United States
Environmental Protection
Agency
Research and Development
Environmental Research
Laboratory
Gulf Breeze FL 32561
EPA-600/S3-84-083 Sept 1984
&EPA Project Summary
Polychlorinated Biphenyl
Transport in Coastal
Marine Foodwebs
Joseph M. O'Connor
This project was designed to deter-
mine the rates of uptake and elimination
that might be expected when fishes
consume a diet contaminated with
PCBs. The experiments were carried
out under laboratory conditions; field
verification of PCB transport from die-
tary sources was investigated as a
subsidiary objective.
Gammarus tigrinus were labeled with
14C-PCB (Aroclor 1254) and force-fed
to juvenile striped bass in known
volumes, containing known quantities
of 14C-PCB. The distribution of 14C-PCB
in the tissues of the fish was determined
at 6, 12, 24, 48, 96. and 120 hours.
Experiments were also conducted in
which striped bass received 1, 2 or 3
doses of 14C-PCB in food, and were
monitored for up to 120 hours following
the final dose.
The PCBs fed to the striped bass were
assimilated rapidly and almost com-
pletely (85% of administered dose). The
kinetics for PCB assimilation and elimi-
nation were first order; the assimilation
rate constant (ka) was 0.1031 hr~1, and
the whole body elimination rate con-
stant (ke) was 0.0054 hr 1. The elimina-
tion rate constant for the multiple-dose
study was nearly identical to that ob-
served in single-dose studies (0.0059
*r-1).
From these data, rates of PCB body
burden build-up were calculated in
striped bass for fixed periods of time
and estimates were derived of number
of doses to "steady state," half-time for
body burden elimination and the time-
course for shifts from steady state to
steady state assuming changes in PCB
levels in food.
The data were also available for calcu-
lation of elimination rate-constants for
individual tissues that enabled calcula-
tion of rates and routes for elimination
of the PCB burden from the whole
body, via the hepatic pathway.
A pharmacokinetic model was derived
and is proposed as a means for estimating
PCB body burdens in fishes using PCB
concentration in the food as the princi-
pal data input.
This Project Summary was developed
by EPA's Environmental Research
Laboratory. Gulf Breeze. FL, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Between 1976 and 1979, several
studies aimed at describing the distribu-
tion and fate of contaminant inputs to the
New York Bight region were conducted.
The conclusion reached showed that
sewage sludge and dredged material
disposal comprised the major source of
several contaminants in the Bight Apex.
Among the major contaminants deriving
from these sources were the polychlon-
nated biphenyls (PCBs).
Efforts to determine the potential haz-
ards and effects of PCBs on organisms
from the Bight Apex were hampered by a
lack of information in two areas: (1) the
chemical and physical characteristics of
the environment that render PCBs avail-
able to marine biota; and (2) the extent to
which PCBs may be transported within
the marine environment, from sediment,
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to prey species, to predators. Whereas
many predictive models had been pub-
lished showing that bioconcentration of
PCB from water was the dominant route
of uptake (e.g., Hamelmk et al , 1971;
Mackay, 1 982), equally strong arguments
could be made for diet as the major route
of uptake (Norstrom et al., 1976; Thomann,
1981). Resolution of the problem was
impossible from either published data or
from proposed field sampling; the pre-
sence of PCB in any organism does
nothing to identify its source, and the
Bight Apex region was subject to PCB
input from many and varied sources
A two-part research project was de-
veloped, therefore, aimed at providing
critical data on PCB availability and the
accumulation and retention of PCB from
diet by marine fishes. Part I of the project
was conducted by the USEPA Gulf Breeze
Environmental Research Laboratory. Part
II, reported here, was carried out by the
New York University Institute of Environ-
mental Medicine and was aimed at
describing the kinetics of dietary PCB
transport from food orgamsmsto a model
species, the striped bass (Morone
saxatilis).
Laboratory studies were designed to be
as realistic as possible. A mixture of PCB
congeners similar to the industrial mix-
ture, Aroclor 1254, was chosen. Aroclor
1254 contains a high proportion of tn-,
tetra-, and pentachlorobiphenyl congener
not unlike the dominant peaks found in
fishes from environmental samples.
The PCB used in experiments was
uniformly ring-labeled with 14C; since
PCBs are not metabolized to any signifi-
cant extent by fishes, the PCB compound
could be tracked from food to fish and
environment, with a mass-balance main-
tained, and pharmacokinetic analyses
could be applied to the data.
Cultures of a natural food organism,
Gammarus tigrinus, were labeled with
14C-PCB and force-fed to striped bass. In
all experiments care was taken to provide
a known volume of food containing a
known quantity of 14C-PCB. Care was also
taken to control the experiments, with the
use of sham-fed fish to determine what
proportion of the total body burden was
from food and what proportion was due to
secondary uptake from the water.
