2,6-dibromo-4-cyanophenyl octanoate

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EPA OPP 165-4 (Laboratory Studies of Pesticide Accumulation in Fish)

Version / remarks:

1982

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

yes

Details on sampling:

- Sampling intervals/frequency for test organisms: 3, 21, 28, 35 and 42 days after start of exposure to the test substance, followed by a depuration period of 14 days.
- Sampling intervals/frequency for test medium samples: 3, 21, 28, 35 and 42 days after start of exposure to the test substance, followed by a depuration period of 14 days.
- Sample storage conditions before analysis: The fish samples were frozen immediately and remained frozen throughout storage and processing for radioanalysis. The water samples remained frozen until they were analyzed.
- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods):
At each sampling day, six fish were sampled; three of these were separated into fillet (edible: body, muscle, skin, and skeleton) and viscera (non-edible: fins, head, and internal organs). The other three fish were treated as whole fish.
At each sampling day, 500 mL of water was taken from each aquarium. Polyethylene bottles were used for the control aquarium, and amber glass bottles were used for the test aquarium. On days 21, 28, and 42 of the uptake phase and on day 14 of the depuration phase, an additional 500 mL of water was taken for verification of the composition of the 14C-material in the exposure tank. The water was sampled for determination, then frozen for shipment to the sponsor.

Vehicle:

yes

Remarks:

Acetone

Details on preparation of test solutions, spiked fish food or sediment:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Diluter stock solutions were prepared from the Bluegill Bioconcentration Stock Solution (7.3 mg/mL in acetone) as needed by transferring a 0.68 mL aliquot to a 100 mL volumetric or a 1.71 mL aliquot to a 250 mL volumetric flask and diluting with acetone. The resultant diluter stock (50 mg/L) was then transferred to a brown glass bottle for use by the diluter toxicant injection system. The remaining stock was stored in the freezer until needed. The diluter system was calibrated by volumetric measurements of the mixing cell volumes. A 0.10 mL aliquot of 14C-bromoxynil octanoate diluter stock solution (50 mg/L) was delivered to 1664 ml of dilution water in the toxicant mixing cell to yield a nominal exposure concentration of 3.0 µg/L.
- Controls: The control aquarium received acetone (0.10 mL), the same amount delivered to the treated aquarium.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Acetone
- Concentration of vehicle in test medium (stock solution and final test solution(s) at different concentrations and in control(s)): Concentrations of aceton in treatment and controls was 0.0001%.

Test organisms (species):

Lepomis macrochirus

Details on test organisms:

TEST ORGANISM
- Common name: Bluegill Sunfish (Lepomis macrochirus)
- Source: The 240 Bluegill Sunfish (Lepomis macrochirus) , Lot No. 6990, used in the study were obtained from Osage Catfisheries, Inc. (Osage Beach, MO) on October 31, 1990.
- Age at study initiation: The age of the fish at the time of testing was estimated to be less than one year.
- Length at study initiation (length definition, mean, range and SD): The Bluegill Sunfish used for this experiment had an initial mean standard length of 56 ± 2.0 mm.
- Weight at study initiation (mean and range, SD): The Bluegill Sunfish used for this experiment had an initial mean weight of 6.33 ± 1.27 g.
- Weight at termination (mean and range, SD): The Bluegill Sunfish from the control sampling at the end of the depuration phase had a mean weight of 11.7 ± 2.3 g and a mean standard length of 68.5 ± 4.5 mm.
- Health status: The test fish appeared to be in good health throughout the study. No fish died during the conduct of the study.
- Description of housing/holding area: All test fish were held in culture tanks on a 16-hour daylight, 8 hour dark schedule with a 30-minute transition photoperiod.
- Food type, amount and frequency: During the holding (culture) and test periods, the fish received Rangens® Salmon Starter (ABC Lot #'s 38510-2, 39106-2 and 39107) ad libitum (~3.0 grams per aquarium per day).

ACCLIMATION
- Acclimation period: The uptake phase was initiated by impartially transferring 120 fish in small groups from the culture tank to the control and treatment aquaria. Since the temperature of the culture and test chambers at study initiation were both 21°C and the dilution water used in the culture and test systems were identical, no acclimation period was necessary.

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Total exposure / uptake duration:

42 d

Total depuration duration:

14 d

Hardness:

212 - 330 mg/L as CaCO2

Test temperature:

22 ± 2 °C

pH:

The pH was measured in the control and treated chambers throughout the test. The pH values of the treated aquarium were consistent with the control throughout the study and ranged from 7.6 to 8.3.

Dissolved oxygen:

Dissolved oxygen was measured in the control and treated chambers throughout the test. The dissolved oxygen concentrations, which ranged between 5.5 and 8.3 mg/L, and stayed between 65 and 99-percent saturation at 22°C, respectively, which was considered adequate for testing.

