Persistent Organic Pollutants and Heavy Metals (Including Mercury) - The Changing Arctic Environment: The Arctic Messenger - page 151

and mercury (Hg). All three are natural substances with known acute toxic characteristics
but whose distribution in the environment can be greatly influenced by human activities.
Therefore, the main task from an Arctic perspective was to measure levels in different en-
vironmental compartments, to assess levels against potential adverse effects and to look for
patterns that may reflect transportation pathways.
In the early 1990s, the largest sources causing metal contamination in the Arctic from
within the Arctic itself were thought to come from the nickel-copper smelting industry loc-
atedinthefarnorthofRussiaintheKolaPeninsula,fromtheUralsandfromNorilsk.Here,
large swathes of denuded forest spread downwind of the smelters, reflecting the combined
deposition of metals and acids. High local sources were also associated with mining op-
erations in Greenland (Black Angel) and Canada (Nanisivik beside Strathcona Sound on
Baffin Island) and at the Polaris mine on Cornwallis Island, where a lake (in the case of
Polaris) or a deep fjord with restricted vertical water circulation (such as Black Angel) was
used as a dumpsite for mine discharge. In fresh and marine waters, Arctic levels of lead,
cadmium and mercury away from the local sources were generally quite low.
Lead usually strongly partitions to soils and sediments and is therefore not easily ab-
sorbed by plants and animals. The main atmospheric source came from leaded gasoline
and levels were already declining by the early 1990s. Lead normally accumulates in bone.
However, its main toxicological impacts are its interference with red blood cell formation
and with the neurological development of children. Exposure in the Arctic was generally
low, but there were significant exceptions. Local elevated levels were found in some indi-
genous communities and appeared to be related to the use of lead shot during hunting.
Cadmium partitions into the dissolved phase and is therefore easily taken up into the
biotic environment. In mammals, cadmium accumulates (but does not biomagnify) in the
kidneys and liver. Here, it is mopped up by a class of proteins called metallothioneins ,
which, however, can be overwhelmed by very high cadmium levels. If this occurs, kidney
damage results, the metabolism of calcium is upset, and the skeleton decalcifies. In some
populations of caribou and willow and rock ptarmigan in the Yukon and northern Norway,
cadmium levels in kidneys were in the range where effects would be expected. However,