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

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: long-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:

other: BBA recommended methodology, Streloke, M. and Kopp, H. Long term toxicity test with Chironomus riparius: Development and validation of a new test system

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Haloxyfop-R [pyridine-3, 5-14C] methyl ester
Lot #: B844-161A
Radiochemical purity: >97%
Specific activity: 29.4 mCi/mmol

Analytical monitoring:

no

Vehicle:

yes

Remarks:

Acetone

Test organisms (species):

Chironomus riparius

Details on test organisms:

TEST ORGANISM
- Common name: Harlequin fly
- Strain/clone: Meigen
- Source: CEFAS, Burnham-on-Crouch, Essex
- Breeding conditions:
- Handling of egg masses and larvae: Chironomid larvae were cultured in five-litre vessels containing 1-2 cm depth of sediment substrate, and approximately 5 cm depth Elendt M4 culture medium. Cultures were maintained in temperature controlled conditions at a nominal 20 ± 2°C, with a 16 hour light photoperiod. Cultures were aerated with compressed air through narrow glass tubes at approximately 2-3 cm above the substrate surface. The larval rearing vessels were held in a sufficiently large enclosure (minimum 30 x 30 x 30 cm) to allow swarming of the emerged adults to ensure that copulation occurs. Following copulation, egg masses (ropes) were deposited at the air-water interface of the culture vessels. Chironomid larvae were cultured in five-litre vessels containing 1-2 cm depth of sediment substrate, and approximately 5 cm depth Elendt M4 culture medium. Egg masses were removed by gently loosening their attachment to the holding vessel with a pair of tweezers. Each egg mass was placed in a separate scintillation vial containing 10 ml of Elendt M4 medium.
- Age of animals at beginning of exposure: <36 h

Feeding during test
- Food type: Suspension of Tetramin® fish food, which was dispersed in dilution water (2.5 g : 250 ml Elendt M4), using a domestic liquidiser.
- Amount: 0.5 mg/larva per day for Days 0-9 and 1 mg/larva per day for the remaining culture period.
- Frequency: Daily

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

artificial sediment

Limit test:

no

Duration:

28 d

Exposure phase:

larvae from first generation (P)

Test temperature:

20 ± 1°C

pH:

4.4-7.3

Dissolved oxygen:

3.1-8.2 mgO2/L

Nominal and measured concentrations:

Range finding study: 0.01, 0.1, 1.0 and 10 mg/L
Definitive study: 0.10, 0.32,1.0, 3.2 and 10 mg/L

Details on test conditions:

TEST SYSTEM
- Test container (material, size): Tall-form glass vessels, 13 cm in diameter
- Sediment volume: Approximately 2 cm depth and 20 cm of overlying water (2.5 litres in volume)
- Depth of sediment and overlying water: 2 cm and 20 cm, respectively
- Aeration: Yes
- Aeration frequency and intensity: Aeration was provided through a narrow bore glass tube, secured 2-3 cm above the sediment layer to avoid disturbance (approximately 1 bubble/sec). Aeration started four to five days after the initial assembly, after the sediment constituents had settled out. Twenty-four hours before application (Day -1) the aeration was stopped and 25 first instar chironomid larvae were added to each vessel. Aeration was re-started after 24 hours.

EXPOSURE REGIME
- No. of organisms per container (treatment): 25
- No. of replicates per treatment group: 4
- No. of replicates per control and vehicle control: 4 and 8, respectively
- Type and preparation of food: Tetramin® suspension, was added daily
- Amount of food: Equivalent to approximately 1 mg/larvae/day

OVERLYING WATER CHARACTERISTCS
The water used for the culture of the test species and experimentation was reconstituted Elendt M4

CHARACTERIZATION OF ARTIFICIAL SEDIMENT
- 10% sphagnum peat
- 20% kaolin clay
- 70% industrial sand - acid washed fine sand
The final pH of the sediment was adjusted to 5.6 by the addition of chemically pure quality calcium carbonate. Approximately 200 g artificial sediment was mixed with 50 ml of test water to a 'plastic' consistency, then carefully placed in a test unit.

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light: 8 hours darkness

EFFECT PARAMETERS MEASURED: Once the study was initiated, the vessels were monitored daily for signs of growth and development of the chironomids. From Day 13, when the first flies emerged, adults were sexed and removed from the vessels. The 28-day percentage emergent success was calculated for each treatment.

VEHICLE CONTROL PERFORMED: Yes

TEST CONCENTRATIONS
- Spacing factor for test concentrations:
Range finding study
- Test concentrations: 0.01, 0.1, 1.0 and 10 mg/L
- Results used to determine the conditions for the definitive study: Mortality was not seen at any test concentration except at 10 mg/L where 100% mortality was observed.

