fish impair memory, learning
Lake Michigan catch poses health risk to adults, pregnancies
Lee Bowman /
Scripps Howard News Service
October 17, 2001
Eating large amounts
of PCB-laden fish from Lake Michigan impairs the memory
and learning of adults, a new study has found.
Heavy fish eaters -- more than 24 pounds
of sport-caught fish a year -- who are older than age 49
are having problems learning and remembering new verbal
information, according to the researchers' report in the
journal Environmental Health Perspectives.
"This study suggests, for the first time,
that PCB (polychlorinated biphenyls) body burdens in adulthood
may be associated with impairments in certain aspects of
memory and learning," said Susan Schantz, a researcher at
the University of Illinois College of Veterinary Medicine
who has been studying Lake Michigan fish-eaters since 1992.
"The focus has been almost exclusively
on increased health risks of exposure to children and pregnant
women," Schantz said. "It had been assumed that mature adults
are less susceptible than are developing fetuses, but this
may not be the case."
A decade ago, Drs. Joseph and Sandra Jacobsen
of Wayne State University reported that exposure to low
levels of PCBs disrupted fetal brain development, and caused
neurological abnormalities and learning disabilities, including
memory problems, in affected children.
Until they were banned in the late 1970s,
PCBs were widely used as electrical insulators and lubricants,
and as extenders in paints and varnishes. The chemicals
decompose very slowly and are still in use in a variety
of older electrical equipment.
In the Great Lakes, the PCBs make their
way up the aquatic food chain and accumulate in increasing
levels in the fatty tissue of game fish.
The new study measured how fish-eaters
with different concentrations of the chemical performed
on tests of memory and verbal learning.
They found that those with the highest
blood PCB levels had difficulties recalling a story told
just 30 minutes earlier. They were also less likely to be
able to cluster according to meaning a group of words presented
orally, suggesting problems in thinking ability.
The researchers found that heavy fish
eaters had higher levels of DDE (a breakdown product of
the banned pesticide DDT), lead and mercury than did less
frequent consumers, but the only negative cognitive effects
were among people with high blood levels of PCBs.
Schantz previously had reported that having
high blood levels of PCBs had little or no significant effect
on fine motor skills. And in the new research, they found
no impact on other thinking factors, such as planning ahead,
attention span and visual spatial function.