Fish is an extremely important component of the human diet in
many parts of the world and provide nutrients such as protein,
omega-3 (n-3) fatty acids (that reduce cholesterol levels and the
incidence of heart disease, stroke, and preterm delivery) and others
that are not easily replaced Fish can be preserved in so
many ways including freezing, salting, pickling, smoking and drying.
But the most useful way of preserving seafood is through canning.
Canned products especially canned fish have been found to
contain increasingly high amounts of Hg, Pb and Cd as well as some
other heavy metals. These metals are considered the most important
form of pollution of the aquatic environment because of their
toxicity and accumulation by marine organisms; and also because
of their persistent and being not easily biodegradable in nature.
Metal pollution of the sea is less visible and direct than other types
of marine pollution but its effects on marine ecosystems and
humans are intense and very extensive