Environmental Engineering Reference
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In 1998, Klevaine and Skaare published their fi ndings on the chemical concentra-
tions in some 72 minke whales stranded along the northeastern Atlantic seaboard
(coastal Norway, West Spitsbergen Island, and Bear Island) in 1992. Although they
found no signifi cant differences in mean DDT concentrations between juvenile males
versus females (1.94 ppm versus 2.77 ppm lipid weight, respectively), they did con-
clude differences existed between adult males and females (3.86 ppm versus 1.51 ppm,
respectively), as well as between juveniles and adults (both males and females).
The DDT concentrations were also determined for some 155 minke whales har-
vested in 1998 from the North Atlantic and European Arctic Oceans (Hobbs et al.
2003 ). Results ranged from 65.3 to 6,280 ppb (lipid weight basis), which encom-
pass the concentrations measured in whales taken 6 years earlier by Klevaine and
Skaare ( 1998 ).
Finally, in one of the few mechanistically-oriented papers involving any cetacean,
Niimi et al. ( 2005 ) reported the full-length cDNA sequences of two cytochrome
P450 (CYP) isozymes, from minke whale liver, responsible for either the bioactiva-
tion or detoxifi cation of xenobiotic chemicals. While CYP1A1 consisted of 516
amino acid residues and was deemed most closely related to that from sheep and
pigs, CYP1A2, also consisting of 516 residues, was deemed most closely analo-
gous to that from humans, indicating that the enzyme's function in minke whales
may be similar to that of humans. However, Niimi et al. ( 2005 ) found no signifi cant
correlation between hepatic DDT levels and mRNA expression levels of CYP1A1
and CYP1A, indicating that DDT may not be responsible for their induction in
minke whales.
Lailson-Brito et al. ( 2012 ) reported DDT levels (lipid weight basis) of 125.6 ppm
in blubber from a female killer whale ( Orcinus orca ) and 17.9 ppm in a neonatal
female false killer whale ( Pseudorca crassidens ) from the southern Brazilian coast.
Considering that female marine mammals tend to have lower residues of DDT than
males due to lactation, male killer whales would have even higher residues than
existed in the females mentioned above. Transient killer whales, known to feed
primarily on marine mammals (the authors of this study reported the presence of a
dolphin remains in the stomach of the killer whale), are at the highest point in the
marine food-chain and therefore would be expected to have the highest residues of
DDT as reported in this study.
Elfes et al. ( 2010 ) collected blubber biopsies from adult male humpback whales
( Megaptera novaeangliae ) along the North American Pacifi c coast in 2003-2004
and in the Gulf of Maine in 2005-2006. Whales sampled in southern California had
the highest levels (lipid weight basis) of DDT at 4,900 ppb. Residues decreased
more than one order of magnitude as the sampling points moved north to the Bering
Sea. DDT residues increased with age.
Hoguet et al. ( 2013 ) sampled blubber in Beluga whales ( Delphinapterus leucas )
from the Alaskan artic from 1989 to 2006. The median DDT level (lipid weight
basis) in blubber was 1,890 ppb. Male residues were more than three times the resi-
due level in females. The authors note that the wide fl uctuation in seasonal blubber
thickness may result in mobilization of DDT from lipid stores in blubber.
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