Specific accumulation of perfluorochemicals in harbor seals
(Phoca vitulina concolor) from the northwest Atlantic
Susan Shawa,*, Michelle L. Bergera, Diane Brennera, Lin Taob, Qian Wub, Kurunthachalam Kannanb
aMarine Environmental Research Institute, Center for Marine Studies, P.O. Box 1652, Blue Hill, ME 04614, USA
bWadsworth Center, New York State Department of Health and Department of Environmental Health Sciences, School of Public Health,
State University of New York at Albany, P.O. Box 509, Albany, NY 12201-0509, USA
a r t i c l ei n f o
Received 10 July 2008
Received in revised form 30 October 2008
Accepted 31 October 2008
Available online 19 December 2008
Perfluoroalkyl carboxylic acids
Perfluoroalkyl sulfonic acids
a b s t r a c t
Concentrations of perfluorochemicals (PFCs) including perfluoroalkylsulfonates (PFSAs), and perflu-
oroalkylcarboxylates (PFCAs) were determined in liver of harbor seals (n = 68) collected from the north-
west Atlantic between 2000 and 2007. Of ten PFCs measured, perfluorooctane sulfonate (PFOS)
concentrations were the highest in liver (8–1388 ng/g, ww), followed by perfluoroundecanoic acid (PFUn-
DA) (<1–30.7 ng/g, ww). An unusual accumulation profile of long-chain (C7-C12) PFCAs, and the predom-
inance of PFUnDA, followed by PFNA in seal liver suggested that fluorotelomer alcohols (FTOHs) may be a
major source of PFCAs in the northwest Atlantic. No gender-related differences in the concentrations of
individual PFCs or total PFCs were found. Concentrations of PFOS and PFDS were higher in tissues of the
pups than the adults, whereas concentrations of the PFCAs were similar between pups and adults. PFOS
concentrations in the pups were 2.6-fold higher than those in the adult females, suggesting the impor-
tance of maternal transfer of PFCs. Hepatic PFOS concentrations were strongly, positively correlated with
PFOSA, PFDS and individual PFCAs, indicating that harbor seals are exposed simultaneously to these com-
pounds. Temporal comparisons of hepatic PFC concentrations showed a marginal increase of PFOS and
PFCAs in the adult seals from 2000 to 2007. Unlike the spatial trend observed for polychlorinated biphe-
nyls (PCBs), no south to north (urban–rural–remote) decreasing trend was observed for PFCs, suggesting
the presence of diffuse sources of PFC contamination throughout the northwest Atlantic.
? 2008 Elsevier Ltd. All rights reserved.
Perfluorochemicals (PFCs) are persistent contaminants of
anthropogenic origin that are found distributed in the environ-
ment, in wildlife, and in humans worldwide (Giesy and Kannan,
2001; Kannan et al., 2001, 2002, 2004; Houde et al., 2006). For
over 40 years, PFCs have been used in a variety of industrial and
consumer products, including protective coatings for carpets and
apparel, nonstick cookware, paper coatings, insecticide formula-
tions, and surfactants in fire-fighting foams (Giesy and Kannan,
2002). PFCs are oleophobic and hydrophobic, thus their accumula-
tion is not driven by lipophilicity (Kannan et al., 2001). Some PFCs
have been shown to bioaccumulate and biomagnify in marine food
webs (Tomy et al., 2004; Houde et al., 2006) and elevated
concentrations are detected in apex predators such as marine
mammals (Kannan et al., 2001; Van de Vijver et al., 2005; Houde
et al., 2006).
