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#512 - PCB Exposure Linked to Low IQ, 18-Sep-1996

A study published September 12, 1996, in the NEW ENGLAND JOURNAL OF
MEDICINE confirms that children exposed to low levels of PCBs in the
womb grow up with low IQs, poor reading comprehension, difficulty
paying attention, and memory problems.[1] PCBs are a family of toxic
industrial chemicals commercialized in 1929 by Monsanto, and now found
in nearly all humans on earth. (See REHW #327.) This latest study
describes a group of 11-year-old children whose mothers ate 2 to 3
meals per month of fish from Lake Michigan for at least 6 years before
giving birth. The children's mental and physical growth have been
followed since birth. The greatest mental deficits have occurred in the
11% of the children whose mothers ate the most fish.[2]

Since 1980, Joseph and Sandra Jacobson, psychologists at Wayne State
University in Detroit, Michigan, have studied 242 children whose
mothers had eaten salmon and lake trout from Lake Michigan an average
of 2 to 3 times each month for many years.[3] Those children have been
compared to a control group of 71 babies whose mothers had not eaten
any Lake Michigan fish. (See REHW #295, #372, #411.) Large fish in Lake
Michigan, such as lake trout and salmon, are typically contaminated
with PCBs, mercury, and a host of other chlorinated organic chemicals.

The Jacobsons analyzed PCB levels in the blood of the babies' umbilical
cords, thus providing a reliable measure of pre-natal exposure. At
birth, a mother's overall fish consumption and the PCB level in her
baby's blood both correlated with the baby's birth size. Eating more
fish was linked to babies with reduced head size, diminished girth in
the chest and shorter gestation.[3] On standardized tests for infant
development, higher fish consumption was correlated with abnormally
weak reflexes, less responsiveness to stimulation, more jerky,
unbalanced movement, and more startles in the babies.[5] At birth, the
babies whose mothers had eaten the most PCB-contaminated fish were
clearly different from normal children.

At age seven months, 123 of the original 242 infants were tested for
"visual recognition memory." Each baby was shown a pair of identical
photos of human faces for about 20 seconds; then one of the photos in
the pair was changed and the new pair was presented to the infant.
Normal babies spend more time looking at the new face. Babies with more
PCBs in their blood, and babies whose mothers had eaten more Lake
Michigan fish, spent less time looking at the new faces. The Jacobsons
concluded that the high-PCB babies had memory problems: they could not
remember the first photo pair well enough to recognize that the second
photo pair was different. Lower scores on this test (which is known as
the Fagan Test of Visual Recognition or the Fagan Test of Infant
Intelligence) have been shown to correlate with lower intelligence
later in life.[6]

Two hundred and thirty-six of the original 242 children were tested
again at the age of four.[7] Two effects became apparent. First, 17 of
the children whose mothers had the highest levels of PCBs in their
breast milk refused to complete the tests; they were balky and
uncooperative. Secondly, the remainder of the children were given a
series of tests to measure memory and general mental capabilities and,
again, the children whose mothers had eaten the most fish had the
poorest memories.

The balky, uncooperative behavior is of some interest by itself. Helen
Daly, of the Center for Behavioral Effects of Environmental Toxins at
the State University of New York (SUNY) at Oswego, has been studying
humans and laboratory animals exposed to PCBs and other chlorinated
hydrocarbons. She reports that when rats were fed contaminated salmon
from Lake Ontario, they overreacted to negative events when life was
made unpleasant (by such means as mild electric shock, or
disappointment at feeding time). Significantly, the offspring of those
rats showed the same pattern of altered responses to stress, even
though the offspring themselves were not fed contaminated fish. Helen
Daly wonders whether rats and children don't develop similar
overreactions to stress after being exposed to PCBs while in the womb.
Commenting on the refusal of 17 4-year-olds to complete the Jacobsons'
tests, Daly says, "If one can assume that taking a test is a mildly
negative experience for 4 year olds, it appears as if those children
probably exposed to higher levels of toxins due to breast feeding
reacted more negatively to the testing procedure."[8]