TOC:

<1.0 - 1.14ppm

Conductivity:

380 - 580 µMhos/cm

Details on test conditions:

- A modified proportional diluter system described by Mount and Brungs, with a Hamilton® Model 420 dual syringe dispenser, was used for the intermittent introduction of 14C-bromoxynil octanoate and diluent water into the 100-liter glass test aquaria.
- Aerated well water was delivered to the test aquaria at an average rate of 320 mL/minute/aquarium during the 42-day exposure period, an amount which was sufficient to replace the 70-liter test volume approximately 6.6 times in a 24-hour period.
- The diluter system consisted of one 3.0 µg/L nominal concentration treated aquarium and one control aquarium. The control aquarium also received an amount of acetone (0.10 mL) which was equivalent to that delivered to the treated aquarium.
- All diluter components which came into contact with the test compound were constructed of glass.
- The aquaria were also covered with glass to prevent any potential compound volatility problems.
- The test aquaria were immersed in a water bath which was brought up to the test temperature of 22°C (±2°C) by electronically controlled- submersible heating elements and circulating water after the test fish were added.

Test Procedure - Uptake Phase
- Before initiating the uptake portion of the study, the test solution was allowed to flow through the test aquaria for an equilibration period of ~ 12 days. The concentration was confirmed by radioanalysis before introducing the test fish.
- The uptake phase was initiated by impartially transferring 120 fish in small groups from the culture tank to the control and treatment aquaria. Since the temperature of the culture and test chambers at study initiation were both 21°C and the dilution water used in the culture and test systems were identical, no acclimation period was necessary. These fish were observed initially and twice daily during the exposure period for any mortality and/or adverse behavior.
- Fillet (edible) and viscera (non-edible) portions were sectioned. After sampling the fish tissue and water, all samples were frozen. The fish tissue remained frozen throughout storage and processing for radioanalysis. The water and tissue samples were radioassayed following the procedure outlined in the Analytical Methods Section.

Test Procedure - Depuration Phase
- On day 42 of the exposure period, the addition of the 14C-bromoxynil octanoate test material was terminated. The water in each test aquarium was removed by siphoning until a depth of approximately 8 cm of water remained (~20 L) in each aquarium. The aquaria were filled to a volume of approximately 70 liters with well water. This water was then removed until a depth of approximately 8 cm of water remained and the aquaria were filled again with approximately 70 liters of well water.
- The fish were then exposed to flowing well water for 14 days.
- Water and fish tissue samples were frozen in the same manner as during the uptake phase.

TEST MEDIUM / WATER PARAMETERS
- Metals: Aluminum <0.20 ppm, Arsenic <5.00 ppb, Boron 0.378 ppm, Cadmium < 0,007 ppm, Chromium <0.05 ppm, Cobalt <0.05 ppm, Copper < 0.025 ppm, Fluoride 1.1 ppm, Iron 0.148 ppm, Lead <3.0 ppm, Mercury <0.40 ppb, Nickel <0.04 ppm, Silver <1.00 ppb, Zinc <0.02 ppm

Nominal and measured concentrations:

Nominal concentration: Sub-lethal concentration, 3.0 µg/L
Measured concentration: 3.1 µg/L

Reference substance (positive control):

no

Details on estimation of bioconcentration:

- The uptake rate constant (K1) and depuration rate (K2) were determined by the Dow BIOFAC computer program. This is a non-linear kinetic modeling program which provides optimal parameter estimates of rate constants K1 and K2 by utilizing the actual (observed) bioconcentration study data. The bioconcentration factor at steady-state, the time to reach 90% of steady-state and the time to reach 50% of test 14C-bromoxynil octanoate clearance (depuration) were also calculated from the estimated rate constants. A measure of the variability of the estimated parameters were provided by the standard deviation of each estimate. All calculations are based on the values for whole fish analysis.

Conc. / dose:

3.1 µg/L

Temp.:

22 °C

pH:

7.7

Type:

BCF

Value:

>= 120 - <= 220 dimensionless

Basis:

other: Whole fish

Calculation basis:

steady state

Remarks on result:

other:

Remarks:

BCF: 180 ± 40

Conc. / dose:

3.1 µg/L

Temp.:

22 °C

pH:

7.7

Type:

BCF

Value:

>= 40 - <= 60 dimensionless

Basis:

other: Fillet

Calculation basis:

steady state

Remarks on result:

other:

Remarks:

BCF: 50 ± 10

Conc. / dose:

3.1 µg/L

Temp.:

22 °C

pH:

7.7

Type:

BCF

Value:

>= 230 - <= 370 dimensionless

Basis:

other: Viscera

Calculation basis:

steady state

Remarks on result:

other:

Remarks:

BCF: 300 ± 70

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

2.6 d

Rate constant:

overall uptake rate constant (L kg-1 d-1)

Value:

46.88

Rate constant:

overall depuration rate constant (d-1)

Value:

0.27

Details on kinetic parameters:

- Uptake rate constant k(s): 46.88 ± 7.8 mg/kg fish per mg/L water per day
- Depuration rate constant k(e): 0.27 ± 0.04 per day
- Computation / data analysis: A BIOFAC modeling computer program was used to analyze the data and to calculate the uptake rate constant and the depuration rate constant for the whole fish.

