and adult D. magna were observed and transferred daily. Any juveniles produced, both live and dead were counted.

Samples for analysis of the ester and acid hydrolysis product of test substance were taken on six occasions during the 21-day exposure period. Three sets of new test solutions and three sets of 24 h old solutions were analysed. Mean measured concentrations were based on the sum of the acid, converted to ester equivalent and ester measured concentrations.

The control and solvent control test media contained no detectable quantities of test substance.

The toxicity of test substance to D. magna was based on mean measured concentrations (sum of acid, converted to ester equivalents and ester components) in the test media.

No live juveniles were produced at the highest concentration however some dead juvenile were observed. At a mean measured concentration of 1.48 mg/L large numbers of dead juveniles were found.

At the end of the study all surviving adult D. magna were weighed (wet weight) and measured. There were significant differences in adult length between the solvent control group and the control (p <0.001) and the 4.59 mg/L group (p <0.001), which was significantly smaller. There were significant differences in wet weight between the solvent control and the control group (p <0.001). There were also significant differences between the solvent control group and the 1.48 mg/L (p <0.001) and 4.59 mg/L (p <0.01) treatments which were all significantly smaller.

The 21 day EC50 for mean numbers of live juveniles per adult D. magna was 1.13 mg/L (95% confidence limits of 0.983 to 1.30 mg/L). The highest no observed effect concentration was 0.509 mg/L.

Description of key information

21-day NOEC (Daphnia magna): 0.509 mg/L (reproduction and adult survival); OECD 202; Reliability = 1

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

0.509 mg/L