PCBs
The letters PCB stand for polychlorinated biphenyl, a group of
now-banned but still ubiquitous environmental contaminants that often
give fish a bad name. But perhaps they ought to stand for Poor Cognitive
Behavior. A team of researchers has found that children exposed
prenatally to the substances have cognitive deficits that can adversely
affect their learning abilities.
Specifically, reports psychologist Joseph L. Jacobson, Ph.D., and
colleagues of Wayne State University in Detroit, it takes such children a
longer than normal time to process information, limiting general
intelligence. PCBs seem to target short-term memory processes and visual
discrimination. Both are essential for mastering reading and
arithmetic.
For infants, PCB exposure occurs throughout gestation via the
umbilical cord, which transports nutrients from mother to growing baby.
Acquired by the mother primarily through consumption of contaminated
foods, such as freshwater fish in some regions, PCBs are stored in
body-fat deposits until mobilized by demands such as development of a
fetus.
Jacobson and company tested the cognitive functions of 224
four-year-olds from western Michigan. And they tested the PCB levels of
their mothers, as measured in samples of the umbilicus at birth. Some of
the women had consumed large amounts of contaminated Lake Michigan fish
during their pregnancies; others had low PCB levels.
In tests of short-term memory and visual acuity, kids with lower
PCB exposure as measured at the time of birth performed significantly
better than those with high exposure. The higher the PCB level, the more
errors on the memory test and the longer it took them to reach correct
solutions of visual discrimination problems. In a test of attention span,
there were no noticeable differences between the two groups.
Following birth, many infants get an even larger wallop of PCBs
through breast milk. However, there was no consistent pattern of deficits
among infants who were breast-fed, and cognitive deficits correlated only
with PCB exposure in utero.
In fact, as a group, those breast-fed as babies outperformed their
bottle-fed brethren on tests of sustained attention. The researchers
believe breast-fed children become quick learners because their mothers
are usually more highly educated and spend more time teaching them. They
may also be spared PCB effects after birth because the blood-brain
barrier has matured enough to protect the brain.
Pregnant women have some control over the amount of PCBs they take
in; they can easily avoid eating fish from water known to be
contaminated, such as the Great Lakes. Trouble is, many women just don't
know when they're being exposed.
And it still isn't clear whether PCBs affect cognitive powers over
the long haul. A follow-up study on 10-year-olds who were exposed in
utero is now under way to determine whether PCBs still have an adverse
affects their ability to learn later on in their lives.
Tags:
attention span,
children,
cognitive behavior,
cognitive deficit,
cognitive deficits,
cognitive functions,
correct solutions,
development of a fetus,
discrimination problems,
environmental,
environmental contaminants,
four year olds,
freshwater fish,
lake michigan fish,
memory processes,
memory test,
noticeable differences,
pcb level,
pcb levels,
polychlorinated biphenyl,
polychlorinated biphery,
pregnancy,
short term memory,
visual discrimination,
wayne state university
