Common chemicals pose danger for fetuses, scientists warm

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Science & Medicine Print

Common chemicals pose danger for fetuses, scientists warm

Exposure to toxic materials in the womb can cause health problems

later in life, an international panel declares.

By Marla Cone, Times Staff Writer

May 25, 2007

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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: Eskenazi of UC Berkeley, Irva Hertz-Picciotto of UC

, Beate Ritz of UCLA, Jerry Heindel and 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, Bellinger of Harvard University and

Hu of the University of Michigan.

marla.cone@...

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