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Bioaccumulation: aquatic / sediment

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Reference
Endpoint:
bioaccumulation in aquatic species: fish
Type of information:
experimental study
Adequacy of study:
key study
Study period:
31 Jan 2018 to 21 Feb 2018
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:
OECD Guideline 305 (Bioaccumulation in Fish: Aqueous and Dietary Exposure) -I: Aqueous Exposure Bioconcentration Fish Test
Version / remarks:
Pilot study
Qualifier:
according to
Guideline:
EPA OPPTS 850.1730 (Fish Bioconcentration Test)
Version / remarks:
Pilot study
GLP compliance:
no
Remarks:
The pilot study was performed under non-GLP conditions
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Name of test material (as cited in study report): Perkacit ZDEC (also known as ZDEC)
- Zinc content: 18.2%
- Lot Number: 50722504
- Supplier: Chemspec, Ltd.
- Appearance: Solid
- Date Received: September 26, 2017
- Expiration Date: Not provided
- Storage Conditions: Ambient

RADIOLABELLING INFORMATION
- Identity: ZDEC-[14C]
- Radiochemical Purity: 99.28%
- Specific Activity: 140.2 µCi/mg
- Lot Number: 86522-1-21-1
- Supplier: EAG Laboratories - Columbia
- Appearance: Solid
- Date Received: January 9, 2018
- Storage Conditions: Frozen
Radiolabelling:
yes
Details on sampling:
Whole fish were collected on days 7 and 14 of the uptake phase, and days 3 and 7 of the depuration phase. At each tissue sampling interval, four fish were removed from each control and treatment group. Twenty additional fish were also collected on Day 14 of uptake for possible metabolite analysis. Fish were impartially removed from the test chambers and euthanized by making an incision from just posterior to the base of the pectoral fin dorsally through the spinal cord. The fish were rinsed with dilution water, blotted dry and measured for total length and wet weight within approximately 15 minutes of collection, when possible. All tissue samples were processed immediately for analysis or stored frozen.
Vehicle:
yes
Details on preparation of test solutions, spiked fish food or sediment:
Isotopic dilutions were prepared for the dosing stocks. A primary 14C-test item stock solution was prepared in dimethylformamide (DMF) at a measured concentration of 105 mg/L. Additionally, 12C-test item primary stocks were prepared daily in DMF at a nominal concentration of 1.0 mg/mL. The non-radiolabelled primary stocks were mixed through 15 minutes of sonication and then inversion. The dosing stocks were prepared twenty-three times at a nominal concentration of 0.16 mg/mL. A 0.16 mg/mL dosing stock was prepared by proportionally diluting the radiolabeled and non-radiolabeled primary stock solutions and bringing to volume with DMF. The dosing test stock solutions were mixed by inversion. The final specific activity of the aqueous exposure test solution was 62,516 dpm/µg. The final nominal radioactivity in the aqueous exposure solution was 200 dpm/mL. The dispensing stock solutions were pumped into the diluter mixing chamber assigned to the treatment group at a target rate of 0.007 mL/min and were mixed with well water in the mixing cambers, delivered at a target rate of 350 mL/min to achieve the nominal test concentration of 3.2 µg/L. The solvent control was prepared by delivering DMF to the mixing chamber for the solvent control. The concentration of DMF in the control and treatment group was 20 µL/L. Dilution water was delivered at a target rate of 197 mL/min during the depuration phase. Flows to the test system were initiated 9 days prior to initiation of the uptake phase.
Test organisms (species):
Lepomis macrochirus
Details on test organisms:
TEST ORGANISM
- Common name: Bluegill
- Source: Osage Catfisheries, Inc., Osage Beach, Missouri
- Age: Juveniles (hatched on April 18, 2017)
- Feeding: Fed at least once daily during holding with a commercially-prepared diet supplied by Sera North America, Inc.
- Mortality prior to test: None

ACCLIMATION
Organisms were held for 6 days in well water from the same source and at approximately the same temperature as used in testing.
Route of exposure:
aqueous
Justification for method:
minimised test method used for following reason: pilot study
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
14 d
Total depuration duration:
7 d
Hardness:
127 mg/L as CaCO3 (mean of 4 weekly measurements prior to initiation)
Test temperature:
21.85 - 22.30 °C
pH:
8.0 - 8.5
Dissolved oxygen:
- Solvent control: >7.0 mg/L (≥ 81% of air saturation value)
- Treatment group: >6.7 mg/L (≥ 77% of air saturation value)
TOC:
<1 mg C/L (based on monthly measurement of TOC in dilution water)
Conductivity:
351 µS/cm (mean of 4 weekly measurements prior to initiation)
Details on test conditions:
TEST SYSTEM
- Test vessel uptake phase: 127 L Teflon-lined stainless steel tanks
- Test vessel depuration phase: 54 L Teflon-lined stainless steel tanks
- Test volume uptake phase: 80 L
- Test volume depuration phase: 45 L
- Depth of Test Solution uptake phase: 17.2 cm
- Depth of test solution depuration phase: 26.7 cm
- Aeration: Yes
- Type of flow-through: Diluter
- No. of organisms per vessel: 70
- No. of vessels per concentration: 1
- No. of vessels per control / vehicle control: 70
- Maximum loading: 0.26 g fish/L/day

