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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:
20 July to 1 September 1987
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
GLP compliance:
yes
Specific details on test material used for the study:
RADIOLABELLED TEST SUBSTANCE
- Date of arrival: 26 January 1987
- received in a glass vial labelled: Trichloromethyl C-14] Captan; 5.0 mci
- Specific activity: 38 mCi/mMole, 126 mCi/g
- radiochemical purity: 92%
- Source: Chevron Chemical Company
- Batch number: J42893
- manufactured by Amersham
- Storage: refrigerated

NON RADIOLABELLED TEST SUBSTANCE
- Date of arrival: 6 March 1987
- Physical state: white powder
- Source: ICI Americas Inc., Richmond, California
- Lot: #WRC 4921-26-17
- Purity: 89.7 %
Radiolabelling:
yes
Vehicle:
yes
Test organisms (species):
Lepomis macrochirus
Route of exposure:
aqueous
Test type:
flow-through
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
29 d
Total depuration duration:
14 d
Hardness:
26-36 mg/L
Test temperature:
17±1 °C
pH:
6.5 - 7.7
Dissolved oxygen:
6.4 - 9.6 mg/L (69-98% of saturation)
Conductivity:
100-130 µmhos/cm
Nominal and measured concentrations:
nominal concentration of 5.0 μg/L in well water for 29 days
Key result
Conc. / dose:
5 µg/L
Temp.:
16 - <= 18 °C
Type:
BCF
Value:
140 dimensionless
Basis:
whole body w.w.
Remarks on result:
other: Conc. in environment / dose: measured concentration of captan in the exposure solution was 4.0 µg/L (80% of the nominal)
Conc. / dose:
5 µg/L
Temp.:
>= 16 - <= 18 °C
Type:
BCF
Value:
56 dimensionless
Basis:
edible fraction
Remarks on result:
other: Conc.in environment / dose: measured concentration of captan in the exposure solution was 4.0 µg/L (80% of the nominal)
Conc. / dose:
5 µg/L
Temp.:
>= 16 - <= 18 °C
Type:
BCF
Value:
280 dimensionless
Basis:
non-edible fraction
Remarks on result:
other: Conc.in environment / dose:measured concentration of captan in the exposure solution was 4.0 μg/L (80% of the nominal)
Elimination:
yes
Parameter:
other: Elimination of 72, 92 and 83%
Depuration time (DT):
14 d
Remarks on result:
other: from the edibles, viscera and whole body tissue
Elimination:
yes
Parameter:
DT50
Depuration time (DT):
3 d
Remarks on result:
other: 1-3 days in the nonedible and whole body tissue

The flow-through bioconcentration study exposing bluegill to anominal concentration of 5.0 µg/L Trichloromethyl 14C-Captan and a control solution was terminated after 29 days of exposure and 14 days of depuration. The bluegill during both the exposure and depuration periods exhibited normal behavior, fed readily and were in excellent physical condition. No mortality occurred during the 43-day exposure and depuration phases.


The water quality of the dilution water was characterized as having total hardness and alkalinity ranges as CaC03of 26-36 mg/ and 27-30 mg/L, respectively, and a specific conductance range of 100-130 µmhos/cm. The dissolved oxygen concentration, measured in both aquaria ranged from 6.4 - 9.6 mg/L (69-98% of saturation) and the pH, measured in both aquaria, ranged from 6.5 - 7.7. The temperature range in each aquarium was 16-18°C throughout the study.


The concentration of 14C-residues in aqueous solution measured in the exposure aquarium immediately prior to the introduction of the bluegill was 4.0 µg/h, 80% of the nominal concentration of 5.0 µg/L. Based on this observation, the fish exposure phase was initiated. The mean (± S.D.) 14C-residue concentration in the water of the treated system during the 29-day exposure period was 3.6 ± 1.1 µg/L. This was 72% of the nominal concentration. Toxicant delivery system problems occurring between exposure days 7 and 14 were responsible for variability in the measured 14C-residue concentrations in water and consequently in the fish tissue concentrations during this period of the uptake phase of the study.


On exposure day 7 an adjustment to the calibration of the toxicant syringe mechanism resulted in the injection of an amount of stock solution into the treatment aquarium sufficient to elevate the water concentration to 14 µg/L at the time of sampling. Based on the amount of stock solution used during that 24-hour period, it would have been impossible for that concentration level to have existed for more than a brief interval. Therefore, the results of the day 7 water sampling were not included in the calculation of the mean measured water concentration for the study. On exposure day 14, when the results of the day 10 water sampling were reported, the 14C-residue concentration was found to be below the detectable level. Since the appropriate amount of stock solution had been used each day during this period, it was apparent the stock solution was not reaching the test aquarium. Careful examination of the syringe delivery system revealed a small leak at the syringe tubing coupling which was allowing the stock solution to leak out, evaporate and go undetected. This was repaired and by the end of exposure day 14, the 14C-residue water concentration was confirmed by analysis to be 4.2 µg/L.


