Environmental Engineering Reference
In-Depth Information
As follow up to the 1971 study, Le Boeuf et al. (
2002
) revisited the topic of
organochlorine pesticides in marine mammals. They collected blubber samples
from some 36 stranded animals along the coast of California in 2000, and deter-
mined geometric mean DDT concentrations of 37 ± 27 ppm (wet weight basis) and
150 ± 257 ppm (lipid weight basis). They found no signifi cant differences in concen-
trations with differences in age or sex, but did conclude that DDT levels decreased
by more than one order of magnitude between 1970 and 2000. Kannan et al. (
2004
)
also reported the results of DDT analysis performed on the blubber of some 36
stranded California sea lions collected in 2000. As Kannan is a co-author of the Le
Boeuf et al. (
2002
) study, it is unclear if the animals used were the same in both
studies. However, he reports a mean DDT concentration of 143 ± 253 ppm, with a
geometric mean of 69 ppm.
More recently, two studies designed to correlate toxic actions with DDT in
California sea lions have been published. Debier et al. (
2005
) investigated a possible
relationship between DDT in the serum of 12 healthy California sea lions and circu-
lating levels of vitamins A and E and the thyroid hormones thyroxine (T4) and tri-
iodothyronine (T3). Although several negative correlations were reported for PCB,
only vitamin A was signifi cantly correlated with DDT, and only when concentra-
tions were reported on a lipid weight basis.
In
2005
, Ylitalo et al. used a logistic regression model with California sea lions
in an attempt to correlate the unusually high prevalence of neoplasms (carcino-
mas—found in 18% of stranded adults) with blubber DDT concentrations. Although
concentrations were signifi cantly higher in animals that died from carcinomas ver-
sus those that did not, after controlling for other confounding factors only blubber
thickness proved to be a reliable predictor of death via carcinoma—ultimately DDT
was proven not signifi cant.
Blasius and Goodmanlowe (
2008
) reported that DDT levels in blubber collected
from marine mammals in the southern California bight were higher in resident har-
bor seals and sea lions than in the transient northern elephant seal. Adult female sea
lions had lower residue levels than pups, yearlings and adult males. DDT levels in
sea lion blubber declined approximately tenfold to a mean (lipid weight basis) of
approximately 200 ppm from 1994 to 2006, but not in the transient northern ele-
phant seal that was less impacted by the high levels of contamination attributed to
production wastes released prior to 1970. The highest concentrations of DDT in
blubber, as high as 13,271 ppm (lipid weight basis), were measured in stressed sea
lions that had lost almost all of their blubber.
In contrast to the high blubber residues of DDT in the highly contaminated
southern California bight, blubber from sea lions stranded along the Baja California
coast in 2000 and 2001 had residues averaging 3.8 ppm on a lipid weight basis (Del
Toro et al.
2006
). Nino-Torres et al. (
2009
) reported a mean DDT level of 3.4 ppm
(lipid weight basis) in blubber collected from sea lions in 2005 and 2006 in the Gulf
of California.
Ramsdell (
2010
) reported a novel zebra fi sh model for the interaction of DDT
and the diatom poison, domoic acid, in sea lions feeding in the highly contaminated
Channel Islands of the southern California bight. Pretreatment of embryonic zebra
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