Fenamiphos

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:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EPA OPP 72-6 (Aquatic Organism Accumulation Tests)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: EPA 40 CFR, Sec. 158.145

Deviations:

no

GLP compliance:

yes

Radiolabelling:

yes

Details on sampling:

- Sampling intervals/frequency incl. sample preparation for test organisms: Fish were sampled during the uptake phase 1, 3, 7, 14, 21, 28 d, in the uptake phase on day 1, 3, 7, 10 and 14. On these dates, three fish from each chamber were collected and pooled into control and treated samples (total of six fish each for control and treated). Three of the pooled control and treated fish were dissected into fillet/edible (body, muscle, skin, skeleton) and viscera/nonedible (fins, head, internal organs). The remaining three fish from the pooled control and treated samples were reserved for whole fish analysis. The fillet, viscera and whole fish samples for the control and treated groups were stored frozen until radioassay. At this time, the individual samples were homogenized with dry ice in a grinder, allowed to sublime, weighed and combusted in a Packard® 306B Tricarb Sample Oxidizer. Additional fish were collected for metabolite characterization on certain sampling dates. On metabolite sample days 21 and 28 of the uptake phase, additional fish from each aquarium were sampled and pooled into control and treated groups. These fish from each group were dissected in the same manner as described above. All remaining tissue samples were stored frozen until shipment to the study sponsor for possible metabolite characterization. The levels of C-14 calculated as concentrations of the radiolabelled test item in whole fish, fillet and viscera samples were determined by duplicate analysis of samples from the homogenates using sample combustion followed by liquid scintillation counting.

- Sampling intervals/frequency for test medium samples: On each sampling day, approximately 500 mL of water was removed from each aquarium using 16 oz. polyethylene bottles designated for the control and treated aquaria. An additional 500 mL of water was collected on days 21 and 28 of the uptake phase and day 14 of the depuration phase for possible metabolite characterization. The concentrations of carbon-14 calculated as C-Nemacur in water were calculated by liquid scintillation counting of duplicate 10-mL samples pipetted directly from each control and test tank. This yielded 4 control and 4 treated samples. These samples received a 10-mL aliquot of scintillation cocktail Counting efficiencies were determined for each treatment sample using a quench calibration curve based upon the external standard ratio (ESR) method of analysis.

- Sample storage conditions before analysis: deep frozen until analysis

Vehicle:

yes

Remarks:

acetone

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

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:flow-through using proportional diluter
- Controls: negative control
- Chemical name of vehicle: acetone
- Concentration of vehicle in test medium: not specified

Test organisms (species):

Lepomis macrochirus

Details on test organisms:

TEST ORGANISM
- Common name: Bluegill Sunfish
- Source: Osage Catfisheries, Inc., Osage Beach, Mo. USA
- Length at study initiation: 64 mm (+/- 4.4 mm, mean for control)
- Weight at study initiation: 8.2 g (+/- 1.9 g, mean for control)

Route of exposure:

aqueous

Justification for method:

aqueous exposure method used for following reason: preferred exposure route to derive BCF

Test type:

flow-through

Water / sediment media type:

natural water: freshwater

Remarks:

clean wellwater

Total exposure / uptake duration:

28 d

Total depuration duration:

14 d

Hardness:

225-275 ppm CaCO3 (hardness of dilutionwater)

Test temperature:

22 (+/- 2) °C

pH:

7.8 - 8.3 (pH of dilutionwater)

Dissolved oxygen:

9.2 - 10.1 ppm (dissolved oxygen in dilution water)

Salinity:

not applicable

Conductivity:

not specified

Details on test conditions:

TEST SYSTEM
- Test vessel: aquaria
- Material, size, headspace, fill volume: glass, 120 L
- Aeration: test chambers were aerated throughout the test to maintain dissolved oxygen-levels at or above 40 % saturation
- Type of flow-through: proportional diluter
- Renewal rate of test solution: 373 mL/minute/aquarium
- No. of organisms per vessel: 125 fish
- No. of vessels per concentration: 2
- No. of vessels per control: 2


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: aquatic lab well water

OTHER TEST CONDITIONS
- Photoperiod: 16 hours light, 8 hours darkness
- Light intensity: daylight


RANGE-FINDING / PRELIMINARY STUDY: performed, dynamic acute fish toxicity test
- Results used to determine the conditions for the definitive study: yes

Nominal and measured concentrations:

nominal: 0.80 µg/L; measured value not specified

Reference substance (positive control):

not required

Details on estimation of bioconcentration:

In evaluating the data obtained from the bioconcentration study, a steady-state approach was used. Bioconcentration factors for the uptake period were determined by dividing the concentration of the radiolabelled test item in the tissue by the mean concentration of the radiolabelled test item in water up to and including that day. The uptake rate constant (k1) and depuration rate constant (k2) were determined by using a non-linear kinetic modeling program which provided optional parameter estimates of rate constants k1 and k2 by utilizing the actual (observed) bioconcentration study data. The concentration factor at steady-state, the time to reach 90 % of steady-state, and the time to reach 50 % of test compound 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.

