Environ. Sci. Technol. 2002, 36, 3490-3496
Polychloronaphthalenes and Other
Dioxin-like Compounds in Arctic and
Antarctic Marine Food Webs
S I M O N E T T A C O R S O L I N I , * ,†
KURUNTHACHALAM KANNAN,‡
TAKASHI IMAGAWA,§
SILVANO FOCARDI,† AND JOHN P. GIESY‡
Dipartimento di Scienze Ambientali, Università di Siena,
I-53100 Siena, Italy, National Food Safety and
Toxicology Center, Michigan State University,
East Lansing, Michigan 48824, and National Institute for
Resources and Environment, 16-3 Onogawa,
Tsukuba 305-8569, Japan
Here we report accumulation patterns of polychlorinated
naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins
(PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and pesticides (HCB, p,p′DDE)
in polar organisms (polar bear from Alaskan Arctic and krill,
sharp-spined notothen, crocodile icefish, Antarctic
silverfish, Adélie penguin, South polar skua, and Weddell
seal from the Ross Sea, Antarctica). PCNs, found in most of
the samples, ranged from 1.5 pg/g in krill to 2550 pg/g in
South polar skua on a wet weight basis. Lower chlorinated
PCNs were the predominant congeners in organisms
except skua and polar bear that showed similar PCN
homologue patterns. PCDD/F concentrations were <90
pg/g wet wt in polar organisms; PCDD congeners showed
peculiar accumulation patterns in different organisms.
Correlation existed between PCN and PCB concentrations.
PCB, HCB, and p,p′DDE levels were the highest in skua
liver (11150 ng/g wet wt, 345 ng/g wet wt, and 300 ng/g wet
wt, respectively). Contribution of PCNs to 2,3,7,8tetrachlrodibenzo-p-dioxin equivalents (TEQ) was negligible
(<0.1%) because of the lack of most toxic congeners.
The highest TEQ was found in South polar skua liver (45 pg/
g, wet weight). This is the first study to document the
occurrence of PCNs in Antarctic organisms. High levels
of dioxin-like chemicals in skua suggest the importance of
intake via diet and migration habits, thus POP detection
can be useful to trace migration behavior. Moreover, POP
concentrations in penguin and skua eggs prove their
transfer from the mother to eggs.
Introduction
Polar regions were considered to be pristine until the
contamination by anthropogenic compounds was documented in the 1960s and 1970s (1, 2). Since then, there is a
continuing concern about the potential effects of persistent
* Corresponding author phone: ++39 0577 232939; fax: ++39
0577 232806; e-mail: corsolini@unisi.it. Corresponding address:
Dipartimento di Scienze Ambientali, Università degli Studi di Siena,
Via delle Cerchia, 3-53100 Siena, Italy.
† Università di Siena.
‡ Michigan State University.
§ National Institute for Resources and Environment.
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 36, NO. 16, 2002
organic pollutants (POPs) on polar environments. Arctic and
Antarctic are both remote polar regions. While the former is
a perennial frozen sea surrounded by continents, the latter
is a snow covered continent surrounded by ocean. Apart
from geographical features, several factors such as proximity
to sources and physicochemical properties of POPs may
determine their occurrence and deposition in those regions.
Oceans are a major sink for persistent chemicals, which are
transported from continental areas by atmospheric and
oceanic currents (3-6). The Southern Ocean isolates Antarctica from the other oceans, therefore volatile contaminants
can reach Antarctica only via the transport of air mass.
Furthermore, the southern hemisphere is mainly occupied
by oceans, and land is relatively less populated than the
northern hemisphere. It is therefore expected that Arctic and
Antarctic organisms show a different pattern of contamination by POPs. Global contamination and decreasing levels of
polychlorinated biphenyls (PCBs) and organochlorine pesticides from the northern to the southern hemisphere are
well documented (5-9). Global distillation or fractionation
by condensation in cold polar environments has been
proposed as a mechanism whereby the polar regions may
become sinks for some POPs (7). Due to the low temperatures
and winter darkness, POP degradation is very slow in the
polar regions. Ice can entrap POPs for a longer period and
release them in the environment through ice melting (10)
where they enter the trophic webs, bioaccumulate in the
tissues of organisms, and biomagnify (9). Migratory animals
(South Polar skua and other seabirds, whales) are another
source of pollutants in polar regions with their excrements
and carcasses.
