Marine Pollution Bulletin 87 (2014) 140–146

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Marine Pollution Bulletin

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Contaminant levels in the world’s northernmost harbor seals(Phoca vitulina)

http://dx.doi.org/10.1016/j.marpolbul.2014.08.0010025-326X/� 2014 Elsevier Ltd. All rights reserved.

⇑ Corresponding author. Tel.: +47 77750541.E-mail address: heli.routti@npolar.no (H. Routti).

Heli Routti a,⇑, Christian Lydersen a, Linda Hanssen b, Kit M. Kovacs a

a Norwegian Polar Institute, Fram Centre, 9296 Tromsø, Norwayb Norwegian Institute for Air Research, Fram Centre, 9296 Tromsø, Norway

a r t i c l e i n f o

Article history:Available online 22 August 2014

Keywords:ArcticPersistent organic pollutantsPerfluoroalkyl substancesBiotransformationOH-PCB

a b s t r a c t

The world’s northernmost harbor seal (Phoca vitulina) population, which inhabits Svalbard, Norway,constitutes a genetically distinct population. The present study reports concentrations of 14 PCBs, 5chlordanes, p,p0-DDT, p,p0-DDE, hexachlorobenzene (HCB), mirex, and, a-, b-and c-hexachlorocyclohex-ane (HCH) in blubber, and pentachlorophenol, 4-OH-heptachlorostyrene, 10 OH-PCBs and 14 perfluoro-alkyl substances in plasma of live-captured harbor seals from this population (4 males, 4 females, 4juveniles), sampled in 2009–2010. Concentrations of PCB 153, p,p0-DDE, oxychlordane, a-HCH and mirexand perfluoroalkyl sulfonates in Svalbard harbor seals were considerably lower than harbor seal frommore southerly populations, while concentrations of HCB, OH-PCBs and perfluoroalkyl carboxylates weresimilar for harbor seals from Svalbard and southern areas. Concentrations of PCBs and pesticides in theSvalbard harbor seals were 60–90% lower than levels determined a decade ago in this same population.Current concentrations of legacy POPs are not considered a health risk to the harbor seals from Svalbard.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

The harbor seal (Phoca vitulina) is a widely distributed seal spe-cies that inhabits coastal areas in the north Atlantic and north Paci-fic Regions. This species is frequently serves as a sentinel forpollutants in the northern hemisphere because it occupies a hightrophic level in marine ecosystems and is thus a good subject forthe study of accumulation of persistent organic pollutants (POPs).POPs biomagnify in food webs and can pose health risks due totheir toxicity, particular to species at high trophic levels. For thesereasons their production and use has either been banned orrestricted by the Stockholm Convention (Stockholm Convention,2001). Extremely high concentrations of legacy POPs, such aspolychlorinated biphenyls (PCBs), 1,1,1-Trichloro-2,2-bis(p-chloro-phenyl)ethane (DDT) and its metabolite 2,2-bis(p-chlorophenyl)-1,1-dichloroethylene (DDE) and chlordanes (CHLs) have beenreported in harbor seals from industrialized areas such as theNorth Sea (Weijs et al., 2009b). Although POPs are subject forlong-range transport, considerably lower concentrations have beenreported in the same species from remote northern populations(Wang et al., 2007; Wolkers et al., 2004).

Effects of chronic POPs exposure on the immune and endocrinesystems of harbor seals have been demonstrated by experimentalfeeding studies, and later supported by correlative studies onfree-ranging seals (Brouwer et al., 1989; de Swart et al., 1996;Levin et al., 2005a; Mos et al., 2006; Tabuchi et al., 2006). In vitrostudies indicate that several compounds including PCBs and2,3,7,8-tetrachlorodibenzo-p-dioxin have immunotoxic potentialin harbor seals (Hammond et al., 2005; Levin et al., 2005b). In con-trast, thyroid hormone disruption has been linked mainly tohydroxy (OH) PCBs (Brouwer, 1991; Simon et al., 2011). Formationof OH-PCBs occurs mainly in the liver via the xenobiotic metaboliz-ing enzyme system, which is induced via exposure to POPs (Letcheret al., 2000). This process is called biotransformation. SeveralOH-PCBs are retained in the body, and due to their structuralsimilarity to natural hormones, they pose a high toxicity towardsendocrine system.

