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

Abstract

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 4months 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 Σ21PCBs (1997/1998: 5710±3090ng/g lipid weight [lw], 2008: 2560±1500ng/g lw) and Σ6OH-PCBs (1997/1998: 228±60ng/g wet weight [ww], 2008: 80±38ng/g ww) in mothers were significantly lower in 2008 compared to in 1997/1998. In cubs, the plasma concentrations of Σ21PCBs (1997/1998: 14680±5350ng/g lw, 2008: 6070±2590ng/g lw) and Σ6OH-PCBs (1997/1998: 98±23ng/g ww, 2008: 49±21ng/g ww) were also significantly lower in 2008 than in 1997/1998. Σ21PCBs 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, Σ6OH-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.