Throughout the 14-day depuration period concentration in the water remained < 0.27 µg/L. Analyses of control water indicated that no 14C-residues were present above detectable limits throughout the entire study-period.


The mean 14C-residue concentrations measured in the edible, nonedible and whole body portions of the bluegill are also presented in Table 5.3.1-1


 


Table 5.3.1-1 [14C] captan residues in water and tissues of bluegill sunfish and bioconcentration factors following 29-day exposure to [14C-trichloromethyl] captan


 































Matrix



Mean measured concentrations


of [14C] residues1



BCF2



Water



3.6 μg/L


(days 0 - 29)



-



Edibles



200 μg/kg


(days 21 - 29)



56



Viscera



1000 μg/kg


(days 1 - 29)



280



Whole fish



500 μg/kg3(days 1 - 29)



140



1The period over which the mean is calculated is given in parenthesis.


2Calculated by mean tissue residue divided by mean water concentration.


3Calculated from relative tissue weight and tissue residues.


 


The mean 14C-residue concentrations measured in the edible tissue reached steady state


on day 21, within 7 days of constant exposure following repair of the syringe delivery mechanism, and remained relatively constant throughout the remainder of the exposure (range: 190-220 µg/kg) . ,


Based on a mean equilibrium concentration of 200 ± 39 µg/kg measured in edible tissue and a mean concentration of 3.6 ± 1.1


µg/L in the water during the period from 0 - 29 days of exposure, the mean equilibrium bioconcentration factor for Trichloromethyl 14C-Captan in bluegill edible tissue was 56x.


 


The mean 14C-residue concentrations measured in nonedibletissue reached steady state on day 1 and ranged from 400-1300 µg/kg during the remainder of the 29-day exposure. Based on a mean concentration of 1000 ± 430 µg/kg measured in nonedible tissue and a mean concentration of 3.6 ± 1.1 µg/L in water during the period from 0-29 days of exposure, the mean equilibrium bioconcentration factor for Trichloromethyl 14C-Captan in bluegill nonedible tissue was 280x.


The analytical results for the edible and nonedible portions of the bluegill were also used to estimate the total 14C-residue concentration on a whole fish basis. These data are expressed as averaged 14C-residue concentrations and are based on individual measured concentrations of 14C-residues in each tissue type portion and the weight of each tissue type sample from two bluegill sampled at each interval during the study (Table 5.3.1-1).


The pattern of accumulation and elimination of 14C-residues on a whole fish basis was similar to that observed in the nonedible tissues. Based on a mean equilibrium 14C-residues concentration in whole fish of 500 ± 230 µg/kg (range 200-740 µg/kg) and a mean concentration of 3,6 ± 1.1 µg/L Trichloromethyl 14C-Captan measured in the water during the period of 0-29 days of exposure, the mean equilibrium bioconcentration factor for Trichloromethyl 14C-Captan in the whole body of bluegill was 140x. 14C-residue concentrations in control fish tissue were below the detectable level during the entire exposure period.


Variability in toxicant delivery affected the relative tissue concentration (edible and non-edible) of Trichloromethyl 14c-captan during the period of malfunction. Tissue concentrations decreased in the absence of toxicant, i.e. day 10, but returned quickly .to pre-malfunction levels following syringe repair. The pattern of accumulation observed during the last 14 days of continuous exposure (sampling days 14, 21, 25 and 28) was similar to the pattern of accumulation observed during the first 7 days of continuous exposure. Under conditions of constant exposure, equilibrium (plateau) conditions were generally achieved within 7 days. Estimates of bioconcentration factors based on the last 14 days of exposure (mean exposure concentration 3.98 µg/L) were:


 


Edible: 42x


Nonedible: 250x


Whole body: 140x


 


Bioconcentration factors for edible, nonedible and whole body fish tissue were also estimated by using the uptake constant (Ku) and depuration constant (Kd) for each tissue type, where Ku/Kd = bioconcentration factor (BCF).