Harbor seals living near industrialized areas are exposed to highconcentrations of currently used chemicals, such as various per-fluoroalkyl substances (PFAS) (Ahrens et al., 2009; Dietz et al.,2012; Shaw et al., 2009), in addition to PCBs and organochlorinepesticides still in the ecosystem. Although the production anduse of the major PFASs, perfluorooctane sulfonic acid (PFOS) andrelated substances, have recently been restricted by the StockholmConvention (Stockholm Convention, 2009), it is still manufacturedin relatively large quantities in China (Xie et al., 2013). The

H. Routti et al. / Marine Pollution Bulletin 87 (2014) 140–146 141

production and use of other types of PFASs, such as perfluoroalkylcarboxylates (PFCAs), and their precursors are currently notrestricted. Several PFASs accumulate in the food web in a mannersimilar to lipophilic POPs (Kelly et al., 2009), although they aremore hydrophilic than for example PCBs. They are therefore asso-ciated with proteins rather than lipids in the body (Jones et al.,2003). PFAS pose toxicity risks to proper functioning of both lipidmetabolism and the nervous system (Mariussen, 2012).

Pentachlorphenol (PCP) which is a pesticide that is currently inuse, has also been detected in harbor seals (Dupont et al., 2013).This compound has been proposed for listing under the StockholmConvention (Stockholm Convention, 2011). The presence of PCP inwildlife has received little attention, although it has a high poten-tial to disrupt thyroid hormone transport in plasma (van den Berg,1990).

The world’s northernmost harbor seal population inhabits theSvalbard Archipelago, more specifically the west coast of Prins KarlsForland (Prestrud and Gjertz, 1990). This population is geneticallydistinct, has very limited gene flow with neighboring populationsand also has low levels of genetic variation (Andersen et al.,2011). It exhibits a high degree of sexual dimorphism and short lon-gevity compared to conspecifics living in more southerly areas(Lydersen and Kovacs, 2005). Its isolation in combination with therelatively small size of this population (approximately 2000 indi-viduals) (Merkel et al., 2013) might reduce its resilience to changingenvironmental conditions and diseases (Andersen et al., 2011). TheSvalbard harbor seal population is on the national Red List for Nor-way and is afforded complete protection from hunting. The singleinvestigation of contaminants in Svalbard harbor seals reported rel-atively low concentrations of legacy POPs compared to other harborseal populations (Wolkers et al., 2004). This earlier study byWolkers et al. (2004) was conducted on seals sampled in 1999,and there is a need to reassess concentrations of legacy POPs in thislocale for monitoring. In addition, the Svalbard harbor sealpopulation has not been studied with respect to OH-PCBs, whichhave high toxic potential towards the thyroid system or PFASs,which have been detected at higher concentrations than legacyPOPs in polar bears and seabirds living in Svalbard (Bytingsviket al., 2012; Nøst et al., 2012). In the present study we investigatecurrent concentrations of PCBs, a wide range of chlorinated pesti-cides including current-used (or recently-banned compounds),OH-metabolites of PCBs and PFASs in the world’s northernmost har-bor seal population from Svalbard, Norway. PCBs and neutral pesti-cides were measured in blubber, and phenolic compounds andPFASs in plasma, respectively.

Table 1General biological information on the seals in the present study (median and range);sample size (n) body mass (kg) and length and girth (cm).

n Age Body mass Length Girth

Male 4 7 (6–8) 82 (81–94) 143 (134–153) 112 (111–119)Female 4 7 (5–8) 66 (54–75) 135 (132–137) 106 (100–114)Juvenile 4 1 (1–1) 35 (33–38) 106 (104–115) 81 (77–83)

