Persistent organic pollutants and penile bone mineral density in East Greenland and Canadian polar bears (Ursus maritimus) during 1996–2015

Environment International Volume 114, May 2018, Pages 212-218 Author links open overlay panelTobiasDaugaard-PetersenaRikkeLangebækbFrank F.RigétaMarkusDyckcRobert J.LetcherdLarsHyldstrupeJens-Erik BechJenseneRuneDietzaChristianSonnea a Aarhus University, Faculty of Science and Technology, Department of Bioscience, Arctic Research Centre (ARC), Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark b University of Copenhagen, Faculty of Health and Medical Sciences, Department of Veterinary Clinical and Animal Sciences, Dyrlægevej 16, 1-72, DK-1870 Frederiksberg C, Denmark c Wildlife Management Division, Department of Environment, Government of Nunavut, PO Box 209, Igloolik, NU X0A 0L0, Canada d Ecotoxicology and Wildlife Health Division, Science and Technology Branch, Environment and Climate Change Canada, National Wildlife Research Centre, Carleton University, Ottawa, ON K1A 0H3, Canada e University Hospital of Hvidovre, Kettegaards Allé 30, DK-2650 Hvidovre, Denmark Received 13 December 2017, Revised 11 February 2018, Accepted 11 February 2018, Available online 6 March 2018. Handling Editor: Olga-Ioanna Kalantzi crossmark-logo https://doi.org/10.1016/j.envint.2018.02.022 Get rights and content Highlights • Bone density and POPs was analysed in 634 polar bear bacula. • Bone density was lowest in East Greenland polar bears. • POP concentrations were highest in East Greenland bears. • Bone density was positive correlated to POPs. • Environmental changes and POPs may affect baculum bone density. Abstract Persistent organic pollutants (POPs) are long-range transported to the Arctic via atmospheric and oceanic currents, where they biomagnify to high concentrations in the tissues of apex predators such as polar bears (Ursus maritimus). A major concern of POP exposure is their physiological effects on vital organ-tissues posing a threat to the health and survival of polar bears. Here we examined the relationship between selected POPs and baculum bone mineral density (BMD) in the East Greenland and seven Canadian subpopulations of polar bears. BMD was examined in 471 bacula collected between years 1996–2015 while POP concentrations in adipose tissue were determined in 67–192 of these individuals collected from 1999 to -2015. A geographical comparison showed that baculum BMD was significantly lowest in polar bears from East Greenland (EG) when compared to Gulf of Boothia (GB), Southern Hudson (SH) and Western Hudson (WH) Bay subpopulations (all p < 0.05). The calculation of a T-score osteoporosis index for the EG subpopulation using WH bears as a reference group gave a T-score of −1.44 which indicate risk of osteopenia. Concentrations of ΣPCB74 (polychlorinated biphenyls), ΣDDT3 (dichlorodiphenyltrichloroethanes), p,p′-DDE (dichlorodiphenyldichloroethylene), ΣHCH3 (hexachlorohexane) and α-HCH was significantly highest in EG bears while ΣPBDE (polybrominated diphenyl ethers), BDE-47 and BDE-153 was significantly highest in SH bears (all p < 0.04). Statistical analyses of individual baculum BMD vs. POP concentrations showed that BMD was positively correlated with ΣPCB74, CB-153, HCB (hexachlorobenzene), ΣHCH, β-HCH, ClBz (chlorobenzene), ΣPBDE and BDE-153 (all p < 0.03). In conclusion, baculum density was significantly lowest in East Greenland polar bears despite the positive statistical correlations of BMD vs. POPs. Other important factors such as nutritional status, body mass and body condition was not available for the statistical modelling. Since on-going environmental changes are known to affect these, future studies need to incorporate nutritional, endocrine and genetic parameters to further understand how POP exposure may disrupt bone homeostasis and affect baculum BMD across polar bear subpopulations. Previous article in issue Next article in issue Keywords Bone mineral density Canada EDCs Endocrine disrupting chemicals Global climate change POPs 1. Introduction Climatic changes as well as infectious diseases and persistent organic pollutants (POPs) are considered the most substantial environmental stressors of the Arctic ecosystem (AMAP, 2015; Jenssen et al., 2015; Letcher et al., 2010; Sonne et al., 2012). The presence of POPs in the Arctic marine environment is the result of long-range atmospheric and oceanic transport, which has occurred since the 1940s from lower latitude sources in the industrialized parts of the world (AMAP, 1998, AMAP, 2004). Due to the lipophilic nature of many POPs, these chemicals persist in the slow-growing and lipid-rich Arctic food chains (Letcher et al., 2010). Consequently, high POP concentrations are found in the Inuit populations and in marine top predators that consume large amounts of high trophic level marine mammals with East Greenland and Hudson Bay as particular hotspots (AMAP, 2015; Dietz et al., 2013a, Dietz et al., 2013b; Letcher et al., 2010, Letcher et al., 2018; McKinney et al., 2013). Recently, polar bears have received considerable attention as a vulnerable Arctic species that is highly influenced by climatic change (Jenssen et al., 2015; Wiig et al., 2015). Thus, it is argued that the projected sea ice loss across the Arctic Ocean will restrict polar bears' access to principal prey such as ringed seals (Phoca hispida) during autumn (Durner et al., 2009; Molnár et al., 2011; Stirling and Derocher, 2012). In addition, polar bears are top predator species and therefore at greater risk of severe population declines due to POP exposure (Jenssen et al., 2015; Letcher et al., 2010; Sonne, 2010). The East Greenland ecosystem carry the highest loads of POPs in the Arctic and therefore polar bears from these subpopulations are among the most contaminated (Letcher et al., 2010). Increases in biomagnification of POPs has occurred in East Greenland polar bears over the last decades mainly because changes in ice dynamics that has led to dietary changes and toward more highly polluted prey i.e. hooded (Cystophora cristata) and harp (Pagophilus groenlandicus) seals (McKinney et al., 2013). The consequence of these dietary changes and elevated POP exposure is an increase in the risk for effects on growth and development of, for example, reproductive organs and the immune and skeletal system (Desforges et al., 2016; Dietz et al., 2015; Letcher et al., 2010; Sonne, 2010; Sonne et al., 2006, Sonne et al., 2012). Bone formation and resorption is controlled by multiple physiological factors such as hormones, vitamins and micronutrients (Barret et al., 2010; Herlin et al., 2010). POPs are known to disrupt bone homeostasis (Lind et al., 2003, Lind et al., 2004) and in polar bears there has previously been reported inverse relationships between bone density and several POP compounds (Sonne, 2010; Sonne et al., 2004, Sonne et al., 2006). A study by Sonne et al. (2015) even suggested that changes in the baculum density of East Greenland polar bears may lead to population declines as reduced strength could lead to fractures and inability to successfully mate. Canadian polar bear subpopulations are, with the exception of Hudson Bay, less contaminated with POPs compared the East Greenland subpopulation (Norstrom et al., 1998; McKinney et al., 2011; Verreault et al., 2005). A comparative study of baculum bone density and POPs in East Greenland and Canadian polar bears is therefore warranted (Sonne et al., 2015). The aim of the present study was to investigate possible geographical differences in baculum BMD, as well as correlations between POP concentrations and baculum BMD.