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: UV-sterilized freshwater from a well located on the EAG Laboratories–Easton site.
- Alkalinity: 170 mg/L as CaCO3 (mean of 4 weekly measurements prior to initiation)
- Holding medium different from test medium: Only difference was that holding water was not UV-sterilized.

OTHER TEST CONDITIONS
- Photoperiod: 16-hrs light and 8-hrs dark daily, with a 30-minute transition period of low-light intensity at the beginning and end of photoperiod.
- Illumination: The test systems were illuminated using fluorescent tubes that emit wavelengths similar to natural sunlight.
- Light intensity: 722 lux at the beginning of uptake; 506 at the beginning of depuration.
Nominal and measured concentrations:
- Nominal test concentration: 3.2 µg/L
- Mean measured concentration during uptake phase: 3.0 µg/L
- Mean measured concentration depuration phase: Overviews of the measured concentrations of the test item in water samples collected prior, during uptake phase and during depuration phase are presented in 'Any other information on materials and methods incl. tables'
Reference substance (positive control):
no
Details on estimation of bioconcentration:
The estimates of the kinetic bioconcentration factor (BCFK) for the test organisms is based on total radioactivity. The data collected from the uptake and depuration phases for the treatment group were used to calculate the uptake rate constant (k1), the depuration rate constant (k2), the BCFK, the time to reach 95% steady state and the time to 50% clearance.
Remarks on result:
not measured/tested
Key result
Conc. / dose:
3.2 µg/L
Temp.:
>= 21.85 - <= 22.3 °C
Type:
BCF
Value:
9.97 dimensionless
Basis:
whole body w.w.
Time of plateau:
18.4 h
Calculation basis:
steady state
Remarks:
95% Steady state
Remarks on result:
other: pH in the exposure group ranged from 8.1 - 8.5 throughout the study
Remarks on result:
not measured/tested
Rate constant:
overall uptake rate constant (L kg-1 d-1)
Value:
1.62
Rate constant:
overall depuration rate constant (d-1)
Value:
0.163
Details on results:
The mean measured concentrations of the test item in fish tissue were 28.7 and 26.8 µg/kg on days 7 and 14 of the uptake phase. The mean measured concentrations of the test item in fish tissue were 10.9 and 8.6 µg/kg on days 3 and 7 of the depuration phase. The BCFK value for the nominal 3.2 µg/L treatment group was 9.97. The time to reach 95% steady state (BCFSS) was 18.4 days and the estimated times to reach 50% clearance was 4.3 days. Detailed overviews of the measured concentrations of the test item in tissue samples collected from the treatment group during the uptake phase and depuration phase are presented in 'Any other information on results incl. tables'.
- Test solution appearance: Clear and colorless in mixing and test chambers at test initiation and termination.
- Mortality of test organisms: No mortality observed

 Table: Measured Concentrations of Total Radioactivity in Whole Fish Tissues from a Bluegill Bioconcentration Pilot Study During the Uptake and Depuration Phases

Nominal ZDEC Concentration

(µg/L)

Study

Phase

Sampling

Interval

(Day)

ZDEC

Mean Equivalents

Found1,2,3

(µg/L)

Number of

Samples

Percent

of

Nominal

Mean Measured Concentration (µg/L)

Solvent Control

Uptake

0

<LOQ

1

--

--

Uptake

7

<LOQ

1

--

 

Uptake

14

<LOQ

1

--

 

Depuration

3

<LOQ

1

--

 

Depuration

7

<LOQ

1

--

 

3.2

Uptake

0

3.02

2

 

3.0 ± 0.02

Uptake

7

2.98

2

 

 

Uptake

14

2.98

2

 

 

Depuration

3

<LOQ

2

 

--

Depuration

7

<LOQ

2

 

 

1)        The sample volume was 10 mL (10 mL for background samples).

2)        ZDEC Equiv. = [(Total dpm found - background contribution)/Sample Volume]/Specific Activity x 1000 mL/L.

3)        LOQ = {[(50 dpm Instrument LOQ)/Sample Volume of 10.0 mL]/Specific Activity of 62516 dpm/µg} x 1000 mL/L = 0.0800 µg/L.