2. Materials and methods

2.1. Field sampling

Fieldwork was conducted on the west coast of Prins Karls For-land (78�200N, 11�300E), which is the westernmost island of theSvalbard Archipelago, Norway. Twelve animals (4 adult males, 4adult females, 4 juveniles) were captured during 2 Aug–9 Sept2009–2010. The seals were caught using nets set from shore nearhaul-out sites. After capture, seals were transferred into individualrestraint-nets and weighed (Salter spring scales ±0.5 kg). The sealswere then immobilised with an intramuscular injection of Telazol(1 mg kg�1 body mass for sub-adults of both sexes and adultfemales; 0.75 mg kg�1 body mass for adult males) before a lowerincisor was extracted for age determination (this population isthe subject of ongoing demographic studies, see Lydersen andKovacs, 2005). Standard length and girth was measured to thenearest cm while the seals were sedated, and a 50 ml blood samplewas taken from the epidural vein. A blubber biopsy was then taken

using a custom-made hollow stainless steel tube (6 mm diameter)sharpened and sloped at one end to enable a rapid clean cutthrough the skin and collection of a complete core through theentire blubber layer. The biopsy was sampled dorsally, at a pointlocated about 60% of the body length from the cranial end. Thesamples were wrapped in aluminum foil and frozen at �20 �C untilanalyses. All seals were tagged with a Rototag in the webbing ofeach hind flipper before being released. Blood samples were col-lected in heparinised blood tubes, centrifuged for 10 min and thenthe plasma was removed using pipettes. The plasma was subse-quently frozen at �20 �C until analyses. All research activities con-ducted during this study were carried out under permits from theNorwegian Animal Care Authority (Forsøksdyrutvalget Ref. 2009/1449) and the Governor of Svalbard (Sysselmannen på SvalbardRef. 2009/00103-2 a.512). General biological information for theseals is shown in Table 1.

2.2. Chemical analysis

Laboratory analyses of all compounds were performed at theNorwegian Institute for Air Research (NILU), at the Fram Centre,Tromsø, Norway.

2.2.1. PCB and chlorinated pesticides in blubberThe blubber samples were extracted and analyzed for PCBs and

chlorinated pesticides, according to Herzke et al. (2009), with thefollowing modifications, blubber was extracted with a cyclohex-ane–acetone solvent mixture (3:1) followed by purification steps(first using a Gel Permeation Chromatography (GPC) system, witha subsequent clean-up using a florisil-column). Quality assuranceof the analyses was performed by including laboratory blanks andcertified standard reference materials (SRM 1945 – from TheNational Institute of Standards and Technology, Gaithersburg,USA). Results from the SRM analyses indicate that the uncertaintiesin the results are within ±20% of the reference values. Limit ofdetection (LOD) was defined as 3� the signal to noise ratio for theanalyzed matrix. Samples were analyzed on an Agilent 7890A gaschromatograph equipped with a single quadrupole mass spectrom-eter (MS), 5975C inert XL (Agilent Technologies, Böblingen, Ger-many). Electron ionization (EI) was used as ionization method forthe PCBs, DDTs and DDEs, whereas the chlorinated pesticides wereionized by negative chemical ionization (NCI). The MS was operatedin the single ion monitoring mode (SIM). Quantification wasconducted using QuanLynx (Version 4.1) software from Waters(Milford, MA, USA) for PCB28/31, -52, -99, -101, -105, -118, -138,-149, -153, -170, -180, -183, -187 and -194, cis-chlorane, trans-chlorane, cis-nonachlor, trans-nonachlor, oxychlordane, p,p0-DDT,p,p0-DDE, hexachlorobenzene (HCB), mirex, and, a-, b-andc-hexachlorocyclohexane (HCH).

2.2.2. Phenolic compounds in plasmaPlasma samples were extracted, cleaned-up and analyzed

according to the method described by Rylander et al. (2012), withminor modifications. The amount of plasma ranged from 0.75 to1 ml. There are limited reference materials available for the determi-nation of OH-PCB and PCP, but comparisons with other laboratories

142 H. Routti et al. / Marine Pollution Bulletin 87 (2014) 140–146

suggest that uncertainties in our determinations were well withinaccepted norms (±30%). Similar to the PCB and chlorinated pesticideanalyses LOD was defined as 3� the signal to noise ratio for the ana-lyzed matrix. Samples were analyzed on the instrument described inSection 2.2.1. The phenolic compounds were ionized by NCI. The MSwas operated in SIM mode. The quantification of PCP, 4-OH-hepta-chlorostyrene (HpCS), 4-OH-PCB107, 4-OH-PCB120, 4-OH-PCB130,3-OH-PCB138, 4-OH-PCB146, 3-OH-PCB153, 4-OH-PCB163, 4-OH-PCB172, 4-OH-PCB187 and 40-OH-PCB193 was conducted usingQuanLynx (Version 4.1) software from Waters.

