Santicizer 2148

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

Study period:

15 March 1993 - 20th September 1993

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:

not specified

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 305 C (Bioaccumulation: Test for the Degree of Bioconcentration in Fish)

Deviations:

not specified

GLP compliance:

yes

Specific details on test material used for the study:

Nonradiolabled analytical grade Santicizer 2148
Lot #DB 0504B
Purity not given
Stored in a freezer

Radiolabled 14C-santicizer 2148
99.7% Purity
Transferred with acetone to a 10 ml calibrated culture tube.

Radiolabelling:

yes

Remarks:

Isotope:14C-52148, Amount: 2.0 mCi, specific activity 70.1 mCi/mM

Details on sampling:

Radiopurity test
14C-Santicizer 2148 sample was transferred with acetone to a 10 mL calibrated culture tube, and designated radiolabelled primary stock solution. Radiopurity test solution was prepared by diluting 0.025 mL of the primary radiolabelled stock solution to 50 mL with DCM.

Bluegill Bioconcentration stock solution
3 mL of the bluegill bioconcentration stock solution was transferred to a 50 mL volumetric flask and brought up to 50 mL with acetone. LSC/Gas-liquid chromatography (GLC)-2 test solutions were prepared by diluting 0.1 mL stock to 5 mL in hexane.

Non-radiolabelled standard solution
1.37 mg/mL primary non-radiolabelled standard solution was prepared in acetone, and subsequent dilutions for chromatographic standards were prepared in DCM and hexane.

Water samples of ~500 mL were taken on each sampling day from each aquarium, and additional 500 mL water samples were collected days 21 and 35 of exposure phase.

Fish were sampled during the exposure phase following the schedule in table III. 6 fish form each chamber (control and test) were collected and pooled into control and test samples. 3 of the control and test fish were dissected into fillet/edible (body, muscle, skin, skeleton) and viscera/nonedible (fins, head, internal organs) and 3 were reserved for whole fish analysis. On days 21 and 35 of exposure additional fish were collected from each aquarium and pooled and dissected as above. Fish samples were frozen immediately and stored frozen until processing for radioassay.

Samples of the dosing solution (Diluter stock solution) were taken directly from the diluter and analysed days 0 and 35 of the uptake phase of the study.

Vehicle:

yes

Remarks:

Acetone

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

Diluter stock solution preparation
Diluter stock solutions were prepared from a primary stock solution (98.4 μg/mL) by transferring either 2.12- or 1.06-mL aliquot to either a 1000- or 500-mL volumetric flask and diluting with acetone. Resulting 208.6 μg/L diluter stocks were transferred to an amber glass bottle for use by the diluter toxicant injection system.

The diluter system was calibrated by volumetric measurements of the mixing cell volumes. 0.7 mL aliquot of 14C-Santicizer 2148 diluter stock solution (208.6 μg/L) was delivered to 1460 mL of dilution water in the toxicant mixing cell to yield a nominal exposure concentration of 0.10 μg/L

Test organisms (species):

Lepomis macrochirus

Details on test organisms:

120 fish in control, 128 in treated aquaria

TEST ORGANISM
- Common name: Bluegill sunfish
- Source: Osage catfisheries Inc
- Age at study initiation (mean and range, SD): <1 year old at times of testing
- Length at study initiation (length definition, mean, range and SD): 56 ± 8mm
- Weight at study initiation (mean and range, SD): Initial mean weight of 5.5 ± 2.3 g
- Weight at end of depuration phase (mean and SD): 11.6 ± 3.6g
- Length at end of depuration phase (mean and SD): 70 ± 8 mm
- Feeding during test
- Food type: Rangens Salmon Starter
- Amount: (~3.0g per aquarium per day)
- Frequency: ad libitum