In single-dose studies groups of fish
were force-fed and samples were taken
at 6, 12, 24, 48, 72, 96 and 120 hours
after feeding. Individual tissues were
dissected and analyzed for 14C-PCB with
the use of liquid scintillation counting
techniques. In the multiple-dose studies,
groups of fish were given 1, 2 or 3
feedings at 48-hour intervals and were
sampled for 14C-PCB analysis at intervals
ranging up to 120 hours after feeding.
Single-dose studies were used to deter-
mine PCB assimilation rate constants(ka).
The data from both single-dose and
multiple-dose studies were used in the
calculation of elimination rate-constants
for whole body and individual organ PCB
burdens. Mathematical treatment of the
data followed the format of Goldstein et
a I. (1974). From the pharmacokinetic data
we were able to progress to a preliminary
model for dietary PCB accumulation in
fishes (O'Connor and Pizza, in press) by
incorporating into the dose/uptake model
several parameters of growth, metabolism
and feeding wich emulate those of striped
bass in the natural environment.
Results
Assimilation Rate Constant
After application of a known dose, PCBs
at the site of absorption, the gut, declined
100 <
rapidly, decreasing from 100% of the
administered dose to <10% within 24
hours (Figure 1). At the same time, the
proportion of the administered dose in the
whole body (Figure 2) remained above
85%. This demonstrates that PCB loss
from the gut was primarily due to cross-
gut transport to the tissues. Regression of
the percent dose in the gut versus time
yielded the assimilation rate-constant (ka)
= 0.1031 hr~1 and a calculated assimila-
tion half-time of 6.7 hours.
Elimination Rate Constant
Proportional loss of PCB from the whole
body over 1 20 hours yielded an elimina-
tion rate constant (ke) of 0.0054 hr"1, or a
half-time for PCB elimination of 120
hours. Data from the multiple dose study
gave essentially the same ke; 0.0059 hr"1
Approach to Plateau
Using values for ka and ke as determined
from single-dose studies and empirical
body burden data from multiple-dose
studies, we fitted a curve (Figure 3)
o
Q
§
-Q
to
Phase I
95% C.I. for K,= 0.1031±0.0181 hr~
Phase 2
I
I
24
48
72
Time (hr.)
96
120
Figure 1. Percent unabsorbed dose as a function of time. PCB removal from the alimentary
tract as determined by two processes: (1) absorption of administered dose (phase
1), and (2) elimination from tract tissue (phase 2).
-------
35% C.I for Ke = 0 0054±0.0008 hf
100
c
0)
fl
o
Q
120
Figure 2. Percent dose in body as a function of time PCB elimination from whole-body
after a single dietary exposure.
c
"oi
8
1200
800
400
90%.
O1-
Time fhr) 0
Dose Number 1
_L
J 1_
_l_
\
1
48
2
96
3
144
4
192
5
240
6
288
7
336
8
384
9
432
10
480
11
Figure 3. Curve for the cumulative retention of PCB from multiple dosing Solid lines present
the actual levels attained during the experiment. Dashed lines are the calculated
extension of the data. The plateau burden (X°°) is the steady state level attained
from peak values after sufficient dosing (see text}.
depicting for striped bass the rate of
approach to "steady-state" or "plateau"
burden. According to the model, for a diet
with a fixed, arbitrary, concentration of
PCB, a striped bass would have accumu-
lated 90% of the expected final body
burden in about 8 doses, a rate much
faster than that expected from exposure
to PCBs in water.
Tissue Burdens
PCB concentrations in tissues (liver,
brain, gill, heart, muscle, etc.) built up
gradually over the course of several doses
(Table 1). The greatest mass of PCB
accumulated in the muscle ("carcass");
the greatest concentration of PCB built up
in the liver/gall bladder compartment
Elimination rate-constants(ke)for indivi-
vidual tissues were similar (Figure 4). The
greatest turnover rate, therefore, was in
the liver/gall compartment.
Interpretations
From these data, it can be concluded
that, due to the rapid and nearly complete
uptake of PCB from food by striped bass,
dietary sources of PCBs to fish are. (1)
certainly significant, and (2) possibly
dominant as sources for existing body
burdens.
It is also apparent from these data that
PCBs assimilated by fish are not "recal-
citrant"; that is, the potential exists for
elimination, albeit slow(ti/2= 120 hours).
The pharmacokmetic interpretations of
uptake and elimination can be expanded
into a predictive model for PCB accumula-
tion if appropriate constants for growth,
metabolism, and dietary burdens are built
in. We constructed a preliminary model
(Figure 5) using a variety of constants.
The model yielded predicted body burdens
over a two-year period of striped bass
growth, but with some unexpected char-
acteristics Prominent among these was
the failure of body burden to become
asymptotic to a "steady-state" value,
dictated primarily by a gradual decline in
ke with growth.
References
Goldstein, A , L Aronow, and S. M
Kalman. 1974. Principles of Drug
Action: The Basis of Pharmacology J.