2.2.3. PFAS in plasmaPlasma samples were extracted, cleaned-up and analyzed

according to the method described by Hanssen et al. (2013), withminor modifications. The amount of plasma used was 200 lL,and for the determination of perfluorohexane sulfonic acid(PFHxS), the internal standard was mass labeled PFHxS(13C4PFHxS). Quality assurance of the analyses was performed byincluding laboratory blanks and certified standard reference mate-rials (SRM 1958 – from The National Institute of Standards andTechnology, Gaithersburg, USA). The results for the SRM analyseswere within ±20% of the reference values. LOD was set to threetimes the mean concentration determined in blank samples. Thesamples were analyzed by ultrahigh pressure liquid chromatogra-phy triple–quadruple mass-spectrometry (UHPLC–MS/MS). Theanalyses were performed on a Thermo Scientific quaternary Accela1250 pump with a PAL Sample Manager coupled to a Thermo Sci-entific Vantage MS/MS (Vantage TSQ) (all by Thermo Fisher Scien-tific Inc., Waltham, MA, USA). Ionization was conducted in thenegative electrospray ionization mode (ESI-). Quantification wasconducted using LCQuan software from Thermo Scientific (Version2.6) (Thermo Fisher Scientific Inc., Waltham, MA, USA). The follow-ing PFAS were quantified: perfluorobutane sulfonic acid (PFBS);perfluorohexane sulfonic acid (PFHxS); PFOS; perfluorodecanesulfonic acid (PFDS); perfluorooctane sulfonamide (FOSA);perfluorohexanoic acid (PFHxA); perfluoroheptanoic acid (PFHpA);perfluorooctanoic acid (PFOA); perfluorononanoic acid (PFNA);perfluorodecanoic acid (PFDA); perfluoroundecanoic acid(PFUnDA); perfluorododecanoic acid (PFDoDA); perfluorotrideca-noic acid (PFTrDA) and; perfluorotetradecanoic acid (PFTeDA).

2.3. Data analyses

Statistical analyses were performed using R 3.0.2 (RDevelopment Core Team, 2013). Only the compounds detected in80% or more of the seals were included in sum concentrations ofeach compound group. For these compounds, values below theLOD were replaced by half of the LOD (2 values in total). Concen-trations of PCBs and chlorinated pesticides measured in blubberwere converted to lipid weight. The animals were grouped toadults and juveniles based on age and body masses (Lydersenand Kovacs, 2005). Differences in contaminant concentrationsbetween age groups (adult male, adult female and juvenile seals)were tested using analysis of variance followed by Tukey’s HonestSignificant Difference method. Variables were ln-transformed inorder to improve homogeneity of variance and normality. IfTukey’s Honest Significant Difference method indicated differencesbetween juveniles and adults, but not between adult females andmales, adult females and males were combined because samplesizes were small. Null hypothesis was rejected if a < 0.05.

Evaluation of differences between contaminant concentrationsin the harbor seals in the present study and those previouslyreported for other harbor seal populations sampled after 2000were made by comparing similar sex/age groups.

3. Results and discussion

3.1. PCBs and chlorinated pesticides

The contaminant pattern in the harbor seal blubber was domi-nated by RPCBs followed by RDDTs and RCHLs (Table 2). Mirex,HCB and RHCH accounted for only a minor part of the total con-taminant burden in the seals (Table 2). PCB153 and -138 werethe major PCB congeners. p,p0-DDE was detected at eight timeshigher concentrations than its parent compound p,p0-DDT. Thecomposition of RCHLs was dominated by oxychlordane andtrans-nonachlor, which is in accordance with a previous study onringed seals (Pusa hispida) from Svalbard. aHCH made up most ofthe RHCHs, while bHCH accounted for only a few percent of thetotal HCH load. cHCH was not detected in any of the samples.These patterns are in general agreement with previous studies onthe blubber of harbor and ringed seals from Svalbard (Wolkerset al., 2008, 2004).

