Polar bears (Ursus maritimus) are among the world's highest trophic level marine predators and as such have some of the highest tissue concentrations of organohalogen contaminants (OHCs) among Arctic biota. In this paper we present the results of a three decade (1983–2013) risk assessment of OHC exposure and effects on reproduction, immunity, and cancer (genotoxicity) in polar bears from Central East Greenland. Risk of adverse effects are evaluated using a risk quotient (RQ) approach with derivation from measured OHC concentrations in polar bear tissue and critical body residues (CBR) extrapolated for polar bears using physiologically-based pharmacokinetic modelling (PBPK). The additive RQs for all OHCs in polar bears were above the threshold for all effect categories (RQ > 1) in every year, suggesting this population has been at significant and continuous risk of contaminant-mediated effects for over three decades. RQs peaked in 1983 (RQ > 58) and again in 2013 (RQ > 50) after a period of decline. These trends follow ΣPCB levels during that time, and contributed almost all of the risk to immune, reproductive, and carcinogenic effects (71–99% of total RQ). The recent spike in RQs suggests a major shift in polar bear contaminant exposure from climate related changes in food composition and hereby the increased risk of adverse health effects. In the context of lifetime exposure ΣPCB and PFOS levels showed the interactive importance of year of birth, age, and emission history. In conclusion, the results indicate that East Greenland polar bears have been exposed to OHC levels over the period of 1983–2013 that potentially and continuously affected individual and theoretically also population health, with a peaking risk in the more recent years.

北极熊（学名Ursus maritimus）是世界上营养最高的海洋捕食者之一，因此在北极生物区系中某些有机卤素污染物（OHC）的组织浓度最高。在本文中，我们介绍了中东部格陵兰岛北极熊中OHC暴露及其对繁殖，免疫和癌症（遗传毒性）影响的三年（1983-2013年）风险评估结果。使用风险商（RQ）方法评估了不良反应的风险，并使用基于生理的药代动力学模型（PBPK）从北极熊组织中测得的OHC浓度和为北极熊推断的关键身体残留物（CBR）推导得出。每年，北极熊中所有OHC的加性RQ均高于所有效应类别的阈值（RQ> 1），这表明该人群在过去三十年中一直处于受到污染物介导影响的重大且持续的风险中。经过一段时期的下降之后，RQ分别在1983年（RQ> 58）和2013年（RQ> 50）达到顶峰。在此期间，这些趋势遵循ΣPCB的水平，几乎对免疫，生殖和致癌作用造成了所有风险（占总RQ的71–99％）。RQs最近的上升表明，与气候相关的食物成分变化会导致北极熊污染物暴露发生重大变化，从而增加不利健康影响的风险。在终生暴露的背景下，ΣPCB和PFOS的水平显示出出生年份，年龄和排放历史的交互重要性。综上所述，