Pesticide Residues in Birds and Mammals - Pesticides: Evaluation of Environmental Pollution - page 428

Borrell and Aguilar 2005; Fisk et al. 2005; Fossi et al. 2007; Sonne et al. 2008, 2009; Bernanke
and Köhler 2009; Letcher et al. 2010; Routti et al. 2010; Sonne 2010). Since the 1980s, mass
mortality events of aquatic mammals occurred all over the world (Gulland and Hall 2007).
Immunological impairment caused by POPs was considered relevant in the extension of
the epizootic, which started in the summer of 1990 and continued through 1991 and 1992 in
the striped dolphins ( Stenella coeruleoalba ) in the Mediterranean Sea, an infection produced
by a morbillivirus (Domingo et al. 1990, 1992), when it was speculated that the total popula-
tion declined to just a third of its initial level (Aguilar and Raga 1993; Guitart et al. 1996a).
The much less important epizootic event that occurred in 2007-2008 in the Mediterranean
striped dolphins was also associated with lower levels of OCs, with mean levels for ΣDDTs
of 73,000 ng/g LW in the 2007-2008 outburst compared to 392,000 ng/g LW in 1990, and the
authors considered the extension of the epizootic not to have enhanced this time (Castrillon
et al. 2010).
Until recently, the levels of DDTs in marine mammals were among the highest ever
recorded in vertebrates; and, in some cases, they still remain very high. In Table 14.4, we
can find seven species that contain concentrations above 20,000 ng/g LW of this group
of chemicals: short-beaked common dolphin ( Delphinus delphis ), Mediterranean monk
seal ( Monachus monachus ), finless porpoise ( Neophocaena phocaenoides ), harbor porpoise
( Phocoena phocoena ), killer whale, striped dolphin, and common bottlenose dolphin from
different parts of the world (Borrell and Aguilar 2005; Kajiwara et al. 2006; Ramu et al.
2006; Borrell et al. 2006, 2007; Krahn et al. 2007; Haraguchi et al. 2009; Isobe et al. 2009;
Castrillon et al. 2010; Weijs et al. 2010). As a matter of fact, marine mammals from the Arctic
and some regions of Europe, North America, and Asia have been found to be particularly
contaminated with OC pesticides (Guitart et al. 1996a; Aguilar et al. 2002; Houde et al.
2005; Kajiwara et al. 2006; Ramu et al. 2006; Rigét et al. 2010). Overall, Houde et al. (2005)
point out that the highest concentrations of POPs were found in delphinoid cetaceans from
industrialized areas of the Northern hemisphere compared to the Southern hemisphere.
But regional differences not related to big latitude changes also occur: one recent example
is the Mediterranean monk seal, for which extremely significant differences were found
between two separate populations collected in the 1995-1999 period from Greece, in the
Mediterranean Sea, and the Western Sahara, in the Atlantic Ocean (Borrell et al. 2007).
The usually high or very high levels of DDTs and other OC pesticides found in these
animals and the quantity of tissues available, for example, from stranded animal episodes
have led some authors to investigate the tissue distribution of these pollutants (Guitart et al.
1996a; Kannan et al. 2005; Ramu et al. 2005; Fillmann et al. 2007; Carballo et al. 2008; Isobe
et al. 2009; Schiavone et al. 2009; Shoham-Frider et al. 2009; Moon et al. 2010; Weijs et al.
2010). In striped dolphins, for example, studies indicate that the distribution of POP insec-
ticides in the body (muscle, liver, blubber, etc.) depends on the lipid content, as usually
lipid normalized concentrations showed no significant differences, with the brain being an
exception: lower levels in this organ are probably due to the existence of the blood-brain
barrier (Guitart et al. 1996a; Isobe et al. 2009).
Less obvious or studied in birds or terrestrial mammals, in marine mammals there
are many works reporting differences of OC pesticide concentrations between males
and females with growth (Guitart et al. 1996a; Hobbs et al. 2001, 2003; Dietz et al. 2004a;
Metcalfe et al. 2004; Wolkers et al. 2004; Stern et al. 2005; Carballo et al. 2008; Borrell et al.
2010; Mwevura et al. 2010; Park et al. 2010). These sex- and sexual maturity-related vari-
ations are generally attributed to the transfer of pollutants from the mother to the calf
or pup during lactation, resulting in lower OC levels in the mother, although variation
in diet, body size, metabolic ability, and other biological traits may partially account for