RPCB concentrations in the juvenile harbor seals were lowerthan in adults (F1,10 = 10.8, p = 0.008, Fig. 1). The same patternwas evident for the other major POPs, RDDTs and RCHLs, althoughthe age groups were not statistically different with respect to thesecompounds (F1,10 = 4.2, p = 0.068 and F1,10 = 4.7, 0.055, respec-tively; Fig. 1). Other studies have found similar results, with lowerconcentrations of POPs in juvenile seals compared to adult males(Muir et al., 2000; Nakata et al., 1995). Generally, age-related accu-mulation does not occur in female phocid seals due to lactationaltransfer of lipophilic POPs (Addison and Brodie, 1987; Nakataet al., 1995). Higher contaminant concentrations in the adultfemale seals in this study compared to juveniles might be relatedto the sampling period taking place in the fall following the breed-ing period in June and the annual molt in July/August. During lac-tation harbor seal females lose �30% of their body mass, mainlyfrom the blubber layer lipids (Bowen et al., 2001) and they transfersome lipophilic POPs stored in their blubber to their offspring inthe process (Wolkers et al., 2004). However, concentrations of lipo-philic contaminants have actually been reported to increase in theblubber of pinniped females during the course of lactation becauselipids are more readily mobilized from blubber than contaminants(Debier et al., 2003).

A previous assessment of contaminant concentrations in harborseals from Svalbard was conducted on seals sampled a decadebefore the present study (Wolkers et al., 2004). The sampling in1999 was conducted in June–July during the lactation and breedingperiod, while the present study sampled seals during the earlyautumn (late August and early September) after the reproductionand molting seasons. This might introduce a bias particularly inadult female seals, so in our period comparisons we use only adultmales. Comparing only adult males sampled during the two timeperiods, RPCB, DDE and aHCH concentrations decreased 80–90%from 1999 to 2009–2010, while a 60% decrease was observed forHCB. Such decreasing trends in PCBs and chlorinate pesticidesare in accordance with numerous temporal trend studies on biotain the Arctic as a result of bans and restrictions by internationalconventions (reviewed by Rigét et al., 2010).

Blubber concentrations of PCB153 were over one hundred timeshigher in stranded harbor seals from the North West Atlantic andNorth Sea compared to present Svalbard harbor seals (Shawet al., 2005; Weijs et al., 2009b), while smaller differences werefound when comparing harbor seals from California and BritishColumbia to Svalbard (Cullon et al., 2012; Greig et al., 2011). Thispattern in the animals from these different regions follows the pat-tern of usage of PCBs geographically, which has been highest inEurope and the east coast of United States, followed by the west-coast of North America (Breivik et al., 2002). Concentrations of

Table 2Concentrations (median [range] ng/g lipid weight) of polychlorinated biphenyls and chlorinated pesticides in blubber of male (n = 4), female (n = 4) and juvenile (n = 4) harborseals sampled in 2009–2010 from Svalbard.

Lipid% R14PCBa R5CHLb R2DDTc R2HCHd HCBe Mirex

Male 36 (24–61) 474 (274–658) 162 (102–243) 188 (119–217) 1.5 (1.0–2.2) 2.9 (1.4–3.5) 14 (8.6–19)Female 30 (25–47) 497 (355–800) 152 (91–210) 222 (119–350) 2.9 (1.5–6.2) 4.3 (2.5–6.1) 16 (16–18)Juvenile 26 (25–29) 274 (199–286) 105 (82–109) 128 (91–141) 2.1 (1.6–2.7) 3.9 (3.5–4.9) 7.4 (6.9–9.1)

a R14PCB: PCB28/31, -52, -99, -101, -105, -118, -138, -149, -153, -170, -180, -183, -187 and -194.b R5CHL: cis-chlorane, trans-chlorane, cis-nonachlor, trans-nonachlor and oxychlordane.c R2DDT: p,p0-DDT and p,p0-DDE.d R2HCH: a and b-hexachlorocyclohexane.e HCB: hexachlorobenzene.

ad juv

200

400

600

800

ΣPC

Bs

(ng/

g lw

)

ad juv

100

200

300

ΣDD

Ts

(ng/

g lw

)

ad juv

100

150

200

ΣCH

Ls (

ng/g

lw)

Fig. 1. Concentrations of R14PCBs, R2DDTs and R5CHLs in blubber of adult (n = 8) and juvenile (n = 4) harbor seals sampled in 2009–2010 from Svalbard.

