2,6-dibromo-4-cyanophenyl octanoate

Long-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

08 Feb - 15 Mar, 1991

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EPA OPP 72-4 (Fish Early Life-Stage and Aquatic Invertebrate Life-Cycle Studies)

Version / remarks:

1982

Deviations:

yes

Remarks:

as mentioned in the report: conductivity and samples anaysis

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

During the in-life phase of the definitive study, water samples were removed from both replicate test solutions of each treatment level and both types of the controls on test days 0, 2, 4,11,18, 25, 32, 34 and 35 for analysis of test material concentration.
Sampling procedures typically include syphoning from the midpoint of the test container into graduated cylinders for volumes greater than 200 mL and pipetting from the midpoint of the test container for sample volumes less than or equal to 200 mL. All sample volumes are transferred directly into 250-mL screw cap bottles.
The glass bottles into which the sample was delivered must be unetched. Additionally, it was deemed necessary to add 1 mL of 1M NaOH to the collection/reaction bottle immediately following collection of samples analyzed for test substance; otherwise the relative yield of analyte was significantly diminished.

Vehicle:

yes

Remarks:

Acetone

Details on test solutions:

Throughout the exposure period, no visible sign of insoluble material (e.g., film of material on the surface of the test solution, precipitate) was observed in the diluter system's mixing chamber or any of the exposure aquaria.
Stock solutions (e.g., 4.46 mg a.i./mL) were prepared on test days -4, 3, 14 and 28 by diluting 0.459 g of test substance (0.446 g as active ingredient) with acetone to a total volume of 100 mL.
A 50-mL gas tight syringe with a stainless steelneedle was mechanically activated during each diluter cycle to inject 0.035 mL of the stock solution (4.46 mg a.i./mL) into the diluter's chemical mixing chamber containing 1.94 L dilution water. The mixing chamber was positioned over a magnetic stirrer which continuously mixed the contents. The solution contained in the mixing chamber constituted the highest test concentration and was subsequently diluted (50%) to provide the range of nominal exposure concentrations. A mechanical injector similar to that used to deliver the test material stock solution was used to deliver acetone to the solvent control aquaria.

Test organisms (species):

Pimephales promelas

Details on test organisms:

Fathead minnow eggs were obtained from brood stock maintained at Laboratory. On the day prior to test initiation, spawning tiles were placed in the fathead
minnow brood culture unit. The eggs were collected from the tiles and impartially distributed to the egg incubation cups in the following manner: fourteen unlabeled, unassigned petridishes were set in a shallow waterbath maintained at 25 °C. A small amount of water from the control aquaria was placed in each dish. The collected eggs were then counted into each dish sequentially, five at a time, until each dish contained sixty eggs.
During the definitive test, subsequent to the completion of hatch (day 5), the fry were fed live brine shrimp nauplii (Anemia salina) three times daily on weekdays and two times daily on weekends.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

35 d

Hardness:

37 - 39 mg/L CaCO3

Test temperature:

25 °C

pH:

6.9 - 7.1

Dissolved oxygen:

7.2 - 7.7 mg/L

Conductivity:

153 - 155 µmhos/cm

Nominal and measured concentrations:

Nominal concentrations: 5.0, 10, 20, 40, 80 µg a.i./L
Mean measured concentrations: 3.4, 5.7, 8.6, 18 , 39 µg a.i./L

Details on test conditions:

The test system was designed to provide five concentrations of the test material, a solvent control and a dilution water control. The solvent control contained the maximum amount of acetone present in any test concentration (0.018 mL/L). All treatment levels and both types of controls were maintained in duplicate. Test solutions were not aerated. Sixteen hours of light at 22 - 90 footcandles at the exposure solution surface were provided each day. Each test aquarium measured 39 x 20 x 25 cm with a 19.5-cm high side drain that maintained a constant exposure solution volume of approximately 15 L.
Dead embryos were counted daily until hatching was complete. Hatching was deemed complete (exposure day 5) when no more than 10 % unhatched viable embryos remained in any control or treatment level egg incubation cup. The 30-day post-hatch larval exposure was initiated when 40 live larvae were impartially selected from the surviving larvae in each incubation cup on test day 5 and placed into their respective exposure aquaria. Dead larvae were removed when observed and behavior and appearance of larvae were observed and recorded daily. Following 30 days post-hatch, biomass loading did not exceed 0.12g/L of flowing test solution/day in any exposure aquaria. Larval survival was estimated at least twice weekly. At 30 days post-hatch exposure (test termination), the percentage larval survival was determined.

Key result

Duration:

35 d

Dose descriptor:

NOEC

Effect conc.:

4.9 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

act. ingr.

Basis for effect:

length

Remarks on result:

other: converted from Bromoxynil phenol to Bromoxynil octanoate

Duration:

35 d

Dose descriptor:

NOEC

Effect conc.:

3.4 µg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

other: Bromoxynil phenol

Basis for effect:

length

Details on results:

Fathead minnow survival at the completion of the hatching period (day 5) in the highest test concentration (39 µg/L) was 49 % and was significantly different when compared to the survival of the pooled control organisms.
The larval survival was adversely affected in the 39 µg/L treatment level.
The mean total length of larvae exposed to 3.4 µg/L averaged 32.4 mm which was comparable to the total length of pooled control larvae.
The mean wet weights of larvae exposed to all mean measured concentrations were statistically comparable to the mean wet weight of the pooled control larvae.

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

Validity criteria fulfilled:

not specified

Conclusions:

The present guideline study was conducted in compliance with GLP. Under the test conditions used, the NOEC (35 d), based on length, for Pimephales promelas was 0.0034 mg/L Bromoxynil phenol. This NOEC was converted to 0.0049 mg/L as Bromoxynil octanoate equivalent.

Description of key information

The overall NOEC for the early life stages of P. promelas is 0.0049 mg a.i./L.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Dose descriptor:

NOEC

Effect concentration:

ca. 0.005 mg/L

Additional information

In the key study the long-term effects of the substance towards fish were examined in early-life stage toxicity test with P. promelas under flow-through conditions (1991). The study was carried out according to GLP and US EPA-72.4 guidelines. Fish were exposed to mean measured concentrations of 0.0034 – 0.0057 – 0.0086 – 0.018 – 0.039 mg a.i./L, alongside with a control and a solvent control. Based on mean measured concentrations of the test substance a NOEC 0.0049 mg a.i./L was determined.

In the supporting study (1992), the toxicity of test material to rainbow trout was determined in a flow-through test according to OECD 204 guideline.The 28-days NOEC of the technical active ingredient was determined to be ≥ 0.047 mg a.i./L based on the mean measured concentration. This study wasconsidered suitable for supporting purpose.