ACCLIMATION
- Acclimation period: 14 days
- Acclimation conditions (same as test or not): 16 hour daylight, 8 hour darkness, 30-minute transition photoperiod
- Type and amount of food: Rangens Salmon Starter ad libitum (~3.0g per aquarium per day)
- Feeding frequency: ad libitum
- Health during acclimation (any mortality observed): No mortality observed

Route of exposure:

aqueous

Remarks:

Nominal 14C-Santicizer 2148 concentration of 0,10 μg/L

Test type:

flow-through

Water / sediment media type:

other: Deep well source

Total exposure / uptake duration:

35 d

Total depuration duration:

21 d

Hardness:

264-288 mg/L as CaCO2

Test temperature:

19°C first 2 days of study, 22 +/-2°C afterwards

pH:

7.9-8.2

Dissolved oxygen:

Mean: 7.3 mg/L (range- 5.5 mg/L at 22 °C to 8.5 mg/L at 19 °C), 65-97% saturation

TOC:

<1.0 ppm

Salinity:

Not examined

Conductivity:

440-560 μMhos/cm

Details on test conditions:

A modified proportional diluter system with a Hamilton Model 420 (Hamilton Co., Reno, NV) dual syringe dispenser was used for intermittent introduction of 14C-Santicizer 2148 and diluent water into the 100-L glass aquaria. Aerated well water was delivered to the test and control aquaria at an average rate of 362 mL/min/aquarium during the 56 day study, enough to replace the 70-L aquarium volume ~7.4x in 24 hours. The diluter system delivered a solution of 14C-Santicizer 2148 in acetone to the dilution water added to the test aquarium, maintaining a nominal 14C-Santicizer 2148 concentration of 0.10 μg/L. The equivalent amount of acetone (0.7 mL) without 14C-Santicizer 2148 was delivered to the control aquarium dilution water. The test and control aquaria were immersed in a water bath that was brought up to study temperature of 22 (± 2) °C by electronically controlled submersible heating elements and circulating water 2 days after fish were added. Waterbath temperature was 19°C for the first 2 days of the study

Procedure- Exposure phase
Preliminary 7-day flow-through experiment with nominal concentrations of 0.018, 0.036, 0.075, 0.15, and 0.30 mg/L for 7 days was performed. After 7 days no mortality or abnormal effects were observed in any of the test concentrations. Day 7 LC50 estimated to be >30 mg/L, study sponsor selected treatment concentration of 0.10 μg/L for the definitive bioaccumulation study.

Test solution was allowed to flow through the test aquarium for equilibration period of ~3 days. The 14C-Santicizer 2148 concentration was confirmed by radioanalysis before introducing the test fish. Randomly selected fish in small groups were transferred from the culture tank to the control. 120 fish were added to the control aquaria and 128 were added to the treatment aquaria. No acclimation period was necessary due to temperature of the culture and test chambers being within 3°C and identical dilution water used in both. The fish were observed initially and twice daily during the exposure period for mortality and/or adverse behaviour. Fillet and viscera portions were sectioned, and the fish tissues and water samples were frozen. The water and tissue samples were radioassayed.

Procedure- Depuration phase
On day 35 of exposure, 14C-Santicizer 2148 addition was stopped. The water in each aquarium was removed via siphoning until a depth of ~8cm of water (~20 L) remained. The aquaria were filled to ~70 L with well water, then the water was removed again until a depth of ~8cm of water remained before being finally filled again to 70 L with well water. The fish were exposed to flowing well water for 21 days. During the depuration period the water and fish were sampled and radioassayed, and samples from water and fish tissue were stored as in the exposure phase.

Chemical and Physical Test Parameters
Water quality parameters of temperature, dissolved oxygen, and pH were measured initially and periodically during the study both in control and test aquaria. The aquaria were aerated throughout the study to maintain dissolved oxygen levels >=60% saturation.