Table 3Concentrations (median [range] ng/g ww) of phenolic compounds in plasma of male(n = 4), female (n = 4) and juvenile (n = 4) harbor seals sampled in 2009–2010 fromSvalbard.

PCPa 4-OH-HpCSb R4OH-PCBc

Male 0.34 (0.25–0.42) 0.09 (0.07–0.09) 5.2 (2.3–5.4)Female 0.40 (0.28–0.51) 0.10 (0.04–0.13) 2.5 (1.6–9.0)Juvenile 0.41 (0.22–0.67) 0.10 (0.07–0.15) 3.0 (2.5–3.7)

a PCP: pentachlorophenol.b 4-OH-HpCS: 4-OH-heptachlorostyrene.c R4OH-PCB: 4-OH-PCB107, 4-OH-PCB146, 4-OH-PCB163, 4-OH-PCB187.

H. Routti et al. / Marine Pollution Bulletin 87 (2014) 140–146 143

p,p0-DDE, oxychlordane, a-HCH and mirex in harbor seals from theNorth West Atlantic were also ten to one hundred times higherthan the harbor seals from Svalbard sampled in 2009–2010(Shaw et al., 2005). Interestingly, concentrations of HCB were onlytwo to three times higher in harbor seals from the North WestAtlantic compared to the seals of the present study (Shaw et al.,2005). This reflects that HCB has a global distribution that is closestto equilibrium among POPs (Lohmann et al., 2009; Meijer et al.,2003). Contaminant concentrations (PCB153, DDE and oxychlor-dane) in ringed seals from Svalbard (Wolkers et al., 2008) are sim-ilar to the POP levels measured in the harbor seals in the presentstudy.

3.2. Phenolic compounds

Ninety-eight percent of OH-PCBs were comprised of 4-OH-PCB107, while 4-OH-PCB146, 4-OH-PCB163 and 4-OH-PCB187were detected at only minor concentrations. 4-OH-PCB120,3-OH-PCB153, 3-OH-PCB138, 4-OH-PCB130, 4-OH-PCB172 and40-OH-PCB193 were not detected in any of the samples(<0.014 ng/g ww). Previous reports on harbor and other phocidseals have also found 4-OH-PCB107 to be the major OH-metaboliteof PCBs (Dupont et al., 2013; Gabrielsen et al., 2011; Løken et al.,2008; Routti et al., 2008; Weijs et al., 2009a). 4-OH-PCB107 is mostlikely a biotransformation product of PCB105 or PCB118 formed viaformation of arene-oxide involving NIH-shift (Haraguchi, 1998).Both PCB105 and PCB118 have vicinal ortho-meta hydrogen atomsand 61 ortho-chlorine. Biotransformation of PCBs with this partic-ular structure has also been suggested to occur in harbor sealsbased on relative comparisons of PCB patterns in harbor seal dietsvs the tissues of these seals (Boon et al., 1997).

ROH-PCB concentrations were similar among age classes(F2,9 = 0.65, p = 0.55, Table 3). Although lower ROH-PCB concentra-tions have been reported in hooded seal (Cystophora cristata) pups,compared to their mothers, the ROH-PCB concentrations in thegrowing hooded seal pups rapidly reached the concentrations sim-ilar to adults (Gabrielsen et al., 2011).

Circulating concentrations of 4-OH-PCB107 were similar to pre-vious reports for harbor seals from the North Sea and the coast of

the Norwegian mainland (Løken et al., 2008; Weijs et al., 2009a).Interestingly, 4-OH-PCB107 concentrations in harbor seal plasmawere roughly twenty-five times higher than in the plasma ofringed seals (Routti et al., 2008) although contaminant exposuremeasured in blubber is similar between two Svalbard seal popula-tions (this study, Wolkers et al., 2008). This suggests higher bio-transformation capacity for breaking down PCB105 and PCB118in harbor seals compared to ringed seals. Also, the four and threetimes higher ratio of PCB105 and PCB118 to PCB153, respectively,in ringed seals (Wolkers et al., 2008) compared to the present har-bor seals suggests higher biotransformation capacity of PCB105and PCB118 in harbor seals.