  

Table: Measured Concentrations of Total Radioactivity in Whole Fish Tissues from a Bluegill Bioconcentration Pilot Study During the Uptake and Depuration Phases

Nominal ZDEC Concentration

(µg/L)

Sample ID

(853A-102-)

Day

Whole Fish

Conc.1,2,3,4,5

(µg/kg)

Mean Whole Fish

Conc.1,2,3,4,5

(µg/kg)

Solvent Control

WF-1

7 Uptake

<LOQ

<LOQ

WF-2

7 Uptake

<LOQ

WF-3

7 Uptake

<LOQ

WF-4

7 Uptake

<LOQ

WF-9

14 Uptake

<LOQ

<LOQ

WF-10

14 Uptake

<LOQ

WF-11

14 Uptake

<LOQ

WF-12

14 Uptake

<LOQ

WF-17

3 Depuration

<LOQ

<LOQ

WF-18

3 Depuration

<LOQ

WF-19

3 Depuration

<LOQ

WF-20

3 Depuration

<LOQ

WF-25

7 Depuration

<LOQ

<LOQ

WF-26

7 Depuration

<LOQ

WF-27

7 Depuration

<LOQ

WF-28

7 Depuration

<LOQ

3.2

WF-5

7 Uptake

32.51

28.7

WF-6

7 Uptake

30.09

WF-7

7 Uptake

26.55

WF-8

7 Uptake

25.6

WF-13

14 Uptake

17.2

26.8

WF-14

14 Uptake

32.3

WF-15

14 Uptake

34.8

WF-16

14 Uptake

22.9

WF-21

3 Depuration

6.77

10.9

WF-22

3 Depuration

13.8

WF-23

3 Depuration

12.9

WF-24

3 Depuration

10.0

WF-29

7 Depuration

9.47

8.57

WF-30

7 Depuration

9.16

WF-31

7 Depuration

6.49

WF-32

7 Depuration

9.15

1)        µg/kg concentrations are expressed as equivalents of ZDEC based on specific activity.

2)        Sample mass = 0.200 g for each sample.

3)        Specific Activity = 62,516 dpm/μg

4)        Results were generated using Excel 2010. Manual calculations may differ slightly.

5)        LOQ = [(Instrument LOQ (50 dpm))/Specific Activity (dpm/μg)/Sample mass (g)] x 1000 g/kg = 2.29 µg/kg.

  

Table: Kinetic Estimates of the BCFK for Bluegill Based on Total Radioactivity

Tissue Type

Nominal Concentration

(µg/L)

Uptake1

Rate

Constant

(k1, Day-1)

Depuration1

Rate

Constant

(k2, Day-1)

Kinetic1

Bioconcentration

Factor

(BCFK)

Estimated Time1

To Reach 95%

Steady State

(Days)1

Estimated Time1

To Reach 50%

Clearance

(Days)1

Whole Fish

3.2

1.62

0.163

9.97

18.4

4.3

1)       Calculated using equations outlined in OPPTS guideline 850.1730.

Validity criteria fulfilled:
yes
Remarks:
See 'Any other information on materials and methods incl. tables'

Description of key information

The BCF value of ZDEC is determined to be 9.97.

Key value for chemical safety assessment

BCF (aquatic species):
9.97 dimensionless

Additional information

An experimental study on bioaccumulation in freshwater fish (bluegill) is planned for ZDEC (14324-55-1). However, the non-GLP pilot aqueous exposure bioconcentration study (in accordance with OECD 305 and OPPTS guideline 850.1730) with bluegill fish (lepomis mecrochirus) is already available and therefore used for the determination of the BCF. In this study, fish (70 fish per replicate; maximum loading 0.26 g fish/L/day) were exposed to a solvent control and 3.2 µg/L of radiolabelled test item for 14 days during the uptake phase before being transferred to clean test chambers containing only diluition water for another 7 days (depuration phase). Whole fish were collected on days 7 and 14 of the uptake phase, and days 3 and 7 of the depuration phase for analysis. Measured concentrations of the test item in water before and during the uptake phase remained will within ± 20% of the nominal concentration. The test item was not detected (<LOQ) in the depuration phase. The mean measured concentrations of ZDEC in fish tissue were 28.7 and 26.8 µg/kg on days 7 and 14 of the uptake phase. The mean measured concentrations of ZDEC in fish tissue were 10.9 and 8.6 µg/kg on days 3 and 7 of the depuration phase. The data collected from the uptake and depuration phases were used to calculate the uptake rate constant (k1), 1.62 per day; the depuration rate constant (k2), 0.163 per day; the kinetic bioconcentration factor (BCFK), 9.97; the time to reach 95% steady state, 18.4 days; and the time to 50% clearance, 4.3 days. Based on the results, the test item is determined to have a low bioaccumulative potential.