Nominal and measured concentrations:

Nominal: 0.10 ug/L
Mean average water concentration during exposure phase: 0.097 (± 0.015) μg/L

Reference substance (positive control):

yes

Remarks:

14C-benzoic acid

Details on estimation of bioconcentration:

Evaluation of the data used a steady-state approach, with a 2 compartment model (water and fish) used to describe the movement of the test substance in and out of test fish and is used to determine the steady state bioconcentration factor (BCF), uptake rate constant (K1) and depuration rate constant (K2).
The bioconcentration factors for the exposure period were determined by dividing the 14C-Santicizer 2148 tissue concentration by the running mean 14C-Santicizer 2148 concentration in water up to and including that day.

The uptake rate constant (K1) and depuration rate constant (K2) were determined by the Dow BIOFAC computer program, a nonlinear kinetic modelling program that provides optimal parameter estimates of rate constants K1 and K2 by utilising the actual (observed) bioaccumulation data. The bioconcentration factor at steady state, the time to reach 90% of steady state, and the time to reach 50% clearance (depuration) of the test substance were also calculated from the estimated rate constants, with a standard deviation provided for each.

Counting efficiencies for the test substance in water were determined using a quench calibration curve based on the ESR method of analysis. The following formula was used to calculate the concentration of test substance in water:
ng/mL = (activity of test water (cpm) – background activity of control water (cpm) x 1000 ng/mL, μg/L)/(counting efficiency (cpm/dpm) x specific activity of parent compound (dpm/μg) x sample volume (10 mL))

Counting efficiencies for the test substance in fish tissue were determined for each test sample using a quench calibration curve based upon the external standard ratio (ESR) method of analysis. The following formula was used to calculate the concentration of the test substance in tissue:
ng/g = (activity of test tissue (cpm) – background activity of control tissue (cpm) x (1000 ng/μg)/(counting efficiency (cpm/dpm) x specific activity of parent compound (dpm/μg) x sample weight (g))

Calculations of Santicizer 2148 in dosing solution (diluter stock solution) were determined directly from the standard curve.

Minimum quantifiable limits (MQLs) were determined for each set of samples based upon radiochemical statistics of the replicate controls using the following equation:
MQL (ng/g or ng/mL) = (14.1 σ)(1000 ng/g) / (Average efficiency of control samples (cpm/dpm) x Specific Activity of parent compound (dpm/μg) x Average weight of control samples or volume (g or 10 mL))
Where σ is the standard deviation of the counting rate in cpm-
σ = √(total background counts) / (total counting time) = √ (average of background counting rates / total counting time of control samples)

Key result

Conc. / dose:

0.1 µg/L

Temp.:

22 °C

pH:

8.1

Type:

BCF

Value:

875 dimensionless

Basis:

whole body d.w.

Calculation basis:

steady state

Key result

Elimination:

not specified

Parameter:

DT50

Depuration time (DT):

11 d

Key result

Rate constant:

other: Uptake rate constant (K1) ng/g Fish/μg/L Water/Day

Value:

56

Key result

Rate constant:

overall depuration rate constant (d-1)

Value:

0.064

Details on kinetic parameters:

Uptake Rate Constant (K1) ng/g Fish /μg/L Water/Day = 56 ± 2
Depuration Rate Constant (K2) Day-1 = 0.064 ± 0.003

Results with reference substance (positive control):

14C-Benzoic acid instrument combustion recovery in absence of tissue averaged 98% for the study.

Details on results:

Time to reach 90% of steady state (days) 36 ± 2
T (50%) for depuration (days) = 11 ± 0.5
Bioconcentration Factor (BCF) 875 ± 50

Tissue residues expressed as 14C-Santicizer 2148 equivalents after 35 days of exposure were 20 ng/g for fillet, 74 ng/g for whole fish, and 130 ng/g for viscera. These values correspond to day 35 bioconcentration factors of 210x, 760x, and 1300x for fillet, whole fish and viscera respectively. Daily bioconcentration factors for the exposure phase of teh study ranged from 22-210x for fillet, 12-760x for whole fish, and 19-1300x for viscera.

