Elisabeth Lie

Biomagnification of polybrominated diphenyl ether and hexabromocyclododecane flame retardants in the polar bear food chain in Svalbard, Norway.

Concentrations of brominated flame retardants (BFRs), including polybrominated diphenylethers (PBDEs) and hexabromocyclododecane (HBCD), were investigated in an arctic marine food chain consisting of four invertebrate species: polar cod (Boreogadus saida), ringed seals (Pusa hispida), and polar bears (Ursus maritimus). The most abundant BFR, brominated diphenyl ether (BDE)-47, was found in detectable concentrations even in zooplankton, the lowest trophic level examined in this study. Most of the investigated BFRs biomagnified as function of tropic level in the food chain. A noticeable exception occurred at the highest trophic level, the polar bear, in which only BDE-153 was found to increase from its main prey, the ringed seal, indicating that polar bears appear to be able to metabolize and biodegrade most BFRs. In contrast, lower-brominated PBDEs, particularly BDE-47, showed clear signs of bioaccumulation in zooplankton, polar cod, and ringed seals. We suggest that this discrepancy in the fate of BFRs among the different species may be related to greater induction of oxidative detoxification activities in the polar bear. Absorption and debromination rates may be more important for bioaccumulation rates of BFRs in zooplankton, polar cod, and ringed seals. Lipid weight-based concentrations (LWCs) and whole body-based concentrations (WBCs) of BFRs were used to assess biomagnification factors (BMFs). Whole-body concentrations gave the most realistic BMFs, as BMFs derived from LWCs seem to be confounded by the large variability in lipid content of tissues from the investigated species. This study demonstrates that PBDEs and HBCD have reached measurable concentrations even in the lower trophic levels (invertebrates and fish) in the Arctic and biomagnifies in the polar bear food chain.

Organochlorines Affect the Major Androgenic Hormone, Testosterone, in Male Polar Bears (Ursus Maritimus) at Svalbard

Normal sexual development and subsequent reproductive function are dependent on appropriate testosterone production and action. The regulation of steroid hormones, including androgens, can be influenced by both biological and environmental factors, including environmental chemicals. Concentrations of organochlorines are considerably greater in Svalbard polar bears than in polar bears from other regions. Between 1995 and 1998, samples were collected from 121 male polar bears (Ursus maritimus) from the Svalbard area. In this study, testosterone concentration variations were described for male polar bears during different seasons and for all age groups. To study possible relationships between plasma testosterone concentrations and biological factors, such as age, axial girth, and extractable plasma fat, and organochlorine contaminants including hexachlorocyclohexanes, hexachlorobenzene, chlordanes, p,p′–DDE, and 16 individual polychlorinated biphenyl (PCB) congeners, identical statistical analyses were performed on the total population and a subsample of reproductively active adults. Of the biological factors, axial girth showed a significant positive relationship and percentage extractable fat and a significant negative relationship with the testosterone concentrations. Both the Σpesticides and ΣPCBs made significant negative contributions to the variation of the plasma testosterone concentration. The continuous presence of high concentrations of organochlorines in male polar bears throughout their life could possibly aggravate any reproductive toxicity that may have occurred during fetal and early postnatal development.

Does high organochlorine (OC) exposure impair the resistance to infection in polar bears (Ursus maritimus)? Part I: Effect of OCs on the humoral immunity.

This study was undertaken to assess if high levels of organochlorines (OCs) are associated with decreased ability to produce antibodies in free-ranging polar bears (Ursus maritimus) and thus affect the humoral immunity. In 1998 and 1999, 26 and 30 polar bears from Svalbard, Norway, and Churchill, Canada, respectively, were recaptured 32–40 d following immunization with inactivated influenza virus, reovirus, and herpes virus and tetanus toxoid. Blood was sampled at immunization and at recapture for determination of plasma levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), serum immunoglobulin G (IgG) concentrations, and specific antibodies against influenza virus, reovirus, and herpes virus, tetanus toxoid, and Mannheimia haemolytica. The OCs alone contributed with up to 7% to the variations in the immunological parameters. The combination of ∑PCBs (sum of 12 individual PCB congeners), ∑OCPs (sum of 6 OCPs), and biological factors accounted for 40–60% of the variation in the immunological parameters. Negative associations were found between ∑PCBs and serum immunoglobulin G (IgG) levels and between ∑PCBs and increased antibody titers against influenza virus and reovirus following immunization. In contrast, a positive association was registered between ∑PCBs and increased antibodies against tetanus toxoid. ∑OCPs also contributed significantly to the variations in the immunological responses. OCs did not have the same impact on the antibody production against M. haemolytica. The present study demonstrated that high OC levels may impair the polar bears ability to produce antibodies and thus may produce impaired resistance to infections.

