PCBs and Other Organochlorines
Organochlorines,
including PCB's, DDT, DDE and other pesticide compounds have been shown
to concentrate in the fatty tissues of several species of marine mammals,
with the highest concentrations typically found in the blubber and liver.
For example, harbor porpoise from the Bay of Fundy region carry relatively
high levels of PCB's in their body tissues, with concentrations in sexually
immature of both sexes and adult males being higher than those of adult
females. Levels increase significantly with age in all tissues for males
and decrease significantly in most tissues for females (Gaskin, et.
al., 1983). Woodley, et. al. (1991) found PCB's, DDT, and other organochlorines
in northern right whale biopsy samples from the Bay of Fundy, Browns,
and Baccarro Banks. The sample concentrations fell within the lower
range of values reported for other mysticetes and were expected to be
below those which produce reproductive disorders in marine mammals.
Organochlorines have also been reported in humpback whales (Taruski,
et al. 1975), fin and sei whales (Borrell and Aquilar, 1987), pilot
whales (Muir, et al. 1988), common and Atlantic white-sided dolphins
(Kuehl, et al., 1994), grey seals (Addison and Brodie, 1977), and harbor
seals (Gaskin, et al., 1983).
Several
studies have demonstrated that female marine mammals mobilize and transfer
part of their body burden of chemical residue through lactation (Addison
and Brodie, 1977, Gaskin, et al., 1983, Kuehl, et. al., 1994, Woodley,
1991). For example, Addison and Brodie (1977) estimated that female
grey seals from Sable Island, Nova Scotia lose about 15% of PCB burden
through lactation, with concentrations in pup blubber lipid being the
same or slightly higher than that of the mother's milk. Gaskin, et al.
(1983) reported peak concentrations of PCB's in harbor porpoise in three
and four year old females and males, respectively. These findings were
associated with growth and feeding spurts that occur with the onset
of sexual maturity. A negative correlation of PCB concentrations with
age in females was attributed to mobilization and transplacental transfer
to the foetus, and then to the calf during lactation.
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