Two major classes of PFCs are perfluoroalkyl sulfonic acids
(PFSAs), and perfluoroalkyl carboxylic acids (PFCAs). The PFSAs
(e.g., perfluorooctanesulfonate [PFOS] and perfluorooctane sulfon-
amide [PFOSA]), are degradation products of perfluoroalkyl sulfam-
ido alcohols via biotransformation processes and abiotic oxidation
(Xu et al., 2004; D’eon et al., 2006; Martin et al., 2006). Concerns
about widespread global contamination by PFOS led to a phase-
out of production of PFOS-based compounds by a major producer
in 2001 (3M, 2000); however, PFCAs continue to be manufactured
worldwide for use as emulsifiers and additives in the polymeriza-
tion process (Houde et al., 2006). Recent reports have documented
the occurrence of long-chain PFCAs (C8-12) including perfluorooc-
tanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodeca-
perfluorododecanoic acid (PFDoDA) in biota (Keller et al., 2005;
Butt et al., 2007a,b; Hart et al., 2008a,b; Yoo et al., 2008). It is likely
that there are multiple sources of the compounds, both direct and
indirect, including those related to the manufacture and use of
commercial products, and biotic and abiotic degradation of per-
fluoroalkyl sulfamide alcohols (to PFSAs and PFCAs) and flourotel-
omer alcohols (FTOHs) (to PFCAs) (Ellis et al., 2004). Recent studies
suggest that the global distribution of PFSAs and PFCAs may result
from the airborne transport and degradation of volatile precursor
molecules as well as atmospheric and oceanic transport of PFCAs
0045-6535/$ - see front matter ? 2008 Elsevier Ltd. All rights reserved.
* Corresponding author. Tel.: +1 207 374 2135; fax: +1 207 374 2931.
E-mail address: firstname.lastname@example.org (S. Shaw).
Chemosphere 74 (2009) 1037–1043
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/chemosphere
themselves (Ellis et al., 2004; Yamashita et al., 2005; Prevedourous
et al., 2006; Young et al., 2007).
PFCs are known to adversely affect both pre- and post-natal
development and the neuroendocrine and immune systems in ani-
mals via at least five different pathways (Hu et al., 2002; Houde
et al., 2006; Peden-Adams et al., 2008). Recent field studies suggest
that PFC-mediated effects occur in marine mammals, including
infectious disease in California sea otters (Kannan et al., 2006)
and modulation of the peroxisome proliferator-activated receptor
a-cytochrome P450 4A-signaling pathway associated with carcino-
genesis in Baikal seals (Ishibashi et al., 2008a,b). There is no evi-
dence for biodegradation of PFCs in the environment (Giesy and
Kannan, 2002), thus the toxic potential of PFSAs and long-chain
PFCAs in wildlife and humans is of concern.
Most studies to date have focused on Europe, the Arctic, and the
US Pacific and southeast coasts. Little is known about the status of
PFC contamination in marine mammals from the northwest Atlan-
tic. This is one of the most industrialized, heavily populated regions
in the world and environmental contamination has been a concern
since the 1950s. At the top of the food chain, harbor seals (Phoca
vitulina concolor) feed on teleost fishes in coastal and estuarine
waters and are exposed to high levels of persistent and bioaccumu-
lative contaminants (Shaw et al., 2005, 2007, 2008a,b). In 1991–
1992, a morbillivirus outbreak resulted in a mass mortality of
harbor seals in the southern, urbanized part of the northwest
Atlantic harbor seal range (Duignan et al., 1995). The most recent
event occurred in 2006–2007, resulting in the deaths of more than
1000 animals in the same area (Garron and McNulty, 2008). Immu-
nosuppression resulting from chronic exposure to environmental
contaminants could not be ruled out as a contributing factor in
these events. Analyses of harbor seal tissues have shown that these
seals are highly exposed to polychlorinated biphenyls (PCBs), 1,1,1-
trichloro-2,2-bis (p-chlorophenyl) ethane (DDTs) and other chlori-
nated pesticides, dioxin-like compounds including polychlorinated
dibenzo-p-dioxin (PCDDs) and dibenzofurans (PCDFs), and poly-
brominated diphenyl ethers (PBDEs) (Shaw et al., 2005, 2007,
2008a,b). However, no data are presently available on the current
status of PFC contamination in these seals.