Most volatile compounds are expected to travel from
tropics and other source-areas to polar regions. POPs are
industrial and agricultural chemicals that exhibit several
common properties such as high lipophilicity and high
environmental stability. Moreover, they elicit a variety of
short and long-term toxic responses in organisms including
humans (11-13). Among them, PCNs are a group of 75 compounds based on the naphthalene ring system (C10H8-nCln,
n ) 1-8) where chlorine atoms may substitute one to eight
hydrogens. Because of their good electrical properties,
weather resistance, low flammability, high chemical, and
thermal stability, they were produced and used since the
1930s. They are also byproducts of combustion and chlorinating processes (14). The release and distribution of PCNs
in the environment and their global transport are still not
well-known; apart from production and use of technical
mixtures, chloralkali plants, magnesium refineries, and waste
incinerators are other sources of PCNs (14, 15). As PCNs are
microcontaminants in technical PCB mixtures (16), they are
released into the environment through the use of PCBs and
therefore likely to be transported together, having almost
the same physical and chemical properties (14). PCNs
bioaccumulate in organisms, and they have been detected
in tissues from many areas of the world (i.e. refs 15, 17, and
18). Their bioconcentration factors (BCFs) are moderate to
high depending on the chlorinating level and log BCF ranges
up to 4.53 in several species of fish (17).
In this study, concentrations of polychlorinated naphthalenes (PCNs), polychlorinated dibenzo-p-dioxins (PCDDs),
polychlorinated dibenzofurans (PCDFs), polychlorinated
biphenyls (PCBs), and two pesticides, hexachlorobenzene
(HCB) and p,p′DDE, were measured in tissues of polar bear
from Alaskan Arctic and krill, sharp-spined notothen, crocodile icefish, Antarctic silverfish, Adélie penguin, South polar
skua, and Weddell seal from the Ross Sea, Antarctica.
10.1021/es025511v CCC: $22.00
 2002 American Chemical Society
Published on Web 07/11/2002
FIGURE 1. Sampling locations.
Materials and Methods
Sample Collection. Samples of polar bear (Ursus maritimus)
livers were collected from the tissues archived by the U.S.
Fish and Wildlife Service, Anchorage, AK. Krill (Euphausia
superba), fish (Trematomus pennelli, Chionodraco hamatus,
Pleuragramma antarcticum), Adélie penguin (Pigoscelys
adeliae), South polar skua (Catharacta maccormicki), and
Weddell seal (Leptonichotes weddelli) were collected from
the Ross Sea (Antarctica) in Terra Nova Bay, during the X
(1994/1995) and XI (1995/96) Italian Expeditions. Information
on the sampling sites, methods, and biometric data are given
(Figure 1 and Table 2; see Table 1, Supporting Information).
Chemical Analysis. PCNs, PCBs, and 2,3,7,8-substituted
congeners of PCDDs and PCDFs were analyzed following
the method described elsewhere (19). Tissues of polar bear,
Weddell seal and skua, whole eggs of penguins, and whole
body of krill and fishes were homogenized with sodium sulfate
and Soxhlet extracted with methylene chloride and hexane
(3:1, 400 mL) for 16 h. The extract was rotary evaporated at
40 °C, and an aliquot was used for the determination of fat
VOL. 36, NO. 16, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
3491
TABLE 2. Details of Samples Analyzed j
sample common name
Weddell seal ba
Weddell seal l
krillb
crocodile icefish 3d
crocodile icefish 4
sharp-spined notothen 1e
sharp-spined notothen 2
silverfish 1f
silverfish 4
silverfish 5
adélie penguing
south polar skuah
south polar skua l
south polar skua m
polar bear 7, 8, 9, 10, 11i
sampling method
found dead
bioness
gill net
gill net
gill net
gill net
bioness
bioness
bioness
found unhatched
found unhatched
found dead
sacrified
tissue
sex/age
blubber
liver
wholebody
homogenate
homogenate
wholebody
wholebody
muscle
muscle
muscle
egg
egg
liver
muscle
liver
body wt (g)
length (mm)
adult
nd
nd
52% female
adult
adult
adult
adult
nd/adult
nd/adult
nd/adult
0.6 (av)
299
270
81
61
14.3
13.4
51
42 (av)
nd
nd
nd
nd
135
132
189
adult
nd
nd
nd/adult
nd
nd
n
1
1
poolc
1
1
1
1
1
1
1
5
5
1
1
5
a
Diet: fish, including D. mawsoni, Trematomus, P. antarcticum, cephalopods, krill, zooplankton, decapods. b Diet: ice-attached phyto- and
zooplanktons, invertebrate eggs, its own species. c Pool of whole specimens, total wt ) 20, 22 g. d Diet: fish, krill. e Diet: benthic feeder (fish eggs,
polychaetes, amphipods and molluscs). f Diet: eggs and larvae of copepods and euphausiids, polychaetes, chaetognaths, larger items are ingested
with increase in size. g Diet: plankton, fish, krill. h Diet: fish, krill, eggs and chicks of penguins, other small birds. i Diet: seals, carcasses of
cetaceans. j nd ) not detected, av ) average, b ) blubber, l ) liver, m ) muscle.
