Toxic threat: To gauge the impact of harmful chemicals on humans and wildlife, researchers are focusing on fetal damage caused by exposure to contaminants


Just as Love Canal brought the threat of cancer and chemicals into people's backyards during the 1970s, many observers say a growing scientific hypothesis will dramatically alter the perception of chemicals as environmental health threats in the next century. New research is focusing on endocrine disruption - damage to the fetus caused by exposure to harmful chemicals. The endocrine system is a sensitive system of glands and hormones responsible for proper development of the brain and reproductive organs, as well as other bodily functions. Some researchers hypothesize that extremely small doses of toxic compounds such as PCBs might disrupt the hormonal balance of the developing fetus, resulting in permanent neurological, reproductive and immune system changes. As a result, endocrine disruption - along with cancer - will become a yardstick by which contaminants are evaluated.

While there is scientific uncertainty about the endocrine disruption process in humans, some experts warn this new research might have profound health implications, particularly for children. The Agency for Toxic Substances and Disease Registry (ATSDR), a federal research agency affiliated with the Department of Health and Human Services, reported this year that "many environmentally persistent compounds have the potential to disrupt the normal functions of the endocrine system," which "may have a serious impact on reproductive and developmental parameters in wildlife and human populations." Research is focusing on the subtle effects of chemical exposure (such as diminished intelligence) on the developing young and the embryo, and shifting away from the traditional emphasis on cancer. Some of the most compelling data comes from studies of children born to mothers who consumed PCB-contaminated fish from the Great Lakes.

ATSDR points out that children who were exposed in the womb to higher levels of PCBs from their mothers' consumption of Great Lakes fish are three times more likely to have lower than average IQ scores and twice as likely to be two grade levels behind their peers in reading comprehension. They have poorer short-term and long-term memory and difficulty paying attention. These effects occur at PCB levels only slightly above those found in the general population. Other studies of exposed infants have shown lower birth weights, reduced motor reflexes, poorer neuromuscular function, weakened immune systems, susceptibility to infections and reduced attentiveness, among other problems.

Researchers stress that it is unclear what is causing these effects, and that the endocrine disruption hypothesis needs further study. But the effects are real. "If you start to look at all the data together, you start to see a convergence," said Christopher DeRosa, director of ATSDR's division of toxicology. "We have a real sense of concern regarding the impact on human health."

Those particularly at risk are unborn children and nursing infants exposed to chemicals stored in their mothers' bodies, as well as subsistence and sports fishermen and the elderly. But it is the developing fetus that is most susceptible to permanent damage from toxic chemicals "because of the intrinsic sensitivity in its developing organs," DeRosa said.

In the Chesapeake Bay area, researchers are also concerned about possible human health effects from low levels of industrial chemicals, but funding for expensive health studies is a limiting factor.

EPA's annual budget for monitoring and researching the effects of toxic chemicals for the entire Chesapeake Bay is about $600,000 a year. "We have low levels of hundreds of chemicals in the Chesapeake Bay," said Kelly Eisenman, the toxics coordinator for EPA's Chesapeake Bay Program. "We haven't been able to fund human-health studies similar to what they've done in the Great Lakes." EPA has a list of 14 chemicals of concern in the Chesapeake Bay, including PCBs, and the agency is working to address toxic hot spots in the Baltimore Harbor, Washington's Anacostia River and Virginia's Elizabeth River.

"We've got every kind of pollutant here that they have everywhere else, so it's reasonable to assume low levels of chemicals are in the food chain," said Mike Hirshfield, vice president for resource protection with the Chesapeake Bay Foundation, adding: "We don't have any idea" what the safe exposure levels are for bay fish and wildlife and the people who feed on it.

A push for more research

Recent concerns about human health effects have driven Congress to push for more research, requiring EPA to come up with a plan this year to screen environmental chemicals for their potential hormonal impacts on health. In 1996, Congress ordered EPA to implement a screening program by mid-1999. A panel of scientists and representatives from industry, academia, government and public interest organizations has been convening for more than a year to design a screening program for thousands of commonly used industrial chemicals that have never been tested for their hormonal effects. It is a daunting task that is part of a new model for environmental regulation.

