Environmental Engineering Reference
In-Depth Information
McKinney et al. (
2006
) reported liver DDT levels (lipid weight basis) in beluga
whales from the Saint Lawrence Estuary and Hudson Bay. The average residue level
of DDT was 4,536 ppb for whales from the Saint Lawrence Estuary and 284 ppb for
whales from Hudson Bay.
Nino-Torres et al. (
2010
) reported in DDT levels in blubber biopsies from fi n
whales (
Balaenoptera physalus
) collected in 2004-2005 in the Gulf of California,
Mexico. DDT levels ranged from 200 to 1,900 ppb with an average of 500 ppb in
females and 850 ppb in males. These levels are among the lowest reported world-
wide for fi n whales and other marine mammals.
In summary, the few studies reporting DDT residues in gray and minke whales
indicate that they are also capable of accumulating residues in their blubber and
other tissues. However, since they feed fairly low on the marine food web (inverte-
brates), their residue levels tend to be relatively lower than those of fi sh-eating
marine mammals (viz., seals, sea lions, and dolphins). Similar to the other marine
mammals discussed above, toxic effects from DDT in gray and minke whales have
yet to be conclusively demonstrated.
Conclusions
. The above DDT residue data in marine mammals indicates that fat-
soluble DDT and/or its degradation products have been detected in many marine
mammalian species worldwide since the mid-1960s. In general, during the DDT-use
era blubber concentrations in the parts-per-million range were not uncommon, par-
ticularly for the species that feed primarily on fi shes—thus higher on the marine food
web. Of importance to the Newport Bay region are the harbor seal, California sea lion,
and the Pacifi c bottlenose and common dolphins. Clearly, marine mammals are quite
capable of accumulating residues as long as DDT continues to exist and accumulate
in the aquatic food chain. However, in the years since the U.S. ban on DDT use, tissue
concentrations have decreased in tandem with the decline in environmental concentra-
tions. A similar trend has been observed for gray and minke whales. However, since
baleen whales tend to feed at lower levels of the marine food web, blubber concentra-
tions have tended to be an order of magnitude lower—in the parts-per-billion range.
In this literature review we also sought to assess the role of DDT in causing pos-
sible embryo deformities and/or other measurable health effects in marine mammals.
However, marine mammals are a unique class or animals, in that published reports on
controlled studies documenting such toxic effects were not encountered. There appear
to be two reasons for this. First, they are too large and heavy to be easily housed,
handled and utilized in controlled experiments with sample sizes suffi cient to provide
for statistical analysis. Second, they have been strictly protected by the federal govern-
ment for many years, which has severely limited access. As a result, and as can be
deduced from the chronology above, nearly all studies involving marine mammals
and toxicants have been limited to residue analyses involving either dead/decaying
animals or live, captive animals sampled via blubber biopsies.
Such a restriction has limited the fi eld to speculation of effects, based upon mea-
sured residues and, in some cases, weak correlations. However, since metabolic
activity in blubber is relatively low, it is assumed that large concentrations would
need to be attained before measurable effects would be observed. Thus, to date,
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