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Mediterranean basin. However, persistent organic contaminants, such
as PolyChlorinated Biphenyls (PCB), can easily be dispersed. In
effect, the duration of the half-life in water (suggested by [MAC 92]
to be two years for tri- and tetra-chlorides, and six years for penta- to
hepta-chlorides) does not include transfers in the food chain, one of
the most efficient methods of storage and transport for hydrophobic
substances. Chlordecone, a chlorine insecticide used to combat the
banana-tree weevil in the Antilles, is one of the contaminants
for which it is still difficult to suggest a typical biodegradation
time. In fact, the risks for the open ocean, where ecotoxicology is
concerned, are on the one hand those of persistent contaminants
on the scale of oceanic fluxes (a decade and more), and on the
other hand of substances whose planetary cycle is in part controlled by
specific marine processes. Mercury can be counted among the
latter, of which the atmospheric supplies through snow, then the
arrival at the ice interface of sea and seawater appears to be primordial
[COS 11, DAS 14], but whose planetary cycle remains to be
elucidated.
These compounds are generally hydrophobic - this is what makes
them difficult to biodegrade in an aquatic environment-and
lipophilic, and they, therefore, spread in the trophic chain in spite of
the fairly weak concentrations that cause them to be diluted in the
ocean. Their enduring presence, associated with this particular mode
of transfer, leads large sea predators to become contaminated, whether
these are, for example, tuna [KRA 03], mammals or even birds
[DIE 13]. The risks are, therefore, both the chronic toxicity of these
substances for large organisms and the ecosystems to which they
belong - which for a long time were thought to be unable to carry
pollution of human origin - as well as the fitness of the human
foodstuffs that are taken from them. This concern is even more
important when a population's food supply is mainly taken from
marine sources, as is the case, for example, for the Inuit [DAL 13] and
Polynesians [DEW 08].
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