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Elevated
PCB Levels
Blamed For Mental Decline
NEW
YORK (Reuters Health) - For the first time, researchers have found
that adults with high blood levels of polychlorinated biphenyls
(PCBs) may have more memory and learning problems compared with
people with lower blood levels of the chemicals.
Once used
in everything from fluorescent lights and appliances to insulation
and insecticides, PCBs were banned in 1977 as health hazards and
carcinogens. But PCBs tend to linger in the environment, accumulating
in the fatty tissue of birds, fish and mammals, and potentially
having adverse health consequences in humans.
In a new study,
investigators found that people who routinely ate PCB-contaminated
sport-caught fish had more problems with learning and memory than
people the same age with lower levels of PCBs in their body.
``The main
finding was that older people--who ate sport-caught Great Lakes
fish and had elevated body burdens of PCBs--did more poorly than
non-fish eaters with lower PCB exposure on tests of verbal memory,''
said lead author Dr. Susan L. Schantz, of the University of Illinois
at Urbana-Champaign.
``Specifically,
they did not remember a short story that had been read aloud to
them as well as the less-exposed people when they were asked to
recall it 30 minutes later,'' she explained.
``Also, when
asked to recall items from a shopping list that was read aloud
to them, they tended not to group words by their meanings--a strategy
that helps to boost recall,'' Schantz added.
In the study,
Schantz and her colleagues evaluated the mental functioning of
101 adults aged 49 to 86 who ate more than 24 pounds of fish from
Lake Michigan each year. This group was compared with 78 similarly
aged adults who ate 6 pounds or less of fish from Lake Michigan
every year.
On average,
the men had blood PCB levels of 15.2 parts per billion (ppb) and
women had 9.2 ppb. Non-fish eaters had much lower levels of the
chemical in their blood, according to the report published in
the June issue of Environmental Health Perspectives.
``Previously,
researchers felt it was primarily children exposed to PCBs in
utero who were at risk for neurological problems. This study suggests
that mature adults who have elevated exposure may also be at risk,''
Schantz told Reuters Health.
Although the
researchers do not fully understand the mechanisms through which
PCBs impair brain function, there are some new studies showing
that PCBs disrupt calcium signaling in nerve cells and this may
turn out to be related to the learning and memory problems that
have been seen in laboratory animals, children and now adults
exposed to PCBs, she explained.
PCB levels
vary from person to person, and largely depend on an individual's
diet, life style and where they live. The average PCB blood level
for young adults living in the United States is around 2 ppb.
Older people tend to have higher levels of PCBs in their blood
as do people who eat fish from contaminated waters such as the
Great Lakes or the Baltic Sea for example, Schantz noted.
What's more,
Shantz pointed out that the only treatment is prevention.
``Once PCBs
are in the body they get stored in body fat and remain for a very
long time. That's why older people tend to have higher levels
of PCBs--they gradually build up (bio-accumulate) over the life
span,'' she said.
``There are
no known drugs or procedures to increase excretion (of PCBs).
That is why it is so important for people to be aware of the fishing
advisories in the Great Lakes and avoid eating fish that are contaminated,''
Schantz concluded.
SOURCE:
Environmental Health Perspectives 2001;109:605-611.
Reference
Source 89
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