Organochlorines Affect the Steroid Hormone Cortisol in Free-Ranging Polar Bears (Ursus maritimus) at Svalbard, Norway

Since the polar bear (Ursus maritimus) is among the most highly organochlorine-contaminated species of the Arctic mammals, there is growing concern that in addition to the natural stressors in the polar bears environment, several organochlorines (OCs) may be able to change basic endocrine pathways. Alterations in the hypothalamic–pituitary–adrenal (HPA) axis may affect plasma cortisol concentrations and inhibit physiological processes involved in the maintenance of homeostasis in a way that may endanger the animals health. Between 1995 and 1998, samples were collected from 121 male and 130 female free-ranging polar bears from the Svalbard area. The aim of the study was to investigate relationships between plasma cortisol concentrations, biological factors, and OCs. The variation in plasma cortisol concentrations was determined for the total sample. Axillary girth and body mass together with their interactions explained more than 50% of the variation in the plasma cortisol concentration. The sum of pesticides (Σpesticides) combined with the sum of polychlorinated biphenyls (ΣPCBs) and their interactions explained over 25% of the variation in the cortisol concentration. Although Σpesticides contributed negatively and ΣPCBs contributed positively to the variation in the plasma cortisol, the over-all contribution of the OCs to the plasma cortisol variation was negative. Despite the complexity on stress responses and the interactions with environmental factors, this study demonstrated that high concentrations of OCs in polar bears might alter plasma cortisol concentrations.

Does high organochlorine (OC) exposure impair the resistance to infection in polar bears (Ursus maritimus)? Part II: Possible effect of OCs on mitogen- and antigen-induced lymphocyte proliferation.

Previous studies have reported alarmingly high levels of organochlorines (OCs), particularly polychlorinated biphenyls (PCBs), in free-ranging polar bears (Ursus maritimus). In this study plasma concentration of PCBs ranged from 14.8 to 200 ng/g wet weight. The aim of the study was to investigate associations between OCs and lymphocyte proliferation after in vitro stimulation with different mitogens and antigens. In 1998 and 1999, 26 and 30 free-ranging polar bears from Svalbard and Churchill, Canada, respectively, were recaptured 32–40 d following immunization with inactivated tetanus toxoid and hemocyanin from keyhole limpets (KLH) to sensitize lymphocytes. At recapture, blood was sampled for determination of plasma levels of PCBs and organochlorine pesticides (OCPs) and lymphocyte proliferation after in vitro stimulation with specific mitogens—phytohemagglutinin (PHA), pokeweed mitogen (PWM), concanavalin A (Con A), lipopolysaccharide (LPS), and purified protein derivative of Mycobacterium aviumsubsp. paratuberculosis (PPD)—and antigens: tetanus toxoid and KLH. The combinations of ΣPCBs (sum of 12 individual PCB congeners), ΣOCPs (sum of 6 OCPs), and their interactions contributed up to 15% of the variations in the lymphocyte responses. By using multiple regression analyses, followed by classical mathematic function analyses, thresholds for immunomodulation were estimated. Depending on the lymphocyte proliferation response studied, the estimated thresholds for significant immunomodulation were within the concentration ranges 32–89 ng/g wet weight (ww) and 7.8–14 ng/g ww for ΣPCBs and ΣOCPs, respectively. Thus, this study demonstrated that OC exposure significantly influences specific lymphocyte proliferation responses and part of the cell-mediated immunity, which also is associated with impaired ability to produce antibodies (Lie et al., 2004). The authors thank the Norwegian Research Council (NFR, numbers 125693/720 and 140730/720), the Norwegian Ministry of Environment Transport and Effect Program, and the Toxic Substances Research Initiative in Canada for funding this study. The authors thank Tine Borgen for technical assistance in the lymphocyte proliferation test.