content by gravimetry. The remaining extract was spiked
with 13C-TCDD, 13C-TCDF, 13C-OCDD, and 13C-OCDF as
internal standards and interferences removed by fractionation with multilayer silica gel column. The multilayer silica
gel column was prepared by packing a glass column (20 mm
i.d.) with a series of layers of silica gel in the following order:
2 g of silica, 6 g of 40% acidic-silica, 2 g of silica, and a thin
layer of sodium sulfate at the top. The column was cleaned
with 150 mL of hexane prior to the transfer of sample extracts.
Samples were then eluted with 200 mL of hexane and rotary
evaporated to 5 mL. A portion of the aliquot was taken for
the analysis of PCB congeners other than non-ortho coplanar
PCBs. The remaining samples were passed through a glass
column (10 mm i.d.) packed with 1 g of silica gel impregnated
carbon (Wako Pure Chemical Industries, Tokyo, Japan) for
the separation of ortho-substituted PCBs from PCNs and
PCDD/DFs. The first fraction, which was eluted with 150
mL of hexane contained major PCB congeners, which
interfere with the analysis of PCNs and PCDDs/DFs. The
second fraction, which was eluted with 200 mL of toluene
contained non-ortho substituted PCB congeners (77, 126,
and 169), PCNs and PCDDs and PCDFs.
Identification and Quantification. PCB congeners were
identified and quantified using a gas chromatograph (PerkinElmer series 600) equipped with 63Ni electron capture detector
(GC-ECD), following a method described elsewhere (19). A
fused silica capillary column coated with DB-5MS [(5%phenyl)-methylpolysiloxane, 30 m × 0.25 mm i.d.; J&W
Scientific, Folsom, CA, U.S.A.] having a film thickness of 0.25
µm was used. PCB congeners were identified against a
standard mixture containing 100 congeners of known
composition and content. Further details of PCB analysis
are reported elsewhere (19, 20). Identification and quantification of individual PCN and PCDD/DF congeners were
accomplished with a Hewlett-Packard 6890 series highresolution gas chromatograph (HRGC) coupled to a JEOL
JMS-700 high-resolution mass spectrometer (HRMS). PCN
congeners, hepta- and octa-chlorodibenzo-p-dioxins and
furans, and non-ortho coplanar PCBs were separated by DB1701. Tetra- through hexachlorodibenzo-p-dioxins and furans
were separated by a capillary column coated with SP-2331.
The column oven temperature was programmed from 80 to
160 °C at a rate of 40 °C/min and then to 170 °C at 10 °C/min,
to 250 °C at 4 °C/min and then to 296 °C at 8 °C/min with
a final hold time of 10 min. Injector and transfer line
temperatures were held at 260 and 250 °C, respectively.
Helium was used as the carrier gas. The mass spectrometer
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 36, NO. 16, 2002
was operated at an electron impact (EI) energy of 70 eV. PCN
and dioxin congeners were determined by selected ion
monitoring (SIM) at the two most intensive ions of the
molecular ion cluster. A mixture of Halowaxes 1001, 1014,
and 1051 containing all the tri- through octachloronaphthalenes was used as a standard for the quantification of
PCNs. PCDD and PCDF congeners were quantified by
comparing individually resolved peak areas to the corresponding peak areas of the standards. Recoveries of 13Clabeled PCDDs/DFs, which elute in the second fraction
containing PCNs and non-ortho coplanar PCBs, were 7795%. Reported concentrations were not corrected from the
recoveries of internal standard. Recoveries of PCB, PCN,
PCDD, and PCDF congeners through the analytical procedure
were between 90 and 100%. Procedural blanks were analyzed
through the whole analytical procedure to check for interferences. The detection limits of individual PCN and PCB
congener varied depending on the sample mass, response
factor, and interference. Generally, detection limit for
individual congeners was 1-75 pg/g, on a wet weight basis.