Analysis of depuration rates by day 21 of elimination period showed 40, 64, and 73% depuration in fillet, whole fish, and viscera respectively. 14C-residues calculated for day-21 fillet and whole fish tissues were slightly higher than the corresponding day 14 values and represented nromal biological variability. This indicated that additional extensions of the depuration period would not change the percent depurated in the tissues.

The BIOFAC-calculated BCF value was 115% of the ovserved mean bioconcentration factor of 760 for day 35 for whole fish.

Average MQL data for scintillation counting for water, fillet, whole fish, and viscera for 14C-Santicizer 2148 were 0.0133 ng/mL, 0.615 ng/g, 0.614 ng/g, and 0.619 ng/g respectively. Mean recovery data for 14C-Santicizer 2148 in tissue sample oxidations were 102% for fillet, 103% for whole fish, and 103% for viscera.

Reported statistics:

Average water concentration during exposure phase was 0.097 ±0.015 μg/L, 97% of the nominal 0.10 μg/L concentration.

The dosing solution (diluter stock) was anaylsed and was 259 and 265 ng/mL days 0 and 35 respectively. This represented 124 and 127% respectively of the expected nominal concentration of 208.6 ng/mL, indicating Santicizer 2148 was stable under study conditions.

The percent of fillet in whole fish was determined to be 50.5%, while percent of viscera in whole fish was determined to be 49.5%.

Table I. Chemical Characteristics of Well Water, used by ABC laboratories’ Environmental Toxicology

Monthly/Daily Screens(Values from testing period)
Hardness	268-288	mg/L as CaCO2
Alkalinity	296-312	mg/L as CaCO2
pH	7.7-8.2
Conductivity	440-560	μMhos/cm
Suspended solids	0.2 and 2.6	ppm
Total Organic Carbon	<1.0	ppm
Biyearly Screens(January 1993)
Elements
Aluminium	<0.10
Arsenic	<0.001
Boron	0.416
Cadmium	0.018	ppm
Chromium	<0.01	ppm
Cobalt	<0.005	ppm
Copper	<0.01	ppm
Fluoride	1.26	ppm
Iron	0.236	ppm
Lead	0.0805	ppm
Mercury	<0.0002	ppm
Nickel	<0.015	ppm
Selenium	<0.0020	ppm
Silver	0.0013	ppm
Zinc	0.039	ppm
Organophosphate Insecticides
Endosulfan I	<0.05	ppb
Endosulfan II	<0.10	ppb
Endosulfan	<0.10	ppb
Chlorpyrifos	<0.07	ppb
Diazinon	<0.10	ppb
Methyl Parathion	<0.10	ppb
Ethyl Parathion	<0.10	ppb
Ronnel	<0.10	ppb
Malathion	<0.10	ppb
Chlorinated Hydrocarbons
DDE	<0.10	ppb
DDD	<0.10	ppb
DDT	<0.10	ppb
Dieldrin	<0.10	ppb
α-BHC	<0.05	ppb
β-BHC	<0.05	ppb
γ-BHC	<0.05	ppb
Δ-BHC	<0.05	ppb
Heptachlor	<0.05	ppb
Endrin	<0.10	ppb
H.E.	<0.05	ppb
Aldrin	<0.05	ppb
Methoxychlor	<0.50	ppb
Toxaphene	<5.0	ppb
Chlordane	<0.05	ppb
PCB
Total PCBs	<1.0	μ/L
Miscellaneous
COD	<5.0 mg/L	mg/L
Chlorine	<0.02	mg/L
Ammonia Nitrogen	<0.10	mg/L

 

Table II. Equipment List not included here

 

Table III. Sampling schedule for radioanalysis and water quality determinations during the bioaccumulation study with Bluegill Sunfish (Lepomis macrochirus) exposed to 14C-Santicizer 2148

