Organohalogen concentrations and a gross and histologic ...

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Background and aims
Since 1990 the 8 Arctic countries (Denmark, Norway, Sweden, Finland, Iceland,
Canada, USA and Russia) joined the Arctic Monitoring and Assessment
Programme (AMAP). Through this political and scientific cooperation
these countries have made a substantial effort, to document the general levels
of contaminants as well as investigating temporal and spatial trends of
pollutants in the Arctic. Among the conclusions from the first Arctic Assessment
Report (AAR-1), was a recommandation to investigate biological effects
of these toxic compounds on top predators including the polar bear.
Recently, the second Arctic Assessment Report from phase 2 (AAR-2) was
published, which still calls for effect studies on higher trophic levels and the
present thesis fullfills some of these knowledge gaps.
In AAR-1 and 2 it was stated that polar bears from the Eastern Atlantic Arctic,
including East Greenland, have higher levels of persistent organohalogen
contaminants (e.g. PCBs and DDTs), than reported in tissues of polar bears
from populations elsewhere in the Arctic. The Eastern Atlantic Arctic marine
ecosystems receive relatively high air- and seaborne input of organohalogens
from sources in lower latitudes compared to other Arctic areas, and these are
particularly bioconcentrated and subsequently bioaccumulated in waxy and
fatty tissues due to their lipophilic properties. Polar bears carry the highest
levels of the Arctic predators because they primarily feed on the blubber of
ringed seal (Phoca hispida) and bearded seal (Erignathus barbatus) to maintain
thermoregulation and build up energy storage. The levels found in polar bears
from East Greenland, Svalbard and the Kara Sea, are similar to those believed
to cause negative effects on reproduction and survival of seals from the Baltic
Region.
Therefore, studies of adverse biological effects from these toxic levels were initiated
at Svalbard by Norwegians and Canadians to fill out the knowledge gap.
At Svalbard polar bears are protected and samples from this region can therefore
only be obtained from subcutaneous adipose tissue and blood in connection
with tagging programmes (satellite telemetry) involving the use of helicopters.
From these samples, studies of the relation between organohalogen
compounds (e.g. PCBs and DDTs) and retinol (vitamin A), thyroid hormones,
sex steroids, cortisol, antibody titres and leucocyte activities have been carried
out since early 1990s. These studies can in addition, be linked to the movement
and behavioural pattern including denning and reproductive activity.
In East Greenland, app. 50 polar bears are killed annually during the subsistent
hunting, and the possibility of obtaining unique samples from internal
organs and skulls for new investigations was possible. Therefore, researchers
from The National Environmental Research Institute and The Greenland Institute
of Natural Resources initiated, with great success, a sampling from
these bears through local Inuit hunters in the summer of 1999. In addition to
the sampling, an extensive interview investigation was conducted on aboriginal
knowledge of pathological changes and biology of the East Greenland
polar bear. The aim of the present thesis was to describe the histology and
possible histopathological changes in various target organs in app. 100 polar
bears sampled during 1999-2002 as well as skull morphology and bone mineral
density (BMD) in skulls sampled during 1892-2002 and relate these to organohalogen
contaminants analysed in bears collected during 1999-2001. Additional
investigations on the collected samples will be conducted in the future.