Trends of perfluorochemicals in Greenland ringed seals and polar bears: Indications of shifts to decreasing trends Frank Rigét a,⇑ , Rossana Bossi b , Christian Sonne a , Katrin Vorkamp b , Rune Dietz a a Department of Bioscience, Aarhus University, Arctic Research Centre (ARC), Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark b Department of Environmental Science, Aarhus University, Arctic Research Centre (ARC), Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark highlights  Perfluorinated alkylated substances (PFASs) in Greenland polar bears and ringed seals.  Several PFASs peaked around year 2006.  The peak occurred later in Greenland compared to similar species from Canadian Arctic and European seal species. article info Article history: Received 22 March 2013 Received in revised form 1 August 2013 Accepted 5 August 2013 Available online 8 September 2013 Keywords: Greenland Perfluorochemicals Polar bear Ringed seal Temporal trends abstract Time-series of perfluorinated alkylated substances (PFASs) in East Greenland polar bears and East and West Greenland ringed seals were updated in order to deduce whether a response to the major reduction in perfluoroalkyl production in the early 2000s had occurred. Previous studies had documented an exponential increase of perfluorooctane sulphonate (PFOS) in liver tissue from both species. In the pres- ent study, PFOS was still the far most dominant compound constituting 92% (West Greenland ringed seals), 88% (East Greenland ringed seals) and 85% (East Greenland polar bears). The PFOS concentrations increased up to 2006 with doubling times of approximately 6 years for the ringed seal populations and 14 years in case of polar bears. Since then a rapid decrease has occurred with clearing half-lives of approximately 1, 2 and 4 years, respectively. In polar bears perfluorohexane sulphonate (PFHxS) and perfluorooctane sulphonamide (PFOSA) also showed decreasing trends in recent years as do perfluoro- decanoic acid (PFDA) and perfluoroundecanoic acid (PFUnA). For the West Greenland ringed seal popu- lation perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), PFDA and PFUnA peaked in the mid 2000s, whereas PFNA, PFDA and PFUnA in the East Greenland population have been stable or increas- ing in recent years. The peak of PFASs in Greenland ringed seals and polar bears occurred at a later time than in Canadian seals and polar bears and considerably later than observed in seal species from more southern latitudes. We suggest that this could be explained by the distance to emission hot-spots and differences in long-range transport to the Arctic. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Perfluorinated alkylated substances (PFASs) are used as surfac- tants or raw materials in surfactant production and can be formed in the environment from polyfluorinated precursors (Buck et al., 2011). They are commonly divided into two main groups: perfluo- rinated carboxylic acids (PFCAs) and perfluorinated sulphonic acids (PFSAs). Once emitted to the environment, they are resistant to hydrolysis, photolysis, biodegradation, or metabolism because of the energy of the carbon–fluorine bond (Banks et al., 1994). There- fore PFASs are very persistent in the environment and they are transported world-wide including transport to the Arctic region (Butt et al., 2010). The pathways of PFASs to the Arctic have been subject of great scientific interest and two main transport ways have been proposed: One pathway is that of airborne precursors, such as fluorotelomer alcohols (FTOHs), fluorinated sulphonamides (FOSAs), and sulphonamido ethanols (FOSEs) followed by atmo- spheric oxidative transformations to PFSAs and PFCAs and subse- quent wet and dry deposition (Ellis et al., 2004; Schenker et al., 2008). Young and Mabury (2010) recently reviewed the atmo- spheric formation of perfluorinated acids. The other pathway is as direct long-range oceanic transport (Schenker et al., 2008). The relative contribution of each pathway to PFAS levels in the Arctic is not fully understood (Butt et al., 2010). In biota PFCAs and PFSAs bind to blood proteins and therefore bioaccumulate mainly in liver, kidneys and bile secretions in contrast to the lipophilic legacy persistent organic pollutants (POPs) (Jones et al., 2003). 0045-6535/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2013.08.015 ⇑ Corresponding author. Tel.: +45 30 18 31 15. E-mail address: ffr@dmu.dk (F. Rigét). Chemosphere 93 (2013) 1607–1614 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere