Organohalogen concentrations and a gross and histologic ...

(ng g lw -1)
(ng g lw -1)
(ng g lw -1)
28
12000
10000
8000
6000
4000
2000
0
400
350
300
250
200
150
100
50
0
200
150
100
50
0
PCBs
900
800
DDTs
700
600
500
400
300
200
100
0
HCHs CHLs
3000
CBz
2500
2000
1500
1000
500
0
Jan Feb Mar Apr-Jul Aug Sep Oct Jan Feb Mar Apr-Jul Aug Sep Oct
Adult F Adult M Sub adult
Figure 3
Seasonal changes (mean; ng/g l.w.) of PCBs, DDTs, HCHs, Chlordanes (CHLs), benzenes (CBz) and dieldrin for subadults of both
sexes, adult females and adult males.
0
300
250
200
150
100
50
Dieldrin
Time trend
The levels from the 92 bears were compared to samples from 1990 (n=17) from
the same area reported by Norstrom et al. (1998). A time trend analysis
showed a significant decline in the levels of organochlorines of ca. 28-81%
between the 1990 and 1999-2001 bears in both subadult and adult East Greenland
bears, indicating half-lives of 4 to 20 years depending on the group of
compounds. This was in accordance with analysis of bears from Svalbard
(Henriksen et al. 2001) and is probably explained by the proximity of East
Greenland (and Svalbard) to European sources and the decrease in concentrations
of the long-range transport via the air mass movements towards these
areas. But no strong conclusions could be drawn about a time trend due to
few years of comparisons. Power analysis on polar bears and Greenland
ringed seals (Phoca hispida) shows that at least 10-12 years are requited to draw
such conclusions (Riget et al. 2000, Henriksen et al. 2001).
Although there are indications of a decrease in the levels of organochlorines in
East Greenland polar bears over the period 1990-2001 one must be aware of
new contaminants accumulating in the East Greenland polar bears and
thereby new potential toxic effects. From the rate of increases in brominated
flame retardents in East Greenland polar bears (Muir et al. In prep.) it is estimated
that these compounds could reach toxicity levels comparable to PCBs
within the next 5-10 years if banning will not be enforced. This is also the case
of PFOS and related compounds (Smithwick et al. In prep., Bossi et al. Submitted).