Risks for indigenous mothers, children, and polar bears

High concentrations of toxaphene have been found in the breast milk of indigenous mothers.

The Canadian Arctic Contaminants Assessment Programme has investigated a number of POPs, including toxaphene, in the Arctic regions of Canada. Particulate matter under the ice, planktonic and benthic invertebrate tissues, and abyssal and coastal marine fish were investigated.

The main focus has been on piscivorous fish such as turbot, lake trout, northern pike and Arctic char, because of their importance in the traditional subsistence fishery and because of the interest in possible biomagnification to top predators. While toxaphene and PCBs had the highest concentrations, DDT and chlordane-related compounds were also important.

The highest concentrations in Arctic fish were found in turbot (Greenland halibut). These predacious, bottom-feeding fish have relatively fatty muscle compared with whitefish, char or sculpins. Samples from the eastern Canadian Arctic and the eastern Beaufort Sea both had mean toxaphene concentrations three to five times higher than in ocean char muscle and 15 to 20 times higher than in Arctic cod (whole fish).

Fish is the primary food for the indigenous people in the Canadian Arctic, and high concentrations of toxaphene have been found in the breast milk of indigenous mothers in this region – significantly higher than that of mothers living in large Canadian cities.

Data for Arctic marine mammals show a similar proportionality in abundance between these classes of POPs, although toxaphene does not biomagnify to polar bears to the same extent as PCBs or some chlordane components. A study of 586 polar bears in 18 Arctic regions showed a relatively uniform distribution of POP levels over much of the study area, clearly indicating extensive transport and deposition of POPs to wide areas of the Arctic and subarctic.

The atmosphere is the dominant transport path for toxaphene and PCBs to the Arctic although local sources such as dumped electric equipment are the dominant PCB source within radii of a few tens of km of the dumpsites. An evaluation using criteria established to protect fish-eating wildlife suggests that there is not a large margin of safety for arctic marine or freshwater piscivores. Using these same criteria, carnivores such as polar bears would be at risk due to the consumption of ringed seal tissues.

Source: GESAMP71:18