Even low exposure to chemicals can harm fetuses

Common chemicals a danger for fetuses, scientists warn

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 United States.

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 development.

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.

Genetic Concerns

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 concluded.

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 prevented.

"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 protect children."

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.

In the newest area of research,metabolic systems, which control how nutrients are converted into
energy, have been altered by chemicals administered in animal
experiments ˜ changes that may contribute to obesity and diabetes.

Chemical Danger

"These
adverse effects have been linked to chemical pollutants at realistic
human exposure levels similar to those occurring from environmental
sources," the scientists wrote.

Among the risky chemicals they named are bisphenol A, found in polycarbonate plastic food and water containers; the pesticides atrazine, vinclozolin and DDT; lead; mercury; phthalates used in some cosmetics and soft plastics; brominated flame retardants; arsenic, which contaminates some water supplies; and PCBs, banned but ubiquitous, particularly in fish.

Some of the chemicals have been regulated in the United States, but
many have not. Moreover, the scientists said, tests for developmental
effects are not routinely required, so "the potential for such effects is therefore not necessarily considered in decisions on safety levels of environmental exposures."

There is "an incredible gap," Landrigan said, because 80% of major chemicals in commerce have never been tested to see if they damage early development.

The conference was funded by the World Health Organization, National
Institutes of Health, European Environment Agency and the Centers for
Disease Control and Prevention.

Denmark's Faroe Islands, just
south of the Arctic Circle, were the venue because the region is home
to the longest-running human experiment analyzing prenatal toxic
exposure. Since 1986, Grandjean and Weihe have tracked Faroese children
from the womb to adolescence to monitor neurological effects of mercury
in seafood. Their findings prompted U.S. advisories that children and
women of childbearing age avoid swordfish and other highly contaminated
fish.

In addition to Landrigan, three Californians and six
other U.S. scientists served on the 28-member committee that wrote the
consensus: Brenda Eskenazi of UC Berkeley, Irva Hertz-Picciotto of UC
Davis, Beate Ritz of UCLA, Jerry Heindel and Kimberly Gray of the
National Institute of Environmental Health Sciences, Larry Needham of
the CDC, Terry Huang of the National Institute of Child Health and
Human Development, David Bellinger of Harvard University and Howard Hu
of the University of Michigan.

Copyright © 2007, The Los Angeles Times
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An international group of scientists sounded a warning Thursday that exposure
to even extremely low doses of some chemicals while a fetus is
developing can cause major changes in its future growth, health and
ability to reproduce.

The
warning, dubbed the Faroes Statement, came from 200 chemists,
biologists, toxicologists, epidemiologists and pediatricians at a
conference in the Faroe Islands, between Norway and Iceland. It was
funded in part by the World Health Organization, the National
Institutes of Health and the European Environment Agency.
While
numerous recent research conferences have focused on the topic, this is
the first time a group of respected scientists have publicly called for
a full-court press to research the extent of the problem and to focus
on prevention.
The
amount of a chemical that can affect an adult may be "orders of
magnitude" different from what can seriously interfere with the
development of a baby, said Philippe Grandjean, a professor of
environmental health at Harvard University's School of Public Health
and a conference co-chairman." Both prostate cancer and breast cancer can be generated by exposure to very low concentrations of some chemicals early in life" he said.
Paracelsus,
"the father of toxicology" in the 16th century, first advanced the
paradigm that "the dose makes the poison." That still holds true, but
"equally important is that 'the timing makes the poison,' " the Faroes
Statement said.
Examples
discussed at the conference included the link between hormone-mimicking
chemicals, some of which are used to make pesticides and plastics, and
the increasing occurrence of testicular cancer and poor semen quality,
as well as changes in puberty development. Low doses of chemicals that affect the immune system have been linked to increased susceptibility to allergies.
The message is not a new one, but
scientists have tended to quietly suggest more research was needed,
rather than shouting there's a problem that needs to be dealt with.
"What's
important is that they're saying it," said Andrea Gore, professor of
pharmacology and toxicology at the University of Texas, who has helped
organize previous meetings on the topic.
"This says 'Wake up!'" said
Brenda Eskenazi, a professor of epidemiology at the University of
California, Berkeley who attended the conference. "This is not about us
any more, this is about future generations."