In the NEW ENGLAND JOURNAL OF MEDICINE September 12 the Jacobsons
reported their most recent examination of 212 of the original children.
At age 11, maternal exposure to PCBs was correlated with lower overall
IQ and lower verbal IQ score. The 11% of the children whose mothers had
the highest exposures now have IQs 6.2 points lower than average. In
these 11-year-olds, prenatal exposure to PCBs was linked to poor word
comprehension and poor reading ability. The highest-exposed children
were twice as likely to be at least two years behind their peers in
word comprehension. The Jacobsons summarize: "Our IQ results indicate
deficits in general intellectual ability, short-term and long-term
memory, and focused and sustained attention." They speculate that the
mechanism of harm is PCB interference with thyroid hormones, which are
essential for development of the brain.[1]

It is especially noteworthy that the children's intellectual deficits
correlate most closely with the mother's overall fish consumption. PCBs
passed to the children DURING BREAST FEEDING did not correlate well
with poor mental performance (though, as we saw above, they may
correlate with inability to handle stress). The data indicate that
these children were harmed most by PCBs PASSED TO THEM BY THEIR MOTHERS
PRIOR TO BIRTH. It was not the mother's fish-eating habits during
pregnancy that was important --it was the mothers' CUMULATIVE LIFETIME
EXPOSURE to PCBs that lowered their children's IQs. In other words,
exposure of females to PCBs at any time in their lives before they bear
children may eventually translate into mental deficits for their
offspring. This has profound implications for regulatory agencies. It
means "lifetime exposure" must be regulated.

The children studied by the Jacobsons had PCB exposures which, though
on the high side, are still considered to be within normal background
exposure levels. Many other possible causes, such as exposure to lead
or pesticides, or the mother's use of tobacco or alcohol, were ruled
out. (Unfortunately, maternal exposure to methyl mercury was not
assessed by the Jacobsons, weakening their study.[9])

Four previous studies of children had reported similar problems from
PCB exposures, ranging from small size at birth to developmental

Diminished ability to handle stress, combined with reduced attention
span, short-term memory problems, and reading disabilities add up to a
familiar profile of modern problems shared by many U.S. school
children. No one is saying cause and effect has been proven but
suspicions have certainly been raised by the Jacobsons' studies because
exposure to PCBs and other dioxin-like chemicals is widespread in the
U.S. (as it is among human populations worldwide), and so are problems
of intellectual development. "These were not people who were eating
fish every day," Linda Birnbaum, who is lead scientist for the ongoing
EPA (U.S. Environmental Protection Agency) dioxin study (see REHW #390,
#391), told Katherine Dold of DISCOVER magazine. "I believe the data
suggest there are subtle changes going on in at least a portion of our
population," Birnbaum said.[13]

Importantly, the Jacobsons' latest findings have been mirrored in
several animal studies,[14] and in studies of Taiwanese children
accidentally exposed to high levels of PCBs.[15]

And the PCB problem is not going away soon. Between 1929 and 1989,
total world production of PCBs (excluding the Soviet Union) was 3.4
billion pounds, or about 57 million pounds per year. Even after the
U.S. banned PCBs in 1976, world production continued at 36 million
pounds per year from 1980-1984 and 22 million pounds per year, 1984-
1989. The end of PCB production is not in sight.[16]