Organochlorines in top predators at Svalbard : occurrence, levels and effects

Alarmingly high polychlorinated biphenyl (PCB) levels have been found in the top predators such as glaucous gull (Larus hyperboreus) and polar bear (Ursus maritimus) at Svalbard [Gabrielsen, G.W., Skaare, J.U., Polder, A., Bakken, V., 1995. Chlorinated hydrocarbons in glaucous gull (Larus hyperboreus). Sci. Total Environ. 160/161, 337-346; Bernhoft, A., Skaare, J.U., Wiig, O., 1997. Organochlorines in polar bears (Ursus maritimus) at Svalbard. Environ. Pollut. 95, 159-175; Henriksen, E.O., Gabrielsen, G.W., Trudeau, S., Wolkers, H., Sagerup, K., Skaare, J.U., 1999. Organochlorines and possible biochemical effects in glaucous gull (Larus hyperboreus) from Bear Island, the Barents Sea. Arch. Environ. Contam. Toxicol. (in press). ]. Studies of the possible toxic effects, particularly on the immune system and reproduction, of the very high PCB levels in these species are currently being investigated. Data obtained in the field (f.i. reproductive success in polar bears and intestinal nematodes in glaucous gulls), as well as levels of various biochemical and physiological parameters (f.i. thyroid hormones, retinol, EROD activity, CYP1A, IgG), have been coupled with the PCB levels [Skaare, J.U., Wiig, O., Bernhoft, A., 1994. Klorerte organiske miljogifter; Nivâer og effekter i isbjorn. Norwegian Polar Institute Reportseries no. 86, 1-23 (in Norwegian); Bernhoft, A., Skaare, J.U., Wiig, O., 1997. Organochlorines in polar bears (Ursus maritimus) at Svalbard. Environ. Pollut. 95, 159-175; Bernhoft, A., Skaare, J.U., Wiig, O., Derocher, A.E., Larsen, H.J., 2000. Possible immunotoxic effects of organochlorines in polar bears (Ursus maritimus) at Svalbard (in press); Henriksen, E.O., Gabrielsen, G.W., Skaare, J.U., Skjegstad, N., Jensen, B.M., 1998a. Relationship between PCB levels, hepatic EROD activity and plasma retinol in glaucous gull, Larus hyperboreus. Marine Environ. Res. 46, 45-49; Henriksen, E.O., Gabrielsen, G.W., Trudeau, S., Wolkers, H., Sagerup, K., Skaare, J.U. , 1999. Organochlorines and possible biochemical effects in glaucous gull (Larus hyperboreus) from Bear Island, the Barents Sea. Arch. Environ. Contam. Toxicol. (in press); Sagerup, K., Gabrielsen, G.W., Skorping, A., Skaare, J.U., 1998. Association between PCB concentrations and intestinal nematodes in glaucou gulls, Larus hyperboreus, from Bear Island. Organohalogen compounds 39, 449-451; Skaare, J.U., Wiig, O., Bernhoft, A., 1994. Klorerte organiske miljogifter; Nivâer og effekter i isbjorn. Norwegian Polar Institute Reportseries no. 86, 1-23. (in Norwegian)].

PCBs and OH-PCBs in polar bear mother-cub pairs: A comparative study based on plasma levels in 1998 and 2008