Detection limits of PCDD and PCDF congeners varied from
0.3 pg/g, wet weight to 25 pg/g, wet weight, depending on
the samples. Quality control criteria for positive identification
of target compounds include signal-to-noise ratio over three,
isotope ratios of the two monitored ions for each compound
within 15% of the theoretical chlorine values and the
compound should elute at the same GC retention time as
the standards. PCN and PCB congeners are represented by
their IUPAC numbers throughout this manuscript.
Results and Discussion
Results are shown in Tables 3-5 and are given on a wet
weight basis; lipid content of the tissues analyzed is reported
in Table 3.
Polychlorinated Naphthalenes. PCNs were found in most
of the samples analyzed (Table 3). Mean concentration in
the livers of polar bear was 370 ( 390 pg/g wet weight. The
highest PCN concentration of 2550 pg/g was found in the
liver of South polar skua. PCNs were also detected in other
Antarctic organisms including krill, which are at the lower
trophic level in the food web. Concentrations (on a wet weight
basis) of PCNs were 1.5 pg/g in krill, 1.3-2.8 pg/g in the
sharp-spined notothens, 2.1-4.7 pg/g in icefishes, 86 pg/g
in silverfish, and 77 pg/g and 44 pg/g in the Weddell seal
blubber and liver, respectively (Table 3). Generally, concentrations of PCNs were greater in polar bear liver than in
TABLE 3. Concentration of PCNs, HCB, pp′DDE, and PCBsa
krill
icefish 3
icefish 4
notothen 1
notothen 2
silverfish
seal blubber
seal liver
penguin eggs- average (min-max)
skua eggs- average (min-max)
skua liver
skua muscle
polar bear - average (min-max)
bear (SD)
lipids (%)
ΣPCNs
HCB
p,p′DDE
ΣPCBs
1.5
1.4
3.9
2.2
1.6
9.4
100
2.7
10.5 (7.7-12.8)
9.1 (4.5-13.9)
42
1.7
11.4 (7.8-14.9)
2.6
1.5
2.1
4.7
2.8
1.3
86
77
44
NA
NA
2550
97
370 (<0.1-945)
390
0.2
0.4
<0.1
7.8
3.9
4.4
0.8
0.1
<0.1
< 0.1
345
168
16 (1.1-50)
20
<0.1
0.3
<0.1
2.9
3.8
0.3
17
1.2
<0.1
< 0.1
300
129
13 (2.9-28)
9.6
1.9
4.2
12.6
175
111
138
395
34
2.8 (1.3-5.1)
155 (88-222)
11150
2630
2110 (523-5129)
1874
a Concentrations are expressed in ng/g wet weight for PCBs, p,p′-DDE, and HCB, pg/g wet weight for PCNs; NA ) not analyzed; min-max )
minimum and maximum values; SD ) standard deviation.