"This is the first time since the passage of the Toxic Substances Control Act, more than 20 years ago, that Congress has spoken on the issue of testing chemicals," said assistant EPA administrator Lynn Goldman. "That's a very fundamental change from the kind of legislation we've had in the past. And I think that it will very much increase the amount of information that we have available on toxic chemicals."

This could have huge regulatory implications for the chemical industry, which is not required to test extensively most of the 70,000-plus chemicals commonly used in industrial processes. Last year, the Environmental Defense Fund issued a scathing report showing that 75 percent of all high-volume chemicals, excluding pesticides and drugs, lack minimal health data. For example, every year manufacturers make more than a billion pounds of bisphenol-A, a chemical used in many household plastics and by dentists to protect children's teeth against tooth decay. Recent animal studies have shown that it causes reproductive defects at levels currently being consumed by people. No extensive health data is available on this ubiquitous chemical.

Pushed by threats of new regulations, the chemical industry is taking the endocrine disruption issue seriously, spending tens of millions of dollars on new research. This April, on Earth Day, the Chemical Manufacturers Association announced it would voluntarily increase its environmental testing program to 100 chemicals a year by early next decade. Critics say that only a tiny fraction of the industry's chemicals go through any rigorous tests, and that it would take decades to complete tests of thousands of chemicals, even at the accelerated rate.

Pesticide connection

Scientists also are investigating potential endocrine-disruption effects associated with pesticides, which are required to have more extensive health tests than industrial chemicals. Pesticide industry executives argue there are adequate tests in place to detect these kinds of effects in their products. The U.S. pesticide industry, which had annual sales of more than $11 billion in 1995, is extremely concerned about the potential for new, costly regulations.

A 1997 report assembled by the American Crop Protection Association, which represents the U.S. pesticide industry, concludes that current EPA-mandated pesticide registration studies "are comprehensive and adequate in safeguarding public and environmental health from any chemicals with potential endocrine modulating activity." At the same time this report was being assembled, however, industry wildlife biologists had reached a different conclusion.

An internal memo from pesticide industry biologists to a group studying endocrine disruption states that there is "convincing evidence" that organic chemicals and pesticides have caused reproductive problems in wildlife.

The memo also warns that current EPA regulations "generally do not provide sufficient information to evaluate whether a chemical may cause such effects," and it advises the industry to "assume a leadership role" in devising better testing schemes. The internal memo, which was meant to be an industry position paper on testing for endocrine-disrupting chemicals, was never made public.

This is an example of the pesticide industry philosophy of "Don't test, don't find," said Dawn Forsythe, a former pesticide industry government affairs executive who headed the industry's first endocrine disruption working group. Forsythe is critical of the industry for refusing to admit publicly any connection between its products and health effects in animals and in humans.

"The pesticide industry is still in a state of denial," said Forsythe, who left the industry in late 1996. "It's business as usual."

Pesticide industry executives dispute such comments, saying the industry is doing all it can to investigate potential health problems. "I think what we know so far indicates that there is no cause for concern," said Jay Vroom, president of the American Crop Protection Association. "I think the public, government and industry are all committed together to working at exploring and compiling more information and getting a better understanding of what the science is really all about."

Science is at the heart of this issue, and the debate over the health impacts associated with endocrine disruption will continue for years. But most important, experts say, the environmental health community is increasingly directing its research toward the chemical effects on the most sensitive of humans, the developing fetus. "It has shifted the public health debate back to looking at environmental causes," said Sheldon Krimsky, a professor of environmental studies at Tufts University who is writing a book on the subject. "I think it's caused a whole new way of looking at disease."

The Clinton administration has designated endocrine disruption as one of its top five environmental research priorities, and EPA is scheduled to issue a report this summer outlining a new chemical-screening program. But some researchers say the data showing the impacts on child IQ levels and other problems is serious enough to begin taking action to reduce environmental exposure to toxic chemicals. "It's time for public health action," said ATSDR's DeRosa. "As someone said in a recent meeting, we may not have a smoking gun, but there are bullets all over the floor."

William Kistner is a television producer and journalist in Washington. Kyla Dunn is a science journalist based in San Francisco. They worked with the Center for Investigative Reporting on "Fooling With Nature," a documentary about endocrine disruption that recently aired on PBS' "Frontline."

Pub Date: 6/07/98

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