Health effects from long-range transported contaminants in Arctic top predators: An integrated review based on studies of polar bears and relevant model species

doi:10.1016/j.envint.2010.03.002

Environment International

Volume 36, Issue 5, July 2010, Pages 461-491

https://doi.org/10.1016/j.envint.2010.03.002 Get rights and content

Abstract

The aim of this review is to provide a thorough overview of the health effects from the complexed biomagnified mixture of long-range transported industrial organochlorines (OCs), polybrominated diphenyl ethers (PBDEs), perfluorinated compounds (PFCs) and mercury (Hg) on polar bear (Ursus maritimus) health. Multiple scientific studies of polar bears indicate negative relationships between exposure to these contaminants and health parameters; however, these are all of a correlative nature and do not represent true cause-and-effects. Therefore, information from controlled studies of farmed Norwegian Arctic foxes (Vulpes lagopus) and housed East and West Greenland sledge dogs (Canis familiaris) were included as supportive weight of evidence in the clarification of contaminant exposure and health effects in polar bears. The review showed that hormone and vitamin concentrations, liver, kidney and thyroid gland morphology as well as reproductive and immune systems of polar bears are likely to be influenced by contaminant exposure. Furthermore, exclusively based on polar bear contaminant studies, bone density reduction and neurochemical disruption and DNA hypomethylation of the brain stem seemed to occur. The range of tissue concentration, at which these alterations were observed in polar bears, were ca. 1–70,000 ng/g lw for OCs (blood plasma concentrations of some PCB metabolites even higher), ca. 1–1000 ng/g lw for PBDEs and for PFCs and Hg 114–3052 ng/g ww and 0.1–50 μg/g ww, respectively. Similar concentrations were found in farmed foxes and housed sledge dogs while the lack of dose response designs did not allow an estimation of threshold levels for oral exposure and accumulated tissue concentrations. Nor was it possible to pinpoint a specific group of contaminants being more important than others nor analyze their interactions. For East Greenland polar bears the corresponding daily ΣOC and ΣPBDE oral exposure was estimated to be 35 and 0.34 μg/kg body weight, respectively. Furthermore, PFC concentrations, at which population effect levels could occur, are likely to be reached around year 2012 for the East Greenland polar bear subpopulation if current increasing temporal trends continue. Such proposed reproductive population effects were supported by physiological based pharmacokinetic (PBPK) modelling of critical body residues (CBR) with risk quotients ≥ 1 for ΣPCB, dieldrin, ΣPFC and ΣOHC (organohalogen contaminant). The estimated daily TEQ for East Greenland polar bears and East Greenland sledge dogs were 32–281-folds above WHO ΣTEQ guidelines for humans. Compared to human tolerable daily intake (TDI), these were exceeded for PCBs, dieldrin, chlordanes and ΣHCH in East Greenland polar bears. Comparisons like these should be done with caution, but together with the CBR modelling and T-score estimations, these were the only available tools for polar bear risk evaluation. In conclusion, polar bears seem to be susceptible to contaminant induced stress that may have an overall sub-clinical impact on their health and population status via impacts on their immune and reproductive systems.

Section snippets

Questions addressed by the present review

The present review summarizes the impact from long-range transported contaminants in polar bears (Ursus maritimus) and predator model species (farmed Norwegian Arctic foxes [Vulpes lagopus] and housed Greenland sledge dogs [Canis familiaris]) and may be a useful tool for conventional work and species conservation. Studies of contaminants in the wild can be viewed as a large scale experiment of what happens when a chemical cocktail of thousands of toxic contaminants interact in an uncontrolled

Bioaccumulation of contaminants in polar bears and model species

In this review, Arctic top predators are defined as polar bears while housed West and East Greenland sledge dogs and farmed Norwegian Arctic foxes are included as model species. When obviously stressed, glaucous gulls (Larus hyperboreus) and Inuit data are also referred to while most literature on southern latitude species is excluded due to focus and volume limitations.

Arctic top predators inhabit a cold environment and therefore they rely on energy-rich fatty and waxy tissues as their main

Polar bear necropsy and live-capture sampling

Conducting research on mammal wildlife in the Arctic is logistically difficult and requires large economic resources. The National Environmental Research Institute in Denmark and The Greenland Institute of Natural Resources in Nuuk have succeeded in co-operating with local hunters in East Greenland (Scoreby Sound) since 1983. Thorough cooperation with the hunters has resulted in a unique high-quality sampling of multiple organ tissues and skull necropsies from ca. 200 individual polar bears

Designs of controlled contaminant studies: model species for polar bears

The East Greenland and Svalbard polar bears were chosen as study animals of contaminant and health impacts in the Arctic as these subpopulations contain some of the highest OHC concentrations in the world. Studying effects of contaminants in Arctic wildlife species, such as polar bears, is difficult and it is therefore not always possible to get access to the ideal samples needed to optimize the various analyses. For example, studying pathology in East Greenland polar bears requires a large

Exposure estimates for polar bears and model species

According to Stirling and McEwan, 1975, Kingsley, 1998 the yearly seal blubber consumption of a 200 kg polar bear is approximately 1000 kg. Based on concentrations in ringed seal (Phoca hispida) blubber from East Greenland sampled 1999–2002 (Rigét et al., 2004, Rigét et al., 2006, Rigét et al., 2008, Vorkamp et al., 2004) the mean daily OC exposure of a 200 kg East Greenland polar bear was estimated (Table 1). It is seen that the exposure is increasing in the order HCB < PBDEs < HCHs ∼ Dieldrin <

