Persistent Organic Pollutants and Heavy Metals (Including Mercury) - The Changing Arctic Environment: The Arctic Messenger - page 127

just not enough data to be confident with making the same conclusion for organochlorines.
However, only PCBs of the 13 or so organochlorines found in the Canadian Arctic had
ever been used there in any quantity and one (toxaphene) had never even been registered
for use in Canada. The source could not be local. Freshwater and marine ecosystems were
contaminated. The only natural transport mechanism that would be common to both was
the atmospheric pathway from distant sources, so we began to take a special interest in this
possibility.
The critical component of this early work was a small survey of levels of several
contaminants in the diet, blood and breast milk of Inuit from the small community of
Broughton Island, offtheeast coast ofBaffinIsland. Thedata were collected overtwoperi-
ods: in 1985 and between 1987 and 1988. It showed that all the local Inuit foods tested con-
tained PCBs and mercury, with the highest levels being in narwhal and beluga blubber (the
thickfattylayerthatliesintheinnermostlayeroftheskinofmarinemammals) andinpolar
bear fat. Blood PCBs exceeded Health Canada's “tolerable” levels in 63% of children and
in 39% of women of childbearing age. Only four breast milk samples were available. Three
were comparable to levels in southern Canada, but the fourth exceeded Health Canada's
“tolerable” level. Blood mercury levels exceeded Health Canada's guidelines in three per-
sons - all males. Clearly, the indicated level of contamination could not be ignored.
The first clue to unravelling this mystery came from the Arctic substances themselves.
They all share four basic characteristics:
1. They are very resistant to biological and chemical degradation because the
chlorine-carbon bonds are very strong. As a general rule, the more chlorine
(or other halogen) substitutions that exist on the molecule, the more long
lived the substance. Any degradation that does happen is usually temperature
dependent, grinding to a halt at polar temperatures.
2. They bioaccumulate and biomagnify. Animal physiological processes typically
evolved to get rid of unwanted substances by making them water soluble.
However, organochlorines are said to be lipophilic. This means they are con-