The aim of this study was to characterize exposure to PFCs
including PFSAs and PFCAs in harbor seals inhabiting the north-
west Atlantic. Herein we investigate concentrations, patterns, and
trends of PFCs in liver of harbor seals collected from Maine to
New York between 2000 and 2007. This is the first report of the
occurrence of PFCs in marine mammals from the northwest
2. Materials and methods
Liver samples were collected from 68 harbor seals (8 adult
males, 10 adult females, 25 male pups and 25 female pups) that
stranded along the northwest Atlantic coast (from Maine to New
York) between 2000 and 2007 (see map of stranding locations,
Fig. SI-1). Seals were weighed, and standard length and axillary
girth were measured. Age was estimated based on body size. Con-
dition indices were calculated by dividing axillary girth/standard
length and body weight/standard length. Liver samples were
stored in hexane and acetone rinsed aluminum foil or I-Chem jars
in a freezer at ?40 ?C until analysis.
2.2. Chemical analysis
Concentrations of PFCs in liver were determined by the ion pair-
ing extraction method described elsewhere (Kannan et al., 2001;
Tao et al., 2006). Briefly, liver samples (0.3 g) were homogenized
in 3 mL of Milli-Q water. A 2-mL aliquot was spiked with 5 ng each
standards (Wellington Laboratories, Guelph, Canada). One millili-
ter of 0.5 M tetrabutyl-ammonium hydrogen sulfate solution,
2 mL of sodium carbonate buffer (0.25 M, pH 10), and 5 mL
methyl-tert-butyl ether (MTBE) were added to the sample. After
shaking for 40 min, the organic layer was separated by centrifuga-
tion, and the extraction was repeated with 5 mL of MTBE. The ex-
tracts were combined and evaporated to dryness under a gentle
flow of nitrogen, before being reconstituted in 1 mL of methanol,
vortexed, and filtered into an autosampler vial.
Separation of perfluorinated acids was performed using an Agi-
lent 1100 high performance liquid chromatograph (HPLC). Ten
microliter of the extract were injected onto a 100 ? 2 mm (5 lm)
Keystone Betasil C18column. A gradient mobile phase of methanol
and 2 mM ammonium acetate was used. At a flow rate of 300 lL/
min, the mobile phase gradient was ramped from 10% to 75%
methanol in 7 min and then to 100% methanol at 10 min, held at
100% methanol for 2 min, and then ramped down to 10% methanol.
For quantitative analysis, the HPLC was interfaced with an Applied
Biosystems API 2000 tandem mass spectrometer (MS/MS) in nega-
tive electrospray ionization mode. Analyte ions were monitored
using multiple reaction monitoring mode. Parent and daughter
ion transitions were monitored for detection of PFOSA, PFDS, PFOS,
PFHxS,13C4-PFOS,13C4-PFOA,13C2-PFNA,13C2-PFDA, PFHpA, PFOA,
PFNA, PFDA, PFUnDA, and PFDoDA. Quantitation was performed
using a seven-point external calibration curve produced from con-
centrations of 0.1–100 ng/mL. The coefficient of determination (r2)
for each calibration was >0.99. Quality-control standards were
measured after every 10 samples. The coefficient of determination
(r2) for each calibration was >0.99. Quality-control standards were
measured after every 10 samples. All procedural blank peak areas
were less than half the determined limit of quantitation (LOQ) for
each analyte. The LOQ was estimated as three times the lowest
concentration point on the calibration curve, which is accurately
measured within ±30% of its theoretical value. Matrix spikes were
performed several times for liver samples by spiking 5–10 ng of
each target analyte, and passing through the whole analytical pro-
cedure. The coefficient of variation was <20% for each of the ana-
lytes measured. Recoveries of target analytes from the matrix
were between 65% and 99%. Mean recoveries of internal standards
spiked to samples were between 68% and 81%. Concentrations are
reported on a wet weight (ww) basis.