The whereabouts of 30 percent of all PCBs (roughly a billion pounds)
remains unknown. Another 30 percent reside in landfills, in storage, or
in the sediments of lakes, rivers, and estuaries. Some 30 percent to 70
percent remain in use. The characteristics of PCBs (their stability and
their solubility in fat) tend to move them into the oceans as time
passes. Nevertheless, it is estimated that only one percent of all PCBs
have, so far, reached the oceans.[16] Without major efforts to locate,
capture, and destroy the one-to-two billion pounds of PCBs that are
"out there," future generations will continue to be poisoned by PCBs,
at great social (and individual) cost. We hear much of late about the
good intentions of the Monsanto Corporation. Some of our friends tell
us this corporation has turned over a new leaf, and is committed to
behaving responsibly. If this is so, Monsanto could demonstrate its
awakening by leading an effort to locate and destroy PCBs. Monsanto
created (or licensed the creation of) all the PCBs in the world. This
corporation could demonstrate its commitment to environmental
sustainability by cleansing the planet of this brain-damaging
substance, to the extent possible. An obvious first step would be to
undertake a comprehensive inventory of the problem, assessing the
damage done so far and cleanup-costs, as a demonstration of good faith
and serious intentions.

--Peter Montague (National Writers Union, UAW Local 1981/AFL-CIO)


[1] Joseph L. Jacobson and Sandra W. Jacobson, "Intellectual Impairment
in Children Exposed to Polychlorinated Biphenyls in Utero," NEW ENGLAND
JOURNAL OF MEDICINE Vol. 335 No. 11 (September 12, 1996), pgs. 783-789.

[2] Joseph L. Jacobson and Sandra W. Jacobson, "Dose-Response in
Perinatal Exposure to Polychlorinated Biphenyls (PCBs): The Michigan
and North Carolina Cohort Studies," TOXICOLOGY AND INDUSTRIAL HEALTH
Vol. 12, Nos. 3/4 (1996), pgs. 435-445.

[3] Greta G. Fein and others, "Prenatal exposure to polychlorinated
biphenyls: Effects on birth size and gestational age," THE JOURNAL OF
PEDIATRICS Vol. 105 (August 1984), pgs. 315-320.

[4] Deborah C. Rice, "Neurotoxicity of Lead, Methylmercury, and PCBs in
103 SUPPLEMENT 9 (December 1995), pgs. 71-87. And see Christopher J.
Schmidt and others, "National Contaminant Biomonitoring Program:
Residues of Organochlorine Chemicals in U.S. Freshwater Fish, 1976-
(1990), pgs. 748-781.

[5] Hugh A. Tilson and others, "Polychlorinated Biphenyls and the
Developing Nervous System: Cross-Species Comparisons," NEUROTOXICOLOGY
AND TERATOLOGY Vol. 12 No. 3 (1990), pgs. 239-248.

[6] Sandra W. Jacobson and others, "The Effect of Intrauterine PCB
Exposure on Visual Recognition Memory," CHILD DEVELOPMENT Vol. 56
(1985), pgs. 853-860.

[7] Joseph L. Jacobson and others, "Effects of in utero exposure to
polychlorinated biphenyls and related contaminants on cognitive
functioning in young children," JOURNAL OF PEDIATRICS Vol. 116 (January
1990), pgs. 38-45. And see: Joseph L. Jacobson and others, "Effects of
Exposure to PCBs and Related Compounds on Growth and Activity in
Children," NEUROTOXICOLOGY AND TERATOLOGY Vol. 12 (1990), pgs. 319-326.
And see: Joseph L. Jacobson and others, "Effects of Prenatal PCB
Exposure on Cognitive Processing Efficiency and Sustained Attention,"
DEVELOPMENTAL PSYCHOLOGY Vol. 28 No. 2 (1992), pgs. 297-306.

[8] See Helen B. Daly, "The Evaluation of Behavioral Changes Produced
by Consumption of Environmentally Contaminated Fish," in Robert L.
Isaacson and Karl F. Jensen, editors, THE VULNERABLE BRAIN AND
ENVIRONMENTAL RISKS (New York: Plenum Press, 1992), pgs. 151-171. And
see Helen B. Daly, "Reward Reductions Found More Aversive by Rats Fed
Contaminated Salmon," NEUROTOXICOLOGY AND TERATOLOGY Vol. 13 (1991),
pgs. 449-453.