Metabolites:

Bromoxynil or conjugates of bromoxynil were the only metabolites isolated and identified. These metabolites accounted for 90% of the total radioactive residue from the day 42 fillet samples.

Details on results:

- Water concentrations ranged from 1.3 to 4.7 µg/L through 42 days of the bioconcentration (uptake) phase. The average water concentration (using the mean value for each sample day) daring the uptake phase was 3.1 (±0.75) µg/L. This represented 103% of the nominal concentration of 3.0 µg/L.
- The bioconcentration factors (BCF) were calculated for the whole fish, fillet, and viscera. Bioconcentration Factors: Whole Fish 180 ± 40; Fillet 50 ± 10; Viscera 300 ± 70.
- Daily bioconcentration factors for whole fish increased from 20 at four hours after the initiation of the study to 230 on day 28, with a BCF on day 42 of 210. In fillet tissue, the initial BCF was 8, increasing to 63 on day 28 with a day 42 BCF of 42. In viscera, the four-hour BCF was 29. The BCF increased to 400 on day 28, with a final BCF on day 42 of 250.
- In whole fish, 50% depuration was reached at 2.6 ± 0.42 days into the depuration period.
- An analysis of depuration rates by day 14 of the elimination period showed 97, 91, and 85% depuration in the fillet, whole fish, and viscera, respectively.
- Mean recovery data for 14C-bromoxynil octanoate in tissue sample oxidations were 97% for all three tissue types.
- Temperature in the test aquaria was measured twice daily and ranged from 21° to 23°C during the study. The dissolved oxygen concentrations, which ranged between 5.5 and 8.3 mg/L, and stayed between 65 and 99-percent saturation at 22°C, respectively, which was considered adequate for testing. The pH values of the treated aquarium were consistent with the control throughout the study and ranged from 7.6 to 8.3.

Reference 2

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

other: U.S. Environmental Protection Agency guidelines for pesticide registration

GLP compliance:

no

Radiolabelling:

yes

Test organisms (species):

Ictalurus punctatus

Route of exposure:

sediment

Test type:

static

Water / sediment media type:

natural soil

Total exposure / uptake duration:

30 d

Total depuration duration:

14 d

Conclusions:

A bioconcentration study was conducted exposing channel catfish (Ictalurus punctatus) to 14C-bromoxynil in a static aquatic environment containing sandy loam soil incorporated with 14C-bromoxynil octanoate at a nominal level of 0.5 mg/kg. A control population of channel catfish was treated under the same conditions except that the soil was not treated with 14C-bromoxynil octanoate. The mean treated soil 14C-residues on Day 0 of aging and Day 30 of bioconcentration were 0.40 mg/kg and 0.11 mg/kg (14C-bromoxynil octanoate equivalents), respectively. This represents a 73% reduction of 14C-radioactivity in the soil and could not be accounted for in the water and fish. There was generally no uptake or accumulation of 14C-bromoxynil octanoate in water, whole fish, fillet or viscera as all calculated 14C-residues were below quantifiable limits during the 30 days of uptake. Therefore, metabolite characterization was not needed.

Description of key information

log BCF: 2.26 (BCF= 180±40) for whole fish (Lepomis macrochirus).

Key value for chemical safety assessment

BCF (aquatic species):

180 dimensionless

Additional information

In a GLP study, according to United States EPA Pesticide Registration Guidelines, Subpart N, Environmental Fate, 40 CFR.163 , the bioconentration factor for 14C-labelled 2,6-dibromo-4-cyanophenyl octanoate was investigated in a simulation study. Lepomis macrochirus were exposed to 14C-labelled test substance in a flow-through system for 42 days, followed by a depuration period of 14 days. The BCF for whole fish was 180±40. In whole fish, 50% depuration was reached at 2.6 ± 0.42 days into the depuration period.

 

Another study showed no uptake or accumulation of 14C-2,6-dibromo-4-cyanophenyl octanoate in water, whole fish, fillet or viscera as all calculated 14C-residues were below quantifiable limits.