13C2-PFDA as internal
Concentrations were log normalized prior to statistical analysis
using SPSS 14.0. Concentrations below the level of detection were
calculated by treating the result as if half the detection limit. Two-
way analysis of variance was used to test for effects of age class
(adult vs. pup) and gender on contaminant levels. Since age class
consistently had a significant effect, regional comparisons were
performed with Student’s t-tests within each age class separately.
Time trends were analyzed with linear regressions within each age
3. Results and discussion
3.1. PFC concentrations
Concentrations of total PFCs (sum of 10 PFCs: PFOS, PFDS, PFO-
SA, PFHxS, PFHpA, PFOA, PFNA, PFDA, PFUnDA, and PFDoDA) in
harbor seal livers ranged from 18.8 to 1430 ng/g, wet weight
(overall mean ± standard deviation: 247 ± 289 ng/g, ww; n = 68)
S. Shaw et al./Chemosphere 74 (2009) 1037–1043
(Table 1). PFOS was the dominant PFC found in seal liver at concen-
216 ± 279 ng/g ww). Other perfluoroalkyl sulfonates (PFDS and
PFOSA) were detected at much lower concentrations than PFOS,
ranging from <1 to 25.8 ng/g ww. PFHxS was detected at trace con-
centrations in only 9% of the samples. Perfluoroalkyl carboxylates
(PFCAs, C7-C12) were detected at concentrations ranging from <1
to 87.4 ng/g, ww (overall mean RPFCAs 25.9 ng/g, ww). Among
the PFCAs, PFUnDA (C11) was dominant, followed by PFNA (C9)
and PFDA (C10). PFHpA, PFOA, and PFDoDA were detected at low
concentrations in only 3%, 6%, and 18% of the samples, respectively.
PFC concentrations in northwest Atlantic harbor seals were within
the range of concentrations previously reported in liver of marine
mammals from various mid-latitude locations (Table SI-1). Mean
hepatic PFOS concentrations in our samples (216 ng/g, ww) were
similar to those reported in Baltic gray seals (214 ng/g, ww) (Kan-
nan et al., 2002), harbor seals from the Dutch Wadden Sea (160 ng/
g, ww) (Van de Vijver et al., 2005), and harbor porpoises from the
Black Sea (327 ng/g, ww) (Van de Vijver et al., 2007), but higher
than those reported in harbor seals from the southern North Sea
(range: <10–532 ng/g, ww) (Van de Vijver et al., 2003), and the
US Pacific coast (27 ng/g,ww) (Giesy and Kannan, 2001). Higher
PFOS concentrations were reported in harbor seals from the Danish
coast (794 ng/g, ww) (Kallenborn et al., 2004), Baltic ringed seals
(454 ng/g, ww) (Kannan et al., 2002), harbor porpoises from UK
waters (range 16–2420 ng/g, ww) (Law et al., 2008), and bottlenose
dolphins from the Florida coast (489 ng/g, ww) (Kannan et al.,
2001) and the South Carolina coast (914 ng/g, ww) (Houde et al.,
2006). The highest PFOS concentrations were reported in polar
bears from Greenland (2470 ng/g, ww) (Smithwick et al., 2005)
and the Canadian Arctic (3100 ng/g, ww) (Martin et al., 2004a,b),
reflecting the high trophic position of these animals in the marine
food chain. Much lower hepatic PFOS concentrations were reported
in Arctic seals comprising the polar bear diet ranging from a mean
of 8.2 and 4.6 ng/g, ww in ringed and bearded seals from the Bering
and Chukchi Seas, Alaska (Quakenbush and Citta, 2008) to 95.6 ng/
g, ww in ringed seals from East Greenland (Bossi et al., 2005).
