Early Chemical Exposure In Humans Linked To Disease

By MARLA CONE Los Angeles Times

Published: May 25, 2007

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 the first years after birth.

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 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 Philippe Grandjean of Harvard University and the University of Southern Denmark and Pal Weihe of the Faroese Hospital System, who for more than 20 years have studied 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.

"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 say in a four-page written statement.

Gene Expression Altered

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 of the subsequent generations could be at greater risk of diseases, too.

The Barker hypothesis, conceived by a British scientist in 1992, states that human fetuses are programmed for diseases by their early environment.

Grandjean and Weihe concluded that this now is well-documented through a large body of animal experiments and some data on humans.

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 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."

The growing brain is the most sensitive. Mothers' exposure to mercury and polychlorinated biphenyls in fish and other seafood can cause slight declines in 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 of the neurological disorder, affecting an estimated 560,000 children in the United States, can be attributed to lead exposure or prenatal tobacco smoke exposure, Lanphear reported.

Plastics Among Concerns

Among the risky chemicals they name 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.

The Faroe Islands convention venue 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 led to U.S. advisories that women of childbearing age and children should avoid swordfish and other highly contaminated fish.