Sample	Uptake Phase (Day)									Depuration Phase (Day)
	0	N*	1	3	7	14	21	28	35	1	3	7	10	14	21
Test Organism (number collected)
Total 14C-Residues in Edible and Nonedible
Treatment Chamber	0	3	3	3	3	3	22	3	22	3	3	3	0	3	3
Control Chamber	0	3	3	3	3	3	22	3	22	3	3	3	0	3	3
Total 14C-Residues in Whole Organism
Treatment Chamber	0	3	3	3	3	3	3	3	3	3	3	3	0	3	3
Control Chamber	0	3	3	3	3	3	3	3	3	3	3	3	0	3	3
Total
Treatment Chamber	0	6	6	6	6	6	25	6	25	6	6	6	0	6	6
Control Chamber	0	6	6	6	6	6	25	6	25	6	6	6	0	6	6
Remaining Organisms
Treatment Chamber	128	122	116	110	104	98	73	67	42	36	30	24	24	18	12
Control Chamber	120	114	108	102	96	90	65	59	34	28	22	16	16	10	4
Water
Total Sample (mL)†
Treatment Chamber	500	500	500	500	500	500	1000	500	1000	500	500	500	‡	500	500
Control Chamber	500	500	500	500	500	500	1000	500	1000	500	500	500	‡	500	500
Water Quality	X	X	X	X	X	X	X	X	X	X	X	X	---	X	X

 

* = Intermediate sample taken approx. 3.5 hours after initiation

† = Triplicate 10 mL samples for LSC were taken from the control and treated sample bottles

‡ = Samples for LSC analysis were taken directly from the control and treated tanks

 

Table IV. Total 14C-Radioactivity calculated as 14C-Santicizer 2148 in test water and fish tissue during 35 days exposure and 21 days depuration with Bluegill Sunfish (Lepomis macrochirus)

 

Total 14C Concentration as 14C-Santicizer 2148 (to 2 significant figures)
	Water (μg/L)		Fillet		Whole Fish		Viscera
Day	Actual	Running Mean	ng/g	BCF*	ng/g	BCF*	ng/g	BCF*
Exposure
0	0.012	--	--	--	--	--	--	--
0.17	0.11	0.12	<MQL†	--	1.4	12	2.3	19
1	0.097	0.11	2.4	22	12	110	18	160
3	0.087	0.10	5.1	51	15	150	37	370
7	0.074	0.098	8.5	87	35	360	57	580
14	0.10	0.098	11	110	52	530	82	840
21	0.084	0.096	14	150	62	650	94	980
28	0.11	0.098	21	210	68	690	120	1200
35	0.091	0.097	20	210	74	760	130	1300
Depuration
1	<MQL‡	--	21	--	69	--	110	--
3	<MQL‡	--	18	--	66	--	86	--
7	<MQL‡	--	14	--	50	--	62	--
10	<MQL‡	--	N/A	--	N/A	--	N/A	--
14	<MQL‡	--	11	--	26	--	48	--
21	<MQL‡	--	12	--	27	--	35	--

* = Daily Bioconcentration Factor (BCF) obtained by dividing tissue concentration by mean measured water concentration up to and including the respective sampling day (running mean)

† = below minimum quantifiable limit for fillet. Average MQL for study was 0.615 ng/g

‡ = below minimum quantifiable limit for water. Average MQL for study was 0.0133μg/L

 

Table V. Depuration of total 14C-residue calculated as 14C-Santicizer 2148 equivalents from Bluegill Sunfish (Lepomis macrochirus)during the 21-day clearance period

	Fillet		Whole Fish		Viscera
Depuration Day	Depuration Concentration (ng/g)	Percent Depuration	Depuration Concentration (ng/g)	Percent Depuration	Depuration Concentration (ng/g)	Percent Depuration
1	21	0	69	6.8	110	15
3	18	10	66	11	86	34
7	14	30	50	32	62	52
14	11	45	26	65	48	63
21	12	40	27	64	35	73