Key result

Conc. / dose:

0.95 µg/L

Temp.:

22 °C

pH:

7.8

Type:

BCF

Value:

110 dimensionless

Basis:

whole body w.w.

Time of plateau:

0.72 d

Calculation basis:

steady state

Details on kinetic parameters:

- Uptake rate constant k(s): 370 µg/day
- Depuration rate constant k(e): 3.2 L/day

Metabolites:

not reported

Results with reference substance (positive control):

not applicable

Details on results:

not specified

Reported statistics:

not specified

For supplementary information, please refer to attached tables and figures.

Validity criteria fulfilled:

yes

Conclusions:

The test item is accumulated and excreted very rapidly by bluegill sunfish with a steady state mean biocon-centration factor (BCF) of 110 for whole fish.

Executive summary:

A dynamic 42-day study according to EPA 72-6 and EPA 40 CFR, Sec. 158.145 was conducted under GLP conditions to evaluate the bioconcentration of the 14C-radiolabelled test item by bluegill sunfish (Lepomis macrochirus). A flow-through proportional diluter system was used to maintain a mean water test item concentration of 0.95 (+/- 0.081) µg/L for a 28-day exposure period. Radioanalysis of fillet, whole fish and visceral portions were performed throughout the exposure period. Uptake tissue concentrations of the test item ranged from 6.8 to 24 µg/kg for fillet, 13 to 89 µg/kg for whole fish, and 21 to 230 µg/kg for viscera. To measure the elimination of the test item, the test fish were placed in clean water for 14 days. Radioanalysis throughout the depuration period indicated >95, >98 and >99 % depuration from fillet, whole fish and viscera, respectively. The fillet concentration of the test item dropped from a day 28 uptake value of 20 µg/L to less than minimum quantifiable limits (MQL), 1.03 µg/kg, by day 3 of the depuration period. Whole fish levels decreased from 58 µg/kg on day 28 uptake to less than MQL (1.04 µg/kg) by day 3 of depuration; whereas, viscera concentrations dropped from 93 µg/kg on day 28 uptake to less than MQL (1.08 µg/kg) by day 7 depuration. A non-linear two-compartment kinetic modeling computer program (BIOFAC) was used for analysis of the uptake/depuration whole fish data. This method estimated the uptake rate constant (k1) of 370 (+/- 68), clearance rate constant (k2) of 3.2 (+/- 0.18), time for 50 % clearance of 0.22 (+/- 0.013) days, bioconcentration factor (BCF) of 110 (+/- 22) and time to reach 90 % of steady-state of 0.72 (+/- 0.042) days.

Description of key information

The test item is accumulated and excreted very rapidly by bluegill sunfish (Lepomis macrochirus) with a steady state mean bioconcentration factor (BCF) of 110 for whole fish.

Key value for chemical safety assessment

BCF (aquatic species):

110 dimensionless

Additional information

A dynamic 42-day study according to EPA 72-6 and EPA 40 CFR, Sec. 158.145 was conducted under GLP conditions to evaluate the bioconcentration of the 14C-radiolabelled test item by bluegill sunfish (Lepomis macrochirus). A flow-through proportional diluter system was used to maintain a mean water test item concentration of 0.95 (+/- 0.081) µg/L for a 28-day exposure period. Radioanalysis of fillet, whole fish and visceral portions were performed throughout the exposure period. Uptake tissue concentrations of the test item ranged from 6.8 to 24 µg/kg for fillet, 13 to 89 µg/kg for whole fish, and 21 to 230 µg/kg for viscera. To measure the elimination of the test item, the test fish were placed in clean water for 14 days. Radioanalysis throughout the depuration period indicated >95, >98 and >99 % depuration from fillet, whole fish and viscera, respectively. The fillet concentration of the test item dropped from a day 28 uptake value of 20 µg/L to less than minimum quantifiable limits (MQL), 1.03 µg/kg, by day 3 of the depuration period. Whole fish levels decreased from 58 µg/kg on day 28 uptake to less than MQL (1.04 µg/kg) by day 3 of depuration; whereas, viscera concentrations dropped from 93 µg/kg on day 28 uptake to less than MQL (1.08 µg/kg) by day 7 depuration. A non-linear two-compartment kinetic modeling computer program (BIOFAC) was used for analysis of the uptake/depuration whole fish data. This method estimated the uptake rate constant (k1) of 370 (+/- 68), clearance rate constant (k2) of 3.2 (+/- 0.18), time for 50 % clearance of 0.22 (+/- 0.013) days, bioconcentration factor (BCF) of 110 (+/- 22) and time to reach 90 % of steady-state of 0.72 (+/- 0.042) days.