Chlorpyrifos

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

bioaccumulation in aquatic species: invertebrate

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

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:

14C-chlorpyrifos
Purity: 99+%

Radiolabelling:

yes

Vehicle:

yes

Remarks:

DMF

Test organisms (species):

other aquatic mollusc: Crassostrea virginica

Route of exposure:

aqueous

Test type:

flow-through

Total exposure / uptake duration:

28 d

Total depuration duration:

14 d

Key result

Value:

630 dimensionless

Key result

Value:

730 dimensionless

Validity criteria fulfilled:

yes

Conclusions:

BCF= 630 (Replicate A) and 730 (Replicate B)
RATE OF UPTAKE, k, (mL.g·-1.day-1): 160 (Replicate A) and 660 (Replicate B)
RATE OF DEPURATION, k2 (day-1) 0.30 (Replicate A) and 0.69 (Replicate B)

Executive summary:

Eastern oysters were exposed to one concentration of ['4C]-chlorpyrifos in saltwater and a solvent control containing N-N-dimethylformamide (DMF). Two replicate test chambers (A and B) were used for both the treatment and the solvent control groups. The test was conducted with a continuous flow diluter at the nominal concentration of 0.7 µg chlorpyrifos/ L. The test concentration was selected in consultation with the Sponsor. The solvent concentration administered in the solvent control and treatment groups was less than 0.1 mL DMF/L. Two replicate solvent control chambers each contained 112 oysters and each of two treatment replicate test chambers contained 113 oysters. The test consisted of an uptake phase and a depuration phase. During the uptake phase, oysters in the treatment group were exposed to [14C]- chlorpyrifos. Exposure began at test initiation, and continued for 28 days. At the beginning of the depuration phase, administration of the test substance was terminated. Depuration began on day 28, and continued for an additional 14 days. During both phases, water and whole oysters were sampled and analyzed for residues of total ['4C] activity (chlorpyrifos equivalents) by liquid scintillation spectrometry (LSS). Additional oysters were collected, separated into tissue and shell liquor components, and analyzed to examine the distribution of total ['4C] activity (chlorpyrifos equivalents). Whole oysters and water samples were collected on days 0,3,7,14,21 and 28 of the uptake phase, and on days 1, 3, 7, 10, and 14 during the clearance phase. Additional water samples were collected on day 0 of depuration. Oysters collected for tissue and shell liquor samples were collected on the same days as whole oyster samples during uptake and depuration phases beginning on day 3 of uptake and day 1 of depuration.

 

Eastern-oysters exposed to a nominal test concentration of 0.7 µgr·C14-chlorpyrifos/L using a continuous flow diluter system, accumulated the test substance rapidly. The resulting observed bioconcentration factor for total C14 in whole oysters in two treatment test chambers averaged 680. The observed total 14C bioconcentration factors in the oyster tissue fraction were greater than in whole oysters and averaged 1650 for the two test chambers. Conversely, total [14C]concentrations in the shell liquor fraction were lower and more variable and resulted in approximate BCF of 30 and 54 in the two test chambers, respectively. When uptake and clearance rate constants were calculated for whole oysters using the BIOFACo computer model and available residue data, the average BCF value from the two test chambers was 745. Similar calculations for edible oyster tissue produced on average BCF value of 1400. The clearance half-life for total 14C from whole oysters and oyster tissue averaged 1.6 and 2.2 days, respectively.

Reference 2

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:

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

Deviations:

no

GLP compliance:

no

Specific details on test material used for the study:

Radiochemical purity: 98%
Specific activity: 15.78 mCi/mmole (0.0450 µCi/µg)

Radiolabelling:

yes

Details on sampling:

- Sampling intervals/frequency for test organisms: 0.5, 1, 2, 4, 8, 15, 21, 28 and 30 days during a 30 day uptake period. On days 1, 3, 6, 9, 12 and 16 of the clearance phase, fish were sacrificed from the control and clearance aquariums. Five fish were sacrificed from each aquarium at 3, 6, 9 and 12 days while only four fish from each aquarium were sacrificed for the day 1 sampling. After 16 days of clearance, all the remaining fish in each aquarium were sacrificed.
- Sample storage conditions before analysis: Frozen
- Details on sampling and analysis of test organisms: Uptake period: At all time points except the 30-day sampling, five fish were sampled from the exposure aquarium. The fish were indiscriminately netted, pithed, rinsed with water from a squeeze bottle, dipped in clean water, blotted dry, weighed and individually frozen unless analyzed immediately. Of these five fish, one was combusted for a total radioactivity level in whole fish, one was separated into fillet (muscle) and remainder (head, skin, viscera, skeleton) was combusted for total radioactivity in each portion, two were extracted for parent/metabolite characterization, and the final fish was frozen for future analysis, as a retainer. At all clearance phase sampling points one clearance fish was combusted for total radioactivity in whole fish, one was separated into fillet and remainder was combusted for total radioactivity in each portion, and two were extracted for parent/metabolite characterization. The remaining clearance fish were frozen for future analysis, as a retainer.

