Exposure to toxic materials in the womb can cause health problems
later in life, an international panel declares.
In a strongly worded declaration, many of the world's leading
environmental scientists warned Thursday that exposure to common
chemicals makes babies more likely to develop an array of health
problems later in life, including diabetes, attention deficit
disorders, prostate cancer, fertility problems, thyroid disorders
and even obesity.
The declaration by about 200 scientists from five continents amounts
to a vote of confidence in a growing body of evidence that humans
are vulnerable to long-term harm from toxic exposures in the womb
and during their first years.
Convening in the Faroe Islands in the North Atlantic, toxicologists,
pediatricians, epidemiologists and other experts warned that when
fetuses and newborns encounter various toxic substances, growth of
critical organs and functions can be skewed. In a process called
"fetal programming," the children then are susceptible to diseases
later in life — and perhaps could even pass on those altered traits
to their children and grandchildren.
The scientists' statement also contained a rare international call
to action. The effort was led by Dr. Philippe Grandjean of Harvard
University and the University of Southern Denmark, and Dr. Pal Weihe
of the Faroese Hospital System, who have spent more than 20 years
studying children exposed to mercury.
Many governmental agencies and industry groups, particularly in the
United States, have said there is no or little human evidence to
support concerns about most toxic residue in air, water, food and
consumer products. About 80,000 chemicals are registered in the
Yet the scientists urged leaders not to wait for more scientific
certainty and recommended that governments revise regulations and
procedures to take into account subtle effects on fetal and infant
Chemicals with evidence of developmental effects include compounds
in plastics, cosmetics and pesticides.
"Given the ubiquitous exposure to many environmental toxicants,
there needs to be renewed efforts to prevent harm. Such prevention
should not await detailed evidence on individual hazards," the
scientists wrote in the four-page statement.
The scientists are particularly concerned that the newest animal
research suggests that chemicals can alter gene expression — turning
on or off genes that predispose people to disease. Although the DNA
itself would not be altered, such genetic misfires in the womb may
be permanent, and all subsequent generations could be at greater
risk of diseases too.
"Toxic exposures to chemical pollutants during these windows of
increased susceptibility can cause disease and disability in
childhood and across the entire span of human life," the scientists
The "Barker hypothesis," conceived by a British scientist in 1992,
says human fetuses are "programmed" for diseases by their early
environment. The scientists concluded that this is now
well-documented for toxic exposures by a large collection of animal
experiments and some human data.
"A sad aspect with many of these prenatal exposures is that they
leave the mother unscathed while causing injury to her fetus," said
Dr. Philip Landrigan, a pediatrician who chairs the Mount Sinai
School of Medicine's Department of Community and Preventive
Medicine. He was one of the statement's authors.
In a more optimistic vein, the researchers said that if contaminants
do play a big role in human health problems, some diseases could be
"Reducing exposure would lead to tremendous benefits," said Dr.
Bruce Lanphear, director of the Environmental Health Center at
Cincinnati Children's Hospital Medical Center. "We shouldn't wait
for an epidemic to fully mature before we develop policies to
For centuries, the basic rule of toxicology has been "the dose makes
the poison." Now, the scientists say "the timing makes the poison" —
in other words, when a toxic exposure occurs is as important as the
amount people are exposed to.
The fetus "is extraordinarily susceptible to perturbation of the
intrauterine environment," they wrote.
The growing brain is the most sensitive. Mothers' exposure to
mercury and polychlorinated biphenyls (PCBs) in fish and other
seafood can cause slight declines in a child's IQ and motor skills.
In addition, early exposure to pesticides might trigger Parkinson's
and Alzheimer's diseases.
Also, children exposed to lead, organophosphate pesticides or
cigarette smoke have greater risk of attention deficit hyperactivity
disorder. One of every three cases — or an estimated 560,000
children in the United States — can be attributed to lead exposure
or prenatal tobacco smoke exposure, Lanphear reported in a study
published in December.
The immune, reproductive and cardiovascular systems also are
vulnerable to early damage. Children exposed prenatally to PCBs have
a high rate of infections and weak response to vaccinations. Many
chemicals also can mimic hormones, and in animal tests, they
feminize newborns, lowering sperm counts and promoting prostate,
testicular, uterine and breast cancers.
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