Key result

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

emergence rate

Remarks on result:

other: Highest dose tested

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

3.2 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

emergence rate

Key result

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

development rate

Remarks on result:

other: Highest dose tested

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

3.2 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

development rate

Details on results:

- Other biological observations: There was no difference in the numbers of male and female midges emerging for each treatment except at the applied dose of 10 mg/L, where the male:female ratio was significantly different (p <0.01) at 39:61%

Applied dose (mg test substance/L)	Development and emergence at Day 28
	Mean development rate	Mean % emergence
Combined control	0.068	98
0.10	0.069	99
0.32	0.070	99
1.0	0.068	98
3.2	0.068	97
10	0.063	85

Validity criteria fulfilled:

yes

Conclusions:

28 d EC50 (Chironomus riparius): >10 mg/L (highest dose tested) (emergence and development rate)
28 d NOEC (Chironomus riparius): 3.2 mg/L (emergence and development rate)

Executive summary:

A study was carried out to assess the toxicity of the test substance to the sediment dwelling phase of the non-biting midge Chironomus riparius, using a static test system with application to the aqueous phase.

The study was conducted in accordance with the BBA recommended methodology, Streloke, M. and Kopp, H. "Long term toxicity test with Chironomus riparius: Development and validation of a new test system.

The study was initiated with first instar Chironomus riparius, less than 36 hours old. Daily records, which included the general condition of the larvae and the female : male ratio of successfully emerged adults, were maintained for each test culture. The larvae were fed daily with Tetramin® fish food suspension. dispersed in culture medium, at a rate of 1 mg/larva.

Groups comprising four replicates of 25 chironomid larvae per concentration were exposed for 28 days to nominal concentrations of 0.10 to 10 mg [14C-]test substance/L, dispersed in Elendt M4 culture medium.

A preliminary Wilcoxon test on the total number of emerged adults suggested that there was no statistical difference between the solvent and non-solvent control groups. Therefore, these two groups were pooled for all subsequent analysis and the pooled data classified as the combined control.

EC50 for emergence was >10 mg/L. The percentage emergence rate for midges was significantly lower than that of the combined controls at an applied dose of 10 mg/L (p <0.01). Consequently, in this study the NOEC for emergence was 3.2 mg/L.

EC50 for development rate was >10 mg/L. The development rate was significantly lower than that of the combined controls at an applied dose of 10 mg/L (p <0.01). Consequently, the NOEC for development rate in this study was 3.2 mg/L.

There was no difference in the numbers of male and female midges emerging from each treatment except at 10 mg/L where the male:female ratio was significantly different (p <0.01) at 39:61%.

Environmental data (pH, dissolved oxygen and temperature) were recorded at the start and end of the study, and once weekly throughout the course of the study.

The results of all chemical analyses are based on total radioactivity measurements expressed as concentrations of the active ingredient.

Data from analyses showed that Day 0 overlying water concentrations were in the region of 80-93% of the applied dose for all levels except 3.2 mg/L and 10 mg/L. The overlying water concentrations for the two highest concentrations were 43 and 26% of applied dose, respectively. These low values are not unexpected as the maximum water solubility is quoted by the client as 9.08 mg/L at 20°C, which is only achievable under optimum conditions. Further, visual, evidence was noted on Day 0, after the vessels were spiked, when a small oily globule was seen on the surface of the water in all replicates of 10 mg/L only. This globule was no longer apparent on Day 1 of the study. Analytical results show a steady increase in levels of total radioactivity over the first seven days of the study, culminating in 89 and 69% of the applied dose at the two highest exposure levels.

Based on the liquid scintillation counts, the concentration of [I4C-]test substance in the overlying water was 26-93% of applied dose on Day 0, and 63-79% on Day 28. Loss of test compound from the overlying water during the study period was no greater than 15-20% indicating that, once in aqueous solution (probably in the form of the hydrolysis product, haloxyfop-R acid), the test substance did not greatly partition to the sediment samples of the pore water collected after the 28-day exposure period were highly variable but on average accounted for only 0.93-1.2% of the total test substance added to each vessel. Samples of the dry sediment on Day 28 contained 15-28% of the total amount of test material added to each vessel. The total amount of material accounted for in all of the fractions on Day 28 ranged from 92 to 96% of the total amount of radio labelled material added to each vessel.

Description of key information

28 d EC50 (Chironomus riparius): >10 mg/L (highest dose tested) (emergence and development rate); BBA recommended methodology, Streloke, M. and Kopp, H. Long term toxicity test with Chironomus riparius: Development and validation of a new test system; Reliability = 1

28 d NOEC (Chironomus riparius): 3.2 mg/L (emergence and development rate); BBA recommended methodology, Streloke, M. and Kopp, H. Long term toxicity test with Chironomus riparius: Development and validation of a new test system; Reliability = 1

Key value for chemical safety assessment

EC50 or LC50 for freshwater sediment:

10 mg/kg sediment dw

EC10, LC10 or NOEC for freshwater sediment:

3.2 mg/kg sediment dw