Two decades of biomonitoring polar bear health in Greenland: a review

Abstract

SummaryWe present an overview of studies of anthropogenic pollutants in East Greenland polar bears over the period of 1999-2011. East Greenland polar bears are among the most polluted species, not just in the Arctic but globally, and represent an excellent biomonitoring species for levels and effects of global pollution in an apex predator. Therefore, an international multidisciplinary team joined to monitor and assess the patterns and concentrations of contaminants and their potential negative impact on polar bears. The review showed that East Greenland polar bears are exposed to a mix of chlorinated, brominated and fluorinated organic compounds as well as mercury which are all known to have endocrine, immune and organ-system toxic properties. For example, the concentrations of PCBs (polychlorinated biphenyls) in blubber ranged approximately 800-21,000 ng/g lw while mercury concentrations in liver and kidney ranged 0.1-50 μg/g ww. Regarding health endpoints, bone density seemed to decrease as a function of time and OHC (organohalogen compound) concentrations and further T-score for adult males indicated risk for osteoporosis. .The size of sexual organs decreased with increasing OHC concentrations. In the lower brain stem, mercury-associated decreases in NMDA-receptor levels and DNA-methylation was found The present review indicated that age was one of the major drivers for liver and renal lesions, although contaminants and infectious diseases may also play a role. Lesions in thyroid glands were most likely a result of infectious and genetic factors and probably, together with endocrine disrupting chemical (EDCs), the reason for disturbances/fluctuations in blood plasma thyroid hormone concentrations. Except for bone density reductions and neurological measures, all findings were supported by case-control studies of Greenland sledge dogs exposed long-term orally to similar combinations of contaminant concentrations. The studies of sledge dogs also indicated that the mixture of contaminants and fatty acids in the blubber of prey similar to that of polar bears induces cellular as well as humoral immune toxic changes. These controlled studies using model species for polar bears indicate that the correlative findings between health endpoint and contaminants in polar bears could be a cause-and-effect relationship. Physiologically based pharmacokinetic (PBPK) modelling showed that the risk quotients were ≥1 for ΣPCB, dieldrin and PFOS, which indicate an increased risk of prenatally reproductive pathology. In conclusion polar bears are susceptible to long-range transported chemicals that may have various adverse effects on multiple organ systems such as the reproductive and immune system.

Climate Change in the North American Arctic: A One Health Perspective

“…Average PCB concentrations of 28,409 ng/g and mercury concentrations of 11 lg/g were found in the liver tissues of polar bears from eastern Greenland sampled during 1999-2002(Sonne et al 2012. Average mercury concentrations in polar bear hair samples collected in Greenland during 2008 were 27 times higher than those of museum specimens from the same region dating from 1300 AD, with an average annual increase of 1.7% recorded from 1892 to 2008 (Dietz et al 2011).…”

Steroid hormones in multiple tissues of East Greenland polar bears (Ursus maritimus)

“…Increasing evidence suggests that polar bear reproduction is affected by high POP burdens (Sonne 2010;Sonne et al 2009Sonne et al , 2012Dietz et al 2015;Gustavson et al 2015a), but available information on polar bear reproduction is limited.…”

The Danish Polar Bear Skull Collection 1830–2016

“…The testing has expanded to cover persistent organic pollutants, a group of chemicals that encompass, for example, PCBs, DDT, and dioxins. In 1999, the work was further expanded to cover histopathology, brain biomarkers, and skull and bacula morphometrics and composition (Letcher et al, 2010;Sonne, 2010;Sonne et al, 2012). Skulls and bacula have also been used to detect effects from exposure to (Fig.…”