2,6-dibromo-4-cyanophenyl octanoate

Sediment toxicity

Link to relevant study record(s)

Reference

Endpoint:

sediment toxicity: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 Jan - 20 Feb, 1998

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: BBA GUIDELINE

Version / remarks:

1995

Deviations:

no

Remarks:

according to the report. Slight deviation in the test design and validity criteria compared to OECD 219 (2004).

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

The test solutions were sampled and analyzed for the presence of bromoxynil octanoate and bromoxynil phenol one hour after test initiation, after 7 days and at test termination (Day 22). The stock solutions were also analyzed one hour after test initiation.

Vehicle:

yes

Remarks:

Dimethylformamide

Details on sediment and application:

Dilution water consisted of reconstituted water.
Sediment preparation:
An artificial sediment (according to O.E.C.D. test guideline N° 207) was prepared.
An appropriate quantity of wet artificial sediment (to obtain a depth of 2 cm) was filled into each test beaker and left to stand for 24 hours in a fume cupboard.
The dilution water was then poured into each beaker very slowly, taking care not to disturb the sediment. The test vessels were prepared approximately 1 week before test initiation and were acclimatized under the test conditions. The test vessels contained 200 g of sediment and 2.5 L of dilution water (depth approximately 20.0 cm). The exact volume of water added was recorded, and the level marked outside on the test vessel.

Solutions preparation:
A stock solution for the highest test substance concentration was prepared by dissolving 10.0 mg of test substance in 10 ml of solvent (dimethylformamide: DMF). The test solution for each replicate of this concentration was prepared by adding volumes of this stock solution to the
water column of each test vessel. Stock solutions for the three lower test concentrations were prepared by serial dilutions of the first stock solution with DMF and subsequent addition to the overlying dilution water. The final concentration of solvent at each concentration level was 100 µL/L.

Application:
One day after adding the larvae, the appropriate volume (0.25 mL) of each stock solution was added to the water column of the test system. The additionswere made just below the water surface using a pipette, the water column was then gently stirred to ensure homogeneous distribution without disturbing the sediment. No indications of insolubility of the test substance in the overlying water were observed

Test organisms (species):

Chironomus riparius

Details on test organisms:

The first instar chironomid larvae (2 to 3 days old) used in this toxicity test were hatched from egg masses removed from in-house laboratory cultures. The chironomids were healthy and no treatments were applied to the culture prior to the test.
The chironomids were cultured in 10L aquaria containing a layer of fine quartz sand (depth: 2.0 cm approximately), overlain with a 6 - 10 cm (approximately 5 1) layer of culture medium.
The culture aquaria were held in a temperature controlled room at 20 ± 2°C with a photoperiod of 16 hours light, 8 hours darkness.
One third of the volume of dilution water was renewed three times per week. The dilution water was aerated before use. The larvae were fed 10 - 20 ml of a 20 mg/mL solution of a fish flake food.

Study type:

laboratory study

Test type:

static

Water media type:

freshwater

Type of sediment:

artificial sediment

Limit test:

no

Duration:

22 d

Exposure phase:

larvae from first generation (P)

Hardness:

159 mg/L CaCO3

Test temperature:

19.8 - 21.5 °C

pH:

6.93 - 8.13

Dissolved oxygen:

4.3 - 8.5 mg/L

Conductivity:

548 µS/cm

Nominal and measured concentrations:

Nominal concentrations in overlying water: 12.5, 25, 50 and 100 µg/L
Measured concentrations after 1 hour exposure in overlying water: 6.4, 12.6, 24.2, 60.2 µg/L (48 - 60 % recovery)
Seven days after application of the test substance, the test substance had completely disappeared in the overlying water.

Details on test conditions:

The study was conducted in 3 L glass beakers measuring 10-13 cm in diameter and with a height of approximately 27.5 cm. First instar larvae then (2-3 days old) were introduced into the test vessels one day before test initiation. The test system consisted of four test substance concentrations, a dilution water control group and a solvent control group. Each test group consisted of four replicate vessels. Each test vessel contained 25 test organisms. The larvae were fed at least 3 times per week at a rate of approximately 1 mg fish food per day per larvae. Gentle aeration was provided through a glass Pasteur pipette situated ca. 2.5 cm above the sediment layer. The measured light intensity incident on the test vessels during light hours was within the range 1056 - 1150 lux.
The final emergence of adult midges was observed 14 days after test initiation in the dilution water control group, the test was terminated after 22 days rather than 28 days exposure to the test substance.

Key result

Duration:

22 d

Dose descriptor:

NOEC

Effect conc.:

ca. 100 µg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

emergence rate

Details on results:

At least 84 % emergence was observed in each replicate of the dilution water control group and the mean development rate for larvae in this group was 0.091 (range 0.089 - 0.093).
84 - 92 % emergence was recorded in four replicates of the solvent control group.
80 - 100 % emergence was recorded from the test vessels exposed to the test substance and the development rate for larvae in these groups ranged from 0.085 - 0.092.
No physical or behavioral alterations were observed in any of the test groups compared to the controls.
No trends were observed in the ratio of males to females between replicates and between the control groups and the treated groups. Therefore male and female emergence was pooled for subsequent statistical analysis of the test data.

Please refer to "overall remark/ attached background material" field for result tables.

The biological validation criteria in the control group were fulfilled emergence 70 % (84 %) and mean development rate within the range 0.05 - 0.1 (ranged between 0.089 and 0.093).

The validation criteria for pH 6.0 - 9.0 units (6.93 to 8.13) and oxygen > 2.5 mg/L (at least 4.3 mg/L) were both met.

Validity criteria fulfilled:

yes

Remarks:

According to the report. For further details please refer to “Any other information on results incl. tables”.

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the NOEC 22-d for Chironomus riparius was > 0.100 mg/L, based on emergence.

Description of key information

From toxicity key study, the 22-day NOEC was 0.1 mg test substance/L based on emergence rate.

Additional information

In the key study (1998), the chronic toxicity to sediment organisms was investigated after 22 days of exposure to spiked water. The study was conducted according to BBA Guideline, under GLP conditions. Chironomus riparius were exposed to the nominal concentrations of 12.5, 25, 50 and 100 µg/L, alongside with a solvent control. Mean measured concentrations from day 0 and 1 hour after application ranged from 48 % to 60 % recovery of nominal concentration. Based on the nominal concentration 22-day NOEC was 0.1 mg/L.