Environ. Sci. Technol. 2008, 42, 752–759
Target Tissue Selectivity and Burdens of Diverse Classes of Brominated and Chlorinated Contaminants in Polar Bears (Ursus maritimus) from East Greenland †,‡
WOUTER A. GEBBINK, CHRISTIAN SONNE,§ RUNE DIETZ,§ MAJA KIRKEGAARD,§ ERIK W. BORN,| DEREK C.G. MUIR,⊥ AND R O B E R T J . L E T C H E R * ,†,‡ Science and Technology Branch, National Wildlife Research Centre, Environment Canada, Carleton University, Ottawa, Ontario K1A 0H3, Canada, Department of Chemistry, Carleton University, Ottawa, Ontario K1S 5B6, Canada, Section of Contaminants and Marine Mammals, Department of Arctic Environment, National Environmental Research Institute, University of Aarhus, Frederiksborgvej 399, P.O. Box 358, DK-4000 Roskilde, Denmark, Greenland Institute of Natural Resources, P.O. Box 570, DK-3900 Nuuk, Greenland, Denmark, and Water Science and Technology Directorate, Environment Canada, Burlington, Ontario L7R 4A6, Canada
Received August 3, 2007. Revised manuscript received November 5, 2007. Accepted November 6, 2007.
The tissue-specific composition of sum classes of brominated and chlorinated contaminants and metabolic/degradation byproducts was determined in adult male and female polar bears from East Greenland. Significantly (p < 0.05) higher concentrations of Σ-PCBs, various other organochlorines such as Σ-CHL, p,p′-DDE, Σ-CBz, Σ-HCHs, octachlorostyrene (OCS), Σ-mirex, dieldrin, the flame retardants Σ-PBDEs, and total(R)-hexabromocyclododecane (HBCD), Σ-methylsulfonyl (MeSO2)-PCBs and 3-MeSO2-p,p′-DDE, were found in the adipose and liver tissues relative to whole blood and brain. In contrast, Σ-hydroxyl (OH)-PCB, 4-OH-heptachlorostyrene and Σ-OH-PBDE concentrations were significantly highest (p < 0.05) in whole blood, whereas the highest concentrations of Σ-OH-PBBs were found in the adipose tissue. Based on the total concentrations of all organohalogens in all three tissues and blood, the combined body burden was estimated to be 1.34 ( 0.12 g, where >91% of this amount was accounted for by the adipose tissue alone, followed by the liver, whole blood, and brain. These results show that factors such as protein association and lipid solubility appear to be differentially influencing the toxicokinetics, in terms of tissue composition/ localization and burden, of organohalogen classes with respect to chemical structure and properties such as the type of halogenation (e.g., chlorination or bromination), and the presence * Corresponding author phone: +1 613-998-6696; fax: +1 613998-0458; e-mail:
[email protected]. † National Wildlife Research Centre. ‡ Department of Chemistry. § University of Aarhus. | Greenland Institute of Natural Resources. ⊥ Water Science and Technology Directorate. 752
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 42, NO. 3, 2008
or absence of additional phenyl group substituents (e.g., MeO and OH groups). The tissue- and blood-specific accumulation (or retention) among organohalogen classes indicates that exposure and any potential contaminant-mediated effects in these polar bears are likely tissue or blood specific.
Introduction As the top predator mammal in the arctic marine food web, polar bears (Ursus maritimus) are exposed to high levels of persistent organic pollutants (POPs) and their metabolic/ degradation byproduct relative to other arctic species (1). Relative to other circumpolar populations of polar bears, adipose tissue of East Greenland animals generally has among the highest concentrations of PCBs, methylsulfone-PCB (MeSO2-PCB) metabolites, various classes of organochlorine pesticides (OCs) including chlordanes and DDTs, brominated flame retardants such as polybrominated diphenyl ethers (PBDEs), and hexabromocyclododecanes (HBCDs) (2–6). Until very recently, there have been few reports of the tissue-specific composition of chlorinated and brominated contaminant classes in arctic wildlife species (1). Such information is important with respect to toxicokinetics, exposure and potential contaminant-mediated effects as a function of tissue or organ. Current knowledge on brominated and chlorinated contaminants in polar bears is restricted to mainly adipose tissue and whole blood. PCB, OC pesticide, MeSO2-PCB/-DDE, PBDE, and/or hydroxylated (OH) PCB concentrations have been reported separately and noncomparatively in liver tissue, adipose tissue (including various fat depots), and/or whole blood of polar bears from circumpolar populations in Alaska, Canada, East Greenland, and/or Svalbard (7–10). For other arctic marine mammals and birds, tissue-specific composition has been reported for PCBs and OC pesticides in beluga whale (Delphinapterus leucas) from St. Lawrence estuary the Canadian high arctic (11), and for various chlorinated and brominated contaminants in glaucous gull (Larus hyperboreus) from the Norwegian arctic (12). Most POPs are characterized as lipophilic, and therefore, fat is an important tissue with respect to accumulation, and thus is used as a representative tissue for monitoring POPs in polar bear (3–6). Adipose tissue, which is mostly a subcutaneous layer and delineated from the underlying muscle, represents roughly 82% of total body fat stores in polar bears (13), although liver and brain are also important lipid-bearing tissues. Regardless, emerging organohalogen and degradation/metabolic products continue to be characterized in wildlife, where accumulation (and/or retention) is governed by lipophilic properties but also by other factors such as noncovalent binding to proteins. For example, OHPCBs and OH-PBDEs are retained in blood due to competitive binding affinity for circulating transport proteins such as the thyroid hormone transport protein TTR (transthyretin) (14). The physicochemical properties (e.g., log KOW) of a chemical are a function of molecular structure that can influence the toxicokinetics including tissue-specific localization and concentration. Important molecular attributes of environmentally relevant organohalogens that can influence toxiciokinetics include the type of halogenation (e.g., chlorine and bromine substitution), and the presence or absence of additional phenyl group substituents (e.g., MeO-, MeSO2-, and OH-groups). Organs and body compartments such as liver, brain, adipose, and whole blood possess contrasting biochemical and physiological functions that can influence the localization 10.1021/es071941f CCC: $40.75
2008 American Chemical Society
Published on Web 12/19/2007
TABLE 1. Arithmetic Mean Concentrations (±SE) (ng/g wet wt) of Various Classes of Neutral and Phenolic Organohalogen Compounds in the Adipose Tissue, Blood, Brain and Liver of Polar Bears from East Greenland (n = 20)a analyte
mean ((SE)
no. samples
mean ((SE)
no. samples
mean ((SE)
>MLOQ
mean ((SE)
>MLOQ
lipid (%) Σ-PCBc Σ-MeSO2-PCBd Σ-OH-PCBe Σ-CHLf p,p′-DDE 3-MeSO2-p,p′-DDE Σ-CBzg Σ-HCHh OCS Σ-mirexI dieldrin 4-OH-HpCS PCP Σ-PBDEj total-(R)-HBCD Σ-OH-PBDEk Σ-OH-PBBl Σ-MeO-PBDEm
90 ( 4.1 5,025 ( 2,236 340 ( 193 58 ( 35 1,190 ( 118 324 ( 45 8(6 37 ( 6.3 195 ( 33 12 ( 2.2 3.6 ( 1.3 147 ( 14 0.7 ( 0.1 1.3 ( 0.5 83 ( 19 41 ( 5.6 0.9 ( 0.5 14 ( 10