No gender-related differences were found in concentrations of
RPFCs and individual PFCs in the adult seals (mean RPFCs
129 ± 120 and 127 ± 64 ng/g, ww in adult males and adult females,
respectively). However, the pups had significantly higher concen-
trations of RPFCs (p = 0.02) and PFOS (p = 0.01) than the adult seals
(Fig. 1). Concentrations of PFDS (p = 0.01) were also higher in the
pups, whereas concentrations of PFCAs were similar in pups and
adults. This suggests that PFCs do not increase with age in harbor
seals. A similar pattern of decreasing PFOS concentrations with
age was reported in Baikal seals (Ishibashi et al., 2008a,b), bottle-
1388 ng/gww(mean ± SD:
nose dolphins from the Florida coast (Kannan et al., 2001), Baltic
gray and ringed seals (Kannan et al., 2002), and harbor porpoises
in the North Sea (Van de Vijver et al., 2005). In polar bears from
Greenland, PFOS concentrations were increasing up to about age
six (Smithwick et al., 2005). The general lack of correlation be-
tween concentrations and age implies that the elimination capac-
ity of PFCs may be significant in adult animals and half-lives
of the compounds may be relatively short (Houde et al., 2006). A
t1/2of 21 weeks was estimated for PFOS in bottlenose dolphins,
and urine was indicated as an important depuration pathway for
PFSAs and PFCAs (Houde et al., 2006). This depuration also sug-
gests more or less continuous exposure to and uptake of PFCs to
maintain tissue concentrations. The accumulation pattern of PFCs
in northwest Atlantic harbor seals differs from that previously re-
ported for lipophilic organic compounds such as PCBs, DDTs, and
PBDEs (Shaw et al., 2005, 2008a,b) in which concentrations in-
crease with age in males and decrease with age in females (after
sexual maturity) due to placental and lactational transfer of these
compounds from females to pups. These observations suggest that
the residence time for PFCs may be shorter in adult seals than that
observed for chlorinated and brominated hydrocarbons.
Although our seals were not mother–pup pairs, mean PFOS con-
centrations in the pups (258 ng/g) were 2.6-fold higher than those
in the adult females (100 ng/g), indicating that maternal transfer is
a significant exposure route for PFCs to pups. Placental transfer of
PFOS has been demonstrated in laboratory animals, and was
shown to affect the post-natal survival of rats (Lau et al., 2003).
Although data on maternal transfer in pinnipeds are scarce, placen-
tal and/or lactational transfer of PFCs have been indicated by the
results of paired studies of bottlenose dolphin mother–calves from
Sarasota Bay, Florida (Houde et al., 2006), melon-headed whale
Concentrations of PFCs (ng/g, wet weight) in liver of northwest Atlantic harbor seals.
Adult males (N = 8) Adult females (N = 10) Pups (N = 50)All (N = 68)
Mean ± SD (Min.–max.)Mean ± SD (Min.–max.) Mean ± SD(Min.–max.)% Detect
58.4 ± 10.6
147 ± 9.4
5.8 ± 5.4
5.6 ± 4.9
11 ± 8.1
3.2 ± 2.2
28 ± 17
98 ± 104
1.7 ± 1.3
1.3 ± 0.86
102 ± 106
129 ± 120
62.8 ± 11.2
144 ± 7.1
5.4 ± 5.3
4.9 ± 3.9
9.0 ± 8.1
2.8 ± 3.1
24 ± 15
100 ± 56
1.3 ± 0.95
103 ± 56
127 ± 64
10.4 ± 2.8
81.4 ± 6.8
1.9 ± 1.3
6.6 ± 7.7
4.4 ± 4.8
9.9 ± 7.0
2.4 ± 1.8
26 ± 18
0.68 ± 0.38
258 ± 312
3.0 ± 4.2
1.7 ± 1.9
264 ± 315
290 ± 323
PFOS (ng/g wet wt)
Fig. 1. PFOS concentrations (ng/g wet weight) in harbor seal livers (n = 68) by age
S. Shaw et al./Chemosphere 74 (2009) 1037–1043
mother–fetuses from the Japanese coast (Hart et al., 2008a,b), and
in a harbor porpoise mother–fetus from northern Europe (Van de
Vijver et al., 2005). Compared to concentrations in the mothers,
PFOS concentrations were up to 10 times higher in the dolphin
calves and were detected in milk (Houde et al., 2006), implying lac-
tational transfer of PFOS to the calves. In fetuses of harbor porpoise
and melon-headed whales, PFOS concentrations were more than
twofold higher than in their mothers. Transplacental rates of PFCs
between whale mothers and fetuses were higher than those ob-
served for PCBs and PBDEs, suggesting that significant placental
transfer and fetal exposure to PFCs occur in cetaceans.