TABLE 4. Concentration of the Coplanar PCB, PCN,a TCDD, and TCDF Congeners and TEQsb,c in Krill and Fish from the Ross Sead
krill
33′44′-TCB
33′44′5-PCB
33′44′55′-HCB
ΣNonortho PCBs
12357/12467-PCNs
12456-P5CN
12367-P5CN
12378-P5CN
123467/123567-H6CNs
123457/123568-H6CNs
123578-H6CN
123456-H6CN
123678-H6CN
1234567-H7CN
ΣPCNs
2378-T4CDD
12378-P5CDD
123478-H6CDD
123678-H6CDD
123789-H6CDD
1234678-H7CDD
O8CDDs
ΣPCDD
2378-T4CDF
12378-P5CDF
23478-P5CDF
123478-H6CDF
123678-H6CDF
123789-H6CDF
234678-H6CDF
1234678-H7CDF
1234789-H7CDF
O8CDF
ΣPCDFs
ΣTEQs
4.4
3.3
<1
7.7
0.446
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
1.5
<0.1
<0.306
<0.043
<0.043
<0.043
1.5
0.919
2. 9
<0.085
<0.043
<0.043
<0.085
<0.085
<0.085
<0.085
1.531
1.531
<0.001
3.6
<2
icefish 3
icefish 4
3
1.1
1
1
5
<1
9
2.1
<0.1
0.996
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
2.1
4.7
<0.036
<0.041
0.146
1.4
<0.036
<0.041
<0.036
<0.041
<0.036
<0.041
1.8
<0.204
<0.109
<0.041
2.2
1.8
<0.073
<0.122
<0.036
<0.122
<0.036
<0.122
<0.109
<0.881
<0.109
<0.881
<0.109
<0.881
<0.109
<0.881
<0.182
<0.163
0.292
<0.122
<0.109
<0.122
1.2
4.3
average <4
notothen 1
notothen 2
4.1
1.8
1.4
Int
<5
<2
5.5
1.8
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
1.3
2.8
<0.156
<0.065
<0.156
<0.065
<0.156
<0.065
<0.313
<0.065
<0.313
<0.065
<0.234
<0.100
2.057
<0.100
3. 4
0.5
<0.156
<0.065
<0.078
<0.065
<0.078
<0.065
<1.688
<0.065
<1.688
<0.065
<1.688
<0.065
<1.688
<0.065
<0.313
<0.1
<0.234
<0.1
<0.100
<0.1
7.7
0.7
average <5
silverfish
4
3
<0.001
7
<0.1
<0.1
2.33
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
86
0.242
4.069
<0.081
<0.081
<0.081
<0.161
<0.081
4.8
0.565
<0.161
<0.161
<0.081
<0.081
<0.081
<0.081
<0.969
<0.969
2.018
5.2
<23
a PCN congener concentrations are reported only for those which elicit dioxin-like activity, while ΣPCNs includes all detected congeners.
ΣTEQs: sum of TEQ of the congener listed in the table. c Concentrations are expressed in pg/g wet weight; Int ) severe interference. d For total
PCDD summation, nondetectable congeners were assigned a value of detection limit.
b
Weddell seal but less than that in skua. The concentrations
tend to be great in predatory animals such as Weddell seal,
skua, and polar bear, suggesting biomagnification in the polar
food webs. Polar bear and skua show different feeding
habits, the former is a specialized top predator feeding on
marine mammals (21), while the latter is an opportunistic
omnivorous species. The relationship between feeding habits
and xenobiotic-metabolizing enzyme system activities has
already been suggested (22). It may be responsible of the
differences existing in the accumulation patterns both
between them and the other Antarctic organisms.
Our results suggest widespread distribution of PCNs in
remote marine environments and a contamination level
slightly lower than in organism from other locations than
Antarctica. In fact, concentrations of total PCNs in some
species from different sites varied between few parts per
billion (ppb) to hundreds ppb (Table 6, Supporting Information). For example, they were 13-320 ng/g, lipid weight, in
tissues of fishes from the Baltic Sea (17) and in the ranges
of 84-220 ng/g on a lipid weight basis in guillemot from
Sweden (15). Double-crested cormorants and herring gulls
from the Great Lakes (0.38-2.4 ng/g wet wt and 0.083-1.3
VOL. 36, NO. 16, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
3493
TABLE 5. Concentration of the Coplanar PCB, PCN,a TCDD, and TCDF Congeners and TEQsb,c in Arctic and Antarctic Birds and
Mammalsd
seal blubber seal liver
33′44′-TCB
33′44′5-PCB
33′44′55′-HCB
ΣNonortho PCBs
12357/12467-PCNs
12456-P5CN
12367-P5CN
12378-P5CN
123467/123567-H6CNs
123457/123568-H6CNs
123578-H6CN
123456-H6CN
123678-H6CN
1234567-H7CN
ΣPCNs
2378-T4CDD
12378-P5CDD
123478-H6CDD
123678-H6CDD
123789-H6CDD
1234678-H7CDD
O8CDDs
ΣPCDD
2378-T4CDF
12378-P5CDF
23478-P5CDF
123478-H6CDF
123678-H6CDF
123789-H6CDF
234678-H6CDF
1234678-H7CDF
1234789-H7CDF
O8CDF
ΣPCDFs
ΣTEQs
10.2
29
12
51
<0.1
19.8
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
77
1.54
0.306
0.458
0.458
0.458
0.153
0.306
3.7
12.1
0.458
0.611
0.458
0.458
0.611
0.917
0.458
0.611
0.458
17
17
4.1
3.1
3.8
11
<0.1
<0.100
27
<0.1
<0.1
<0.1
<0.1
<0.1
<0.1
14
44
0.169
27
0.846
0.846
0.846
1.3
0.508
31
6.1
0.169
0.169
0.508
0.508
0.508
0.508
1.2
1. 2
1.01
12
18
penguin eggs
skua eggs
skua liver skua muscle
209
565
678
<0.001
<0.001
1453
224
26
31
n.d.