Health effects in polar bears and model species

The following sections desribe the relationships between contaminant (i.e. OHC and mercury) exposure and multiple organ-system effects in polar bears and relevant model species (Greenland sledge dogs and Norwegian Arctic toxes). It is important to note that the published polar bear data included in this review are correlative and descriptive and therefore do not directly demonstrate contaminant mediated cause and effect relationships. However, the data from model species indicate that what is

Climate change, contaminants and polar bears

Our earth suffers from severe climate change and ca. 10% of the sea ice in the North Pole has disappeared (∼ 72,000 km²/year) during 1970–2009 and the rate is accelerating (ACIA, 2005, Bjørgo et al., 1997, Chapman and Walsh, 1993, Divine and Dick, 2006, Parkinson et al., 1999, Ropelewski, 1985, Vinnikov et al., 1999, Zakharov, 1996). These accelerating biotope changes is suspected to result in the loss of approximately two third of the world's current polar bear population of ca. 25,000 specimens

Conclusions and recommendations

Evidence for multiple OHC and mercury induced sub-clinical health effects were found in East Greenland and Svalbard polar bears and except for bone density reductions, these were successfully supported by controlled studies of West Greenland sledge dogs and Norwegian Arctic foxes. The underlying mechanisms for these effects were thought to be via disruptions of neuro-endocrine loops as well as direct cellular toxicity (Fig. 14). Tissue residues, at which alterations were found, ranged from 1 to

Acknowledgements

I wish to thank The Lundbeck Foundation, Danish Cooperation for Environment in the Arctic (Dancea), The Commission for Scientific Research in Greenland (KVUG) and The Prince Albert Foundation for their financial support. Rune Dietz and Robert J. Letcher are acknowledged for data contribution and national and international colleagues are acknowledged for commenting the MS as are five anonymous reviewers for their valuable inputs. Tinna Christensen and Morten Bjerrum are acknowledged for their

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Review articleHealth effects from long-range transported contaminants in Arctic top predators: An integrated review based on studies of polar bears and relevant model species

Abstract

Section snippets

Questions addressed by the present review

Bioaccumulation of contaminants in polar bears and model species

Polar bear necropsy and live-capture sampling

Designs of controlled contaminant studies: model species for polar bears

Exposure estimates for polar bears and model species

Health effects in polar bears and model species

Climate change, contaminants and polar bears

Conclusions and recommendations

Acknowledgements

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Neurotoxicology

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Toxicol Appl Pharm

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Sci Total Environ

Sci Total Environ

Mar Pollut Bull

Sci Total Environ

Toxicol Appl Pharmacol

Reprod Toxicol

Environ Pollut

Arctic climate impact assessment

Risk assessment of polychlorinated biphenyls

Histopathological effects of mercury in skin-lightening cream

J Environ Pathol Toxicol Oncol

Arctic Monitoring and Assessment Programme: AMAP assessment report — Arctic pollution issues, Oslo

Arctic Monitoring and Assessment Programme: AMAP assessment 2002 — human health in the Arctic. Oslo

Arctic Monitoring and Assessment Programme: AMAP assessment 2002 — persistent organic pollutants in the Arctic. Oslo

Arctic Monitoring and Assessment Programme: AMAP assessment 2002 — heavy metals in the Arctic. Oslo

Arctic Monitoring and Assessment Programme: AMAP Assessment 2009 — Human health in the Arctic. Oslo

Impaired reproductive development in sons of women occupationally exposed to pesticides during pregnancy

Environ Health Perspect

Dopamine, learning and reward-seeking behavior

Act Neurobiol Exp

Mechanisms of methylmercury-induced neurotoxicity

FASEB J

Environmental factors altering thyroid function and their assessment

Environ Health Perspect

Hypospadias and endocrine disruptions: is there a connection?

Environ Health Perspect

Goitres in rats fed polychlorinated biphenyls

Can J Physiol Pharmacol

Is dietary mercury of neurotoxicological concern to wild polar bears (Ursus maritimus)?

Environ Toxicol Chem

Ecotoxicological evaluation of perfluorooctanesulfonate (PFOS)

Rev Environ Contam Toxicol

Temporal and spatial variation in metric asymmetry in skulls of polar bears (Ursus maritimus) from East Greenland and Svalbard

Annal Zool Fenn

Fluctuating asymmetry in metric traits; a practical example of calculating asymmetry, measurement error and repeatability

Annal Zool Fenn

Differences in growth, size and sexual dimorphism in skulls of East Greenland and Svalbard polar bears (Ursus maritimus)

Polar Biol

Skull foramina asymmetry in East Greenland and Svalbard polar bears (Ursus maritimus) in relation to stressful environments

Annal Zool Fenn

Chemotherapy of adrenocortical cancer with o,p′-DDD

Ann int Med

Developmental synergism of steroidal estrogens in sex determination

Environ Health Perspect

Health conditon of the Baltic grey seal (Halichoerus grypus) during two decades

Apmis

Pathology of Baltic grey seal and ringed seal females with special reference to adrenocortical hyperplasia: is environmental pollution the cause of a widely distributed disease syndrome?

Finnish Game Res

Renal lesions in Baltic grey seals (Halichoerus grypus) and ringed seals (Phoca hispida botnica)

Ambio

Review article
Health effects from long-range transported contaminants in Arctic top predators: An integrated review based on studies of polar bears and relevant model species