3.2. PFC profiles
Of the 10 PFCs detected in harbor seal liver samples, PFOS con-
tributed 77–89% of the total PFC content, followed by perfluoroun-
decanoic acid (PFUnDA), accounting for 3–8% of the total (Fig. 2).
Whereas PFOS is the predominant PFC found in most wildlife spe-
cies, elevated ratios of PFOS to RPFCs (>0.7) have been reported in
species from various locations including polar bears from the Cana-
dian Arctic (Martin et al., 2004a,b) and Greenland (Bossi et al.,
2005), bottlenose dolphins from the southeastern US coast (Houde
et al., 2006), and humpback dolphins and finless porpoises from
Hong Kong, China (Yeung et al., 2009).
The PFCA profile in harbor seal liver was dominated by PFUnDA
(C11, mean 9.9 ng/g, ww), accounting for 47–63% of the RPFCA
content in liver, followed by PFNA (C9, mean 6.3 ng/g, ww), PFDA
(C10, mean 4.6 ng/g, ww), and PFDoDA (C12, mean 2.5 ng/g, ww)
(Fig. 2). This profile is interesting because for most marine mam-
mals from North American and European coastal waters, PFNA
dominated the PFCA profile and is the second most prevalent
PFC, after PFOS (Martin et al., 2004a,b; Kannan et al., 2005; Smith-
wick et al., 2005; Van de Vijver et al., 2005). PFUnDA was the sec-
ond most abundant PFC in liver of humpback dolphins and finless
porpoises from Hong Kong waters (Yeung et al., 2009), ringed seals
from Greenland (Bossi et al., 2005), fish from Lake Ontario (Martin
et al., 2004a,b), and birds and fish from the Canadian Arctic (Martin
et al., 2004a,b). Concentrations of PFUnDA in skipjack tuna from
several locations in the western North Pacific Ocean were greater
than the concentrations of PFOS (Hart et al., 2008a,b). Although
there are different exposure pathways and bioaccumulative poten-
tials for individual PFCs in marine mammals, seabirds, and fish, it is
clear that PFOS and PFUnDA are present in the northwest Atlantic
marine environment and these compounds can accumulate in tis-
sues of harbor seals.
Another interesting finding of the present study was the pattern
of PFCA profiles in harbor seal liver: PFUnDA (C11) > PFNA
(C9) > PFDA (C10) > PFDoDA (C12), which differs from the general
odd/even pattern observed in biota. In addition, whereas concen-
trations of PFCAs generally decrease with increasing perfluoroalkyl
chain length (Martin et al., 2004a,b), the profile in harbor seals
peaked at PFUnDA, and there were decreasing concentrations of
longer and shorter PFCA homologues alike. The reason for the dif-
ferent contamination profile in the harbor seals is unknown, but it
may be indicative of common sources such as the FTOHs. The find-
ing of higher concentrations of odd-chain-length PFCAs than even-
chain-length PFCAs also implicates FTOHs as a source of exposure
(Ellis et al., 2004; Kannan et al., 2005). Species-specific differences
in elimination capacity for PFCAs can be ruled out, since a consis-
tent odd/even pattern of PFCAs has been reported in harbor seals
(Van de Vijver et al., 2005). FTOHs are manufactured in even-
chain-lengths but are reported to degrade to even- and odd-
chain-length PFCAs (Ellis et al., 2004). While 8:2 FTOH was shown
to degrade to PFOA and PFNA, 10:2 FTOH degraded to PFDA and
PFUnDA in wastewater treatment (Sinclair and Kannan, 2006).
