PCBs Linked to Low IQ (revised)
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PCB EXPOSURE LINKED TO LOW IQ
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.[4]
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 disorders.[10,11,12]
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 Relation to the Great Lakes," ENVIRONMENTAL HEALTH
PERSPECTIVES Vol. 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, 1976-1984," ARCHIVES OF ENVIRONMENTAL
CONTAMINATION AND TOXICOLOGY Vol. 19 (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," SCANDINAVIAN JOURNAL OF WORK,
ENVIRONMENT, AND HEALTH Vol. 21 (1995), 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 at adult age," ENVIRONMENTAL
TOXICOLOGY AND PHARMACOLOGY (1996), pgs. 217-220. And: Per
Eriksson and Anders Fredriksson, "Developmental neurotoxicty of
four ortho-substituted polychlorinated biphenyls in the neonatal
mouse," ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY (1996), pgs.
155-165. And: Edel Holene and others, "Behavioral Effects of
Pre-and Postnatal Exposure to Individual Polychlorinated Biphenyl
Congeners in Rats," ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY Vol.
14 No. 6 (1995), pgs. 967-976. And: Susan L. Schantz and others,
"Spatial Learning Deficits in Adult Rats Exposed to
Ortho-Substituted PCB Congeners During Gestation and Lactation,"
FUNDAMENTAL AND APPLIED TOXICOLOGY 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.
CORRECTION
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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