[9] Joseph L. Jacobson and Sandra W. Jacobson, "Sources and
Implications of Interstudy and Interindividual Variability in the
developmental Neurotoxicty of PCBs," NEUROTOXICOLOGY AND TERATOLOGY
Vol. 18 No. 3 (1996), pgs. 257-264.

[10] E. Dewailly and others, "Health Status at Birth of Inuit Newborn
Prenatally Exposed to Organochlorines," CHEMOSPHERE Vol. 27 No. 1-3
(1993), pgs. 359-365. And see: Lars Rylander and others, "Decreased
birthweight among infants born to women with a high dietary intake of
fish contaminated with persistent organochlorine compounds,"
pgs. 368-375.

[11] Marcel Huisman and others, "Neurological condition in 18-month-old
children perinatally exposed to polychlorinated biphenyls and dioxins,"
EARLY HUMAN DEVELOPMENT Vol. 43 (1995), pgs. 165-176.

[12] E. Lonky and others, "Neonatal Behavioral Assessment Scale
performance in humans influenced by maternal consumption of
environmentally contaminated Lake Ontario fish," JOURNAL OF GREAT LAKES
RESEARCH Vol. 22 No. 2 (1996), pgs. 198-212.

[13] Catherine Dold, "Hormone Hell," DISCOVER Vol. 17 No. 9 (September,
1996), pgs. 52-59. To reprint quotations from DISCOVER magazine, you
must get permission from Marcia Bell (marcia_bell@cp.disney.com;
telephone: (212) 633-4812).

[14] For monkey data, see note 5 above. And see: Per Eriksson and
Anders Fredriksson, "Neonatal exposure to 2,2',5,5'-tetrachlorobiphenyl
causes increased susceptibility in the cholinergic transmitter system
217-220. And: Per Eriksson and Anders Fredriksson, "Developmental
neurotoxicty of four ortho-substituted polychlorinated biphenyls in the
155-165. And: Edel Holene and others, "Behavioral Effects of Pre-and
Postnatal Exposure to Individual Polychlorinated Biphenyl Congeners in
pgs. 967-976. And: Susan L. Schantz and others, "Spatial Learning
Deficits in Adult Rats Exposed to Ortho-Substituted PCB Congeners
Vol. 26 (1995), pgs. 117-126. And: Susan L. Schantz and others,
"Effects of Gestational and Lactational Exposure to TCDD and Coplanar
PCBs on Spatial Learning," NEUROTOXICOLOGY AND TERATOLOGY Vol. 18, No.
3 (1996), pgs. 305-313.

[15] Yueliang L. Guo and others, "Growth Abnormalities in the
Population Exposed in Utero and Early Postnatally to Polychlorinated
Biphenyls and Dibenzofurans," ENVIRONMENTAL HEALTH PERSPECTIVES Vol.
103 SUPPLEMENT 6 (September 1995), pgs. 17-122.

[16] Carol W. Bason and Theo Colborn, "U.S. Application and
Distribution of Pesticides and Industrial Chemicals Capable of
Disrupting Endocrine and Immune Systems," in Theo Colborn and Coralie
Clement, editors, Chemically-Induced Alterations in Sexual and
Functional Development: The Wildlife/Human Connection [Advances in
Modern Environmental Toxicology Vol. XXI] (Princeton, N.J.: Princeton
Scientific Publishing Co., 1992), pgs. 342-343.


In RACHEL'S #511, we said, "However, most species disappear in natural
aquatic ecosystems at higher pH values (more acidic conditions) than
predicted by laboratory tests, thus suggesting that, in ecosystems,
additional stresses enhance the effects of acidification." Obviously,
this should have said "(less acidic conditions)."

Descriptor terms: pcbs; polychlorinated biphenyls; fish; central
nervous system damage; great lakes; lake michigan; lake ontario;
children; joseph jacobson; sandra jacobson; endocrine disrupters;
oswego; helen daly; monsanto;

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