24
<0.1
<0.1
<0.1
<0.1
<0.1
2550
3.9
3.9
1. 1
1. 3
1.083
9.1
10.6
0.4 (0.1-0.9)
6.5 (2.5-12.1)
31
19.8
3.9
27
0.722
24
0.722
0.722
0.181
0.361
9.1
1.8 (1.1-2.6) 13 (6. 5-31)
87
5
38
45
29
78
91
198
40
<0.1
<0.1
<0.1
4.1
<0.1
<0.1
<0.1
<0.1
7.6
97
0.255
1.8
0.255
0.255
0.34
0.255
0.17
3.4
3.1
0.085
1.96
0.255
0.255
1.8
1.8
0.595
0.51
4.23
15
18
bear average (min-max)
4 (3-6)
10.3 (4-22)
89 (9-403)
104 (16-431)
46 (42-49)
36 (23-50)
82 (9.2-213)
35 (35-35)
<0.1
4.1 (4.1-4.1)
<0.1
<0.1
<0.1
<0.1
370 (<0.1-945)
0.52 (<0.1-1.2)
0.463 (<0.1-0.938)
1.08 (<0.1-3.7)
1.05 (<0.1-3.7)
1. 7 (<0.1-3.7)
2.1 (0.469-8.7)
1.6 (0.172-3.7)
8. 5 (4.1-22)
0.303 (<0.1-0.513)
0.76 (<0.1-1.7)
1.2 (<0.1-3.69)
1.6 (<0.1-3.7)
1.6 (<0.1-3.7)
1.6 (<0.1-3.7)
1.6 (<0.1-3.7)
2.8 (0.344-8.7)
2.3 (0.344-8.7)
3.5 (<0.1-6.1)
17 (4-28)
16 (<0.1-21)
a PCN congener concentrations are reported only for those which elicit dioxin-like activity; ΣPCNs includes all detected congeners. b ΣTEQs:
sum of TEQ of the congener listed in the table. c Concentrations are expressed in pg/g wet weight. d For total PCDD summation, nondetectable
congeners were assigned a value of detection limit.
ng/g wet wt, respectively) contained greater chlorinated PCNs
such as tetra-, penta-, and hexa-CNs (23). Isomer composition
of PCNs in polar bears and in South polar skua tissues was
predominated by higher chlorinated congeners: penta-CNs
> tetra-CNs > hexa-CNs (Figure 2). It is interesting to note
that the pattern of PCN homologues in polar bear and South
polar skua was similar, which might be due to the exposure
of skua to PCNs in its wintering grounds. South Polar skua,
which nests in the Ross Sea are reported to migrate to the
Northern Pacific Ocean to overwinter, making a clockwise
loop migration around the Pacific OceansJapan, British
Columbia, Washington, California (24-26). Adults tend to
remain in more Southerly latitudes even at the edge of the
Winter pack ice (27), while sightings of young birds are
reported in the North Pacific regions and American coasts
(26), where they can get exposed to contaminants. Polar bear
shows a good capacity to eliminate persistent organochlorine
compounds introduced by food (28), in particular hexa- and
heptachlorobiphenyls and 2,5- or 2,5,6-chlorine substituted
congeners (21). These findings are consistent with our results;
polar bear of this study showed a higher concentration of
penta-CBs compared to hexa- and hepta-CBs. PCNs show
similar properties to PCBs thus they may behave similarly.
Interestingly, the patterns of PCNs in polar bear and South
polar skua were similar and were different with respect to
the other Antarctic organisms. In other Antarctic organisms,
PCN homologue pattern was dominated by tri-, tetra-, or
penta-CNs (Figure 2). Lower chlorinated PCNs are more
volatile and can reach polar regions by atmospheric transport.
