Environmental Engineering Reference
In-Depth Information
Vetter et al. (
1996
) reported the mean DDT concentration for 32 harbor seals
collected from the North Sea between 1988 and 1995 to be 3.903 ppm (range,
1.501-11.475). They also found no signifi cant difference in the DDT concentrations
between seal adults and pups collected prior to (1987) and during (1988) a major
seal die-off, which indicated DDT was probably not the cause.
Routti et al. (
2008
) compared DDT levels in gray and ring seals in the more con-
taminated Baltic Sea compared to lower contaminated sites in Canada and Norway.
They reported that changes in circulating vitamin D and thyroid hormone were
associated with DDT and PCB levels in liver, suggesting that bone lesions observed
in Baltic gray seals may be caused by DDT and/or PCBs. Another possible explana-
tion for their fi ndings is that animals stressed by factors unrelated to body burdens
of DDT will result in weight loss with the mobilization of fat stores of DDT. The
mobilization of DDT from blubber to liver could result in a negative correlation
between DDT levels in the liver and the effects of the unknown factor, even though
DDT may not be at a level that is having any toxic effect.
Bredhult et al. (
2008
) did not fi nd an association between DDT in blubber and
uterine leiomyomas in Baltic gray seals.
In
1997
, Hayteas and Duffi eld reported the
p
,
p
-DDE concentrations from the
blubber of some ten harbor seals collected off the Oregon coast to have a geometric
mean of 1.9 ppm (range, 0.4-12.5 ppm);
p
,
p
′
-DDT levels were not reported as they
were negligible in all samples. They concluded that DDT contamination along the
Oregon coast was relatively low, and that animals with higher residue levels may
have migrated from California. Moreover, in
1997
, Mossner and Ballschmiter
reported a mean DDT concentration from two harbor seals collected from the North
Atlantic Ocean to be 18.99 ppm (on a lipid weight basis).
More recently, Kajiwara et al. (
2001
) reported DDT concentrations (based on
lipid weight) in the livers of ten stranded harbor seals collected between 1991 and
1997; the geometric mean concentration was 12 ppm (range, 2.8-85 ppm).
Greig et al. (
2011
) reported DDT levels (lipid basis) of 320-1,500,000 ppb in
blubber from 202 stranded and wild-caught harbor seals in the central California
coast. The highest levels were in pups during the post-weaning fast, suggesting that
fasting pups may be the most vulnerable early life stage to the toxic effects of DDT,
due to mobilization from lipid stores.
Hall et al. (
2009
) reported a negative correlation between blubber concentrations
of DDT and survival in fi rst year gray seal pups sampled from the Isle of May in
2002. Geometric mean DDT levels (lipid basis) were 229 ppb. The authors were
careful to note that their fi nding did not indicate causation. Causation would seem
unlikely considering the relatively low concentrations of DDT in the pups.
Fillman et al. (
2007
) reported 20-2,480 ppb DDT (mean level of 660 ppb) in
blubber from stranded juvenile South American fur seals. The authors point out that
the poor nutritional status of the seals is likely to have mobilized DDT from blubber
to other tissues, increasing their vulnerability to possible toxic effects.
Roos et al. (
2012
) reported a decline in DDT residues in seal blubber from 192
to 2.8 ppm (lipid weight basis) from 1973 to 2010. Increases in uterine health and
pregnancies and reduced uterine cancer were associated during the same period
′
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