Although concentrations of many conventional POPs have decreased in the Arctic over the past few decades, levels of most POPs remain high in Arctic areas, especially in top predators like polar bears (Ursus maritimus). So far, studies generally focused on individual effects only. In the study associated to these data we therefore aimed to estimate the (combined and individual) effect of legacy POPs and mercury on population growth rate of nineteen polar bear subpopulations. We modelled polar bear population development in three scenarios, based on SSDs derived for POPs based on ecotoxicity data for endothermic species.

Exposure data. Data on POP residues in marine mammal species (mainly Phoca hispida, Phoca largha, Phoca groenlandica, Crystophora cristata , Erignathus barbatus, Odobenus rosmarus and Monodon monoceros), assumed to be the main prey of polar bears in the Arctic, were compiled to calculate potential changes in intrinsic growth rates of polar bear populations. POP concentrations (transformed to mg/kg wet weight (w.w.)) were obtained from a literature search using the Web of Knowledge and Google Scholar. Search strings used in queries included POPs (specific compound names (e.g. “p,p’-DDE”, or “CB-153”) or compound groups (e.g. “PCBs” or “DDTs”)) on one side, combined with Arctic species’ names (both scientific (e.g. “Phoca hispida”) and common names (e.g. “ringed seal”)) on the other. Concentrations on lipid basis were converted to wet weight (w.w.) basis, based on the reported lipid content. If no lipid concentration was reported, a lipid content of 85% was assumed for marine mammal blubber samples. To calculate the toxic equivalency of PCBs, we assumed that the planar PCB composition in marine mammal blubber was similar across all sampled individuals. In the present study, the planar PCB composition in blubber was taken from Savinov et al. 2011. All concentration data used in our simulations were collected between 1972 and 2018.

Ecotoxicity data were taken from the USA EPA's ECOTOX database. Ecotoxicity data for PCB mixtures were converted to toxic equivalency values (TEQ) using updated toxic equivalency factors (TEFs) for individual dioxin-like PCB congeners from the WHO (2005), and their relative concentration in Aroclor 1242, 1254 or 1260 mixtures. Concentration data (in µg/g) of individual dioxin-like PCB congeners (PCB 77, PCB 81, PCB 105, PCB 114, PCB 118, PCB 123, PCB 126, PCB 156, PCB 157, PCB 167, PCB 169 and PCB 189) in Aroclors were taken from Wischkaemper et al. (2017) (Wischkaemper 2017).