Thus, the predominance of PFUnDA in our samples is suggestive
of 10:2 FTOH as a source of PFUnDA. Atmospheric oxidation of
10:2 FTOH produces equal amounts of PFDA and PFUnDA (Ellis
et al., 2004), but because PFUnDA is more bioaccumulative, this
odd-chain-length acid is predominant in biota. The finding of PFNA
as the second most abundant PFCA in harbor seal liver suggests
that 8:2 FTOH may also be a significant source, since atmospheric
oxidation of 8:2 FTOH to PFOA and PFNA would lead to the pre-
dominance of PFNA. It is also possible that proximity to ambient
sources such as wastewater effluents in the coastal habitat could
obscure the odd- and even-chain-length pattern in these seals.
PFC homologue profiles in the harbor seals varied by age and
gender (Fig. 2). The pups retained a higher proportion of PFOS
and PFNA compared with the adult seals, and short-chain PFCAs
(PFHpA and PFOA) were present in pup liver but were not detected
in the adults. These differences reflect the various exposure path-
ways between pups and adults and suggest that pups may possess
a limited metabolic/elimination capacity for PFCs. PFUnDA was
more abundant in adult females than adult males or the pups,
while PFDoDA was more abundant in adult males. These differ-
ences in profiles could reflect the effect of maternal transfer in
the females, differences in elimination capacity for individual PFCs,
and differences in habitat and prey selection between males and
Significant positive correlations were found between PFOS and
PFCAs in the harbor seal liver samples. PFOS was significantly cor-
related with PFOSA (p < 0.05), as well as PFDS, PFNA, PFDA, and
PFUnDA (p < 0.01), but not with PFDoDA, probably because of the
low detection of this compound (Fig. SI-2). PFOSA, the precursor
molecule for PFOS, was not correlated with PFDS or any of the
PFCAs. Among the PFCAs, PFNA, PFDA, and PFUnDA were highly
Adult M Adult F Pup
Adult M Adult F Pup
% of Total PFCs
Fig. 2. Perfluorochemical profiles in liver of harbor seals from the northwest Atlantic.
S. Shaw et al./Chemosphere 74 (2009) 1037–1043
intercorrelated in seal liver. Overall, these results suggest that the
harbor seals were exposed to PFOS and PFCAs simultaneously,
probably through the same pathways, and the compounds might
have originated from similar sources (Ellis et al., 2004).
3.3. Temporal trends
Using linear regression statistics, we investigated temporal
trends of PFCs in harbor seals collected between 2000 and 2007
(Fig. 3). A trend of increasing PFOS and RPFCA concentrations
was observed in the adult seals between 2000 and 2007, although
this was not statistically significant (p = 0.18 and 0.17 for PFOS and
RPFCA, respectively). In the harbor seal pups, no temporal trend
was observed for PFOS or PFCA concentrations during this seven-
year period. Several studies have reported an increasing trend in
PFOS and PFCA concentrations in marine mammals over the past
20–30 years (Bossi et al., 2005; Smithwick et al., 2006; Dietz
et al., 2008; Ishibashi et al., 2008a,b). In some locations, PFOS con-
centrations appear to be declining following the phase-out of per-
fluorooctanesulfonylfluoride (POSF)-based compounds in 2001
(Butt et al., 2007a,b; Hart et al., 2008a,b), whereas this pattern is
not observed for long-chain PFCAs (C9-11). To examine possible
changes in homologue composition over time, we compared PFC
profiles in harbor seal livers collected at two time points: 2000–
2002 and 2003–2007. PFOS was the dominant PFC and its relative
abundance was similar over time, indicating that the source com-
position of POSF-based compounds has not changed in the north-
west Atlantic marine ecosystem. PFDA was relatively more
abundant in adults and pups and PFUnDA was less abundant in
the adult seals in 2003–2007 compared with 2000–2002, which
suggests changes in uses/releases of PFCAs during this period. In
recent studies, we found a similar lack of a time trend for PCBs,
DDTs, and PBDEs in blubber of harbor seals from this region be-
tween 1991 and 2005 (Shaw et al., 2005, 2008a,b), suggesting con-
tinuous inputs and/or recycling of these persistent halogenated
compounds in the northwest Atlantic.
