Environmental Engineering Reference
In-Depth Information
including research. Therefore, nearly all the papers published to date involve the
measurement of DDT residues in tissues obtained from either live or dead (stranded
and often decaying) animals. Such information can at least give an approximate
estimate of the residues encountered by the subject marine mammals—and their
ability to accumulate them. The following is a brief summary of the published
reports involving DDT in marine mammals of importance to Newport Bay.
The summary is a chronology by species of DDT studies in marine mammals.
DDT concentrations in these studies are reported as total DDT, which typically
represents the sum of anywhere from three (
p
,
p
′
-DDT +
p
,
p
′
-DDD +
p
,
p
′
-DDE) to six
(
o
,
p
-DDE) analytes.
Unless otherwise indicated, all residue values reported below are based on wet
sample weight—concentrations reported on a lipid weight basis can average four
or more times higher than those reported on a wet weight basis. Also note that
while many reported values are geometric means (delineated below), some are
arithmetic means.
′
-DDT +
o
,
p
′
-DDD +
o
,
p
′
-DDE +
p
,
p
′
-DDT +
p
,
p
′
-DDD +
p
,
p
′
DDT and Seals
. DDT has been detected in harbor seals (
P. vitulina
) throughout the
world for several decades. A series of early studies, centered on the North Sea coast-
line, document the DDT concentrations, with tissue type, commonly encountered
when the insecticide was in widespread use (Koeman and van Genderen
1966
;
Koeman et al.
1972
; Drescher et al.
1977
; Duinker et al.
1979
). DDT concentrations
(in ppm) ranged as follows: blubber, 0.51-25.4; liver, 0.06-1.3; kidney, 0.05-0.76;
brain, 0.038-3.1; spleen, 0.029-0.18; and heart, 0.25-0.60. It was obvious from an
early date that fat-soluble DDT and its associated degradation products selectively
partitioned into relatively inactive adipose tissue. Thus, while tissue-borne residues
could be signifi cant, the potential for toxic effects as a result would be both low and
diffi cult to assess.
In response to declining harbor seal populations in the Dutch Wadden Sea
(the southern coastal North Sea), Reijnders (
1980
) measured DDT concentrations
(in ppm) in kidney, liver, and blubber (on a lipid weight basis) from resident harbor
seals. In adult seals, mean DDT concentrations varied as follows: kidney, 0.2-0.9;
liver, 0.4-2.1; and blubber, 8.5-47.3. He also determined that the decreased repro-
ductive success reported for the Dutch Wadden Sea (vs. the German Wadden Sea)
was strongly correlated to the tenfold higher PCB concentrations of the region;
DDT was not strongly correlated with reproductive success.
In
1990
, Luckas et al. reported mean DDT concentrations (in ppm) in harbor
seals from a number of diverse geographic locations: Norway, 1.226; Sweden,
22.498; Iceland, 1.546; Germany, 3.903, and Antarctica, 0.105. Not surprisingly,
higher concentrations were associated with regions of greater agricultural activity.
In
1992
, Hall et al. compared DDT concentrations in both victims (34) and
survivors (54) of a phocine distemper epizootic to determine if a correlation with the
disease may exist, indicating a possible immunosuppressive role for DDT—one has
been suspected for some chlorinated biphenyls. DDT concentrations ranged from
0.13 to 12.1 ppm for live animals and 0.71-7.17 ppm for dead animals; hence, no
signifi cant correlation could be made to indicate that DDT residues may have
increased seal susceptibility to the disease.
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