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

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

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:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

according to guideline

Guideline:

EPA OPP 72-6 (Aquatic Organism Accumulation Tests)

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Phenyl labelled DOWCO 453 ME
Specific activity: 11.7 mCi/mmole
Radiochemical purity: >98%

Radiolabelling:

yes

Details on sampling:

- Sampling intervals/frequency for test organisms: Fish were sampled at 0.5, 1, 2, 4, 8, 14, 21, and 28 days during a 28-day uptake period and on days 1, 2 and 4 of the clearance phase. After four days of clearance, all the remaining fish in each aquaria were sacrificed.
- Sample storage conditions before analysis: Individually frozen
- Details on sampling:
Uptake phase: Of these five fish, one was combusted for a total radioactivity level in whole fish, two were separated into fillet (muscle) and remainder (head, skin, viscera, skeleton) and combusted for total radioactivity in each portion, and two were extracted for parent/metabolite characterization. The only exception to this was with the 0.5 day sampling for which no fish were extracted; instead two fish were frozen as retainers for future analysis, if necessary. Throughout the uptake phase, fish from the control aquarium were sacrificed at the same frequency as those from the exposure aquarium and used for blanks and recovery determinations. Control fish were sacrificed in a similar manner as described above for exposure fish.
Clearance phase: After four days of clearance, all the remaining fish in each aquaria were sacrificed. At all clearance phase sampling points one clearance fish was Combusted for total radioactivity in whole fish, two were separated into fillet and remainder and Combusted for total radioactivity in each portion, and on days 1 and 2, two were extracted for parent/metabolite characterization. As in the uptake portion of the experiment, the control fish were used for blanks and recovery determinations.
Determinations of total radioactivity in water samples were made by direct counting of 5-ml aliquots of the water mixed with 15 mL Aquasol, on a Beckman LS-9800 Liquid Scintillation (LS) Spectrometer. During the uptake and clearance phases of the experiment daily water samples were taken for LS counting.
Samples of water from the exposure aquarium were analyzed at least once a week for parent and metabolites during the uptake portion of the experiment.

Vehicle:

yes

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

PREPARATION AND APPLICATION OF TEST SOLUTION
- Controls: Yes
- Chemical name of vehicle: Acetone
- Concentration: 3.50 µg [14C] DOWCO453 ME/mL acetone

Test organisms (species):

Lepomis macrochirus

Details on test organisms:

TEST ORGANISM
- Common name: Bluegill
- Strain: Lepomis macrochirus
- Source: Osage Beach Catfisheries, Columbia, Missouri)
- Length at study initiation: 3-4.5 cm
- Weight at study initiation: 0.5-0.7 g
- Description of housing/holding area: 110-L stainless steel tank
- Feeding during test
- Food type: Synthetic feed
- Frequency: Each day after any sampling and the feed was allowed to remain for at least 0.5 hrs

ACCLIMATION
- Acclimation period: 21 days
- Acclimation conditions: same as test
- Type and amount of food: synthetic diet

Route of exposure:

aqueous

Justification for method:

minimised test method used to support BCF estimates based on Kow

Test type:

flow-through

Water / sediment media type:

natural water

Total exposure / uptake duration:

28 d

Total depuration duration:

4 d

Hardness:

73-76 mg/L as CaCO3

Test temperature:

16.3 to 17.9°C

pH:

7.7 to 8.1

Dissolved oxygen:

8.1 to 9.6 mg/L

Salinity:

Alkalinity: 46 to 52 mg/L as CaC03

Conductivity:

140-150 µmhos/cm

Details on test conditions:

TEST SYSTEM
- Test vessel: 40-L glass aquaria. Three aquaria were positioned in the trough, a control aquarium, an exposure aquarium and a clearance aquarium. Each aquarium was equipped with a magnetic stirring bar to ensure that the water was well mixed. All parts of the dilutor system which contacted the dilution, water or exposure water were made of Teflon, glass, or silicone.
- Type of flow-through: Peristaltic diluter
- Renewal rate of test solution: Daily
- No. of fish per vessel: 85
- No. of vessels per control: 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The standard dilution water supply is pumped from the upper Saginaw Bay of Lake Huron off Whitestone Point and is limed and flocculated with ferric chloride at the City of Midland Water Treatment Plant. The water is sand filtered, pH adjusted with CO2 to ~pH 8, carbon filtered, and UV irradiated in the laboratory prior to use.

Nominal and measured concentrations:

0.33 µg/L

Key result

Conc. / dose:

0.33 µg/L

Temp.:

>= 16.3 - <= 17.9 °C

pH:

7.7

Type:

BCF

Value:

< 17 dimensionless

Basis:

other: whole fish

Calculation basis:

kinetic

Key result

Rate constant:

other: uptake rate constant (mL/g/day)

Value:

720

Rate constant:

other: biotransformation of test substance (days-1)

Value:

200

Rate constant:

other: clearance of metabolites (days-1)

Value:

0.82

Details on kinetic parameters:

- Uptake rate constant k(s): A computer simulation model was developed which estimated the uptake rate constant of the test substance from water to be about 720 mL/g/day. In addition, values for the rate constants for the biotransformation of the test substance and the clearance of the metabolites formed were estimated to be 200 days-1 and 0.82 days-1, respectively. These values correspond to half-lives of about 5 minutes and 0.8 days, respectively.

Metabolites:

The total 14C residue level within whole fish averaged about 0.27 µg/g test substance equivalents over the course of the uptake phase. The principal component of the 14C residue was DOWCO453 acid which accounted for an average of about 60% of the radioactivity. Two other polar metabolites were detected in the fish which accounted for an average of about 14% of the radioactivity and an average of about 25% of the radioactivity. Once transferred to clean water. all metabolites cleared quickly with similar clearance rates.

Details on results:

There was no fish mortality in any aquarium during either the uptake or clearance phase of the test and at no time during the entire experiment did the fish appear unhealthy or stressed.

Conclusions:

Estimated BCF (whole fish): <17

Executive summary:

Bluegill (Lepomis macrochirus Rafinesque) were exposed to a 14C-test substance concentration averaging 0.29 µg/L under flow-through conditions for 28 days following the guidelines EPA OPP 72-6 and 165-4. At the end of 28 days, the fish were transferred to clean water for a 4-day clearance period. Bluegill were periodically sampled and analyzed for total radioactivity in fillet (muscle), remainder (head, skin, viscera, skeleton), and whole fish. Whole fish were also extracted and analyzed for the test substance and metabolites.

Bluegill were found to rapidly absorb the ester from water which was then biotransformed at an extremely fast rate within the fish such that essentially no test substance was detected in the fish. The estimated bioconcentration factor for the test substance in whole fish was <17, based upon the detection limit for the ester in fish and the average concentration of the test substance in exposure water.

The total 14C residue level within whole fish averaged about 0.27 µg/g test substance equivalents over the course of the exposure period. The principal component of the 14C residue was DOWCO 453 acid which accounted for an average of about 60% of the radioactivity. Two other polar metabolites were detected in the fish which accounted for an average of about 14% of the radioactivity and an average of about 25% of the radioactivity, respectively. Once transferred to clean water, all metabolites cleared quickly with similar clearance rates.

A computer simulation model was developed which estimated the uptake rate constant of the test substance from water to be about 720 mL/g/day. In addition, values for the rate constants for the biotransformation of the test substance and the clearance of the metabolites formed were estimated to be 200 days^-1and 0.82 days^-1, respectively. These values correspond to half-lives of about 5 minutes and 0.8 days, respectively.

Key value for chemical safety assessment

BCF (aquatic species):

17 dimensionless