Plasma concentrations of PCP were relatively low (<1 ng/g) inthe harbor seals from Svalbard (Table 3). This concurs with previ-ous studies that indicate that PCP is found only at low concentra-tions in pinnipeds from all regions thus far studied (Dupontet al., 2013; Routti et al., 2009; Sandau et al., 2000). AlthoughPCP is a currently used pesticide, it has been suggested that con-centrations of this compound found in pinnipeds are a result of abiotransformation of HCB or pentachloroanisole (Hoekstra et al.,2003; Routti et al., 2009). However, the latter is also a currentlyused pesticide. Concentrations of 4-OH-HpCS, which is a metabo-lite of the industrial by-product octachlorostyrene (Kaminsky andHites, 1984; Sandau et al., 2000), were low (�0.1 ng/g ww) in har-bor seal plasma (Table 3) and corresponded to concentrationsreported for ringed seals from the Arctic and the Baltic Sea(Routti et al., 2009; Sandau et al., 2000).

144 H. Routti et al. / Marine Pollution Bulletin 87 (2014) 140–146

3.3. PFAS

PFOS comprised over 60% of the RPFASs in the harbor sealsfrom Svalbard (Table 4). The other PFSA detected, PFHxS, onlyaccounted for �5% of the PFSA concentrations. PFBS was notdetected in any of the samples and PBDS was only detected intwo samples at very low concentrations. The relatively high occur-rence of PFOS compared to other PFAS is in accordance with previ-ous studies on aquatic biota (reviewed by Houde et al., 2011).PFCAs made up approximately 35% of the RPFASs. Forty percentof PFCAs was PFUnDA, followed by PFNA > PFDA > PFTrDA andPFHpA (Table 4). PFHxA was detected in only a few samples at verylow concentrations (60.04 ng/g). FOSA, which is a precursor ofPFOS, was not detected in any of the harbor seal samples(<0.05 ng/g). This was expected since comparisons of the PFOS/FOSA ratio in the liver of marine mammal species suggested thatpinnipeds have relatively high capacities to biotransform FOSA(Galatius et al., 2013). Furthermore, studies on human blood showthat FOSA is mainly retained in the cellular part of blood and isfound at very low concentrations in plasma (Hanssen et al., 2013).

No differences were observed in concentrations of RPFASsbetween the juvenile, adult male and female harbor seals(F2,9 = 2.5, p = 0.124, Table 4). This is in accordance with previousstudies on harbor porpoises (Phocoena phocoena) (Galatius et al.,2011), while higher RPFAS concentrations have been reported forjuvenile compared to adult bottlenose dolphins (Tursiops truncatus)(Fair et al., 2012).

A previous study reports circulating PFAS concentrationsmeasured in whole blood of harbor seals (Ahrens et al., 2009).For purposes of comparison with the current study these valueswere converted to plasma equivalents using a factor of two(Ehresman et al., 2007). R2PFSA (PFHxS and PFOS) concentrationsin harbor seals from the German Bight were 20 times higher thanthe harbor seals in this study, but interestingly, no difference wasfound in R7PFCA (C8-14 PFCAs) concentrations between these twoseal populations (Ahrens et al., 2009).

3.4. Is the current contaminant exposure a health risk for the harborseals in Svalbard?

Threshold concentrations of POPs in relation to health effects inwildlife are a highly challenging topic because in addition to major

Table 4Concentrations (median [range] ng/g ww) of perfluoroalkyl substances (PFAS) inplasma of male (n = 4), female (n = 4) and juvenile (n = 4) harbor seals sampled in2009–2010 from Svalbard.

Male Female Juvenile

Perfluoroalkyl sulfonates (PFSAs)PFBS <0.001 <0.001 <0.001PFHxS 1.8 (1.6–2.4) 1.4 (1.3–2.3) 2.3 (2.1–3.2)PFOS 43 (40–52) 35 (25–39) 38 (27–46)PFDS <0.02 <0.02 <0.02–0.22RPFSAs 45 (42–55) 37 (26–40) 41 (30–48)