Wiley and Sons. New York 854 pp
Hamelmk, J. L., R. C Waybrant, and R. S
Ball. 1 971. A proposa;: Exchange equi-
libria control the degree hydrocarbons
are biologically magnified in lentic
environments. Trans. Am. Fish. Soc.
100.207-221.
Mackay, D 1982 Correlation of biocon-
centration factors Environ. Sci Tech-
nol. 16.274-278.
Norstrom, R., A. McKinnon, and A.
DeFnetas. 1976 Abioenergetics-based
model for pollutant accumulation by
fish. Simulation of PCB and methyl-
mercury residue levels in Ottawa River
yellow perch (Perca flavescens) J. Fish
Res. Bd. Canada 33 248-267
O'Connor, J. M andJ.C. Pizza in press.
Pharmacokinetic model for PCB accu-
mulation in marine fish. In- Wastes in
the Ocean, Vol. 9 Academic Press, N.Y.
1984.
Thomann, R V. 1 981. Equilibrium model
of fate of microcontammants in diverse
aquatic food chains. Can. J Fish.
Aquatic Sci 38:280-296
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GUI
Liver & Gall Bladder
1 !
£
4 -
cent of Ingested Dose
£ 10
Alimentary Tract 2>'
I 1 ! 1 I 1
Head X "
10
40
Remaining Carcass
20
100
60
40
I I I I I ^^-
I "^ -5 _a
_ Total Fish $
I I I ! I I
40
80
Time (hrs.)
120
Figure 4. Elimination of PCB from the tissues of striped bass from 48 to 120 hours after
feeding. Elimination rate constants for all tissues except the gill were statistically
similar.
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1.63
O.S/
0
K-
60 SO
-Season I
720
0.7 ppmj^ 016
750 /SO 2/0 240 270 300 330
* - Season II - H
7";>ne fcteys,/
Figure 5. Outcome of the pharmacokinetic model describing dietary PCB accumulation in
striped bass. See text for details.
Table 1. Distribution of C-PCB Among Tissue and Organ Compartments Measured49 Hr After Administration of /, 2, or 3 Doses of PCB. Each
Dose was 387 ng "C-PCB. All the Data are presented as'x ±s-x
Doses
Given
One
(n=5)
Two
(n=3)
Three
Percent of retained burden
M PCB/g (dry)
Percent of cumulative dose
Percent of retained burden
ug PCB/g (dry)
Percent of cumulative dose
Percent of retained burden
ug PCB/g (dry)
Percent of cumulative dose
Gill
247
(±0 38)
0.33
(±0.06)
1.92
(±0.42)
2.44
(±0.18)
0.53
(±0. 1 0)
1.61
(±0.26)
2.10
(±0.22)
0.74
(±0.07)
1 25
(±0.18)
Liver +
Gallbladder
594
(±0 66)
1.51
(±0. 1 7)
4.45
(±0.43)
6.12
(±0.88)
2.98
(±0 23)
3.89
(±0.33)
6.15
(±0.34)
4.47
(±0.58)
363
(±0.13)
Alimentary
Tract
5.35
(±041)
0.54
(±0.06)
4.00
(±0.25)
564
(±0 15)
1.10
(±0.11)
3.66
(±0.34)
6.48
(±1.111
1 73
(±0.16)
3.83
(±0.71)
Spleen
+ Heart
0.57
(±0.08)
034
(±0.06)
0.42
(±0.04)
0.58
(±0. 1 1)
095
(±0.13)
036
(±0 04)
0.56
(±0.04)
0 79
(±0.04)
0.34
(±0 04)
Head
28.54
(±1 00)
0.41
(±0.04)
21 70
(±1.82)
30 11
(±1 12)
069
(±0 15)
19.48
(±1 40)
27.61
(±0.41)
1 01
(±0.08)
16.25
(±0 82)
Carcass
5714
(±1 33)
0.32
(±0.03)
46 14
(±5 40)
55 1
(±1 90)
054
(±0 09)
36.21
(±4.92)
5709
(±1 82)
087
(±0.07)
33 60
(±208)
Epaxial
Muscle
026
(±0.041
0.58
(±0.08)
OS5
(±0.07)
Whole
Fish
100
0.37
(±0.04)
76.24
(±6.26)
100
0.63
(±0.11)
6523
(±6.90)
100
098
(±0.081
5891
(±3 28)
S. GOVERNMENT PRINTING OFFICE-1984/759-102/10660
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J. M. O'Connor is with New York University Medical Center, Institute of
Environmental Medicine, Laboratory for Environmental Studies, Tuxedo Park,
NY 10987.
AlBourquin is the EPA Project Officer (see below).
The complete report, entitled "Polychlorinated Biphenyl Transport in Coastal
Marine Foodwebs,"(Order No. PB 84-232 610; Cost: $13.00, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Gulf Breeze, FL 32561
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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