 


Table 5.3.1-2 Estimated and measured BCF´s for edible, nonedible and whole body fish tissue


 


































Tissue Type



Ku



Kd



Estimated BCF



Measured BCF



Edible



22



0.22



110x



56x



Nonedible



269



0.39



690x



280x



Whole body



88



0.35



250x



140x



 


Depuration Phase


Analyses of the edible and nonedible portions of bluegill transferred to flowing, uncontaminated water after 29 days of exposure to Trichloromethyl 14C-Captan indicated that in each case there was a continuous elimination of 14C-residues from the respective tissues during the first 7 days of the 14-day depuration period. Half-life, or the time when 50% of the accumulated 14C-residue was eliminated, was attained in the nonedible and whole body tissue between day 1 and 3 of the depuration period and between day 3 and 7 in the edible tissue. By day 14 of the depuration period the bluegill had eliminated 72, 92 and 89% of the 14C-residues that had been present on the last day of exposure in the edible, nonedible and whole body tissue, respectively.


Control fish tissue (edible, nonedible) was analyzed on day 14 of the depuration period. 14C-residues present in the control fish were below the minimum detectable level.

Validity criteria fulfilled:
yes
Remarks:
validity criteria given by test guideline 72-6 have been fulfilled
Conclusions:
Following exposure for 29 days to [14C-trichloromethyl] captan, the whole fish BCF of captan was 140 in the bluegill sunfish. The edibles and viscera BCF were 56 and 280, respectively. A mean of 82% of residues were eliminated from all tissues in a 14-day depuration period.
Executive summary:

Bluegill (Lepomis macrochirus) were exposed to a nominal concentration of 5.0 µg/L of Trichloromethyl 14C-Captan in well water for 29 days after which 16 fish were transferred to flowing, uncontaminated water for a 14-day depuration period. In addition, a study to establish the stability of Captan in freshwater and to verify the experimental conditions for the exposure of bluegill was conducted. Radiometric analyses of the water and selected fish tissues during exposure and depuration revealed the following:


 


1. Due to a physical malfunction, variable rates of toxicant delivery were experienced prior to the establishment of equilibrium conditions. With the exception of day 7 and day 10, the concentration of aqueous 14C-residues in the treated system remained relatively constant during the 29-day exposure period. The mean (± S.D.) measured concentration was 3.6 (± 1.1) µg/L. Concentrations of 14C-residues present in the water of the depuration aquarium remained < 0.27 µg/L throughout the 14-day depuration period.


 


2. The concentration of 14C-residues in the edible tissue of exposed bluegill reached steady state by day 21. The mean equilibrium bioconcentration factor for Trichloromethyl 14C-Captan in the edible tissue of bluegill during the 29 days of exposure was 56x.


 


3. The concentration of 14C-residues in the nonedible tissue of the exposed bluegill reached steady state by day 1. The mean equilibrium bioconcentration factor for Trichloromethyl 14C-Captan in the nonedible tissue of bluegill was 280x.


 


4. The pattern of accumulation of 14C-residues calculated in the whole body of exposed bluegill was similar to that observed for the nonedible tissue portions. The mean equilibrium bioconcentration factor for Trichloromethyl 14C-Captan in the whole body of bluegill was 140x.


 


5. Continuous elimination of 14C-residues from the edible and whole body tissue portions of bluegill was observed during the first 7 days of the depuration period. Elimination from the nonedible tissue portion was observed after day 1 of depuration. Half-life of the 14C-residues present in the edible tissue portion of bluegill on day 28 of exposure occurred between the third and seventh day of depuration, and between day 1 and day 3 for the 14C residues in the nonedible and whole body tissues. By day 14 of the depuration, the 14C-residues present on day 28 of exposure in the edible, nonedible and whole fish tissues had been eliminated by 72%, 92%, and 89%, respectively.


 


6. Variability in toxicant delivery affected the relative tissue concentration of Trichloromethyl 14C-Captan. In the absence of toxicant, tissue concentrations decreased but returned quickly following re-establishment of constant exposure conditions. Data used to derive bioconcentration factors are based on observed equilibrium (plateau) conditions and were not affected by a system malfunction.


 


7. The in-life stability study indicated the concentration of Captan to be relatively constant from pretest through day 28 of exposure at 38.3 ± 1.8% parent material.

Description of key information

The bioaccumulation factor BCF for bluegill sunfish is determined as 140 according to EPA OPP 72-6.

Key value for chemical safety assessment

BCF (aquatic species):
140 dimensionless

Additional information

According to EPA guideline OPP 72-6 bioaccumulation in bluegill sunfish fish was evaluated. In bioaccumulation studies with bluegill sunfish and captan labelled in two positions, the results were similar with whole fish BCF factors between 100 and 150. The BCF factors were higher in the viscera than the edible tissues. Residues were eliminated rapidly when the fish were transferred to clean water in both studies. The results indicate that captan is unlikely to accumulate in the aquatic environment or pose a significant risk to fish predators.