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Warnings about methylmercury-contaminated fish are not just
for young children and expectant mothers, as research shows
that eating methylmercury-contaminated fish also causes problems
in adults.
Diet, particularly large fish, is the major source of methylmercury.
The contaminant damages or destroys nerve tissue and affects
the visual cortex and the cerebellum, the part of the brain
that controls complex movements and balance.
Exposure to mercury may also result in attention and language
deficits, impaired memory, inability to process and recall
information, and impaired visual and motor function, and adults
who regularly eat contaminated fish may have decreased concentration,
dexterity and verbal memory.
In the study, researchers examined the effects of long-term
exposure to small amounts of methylmercury in adults.
The study involved 129 people living in fishing communities
in Brazil. Researchers took hair samples and analyzed them
for mercury and also used tests to assess mental functions
such as learning and attention.
About one out of four participants were found to have mercury
levels that exceeded the 'safe' level set by the World Health
Organization (WHO) for women and children. WHO is looking
into decreasing the current exposure limit.
Moreover, people with higher levels of mercury in their hair
scored lower on the tests for motor skills, memory and concentration.
Mercury contamination is a growing concern. In the United
States, 43 states have advisories in effect for mercury-contaminated
fish that warn the general population or sensitive groups
of people to reduce or avoid consumption. This is close to
a 60 percent increase from 1993 when only 27 states had mercury
advisories.
In 2001, the U.S. Food and Drug Administration issued a warning
to pregnant women and women of childbearing age to restrict
their intake of shark, swordfish, king mackerel and tilefish
due to mercury contamination. Women who eat severely contaminated
fish may give birth to children with birth defects including
cerebral palsy and mental retardation.
Other advisories extend the warning to children, although
the current study findings suggest that it should be extended
to adults as well.
Researchers concluded that exposure to methylmercury at levels
often encountered by adults in North America may result in
adverse effects on neurobehavioral performance.
Environmental
Health: A Global Access Science Source June 2003, 2:8
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