Depuration rates expressed as a percentage of the day 35 14C-Santicizer 2148 concentrations of 20 ng/g for fillet, 74 ng/g for whole fish, and 130 ng/g for viscera

 

Table VI. Comparison of Bluegill Sunfish (Lepomis macrochirus) observed and BIOFAC-estimated whole fish kinetics during 35 days of exposure to 14C-Santicizer 2148 and 21 days of depuration

	ng/g 14C-Santicizer 2148 equivalents in whole fish
Study day	Time (Days)	Observed	BIOFAC calculated
Exposure
0.017	0.17	1.36	0.92
	0.17	1.40	0.92
1	1	11.80	5.25
	1	12.10	5.25
3	3	14.60	14.80
	3	14.50	14.80
7	7	34.90	30.61
	7	35.20	30.61
14	14	51.60	50.18
	14	61.90	50.18
21	21	60.80	62.69
	21	62.30	62.69
28	28	66.50	70.70
	28	68.50	70.70
35	35	73.90	75.81
	35	74.90	75.81
Depuration
1	36	68.00	71.12
	36	69.10	71.12
3	38	64.20	62.59
	38	68.30	62.59
7	42	50.00	48.48
	42	50.00	48.48
14	49	27.80	31.00
	49	24.90	31.00
21	56	27.10	19.82
	56	27.30	19.82
(Optimal Parameter Estimates and Linearized Standard Deviations)
		Estimate	Linearized Standard Dev.
Uptake Rate Constant K1 (ng/g Fish/ng/mL)		56	2
Clearance Rate Constant K2 (Day-1)		0.064	0.003
T(1/2) for Clearance (Days)		11	0.5
Bioconcentration Factor KB		875	50
Time to Reach 90% of Steady State (Days)		36	2

Calculations were based on an average of the daily means of the water residue levels during the exposure period

 

 

Table VII. Average minimum quantifiable limits (MQL) for scintillation counting of water and fish tissues during the bioaccumulation study with Bluegill Sunfish (Lopomis macrochirus) exposed to 14C-Santicizer 2148

Average MQL
Sample type	(ng/mL, ng/g)	SD
Water	0.0133	0.00055
Filler	0.615	0.0430
Whole Fish	0.614	0.0527
Viscera	0.619	0.0439

 

Table VIII. Recovery data for sample oxidation of tissue during the bioaccumulation study with Bluegill Sunfish (Lepomis macrochirus) exposed to 14C-Santicizer 2148

Day*	Percent recovery of 14C-Santicizer 2148			Percent Recovery of 14C-Benzoic Acid
	Fillet	Whole Fish	Viscera
Exposure
0.17, 1, 3	100	101	97	97
7, 14, 21	101	101	102	98
28, 35	103	105	104	100
Depuration
1‡
3, 7	105	103	103	100
14	101	98	102	97
21	104	107	109	95
x̅	102	103	103	98
SD	2.0	3.2	3.9	1.9

Percentage values rounded to whole percentage. Recovery samples from fish were fortified with 14C-Santicizer 2148

* = Days that appear on the same line indicate that samples for these dates were processed together; therefore only 1 set of recoveries was used for data sets shown. Several study days are processed together in order to more efficiently use the oxidizer. Only 1 set of recoveries per tissue type was needed to confirm the combustibility of 14C-Santicizer 2148 in tissues for that analysis day.

