METALS - Marine Pollution: What Everyone Needs to Know - page 93

high copper environments their tissues acquire a green color-
ation like the Statue of Liberty. Snails that eat these oysters get
affected and become sluggish and reduce their feeding.
What can organisms do to defend themselves against
metal toxicity?
There are a number of mechanisms that organisms use to
reduce the toxicity of metals once they have taken them
up. These include storing them in nontoxic forms such as
metal-binding proteins or granules. Other mechanisms
include stress proteins, and the evolution of tolerance. These
are discussed in detail in Chapter 8.
Can elevated levels of metals in seafood be a risk to humans?
Since meHg biomagnifies in food webs, eating a lot of large
fish that are high up in the food web, like tuna and swordfish,
can be risky. Mean Hg concentrations for each type of seafood
are highly variable. The high variability in Hg in common
seafood has ramifications for public health and complicates
the development of guidelines for how much should be eaten.
Prenatal exposure to meHg has been associated with impaired
performance on attention tasks, but the extent to which this
translates into behavioral problems is not clear. In a study of
Inuit mothers (who consume large quantities of fish) and their
children, umbilical cord blood Hg concentration was associ-
ated with attention problems and ADHD symptoms in chil-
dren, according to O. Boucher and colleagues.
Large tuna and swordfish together account for more than
half of the Hg intake from seafood for the US population.
American children may be ingesting high levels of Hg with
their tunafish sandwiches. Research by the Mercury Policy
Project, a consumer advocacy group ( www.mercurypolicy.
org) found that canned tuna has high levels of mercury. The
group says albacore or white tuna can triple a child's Hg