Perfluoroalkyl carboxylates (PFCAs)PFHxA <0.02–0.04 <0.02–0.04 <0.02–0.04PFHpA 0.03 (0.01–0.04) 0.02 (0–0.02) 0.01 (0–0.01)PFOA 0.8 (0.45–1.75) 0.58 (0.31–0.78) 0.59 (0.5–0.86)PFNA 4.3 (3.6–7.4) 4 (2.6–5) 4.5 (3.4–7.8)PFDA 3.9 (3.2–4.2) 3.1 (2.1–4.2) 3.7 (2.4–4.1)PFUnDA 10 (8.8–11) 8.3 (6.7–11) 9.4 (6.6–10)PFDoDA 1.3 (1–1.4) 1.1 (0.8–1.3) 1.1 (0.8–1.4)PFTrDA 2.9 (2.7–3.2) 2.2 (1.5–3.2) 2.2 (2.1–2.8)PFTeDA 0.24 (0.15–0.36) 0.14 (0.08–0.19) 0.12 (0.1–0.19)RPFCAs 24 (22–26) 20 (15–24) 22 (16–26)

Perfluoroalkyl sulfonamidesFOSA <0.05 <0.05 <0.05RPFASs 69 (66–79) 56 (41–64) 64 (46–73)

differences between species, wildlife is exposed to a wide varietyof mixtures of contaminants. However, a threshold of 1.3 lg/g lipidweight of PCBs has been suggested to be an important toxicity ref-erence value for harbor seals (Mos et al., 2010). Similarly, a thresh-old level for a given compound group of 1 lg/g in a given bodycompartment has been proposed as a general indicator of higherrisk of deleterious impacts from POPs on health (Letcher et al.,2010). None of the POP contaminant groups in the harbor sealsin the present study exceeded 1 lg/g, suggesting that the healthof these seals is not at risk from these compounds in Svalbard.

Although OH-PCB concentrations were far below 1 ppm, theyhave a very high potential to bind to proteins transporting thyroidhormones in plasma (Simon et al., 2011). Thyroid hormones play akey role in regulating metabolic rate and thermogenesis, and theyalso influence growth and developmental processes (McNabb,1992). Transthyrethin (TTR), which is involved in the distributionof thyroxine in mammals, is a highly conserved protein among ver-tebrates (Hennebry et al., 2006). Human TTR has thus been used asa model to evaluate disruption of thyroid hormone transport byenvironmental pollutants (Simon et al., 2011). The major OH-PCBin the harbor seals in this study, 4-OH-PCB107, has 3.5 times higherpotency to bind to human TTR compared to its natural ligand, thy-roxine (T4) (Simon et al., 2011). Multiplying molar concentration of4-OH-PCB107 by its relative potency to bind to TTR reveals that theT4-equivalent concentration of 4-OH-PCB107 in this study rangesfrom 16 to 90 nM. Previous studies on harbor seals and Baikal sealsreport plasma T4 concentrations of 30–90 nM (Hall and Thomas,2007; Kunisue et al., 2011). This suggests that binding site compe-tition might take place although the relative importance of differentproteins in transporting thyroxine in pinniped plasma is not known.

4. Conclusions

The present study shows that the world’s northernmost harborseal population is exposed to a wide range of environmental pollu-tants including both legacy and currently used POPs, as well as theirmetabolites. However, concentrations of most of the legacy POPsand RPFSAs (including PFOS) in these seals are considerably lowerthan levels found in more southerly harbor seal populations. In con-trast concentrations of HCB, OH-PCBs and PFCA were roughly sim-ilar to their southern conspecifics. No major differences were foundin concentrations of HCB and PFCAs between the harbor seals fromSvalbard and populations from industrialized areas. Concentrationsof PCBs, DDE and HCB were 60–90% lower than values determinedfor the same harbor seal population a decade earlier. Current con-centrations of legacy POPs are not considered to be a health riskto the harbor seals from Svalbard. However, relatively high concen-trations of OH-PCBs suggest more efficient PCB biotransformationin harbor seals compared to ringed seals, and these might representa risk to thyroid homeostasis. Information on the pollutant status inthis isolated harbor seal population, which is on the national RedList for Norway, is highly important for monitoring.

Acknowledgements

Bjørn Waalberg, Ben Merkel, Lisa Leclerc and Morten Trylandprovided assistance in the field. Mikael Harju performed the quan-tification of phenolic compounds. This study was funded by theNorwegian Research Council (project nr. 184644) and the Norwe-gian Polar Institute.

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