† =Used to determine oxidiser efficiency, fortified with 14C-benzoic acid

‡ = combusted with exposure days 28 and 35

 

Table IX. Water quality measurements during the 56-day bioaccumulation study with Bluegill Sunfish (Lepomis macrochirus) exposed to 14C-Santicizer 2148

Study Day	Control Chamber*			Test Chamber*
	Temp. °C	D.O. mg/L†	pH	Temp. °C	D.O.mg/L†	pH
Exposure
0	19	8.5	8.3	19	8.6	8.3
0.17	19	7.2	8.1	19	7.2	8.1
1	20	7.5	8.1	20	7.5	8.1
3	20	7.6	8.1	20	7.5	8.1
7	21	6.7	8.0	21	6.7	8.0
14	22	6.9	8.0	22	7.0	8.1
21	22	5.8	8.0	22	6.2	8.1
28	22	6.7	7.9	22	6.5	8.0
35	22	5.5	7.9	22	6.2	8.2
Depuration6.9
1	22	7.3	8.1	22	6.9	8.0
3	22	7.9	8.1	22	6.6	8.0
7	22	8.0	8.1	22	8.0	8.0
14	22	8.2	8.1	22	8.2	8.2
21	22	8.0	8.1	22	8.2	8.2

Temperature was measured via mercury thermometer. pH was measured via pH probe (Fisher Model 13-620-287/SN2198213) used with a Corning Model 140 pH/mV meter

* =Temperature was measured directly in each of the study chambers daily and ranged from 19 to 22 °C
† = Dissolved oxygen concentrations- via dissolved oxygen meter (YSI model 54 ARC). Dissolved oxygen saturation at the temperatures of 19, 29, 21, and 22°C are 8.9, 8.7, 8.5, and 8.4 mg/L respectively corrected for altitudinal pressure at ABC Laboratories

Conclusions:

From the uptake and depuration data for whole fish, 14C-Santicizer 2148 appeared to accumulate at a moderate rate. The BIOFAC model for whole fish appears to fit the actual data points and adequately defines the uptake/depuration kinetics. The BIOFAC model predicts that steady state would not be reached until day 36, and the actual data supported this prediction.

Executive summary:

A dynamic 56-day study was conducted to evaluate the bioaccumulation of 14C-Santicizer 2148 by Bluegill Sunfish (Lepomis macrochirus). A flow-through proportional diluter system was used to maintain a mean measured water concentration of 0.097 (± 0.015)μg/L 14C-Santicizer 2148 for a 35-day exposure period. Radioanalysis of fillet, whole fish, and visceral portions was performed periodically during the exposure period. In this study the fillet (body, muscle, skin, and skeleton) was considered the edible portion of the fish, while the viscera (fins, head, and internal organs) was considered the nonedible portion. Daily bioconcentration factors ranged from 22 to 210 x, 12 to 760 x, and 19 to 1300 x for fillet, whole fish, and viscera respectively. Average tissue concentrations of 14C-Santicizer 2148 during the exposure phase ranged from 2.4 to 21 ng/g for fillet, 1.4 to 74 ng/g for whole fish, and from 2.3 to 130 ng/g for viscera. The bioaccumulation of 14C-Santicizer 2148 in all tissues was consistent through day 28 uptake and by day 35 of uptake the rate slowed considerably in the fillet tissue. Since the accumulation appeared to be continuous in the whole fish and viscera tissues the uptake was terminated on day 35 and depuration was started.

 

To measure the elimination of 14C-Santicizer 2148, the test fish were placed in untreated water for 21 days. Radioanalysis at the end of the 21-day depuration period indicated 40, 64, and 73% depuration from fillet, whole fish, and viscera respectively. Fillet concentrations dropped from 20 ng/g on day 35 of exposure to 12 ng/g by day 21 of depuration. Whole fish levels decreased from 74 ng/g on day 28 of exposure to 27 ng/g by the end of depuration, while viscera concentrations dropped from 130 ng/g on day 35 of exposure to 35 ng/g by day 21 of depuration.

 

Analysis of the uptake/depuration data for whole fish was conducted using a computer modelling program. This method estimated the uptake rate constant (K1) ng/g fish perμg/L water per day of 56 ± 2, depuration rate constant (K2) day-1 of 0.064 ± 0.003, time for 50% depuration of 11 ± 0.5 days, bioconcentration factor (BCF) of 875 ± 50, and a time to reach 90% of stead state 36 ± 2 days. The BIOFAC-calculated BCF value was 115% of the observed mean whole fish bioconcentration factor of 760 x for day 35.