Moreover, PCNs are found in commercial PCB mixtures (16);
therefore, it is likely that they are transported together by air
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masses; correlation existed between concentrations of PCBs
and PCNs in the samples analyzed (r ) 0.98). The PCN profile
observed in polar organisms is different from those observed
in animals from point source areas such as the North
American Great Lakes (19). Concentrations of PCNs in polar
organisms is much less than in organisms from other parts
of the world. The pattern of PCN profiles in technical mixtures
vary (29) (Figure 2). The observed patterns in biota suggest
transfer of low-chlorinated PCNs to Antarctica.
Other Dioxin-like Compounds. PCDD/F congener concentrations in lower trophic Antarctic organisms were less
than the limits of detection; PCDD/F congeners with detectable concentrations were found in livers of skua and polar
bear (Tables 4 and 5). ΣPCDDs/Fs were 31-87 pg/g, wet
weight, in South polar skua liver, 8.5 and 17 pg/g wet weight
(4-28 pg/g wet wt) in polar bear liver, respectively. PCDD/F
congener traces were also found in skua and penguin eggs
(Table 5). The higher concentration of ΣPCNs, ΣPCDDs/Fs,
and coplanar PCBs in predator animals (seal, skua, and bear)
with respect to krill and fish, that occupy a lower trophic
level, may confirm the existence of biomagnification processes although all the analyzed animals do not belong to the
same trophic web. Results were homogeneous in fish and
krill, even if concentrations in the latter were quite high
despite their low position in the trophic web, likely due to
their high lipid content (9). PCNs showed an anomalous high
value in silverfish, but species-specific differences might be
due to different metabolism, lipid composition of tissues or
feeding habits. Lipid composition may be responsible for
the higher PCDD concentration in seal liver compared to the
blubber as for the 1,2,3,7,8-P5CDD that was the highest in
FIGURE 2. PCN isomers pattern in the polar organisms and in some PCN technical mixtures. The graph shows the percentage contribution
of each class of isomers to the total PCN residue; the respective concentrations are given in the table (pg/g wet wt for organisms, µg/g
for technical mixtures; data of technical mixtures are by Yamashita et al. (16)).
seal liver (27 pg/g wet wt). Its value was 3.9 pg/g wet wt in
skua liver, while the opposite pattern was observed for the
O8CDD (10.6 pg/g wet wt in skua liver and 0.508 pg/g wet
wt in seal liver). Anyway the number of samples analyzed
was low. Further studies are needed to better understand
the POP accumulation in Antarctic species, even because,
for example, the 1,2,3,7,8-P5CDD is considered as toxic as
the most toxic 2,3,7,8-T4CDD. Levels in polar bear and skua
are of the same order of magnitude as in double crested
cormorants and herring gull from the polluted Great Lakes
(23). Research bases in Antarctica may contribute to PCDD/F
contamination through incineration activities (30), although
atmospheric transport from other continents is thought to
be the major source.
Mean PCB concentrations in polar bear livers were 2110
(range: 523-5129) ng/g wet weight (Table 3) and fall within
the same ranges reported for the fat of Arctic polar bears
from other locations including the Canadian Arctic (31). In
the Antarctic organisms, the highest concentration of PCBs
was found in South polar skua tissues, with a maximum of
11 150 ng/g and 2630 ng/g, wet weight, in liver and muscle,
respectively. Among the other Antarctic organisms, PCBs
concentrations decreased with trophic level of the food web.
PCBs concentrations were 395 ng/g in the Weddell seal
blubber, 138 ng/g in silverfish, 111-175 ng/g in sharp-spined
notothen, 4.2-12.6 ng/g in crocodile icefish, and 1.9 ng/g in
krill. PCB concentrations in penguin and South polar skua
eggs were 2.8 and 155 ng/g wet weight, respectively. South
polar skuas that nest on the coasts of the Ross Sea spend
about 4 months in Antarctica and then migrate north to
overwinter in the sub-Antarctic or North Pacific regions (2426), that are relatively more contaminated than Antarctic.
Therefore, great concentrations of PCBs in migrating South
polar skua might be due to high position in trophic webs and
feeding habits and to exposure in wintering grounds. PCB
concentration in Weddell seal blubber was slightly less than
the previously reported value of 585 ng/g, wet weight (8).
