Report Links Prenatal PCB
Exposure With Child Development
by Jane E. Brody
from the New York Times, September 12, 1996
Exposure before birth to relatively small amounts of PCBs, a kind of
industrial pollutant, can result in long-lasting deficits in a child's intellectual
development, a new study has shown.
The researchers found higher than expected rates of "low normal"
IQ scores, poor reading comprehension, memory problems and difficulty paying
attention in 11-year-old children who had been prenatally exposed to polychlorinated
biphenyls, or PCBs, in concentrations only slightly higher than those found
in the general population.
Children with the highest levels of exposure were three times as likely
to have low normal IQ scores and twice as likely to be behind in reading
comprehension as the group as a whole.
The researchers, Dr. Joseph L. Jacobson and his wife, Dr. Sandra W. Jacobson,
psychologists at Wayne State University in Detroit, concluded that the fetal
brain damage caused by environmental exposure to PCBs was comparable to
the damage found in children exposed to low levels of lead.
But exposure to these chemicals after birth, through breast milk, did
not seem to cause any further harm to the children's mental abilities, the
study showed. In their report, published in Thursday's issue of The New
England Journal of Medicine, the researchers concluded that "the developing
fetal brain is particularly sensitive to these compounds." A pregnant
woman with PCBs in her body can transfer the chemicals through the umbilical
cord to her fetus. Even if she eats no contaminated foods during her pregnancy,
PCBs from foods eaten before she becomes pregnant will remain in her body
for years and can be transferred to her unborn children, Dr. Joseph Jacobson
said in an interview.
The Jacobsons had previously linked prenatal PCB exposure to poor short-term
memory in infants and young children. The new findings, in older children,
are consistent with reports of reduced IQ scores among more heavily contaminated
children in Taiwan whose mothers, while pregnant with them, ingested rice
oil accidentally laced with PCBs and other chemicals.
Dr. Walter Rogan, an epidemiologist with the National Institute for Environmental
Health Sciences at Research Triangle Park, N.C., said the new study had
been very carefully done and had used highly refined measures to detect
the effects of the PCBs.
"There's no question that PCBs are deleterious to the developing
mammalian nervous system; the only question is dose," Rogan said in
an interview.
PCBs were once widely used in the manufacture of electrical equipment
and in paper recycling. Although their production and their use in newly
manufactured equipment have been banned in the United States and most other
Western nations since the 1970s, and although environmental levels have
since declined, they still contaminate the sediments of many lakes and rivers,
including the Hudson, and remain prominent if diminishing pollutants in
some freshwater fish. Once ingested, they are stored in body fat, and they
dissipate only slowly after ingestion ceases.
Because of PCB contamination, the New York state Health Department advises
people not to eat some species, like river catfish, and to eat other species,
like striped bass, no more than once a month. Women of child-bearing age
and children under 15 are advised to eat no fish from the Hudson.
In the interview, Dr. Joseph Jacobson cautioned that "the majority
of PCBs manufactured are still in use," in old equipment, and that
"even though we are not making more there is still the potential for
getting a lot more PCBs into the potential for getting a lot more PCBs into
the environment unless more care is taken in disposing of them than in the
past," when they were often dumped into waterways.
The main source of exposure to PCBs by the women in the study was the
consumption of contaminated fish from Lake Michigan. But the authors pointed
out that "women who eat no fish may accumulate these compounds from
other food sources, including dairy products such as cheese and butter and
fatty meats, particularly beef and pork," because many animal feeds
have become PCB-contaminated as a result of soil leaching.
"The significance of these findings goes way beyond women eating
Lake Michigan fish," Jacobson said. "Virtually everyone who eats
has some PCBs stored in body fat. Unlike other exposures, which predominate
in economically disadvantaged families, prenatal exposure to PCBs is unrelated
to socioeconomic status."
Jacobson said the study "shows the wisdom" of the ban that
was adopted on PCBs.
"Most environmental legislation has been driven by cancer risk,"
he said. "But this may not be the most significant or the most costly
consequence of environmental pollution. If large numbers of children are
functioning below their native capacity, this would cost society a lot more
than a few cancers."
In the study, the Jacobsons tested 212 children who had been selected
as newborns in 1980 and 1981. Of the group, all studied at the age of 11,
167 had been born to women who had eaten Lake Michigan fish contaminated
with PCBs. At the time of birth, the amount of PCBs in the mothers' blood
serum and breast milk was slightly higher than is found in the general population.
The children were assessed for a wide variety of intellectual skills
important to learning and success in school, including general intelligence,
achievement in spelling and arithmetic, and reading comprehension. Those
prenatally exposed to PCBs, especially those with the highest levels of
exposure, had significantly lower general and verbal IQ scores than would
otherwise have been expected.
Copyright © 1996 The New York Times Company |
