Bowhead whale contaminants: A review of current state of knowledge and possible future research directions

In this paper, we review contaminants in bowhead whale tissues. Mean concentrations of metals (As, Cd, Co, Cu, Pb, Mg, Mn, Hg, Mo, Se, Ag, and Zn) studied in bowhead whale liver, blubber, epidermis, muscle, and kidney are low or normal compared to most mysticete species. From a consumption or subsistence perspective the kidney represents a source of cadmium (Cd) requiring further scrutiny, while other elements and contaminants are not at levels of concern (see O’Hara et al., SC/56/E2). Mercury (Hg) is at very low concentrations and is of no concern. The mean cesium-137 (Cs-137) levels (Bq/kg w.w.) indicate that the increasing rank order for tissues is blubber < kidney/liver < “skin” (epidermis)/muscle; and concentrations (activity) are considered very low. Strontium-90 (Sr-90), and plutonium (Pu-239/240) are mostly below detection concentrations and thus very low. Polonium-210 (Po-210) was above detection level at approximately 5 Bq/kg and considered low. As expected, some organochlorines (OCs) occurred at higher concentrations in longer (older) male whales than younger males (approximately 1,000 ng/g lipid wt in blubber for longer whales). Spatial trends and bioaccumulation (trophic transfer) of organochlorine pollutants in bowhead prey have been described allowing for a quantification of the biomagnification in bowhead whales. Understanding the trophic ecology of bowhead whales using C and N stable isotope signatures and published stomach contents data has assisted in understanding regional and seasonal feeding habits, and the associated differences in exposure to contaminants. To better understand “bioprocessing” of OCs by the bowhead whale enantiomer-specific accumulation of PCB atropisomers has been documented, and for enantiomer-specific biomagnification of α-hexachlorocyclohexane and selected chiral chlordane-related compounds in an arctic marine food web. The role of metabolism or biotransformation in OC “bioprocessing” for bowhead whales is now better understood as hydroxylated and methylsulfone-containing metabolites of PCBs were described in the plasma and blubber of bowhead whales. These OCs data clearly indicate the bowhead whale is highly selective in the chemicals that accumulate, the metabolites that form, and that sexual maturation likely plays a role in this “processing” of OCs. Some halogenated organics are considered natural and have been found in bowhead whales including the halogenated dimethyl bipyrroles. Preliminary data indicates that petroleum hydrocarbons occur at very low