Environ. Sci. Technol. 2008, 42, 2701–2707
Increasing Perfluoroalkyl Contaminants in East Greenland Polar Bears (Ursus maritimus): A New Toxic Threat to the Arctic Bears R . D I E T Z , * ,† R . B O S S I , ‡ F . F . R I G É T , † C. SONNE,† AND E. W. BORN§ Department of Arctic Environment and Department of Atmospheric Environment, National Environmental Research Institute (NERI), University of Aarhus, Frederiksborgvej 399, P. O. Box 358, DK-4000 Roskilde, Denmark, and Greenland Institute of Natural Resources, P. O. Box 570, DK-3900 Nuuk, Greenland
Received November 2, 2007. Revised manuscript received January 17, 2008. Accepted January 17, 2008.
A well-defined subsample of 128 subadult (3–5 years) polar bears (Ursus maritimus) from 19 sampling years within the period 1984–2006 was investigated for perfluoroalkyl contaminants (PFCs). Linear regression analysis of logarithmic-transformed median concentrations showed significant annual increases for PFOS (4.7%), PFNA (6.1%), PFUnA (5.9%), PFDA (4.3%), PFTrA (8.5%), PFOA (2.3%), and PFDoA (5.2%). For four of the PFCs, a LOESS smoother model provided significantly better descriptions, revealing steeper linear annual increases for PFOSA of 9.2% after 1990 and between 18.6 and 27.4% for PFOS, PFDA, and PFTrA after 2000. Concentrations of ΣPFCs, by 2006, exceeded the concentrations of all conventional OHCs (organohalogen compounds), of which several have been documented to correlate with a number of negative health effects. If the PFC concentrations in polar bears continue to increase with the steepest observed trends, then the lowest noadverse-effect level (NOAEL) and lowest-adverse-effect level (LOAEL) detected for rats and monkeys will be exceeded in 2014–2024. In addition, the rapidly increasing concentrations of PFCs are likely to cause cumulative and combined effects on the polar bear, compounding the already detected threats from OHCs.
Introduction Four key criteria exist to include persistent organic pollutants (POPs) in international conventions: chemical persistence, bioaccumulating properties, long-range transport and adverse effects (1). Perfluoroalkyl contaminants (PFCs) have not been fully documented to meet the criteria for inclusion under the Stockholm convention on POPs; but PFCs with 8 or more carbons are likely to be identified for inclusion on the POPs list (e.g., see refs 2–5). The use of most conventional POPs or organohalogenated compounds (OHCs) such as * Corresponding author phone: +45 46301938; fax: +45 46301914; e-mail:
[email protected]. † Department of Arctic Environment, NERI, University of Aarhus. ‡ Department of Atmospheric Environment, NERI, University of Aarhus. § Greenland Institute of Natural Resources. 10.1021/es7025938 CCC: $40.75
Published on Web 02/29/2008
2008 American Chemical Society
PCBs, HCB, PCDD/Fs and DDT are subject to phase outs, emission reductions, or limited use due to national bans and international conventions such as the UNECE LRTAP (Longe Range Transboundary Air Pollution) Convention and its POPs protocol. However, a number of newly emerging contaminants including PFCs, have not yet been regulated (6). Due to the observed toxicity of PFOS, the 3M Company commenced reduction of perfluorooctane sulfonyl fluoride (PFOSF) in 2001 (7, 8). Smithwick et al. (9) argued that polar bears are an important sentinel species for Arctic marine food webs, because they are apex predators with well-studied population dynamics and circumpolar distribution. The presence and distribution of PFOS in liver tissues of this species were first described by Giesy and Kannan (2) for bears from Alaska, and later Bossi et al. (5), Martin et al. (3), and Kannan et al. (10) reported that PFC concentrations in polar bears are the highest in any species to date. Smithwick et al. (11, 12) provided further details on age, gender, and geographic trends of PFCs. In addition, it has been shown that polar bears from East Greenland and southern Hudson Bay carry the highest PFC concentrations among polar bears (12). The high liver tissue concentration observed in East Greenland (e.g., PFOS, 2140 ng/g ww) was in the magnitude of ΣPCB, and such high exposures raised the question of how the concentrations of PCAs have evolved over time. Detecting such a time trend became the goal of the present investigation. Studies on Canadian and Alaskan polar bears have indicated an increase in PFCs in the period from 1982 to 2002 (9). Such time trends have not been conducted since; neither have they been conducted for the Eastern Arctic such as Greenland. Studies of ringed seals (Phoca hispida) from Greenland waters have, however, shown increases in PFCs in both East and West Greenland between 1982 and 2003 (13). Time trend studies on PFCs in Canadian ringed seals from two regions have shown both increases and in some cases followed by decreases, depending on the area, period, and congener in question (8). In 2001, PFCs in the polymers and their degradation product as well as residuals during manufacture and use of fire-fighting foams, cleaners, lubricants, and various coatings were discovered as an anthropogenic and novel group of persistent organic pollutants in the environment and humans (2). Perfluorinated surfactants have distribution patterns similar to those of PCBs, which likewise biomagnify in the marine food webs and show the highest concentrations in East Greenland (e.g., see refs 6 and 14–17). Unlike PCBss which accumulate in lipid-rich tissuesPFCs bind to blood proteins and accumulate mainly in the liver, kidneys, and bile secretions. Due to low volatility of PFCs, their atmospheric transport to remote regions such as the Arctic had been unexpected (18–21). Theories about PFCs being transported to the Arctic waters via ocean currents, where biomagnification will take place, have also been suggested (22, 23). In the present paper we present PFC measurement in livers of a well-defined sample of subadult (3–5 years) East Greenland polar bears including a discussion on health implications and future wildlife exposure scenarios in combination with threats from conventional OHCs and high mercury loads (6, 24–37).
Materials and Methods Samples and Age Determination. Polar bear samples were collected from Ittoqqortoormiit (Scoresby Sound) in Central East Greenland from 1984 to 2006 in cooperation with local VOL. 42, NO. 7, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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TABLE 1. Results of Linear Regression Analysis, Using Log-Transformed Annually Median PFC Concentrations, Including a Test of Whether the LOESS Smoother Defined the Temporal Trend Better than the Linear Modela log-linear regression (1984–2006) contaminant
P
r
n
test whether LOESS smoother (LS) is better than the linear model P
PFOS PFOSA PFOA PFNA PFDA PFUnA PFDoA PFTrA
