Organohalogen concentrations and a gross and histologic ...

sen et al. (2001) studied the trend of CB153 concentrations in polar bear
blood annually between 1990 and 1998. Decreases of ca. 40% occurred in the
early 1990s, and concentrations stabilised thereafter. AMAP, (2004) have
estimated an annual percentage decline of CB concentrations in polar bears
of to be 2.7% for Hudson Bay polar bears and 6.1% for Svalbard bears, for
the period 1989-1999 i.e. 27% and 61%, respectively, over 10 years. The Svalbard
values are almost as high as for the East Greenland polar bears, with a
reduction of 77.9% over a similar 10 year period. However, Svalbard bears
had significantly higher levels of CBs in 1990 than those in Hudson Bay,
probably due to the proximity of Svalbard to European sources and air mass
movements bringing higher loads of OC to Svalbard compared to Hudson
Bay. Hence, PCB levels at Svalbard and in East Greenland may have approached
steady state with global distribution of PCBs later than in Hudson
Bay because of their proximity to the sources mentioned above. Prior to
1990’s, the picture of temporal trends was not quite obvious at Svalbard.
Differences in the OC levels measured between 1967 and 1993–1994 ranged
from a decrease (CB187) to unchanged concentrations in both sexes (CBs
105,118 and 209) to an increase in females (CBs 99 and 128), to increases in
both sexes (CBs 138, 153, 156, 157, 170, 180, 194 and 206 ) (Derocher et al.,
2003). The maximum change observed was a nine-fold increase in concentrations
of CB157 in adult females. Changes from 1967 to 1993–1994 in contaminant
patterns were explained by Derocher et al. (2003) as a combination
of selective metabolism and accumulation of organochlorines in polar bears
and temporal changes in the contaminant mixture being transported to the
Arctic.
Recently organochlorine levels have been determined in ringed seal blubber
and shorthorn sculpin liver sampled in 1994, 1999 and 2000 from Ittoqqqortoormiit,
central East Greenland (Riget et al., In press). Although these data
cover a shorter time span (six years) and year to year variations can be expected,
they supplement the findings of the recent changes in concentrations
in polar bears and may give indications of the concentrations of OC compounds
in the primary food source and at the lower trophic levels of the
marine biota. In Ittoqqortoormiit, ΣCB concentrations (10 congeners) in seals
(adjusted for age) and sculpins were higher in 1994 than in 1999 but similar
to those in the specimens collected in 2000. The difference was only statistically
significant in the sculpins.
In southwestern Hudson Bay a significant decrease of ΣDDT concentrations
occurred throughout the period from 1968 to the 1990s, after which the level
remained constant until 2002 (Norstrom, 2001; Fisk et al., 2003 (and references
therein); Letcher et al. unpublished data; AMAP, 2004). Local sources,
such as the spraying of DDT for insect control in the local communities and
at the large military base at Churchill in the 1950s and 1960s resulted in 2 to
3 times higher ΣDDT levels in polar bear fat in Hudson Bay than in other
areas of the Canadian Arctic in 1984. After the DDT ban and the closure of
the military base the levels declined in subsequent years. In East Greenland
the decrease in concentrations of ΣDDT and p,p’-DDE since 1990 was also
statistically significant, but this decrease was the lowest observed in the
study and so the calculated half-life was the longest (17.1 to 20.6 years) observed.
Concentrations of DDTs in seals and sculpin from Ittoqqortoormiit,
central East Greenland showed no clear temporal trend from 1994 to 1999
and 2000, but as for the CBs the concentrations of DDTs were lower in 1999
than in the two other years in seals (Riget et al., In press).
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