 

Test fish were in good health during the study and no mortality was observed in the treated and control aquaria. Therefore, the data obtained from these fish adequately defined the uptake/depuration of potential 14C-Santicizer 2148.

Description of key information

From the uptake and depuration data for whole fish, ¹⁴C-Santicizer 2148 appears to accumulate at a moderate rate. The BIOFAC model for whole fish appears to fit the actual data points and adequately defines the uptake/depuration kinetics. The BIOFAC model predicts that steady state would not be reached until day 36.

The optimal parameter estimates for the whole fish were determined to be as follows:

Uptake rate constant (K1) ng/g Fish/µg/L Water/day            56 ± 2

Depuration rate constant (K2) Day-1                                       0.064 ± 0.003

T (50%) for depuration (days)                                                   11 ± 0.5

Bioconcentration Factor (BCF)                                                  875 ± 50

Time to reach 90% of steady state (days)                              36 ± 2

Key value for chemical safety assessment

BCF (aquatic species):

875 dimensionless

Additional information

A key EPA OPP Guideline 165-4 dynamic 56-day study (ABC Laboratories Inc., 1993a) was conducted to evaluate the bioaccumulation of ¹⁴C-Santicizer 2148 by Bluegill Sunfish (Lepomis macrochirus). A flow-through proportional diluter system was used to maintain a mean measured water concentration of 0.097 (± 0.015) μg/L ¹⁴C-Santicizer 2148 for a 35-day exposure period. Radioanalysis of fillet, whole fish, and visceral portions was performed periodically during the exposure period. In this study the fillet (body, muscle, skin, and skeleton) was considered the edible portion of the fish, while the viscera (fins, head, and internal organs) was considered the nonedible portion. Daily bioconcentration factors ranged from 22 to 210 x, 12 to 760 x, and 19 to 1300 x for fillet, whole fish, and viscera respectively. Average tissue concentrations of ^14C-Santicizer 2148 during the exposure phase ranged from 2.4 to 21 ng/g for fillet, 1.4 to 74 ng/g for whole fish, and from 2.3 to 130 ng/g for viscera. The bioaccumulation of ¹⁴C-Santicizer 2148 in all tissues was consistent through day 28 uptake and by day 35 of uptake the rate slowed considerably in the fillet tissue. Since the accumulation appeared to be continuous in the whole fish and viscera tissues the uptake was terminated on day 35 and depuration was started.

 

To measure the elimination of ¹⁴C-Santicizer 2148, the test fish were placed in untreated water for 21 days. Radioanalysis at the end of the 21-day depuration period indicated 40, 64, and 73% depuration from fillet, whole fish, and viscera respectively. Fillet concentrations dropped from 20 ng/g on day 35 of exposure to 12 ng/g by day 21 of depuration. Whole fish levels decreased from 74 ng/g on day 28 of exposure to 27 ng/g by the end of depuration, while viscera concentrations dropped from 130 ng/g on day 35 of exposure to 35 ng/g by day 21 of depuration.

 

Analysis of the uptake/depuration data for whole fish was conducted using a computer modelling program. This method estimated the uptake rate constant (K1) ng/g fish perμg/L water per day of 56 ± 2, depuration rate constant (K2) day-1 of 0.064 ± 0.003, time for 50% depuration of 11 ± 0.5 days, bioconcentration factor (BCF) of 875 ± 50, and a time to reach 90% of stead state 36 ± 2 days. The BIOFAC-calculated BCF value was 115% of the observed mean whole fish bioconcentration factor of 760 x for day 35.

 

Test fish were in good health during the study and no mortality was observed in the treated and control aquaria. Therefore, the data obtained from these fish adequately defined the uptake/depuration of potential ¹⁴C-Santicizer 2148.