3.4. Spatial trends
Considered relatively non-migratory, northwest Atlantic harbor
seals nevertheless make seasonal movements along the coast from
Maine southward to the coast of New Jersey (Fig. SI-1) (NMFS,
R2 = 0.12
R2 = 0.02
R2 = 0.11
R2 = 0.02
% of PFCs
Fig. 3. (a) Perfluorochemical concentrations in harbor seals collected along the northwest Atlantic from 2000 to 2007; (b) composition profiles of PFCs in harbor seal liver at
two time points: 2000–2002 and 2003–2007.
S. Shaw et al./Chemosphere 74 (2009) 1037–1043
2007), and accumulate high concentrations of persistent organic
chemicals through consumption of a variety of teleost fishes (Shaw
et al., 2005, 2007, 2008a,b). To examine spatial trends, we com-
pared PFC concentrations in liver of adults and pups from the
industrialized southern area (Massachusetts to New York) with
those from the lightly populated, rural northern area (central and
eastern Maine). PFOS was the dominant PFC in liver at both loca-
tions; mean PFOS concentrations were higher in adult seals from
the southern area (128 ng/g, ww) than the northern area
(70.3 ng/g, ww), although this difference was marginally signifi-
cant (Student’s t-test p = 0.07). This finding is consistent with the
spatial trend reported for loggerhead sea turtles along the US east-
ern coast (Keller et al., 2005). Taken together, the data suggest that
the densely populated mid-Atlantic region may be a large source
region for PFCs. Concentrations of PFCAs were not different by
location in the adult seals, but higher PFDoDA concentrations were
found in pups from the northern area (p = 0.02). This spatial distri-
bution varies from that reported previously for PCBs (Shaw et al.,
2005) and is consistent with the pattern observed for PBDEs in
northwest Atlantic harbor seals (Shaw et al., 2008a,b). Unlike the
trend for PCBs, which decreased with increasing latitude as a func-
tion of distance from sources near industrialized urban centers in
the south, a south to north (urban–rural–remote) decreasing gradi-
ent was not observed for PBDEs or PFCs. It is believed that direct
sources of PFCs including emissions/releases from fluorochemical
plants and airports and military bases with fire-fighting operations
can result in elevated concentrations in urbanized locations
(Houde et al., 2006). However, unlike PCBs, PFCs and PBDEs are
widely used in household and consumer products and therefore
may originate from diffuse common sources within the region
including landfill leachate and wastewater effluent from house-
holds and industries generally (Houde et al., 2006; Law et al.,
2006). Moreover, the PFC contamination pattern in these seals sug-
gests that volatile precursors (sulfonamido alcohols and FTOHs)
are important sources of PFCs. Thus the lack of an urban–rural–re-
mote decreasing spatial gradient in hepatic PFC concentrations im-
plies that such diffuse sources are significant across the harbor seal
range. These results underline the growing problem of PFC con-
tamination of marine ecosystems and the importance of monitor-
ing PFCs in the northwest Atlantic marine food web.
The authors thank Kirk Trabant and members of the NMFS
Northeast Region Stranding Network for providing harbor seal liver
samples for this study. This work was supported by the National
Oceanographic and Atmospheric Administration (NOAA).
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