Nevertheless, PCB concentrations in South polar skua liver
were much greater than those reported earlier (8). This
suggests that Antarctic birds wintering in sub-Antarctic or
North Pacific Islands carry heavy burdens of PCBs from their
wintering grounds, and PCB exposures continue to be of
concern despite the ban on production of PCBs in several
developed countries in the northern hemisphere. POP
concentrations in skua tissue might be a tool to obtain or
confirm investigation on their migration habits; specimens
that overwinter in sub-Antarctic regions can show lower POP
levels compared to those that migrate to the polluted
Northern hemisphere.
VOL. 36, NO. 16, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
3495
We also report here HCB and pp′DDE levels. Concentrations of HCB and pp′DDE in polar bear livers were 16 ng/g
wet wt and 13 ng/g wet wt; highest levels were detected in
skua liver, 345 ng/g wet wt and 300 ng/g wet wt. In the other
Antarctic organisms HCB and pp′DDE were <0.1-7.8 ng/g
wet wt and <0.1-17 ng/g wet wt, respectively (Table 3). HCB
showed a higher concentration than pp′DDE in all the
organisms except the seal and this trend is different from
organisms from other locations (5, 6). DDE has a higher
bioconcentration potential (log BCF ) 4.7 in fish) compared
to the HCB (log BCF ) 3.1-4.5 in fish) but is more volatile
and easily transported by air masses (HCB and pp′DDE vapor
pressure are 1.8 × 10-6 and 1.7 × 10-8 atm, respectively) (32).
Therefore fish-eating seabirds may accumulate a greater
amount of HCB than pp′DDE, that might be lesser available
to organisms in cold polar region. A similar phenomenon
has already been described for HCHs; Lakaschus et al. (33)
reported a strong latitudinal gradient of HCHs with higher
concentration in the Northern hemisphere. Ice can be a trap
for those chemicals such as HCHs and HCB and can release
them during melting (33, 34) as well as PCBs (10).
Toxic Potential. The relative toxic potential of PCNs,
PCDDs, PCDFs, and coplanar PCBs in polar organisms was
calculated by using the Toxic Equivalency Factor (TEF)
approach (11); H4IIE-assay specific relative potency values
of PCNs and PCBs reported earlier (23, 35) were used.
Contribution of ΣPCNs to TEQs was negligible in polar
organisms (<0.1% in skua, 0.2% in polar bear, 0.0003% in
seal, 0.3% in silverfish, 0.0004% in krill, 0% in notothen, and
0.0006% in icefish), because of the lack of toxic higher
chlorinated congeners 123456, 123578, and 123678 (IUPAC
nos. 63, 69, and 70) (Tables 4 and 5). The highest ΣTEQ
concentration was found in South polar skua liver and eggs
(45 and 38 pg/g, wet weight), then in Weddell seal blubber
(18 pg/g) and polar bear (16 pg/g). TEQ values in the other
Antarctic organisms and in penguin eggs were less than 5
pg/g, wet weight (Table 4), except silverfish (23 pg/g wet wt).
These TEQ values are 1-2 orders of magnitude lower than
those considered to elicit toxicological effects in birds and
marine mammals (36, 37). Organochlorine concentrations
in polar animals indicate that top level predators in the food
web such as polar bear and South polar skua are exposed to
considerable levels of these compounds. Differences in POP
levels and patterns suggest differences in metabolism, feeding
habits, and trophic position. Interestingly, levels of different
classes of POPs increase uniformly supporting the hypothesis
that they reach Antarctica depending on their physicochemical properties (7) and from there on biomagnify (9, 38).
Our results confirm widespread global distribution of
PCNs, PCBs, dioxins, and furans. High levels of dioxin-like
chemicals in South polar skua suggest the importance of
intake via diet and migration habits. POP levels in tissues of
Antarctic seabirds and marine mammals can be useful to
trace their migration behavior. Moreover, the detection of
POPs in seabird eggs including penguin and South polar
skua eggs prove their transfer from the mother to eggs, thereby
exposing the future generations.
Acknowledgments
This research was funded by the Italian Antarctic Research
Program (PNRA).
Supporting Information Available
Collection of samples (Table 1) and concentration of polychlorinated naphthalenes in organisms from different locations (Table 6). This material is available free of charge via
the Internet at http://pubs.acs.org.
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Received for review January 8, 2002. Revised manuscript
received May 29, 2002. Accepted June 4, 2002.
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