The aim of this study was to examine the plasma concentrations and prevalence of polychlorinated biphenyls (PCBs) and hydroxylated PCB-metabolites (OH-PCBs) in polar bear (Ursus maritimus) mothers (n=26) and their 4 months old cubs-of-the-year (n=38) from Svalbard to gain insight into the mother-cub transfer, biotransformation and to evaluate the health risk associated with the exposure to these contaminants. As samplings were performed in 1997/1998 and 2008, we further investigated the differences in levels and pattern of PCBs between the two sampling years. The plasma concentrations of Σ(21)PCBs (1997/1998: 5710 ± 3090 ng/g lipid weight [lw], 2008: 2560 ± 1500 ng/g lw) and Σ(6)OH-PCBs (1997/1998: 228 ± 60 ng/g wet weight [ww], 2008: 80 ± 38 ng/g ww) in mothers were significantly lower in 2008 compared to in 1997/1998. In cubs, the plasma concentrations of Σ(21)PCBs (1997/1998: 14680 ± 5350 ng/g lw, 2008: 6070 ± 2590 ng/g lw) and Σ(6)OH-PCBs (1997/1998: 98 ± 23 ng/g ww, 2008: 49 ± 21 ng/g ww) were also significantly lower in 2008 than in 1997/1998. Σ(21)PCBs in cubs was 2.7 ± 0.7 times higher than in their mothers. This is due to a significant maternal transfer of these contaminants. In contrast, Σ(6)OH-PCBs in cubs were approximately 0.53 ± 0.16 times the concentration in their mothers. This indicates a lower maternal transfer of OH-PCBs compared to PCBs. The majority of the metabolite/precursor-ratios were lower in cubs compared to mothers. This may indicate that cubs have a lower endogenous capacity to biotransform PCBs to OH-PCBs than polar bear mothers. Exposure to PCBs and OH-PCBs is a potential health risk for polar bears, and the levels of PCBs and OH-PCBs in cubs from 2008 were still above levels associated with health effects in humans and wildlife.

In Vitro Assay Shows That PCB Metabolites Completely Saturate Thyroid Hormone Transport Capacity in Blood of Wild Polar Bears (Ursus maritimus)

Persistent chemicals accumulate in the arctic environment due to their chemical reactivity and physicochemical properties and polychlorinated biphenyls (PCBs) are the most concentrated pollutant class in polar bears (Ursus maritimus). Metabolism of PCB and polybrominated biphenyl ether (PBDE) flame-retardants alter their toxicological properties and these metabolites are known to interfere with the binding of thyroid hormone (TH) to transthyretin (TTR) in rodents and humans. In polar bear plasma samples no binding of [125I]-T(4) to TTR was observed after incubation and PAGE separation. Incubation of the plasma samples with [14C]-4-OH-CB107, a compound with a higher binding affinity to TTR than the endogenous ligand T(4) resulted in competitive binding as proven by the appearance of a radio labeled TTR peak in the gel. Plasma incubation with T(4) up to 1 mM, a concentration that is not physiologically relevant anymore did not result in any visible competition. These results give evidence that the binding sites on TTR for T(4) in wild living polar bears are completely saturated. Such saturation of binding sites can explain observed lowered levels of THs and could lead to contaminant transport into the developing fetus.

Metal dynamics in an Antarctic food chain.

The concentrations of copper, zinc, cadmium, selenium and mercury were determined in eggs, muscle, liver, kidney and stomach content of nestilings and adults of the Antarctic petrel, Thalassoica antarctica, and its predator, the south polar skua, Chataracta maccormicki, from Svarthamaren, Dronning Maud Land, Antarctica. The dominant food of the petrels is krill, Euphausia superba. The results show relatively high levels of cadmium in krill, which is assumed to be the main reason for the high levels of cadmium in petrels and skuas. Cadmium is almost absent in eggs, but accumulates very rapidly with age in nestlings. The copper concentrations in livers of nestling petrels reach very high levels during growth. This may be seen in connection with physiological development processes. Mercury seems to be accumulated with age and between trophic levels. Among the nestlings, the mercury levels decrease with increasing age, which may be accomplished by the excretion of mercury through the growth of feathers and as a dilution effect during growth. Selenium and mercury are inversely correlated in nestlings. The levels of zinc were similar for different nestling stages and between nestlings and adults in skuas and petrels.

Ecological risk assessment of persistent organic pollutants in the arctic

Ecological risk assessment of persistent organic chemicals in marine mammals in the Arctic would comprise assessments of both exposure and effect and risk characterization. Results from a comprehensive collaborative study between Norwegian and Canadian researchers, comprising epizoological (ecological) studies (reproductive rate, offspring survival), experimental studies on the immune system function, monitoring studies (e.g. physiological assays of thyroid hormones, retinol, IgG and testosterone) and registration of biological data (e.g. sex, age, reproductive status, nutritional status) were coupled with PCB exposure data. Assessment of the results indicates that population status and health of polar bears with very high PCB levels may be at risk.