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: The dilution water was delivered to a mixing chamber where it was mixed with the [14C]test substance in acetone stock solution which was delivered by a syringe pump. The contents of the mixing chambers were continuously stirred by magnetic stir bars and delivered to the appropriate aquarium.
- Controls: Dilution water was delivered to a mixing chamber where it was mixed with acetone which was delivered by a syringe pump
- Chemical name of vehicle: Organic solvent (acetone)
- Concentration of vehicle in the exposure and control water: 0.095 mL/L based on the delivery of dilution water and stock solution

PREPARATION OF SPIKED FISH FOOD
- Details on fish food: Synthetic diet

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Source: Mt. Lassen Trout Farms, Red Bluff, California
- Length at study initiation: 3.5-5 cm
- Weight at study initiation: 0.6-0.7 g
- Description of housing/holding area: 110-L stainless steel tanks with water
- Feeding during test
- Food type: Laboratory prepared diet
- Frequency: Each day after any sampling was completed

Route of exposure:

aqueous

Test type:

flow-through

Water / sediment media type:

other: standard dilution water

Total exposure / uptake duration:

30 d

Total depuration duration:

16 d

Hardness:

74 to 82 mg/L as CaCO3

Test temperature:

11.2-12.8°C

pH:

7.6-8.1

Dissolved oxygen:

8.4-10.1 mg/L

Conductivity:

145 to 160 µmhos/cm

Details on test conditions:

TEST SYSTEM
- Test vessel: 40-L glass aquaria
- Type: Closed
- Type of flow-through: Peristaltic
- No. of organisms per vessel: 85
- No. of vessels per concentration (replicates): 1
- No. of vessels per control / vehicle control (replicates): 1

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The standard dilution water supply for our laboratory 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.
- Particulate matter:
- Metals: Al, Co, Cu, Fe, Pb, Li, Ni, Ag, Tin, Zn
- Pesticides: Chlorinated hydrocarbons and organophosphates (amounting less than 0.05-0.15 µg/L)
- Chlorine: 14600 (total as Cl-)
- Alkalinity: 43-52 mg/L as CaCO3

OTHER TEST CONDITIONS
- Adjustment of pH: ~8 (adjusted with CO2)
- Photoperiod: 16 h light and 8 h dark

Nominal and measured concentrations:

0.30 µg/L

Reference substance (positive control):

no

Details on estimation of bioconcentration:

The results of the fish analyses were evaluated using BIOFAC. It is a computer program which uses a two compartment (fish and water) model to estimate uptake and clearance rate constants from measured concentrations of a compound in fish and water. BIOFAC then calculates other parameters such as time to 90% of steady-state and bioconcentration factor (BCF). BIOFAC was used to calculate K1 (the uptake rate constant), K2 (the clearance rate constant), time to 90% of steady-state, half-life for clearance, and bioconcentration factor using time, average chlorpyrifos concentration in water, and test substance or 14C-residue concentration in fish. BIOFAC also provided a graphical display of the experimental points With simulation curves.

Key result

Conc. / dose:

0.3 µg/L

Temp.:

12 °C

Type:

BCF

Value:

1 374 dimensionless

Basis:

other: whole fish

Calculation basis:

steady state

Key result

Conc. / dose:

0.3 µg/L

Temp.:

12 °C

Type:

BCF

Value:

725 dimensionless

Basis:

other: fish fillet

Calculation basis:

steady state

Key result

Elimination:

yes

Parameter:

DT50

Depuration time (DT):

3 d

Remarks on result:

other: Not only was the test substance almost totally cleared from the fish by the end of the 16 day clearance period but almost all of the 14C residue accumulated, parent or metabolite, has cleared from the fish by the end of the clearance phase.

Metabolites:

Within the fish, the test substance appeared to be first metabolized to 3,5,6-trichloro-2-pyridinol. Enzyme hydrolysis studies indicated that TCP was then further metabolized to a glucuronide conjugate and potentially a sulfate conjugate. The principal component of the 14C residue within the fish was the test substance which accounted for about 40 to 80% of the radioactivity. The conjugates each accounted for about 10 to 30% of the radioactivity while TCP accounted for about 5 to 20%.

Validity criteria fulfilled:

yes

Conclusions:

BCF: 1374 ± 321 (whole fish)
BCF: 725 ± 136 (fish fillet)

Executive summary:

Rainbow trout were exposed to a [14C]test substance concentration averaging 0.30 µg/L under flow-through conditions for 30 days. At the end of 30 days, the fish were transferred to clean water for a 16-day clearance period. The study was conducted following EPA OPP guideline 165-4. Trout were periodically sampled and analyzed for total radioactivity in fillet (muscle), remainder (head, skin, viscera), and whole fish. Whole fish were also extracted and analyzed for the test substance and metabolites.

The uptake and clearance data for the test substance was modeled using BIOFAC, a computer simulation program. The model estimated the bioconcentration factor (BCF) of the test substance in whole fish to be 1374 ± 321. The estimated BCF for the test substance in fish fillet was 725 ± 136. The estimated time to 90% of steady-state for both the test substance and total 14C residue was about 7 to 9 days. Once fish were moved to clean water, both test substance and total 14C residue cleared rapidly with half-lives of about 2 to 3 days.

Within the fish, the test substance was metabolized to 3,5,6-trichloro-2-pyridinol (TCP) which appeared to be further metabolized to two different conjugates. The principal component of the 14C residue within the fish was the test substance (around 40 to 80%). The conjugates each accounted for about 10 to 30% of the 14C residue while TCP accounted for about 5 to 20%. This distribution pattern of parent/metabolites applied to both the uptake and clearance phases of the experiment.

Description of key information

Catfish (Ictalurus punctatus); BMF: 0.045, 0.0085, and 0.16 for whole fish, muscle, and viscera tissue, respectively; EPA 171-4 (g), Reliability = 1

Rainbow trout (Oncorhynchus mykiss) BCF: 1374 ± 321 (whole fish); 725 ± 136 (fish fillet); EPA 72-6, EPA 165-4, Reliability = 1

Key value for chemical safety assessment

BCF (aquatic species):

5 040 L/kg ww