Pollutants pose risk to hormones Disruption: Scientists are evaluating the threat to human and animal reproductive health from a host of man-made chemicals.

When it came to environmental pollution, researchers have said for decades that the biggest threat to humans came from substances that caused cancer. Now, some scientists say there is evidence that an equal risk may come from man-made chemicals that disrupt the body's hormones.

Studies have already indicated that these chemicals, known as endocrine disrupters, can play havoc with sexual development in laboratory animals and wildlife.


After pesticides were accidentally spilled into a Florida lake, for example, male alligator hatchlings showed elevated estrogen levels.

In England, male trout living downstream from a sewage treatment plant were found to be producing a protein used in making eggs -- a protein only female fish are supposed to produce.


Such conditions have earned these compounds the nickname "gender benders."

"There is clear evidence wildlife has been affected," says Michael Gallo, a toxicologist at the Environmental and Occupational Health Sciences Institute at Rutgers University. "The question is, are they having any effect on humans?"

It is a potentially serious question, for endocrine disrupters are found throughout the environment. They are ingredients in paints, detergents, plastics and herbicides. Some of the most notorious toxins -- like DDT, PCBs and dioxin -- are also disrupters.

There are also naturally occurring chemicals that can act as disrupters in wheat, berries, nuts, cow's milk and other foods. Traces of them have been detected in fish swimming in the Great Lakes and in human breast milk.

"The scientific evidence is of concern," says Lynn Goldman, a senior official with the federal Environmental Protection Agency. "But we don't think this should be a cause for panic for the public. We are not saying that people should change their lives."

Some scientists and policy analysts caution that data are still sketchy and the risks of endocrine disrupters may be exaggerated.

"There is a tendency to come upon a new risk and make it a solution to unexplained problems," says Lorenz Rhomberg, a professor at the Harvard University Center for Risk Analysis.

For example, Rhomberg says, when new environmental problems have been identified -- ozone depletion, global warming and now endocrine disrupters -- each has been linked to the puzzling worldwide decline of frogs and other amphibians. "There is this desire to find 'the' solution to a problem," he says, "but when dealing with the environment, sometimes it is more complicated. There may be no single answer."


Rhomberg, however, does not dismiss the potential threat of endocrine-disrupting chemicals: "The magnitude of their impact on the population as a whole has to be worked out."

There is little dispute that certain chemicals -- some man-made, some found in nature -- can act as hormone mimics in experiments in cell cultures and lab animals.

The endocrine system helps regulate development and body functions through hormones that are released by glands and travel through the blood. These chemical messengers trigger activity in cells to do things as diverse as create sexual organs and generate more heat for the body.

Endocrine disrupters can scramble cell activity: They can initiate the wrong reaction or the right reaction at the wrong time. They can also block real hormones and thwart cell reactions that should take place.

Often it takes just infinitesimal amounts of the disrupters to have an effect, particularly in developing fetuses.

There is also ample evidence that these same chemicals have had an adverse impact on some wildlife. In 1980, there was a large spill of dicofol, a DDT-tainted pesticide, in Lake Apopka, a large lake near Orlando, Fla.


Six years later, biologists began to notice that the alligators living in the lake were having reproductive problems. There were a large number of unhatched eggs, and those animals that did hatch had abnormal sex organs.

In the Great Lakes region, the chemicals DDT and PCBs have been linked to birth deformities in bald eagles. Tests have shown that the two durable chemicals are lingering in the environment, even though they have been banned for 20 years. They are being absorbed into the food chain and then concentrated in the larger animals. The fish consumed by the eagles, research showed, were heavily contaminated.

The question is what effect, if any, have these chemicals had on humans? There the data is not as clear, the debate more intense and the questions still unanswered.

Does a trace exposure have nearly the same effect as a larger one? Can the different impacts of different chemicals be sorted out? Can the adverse impacts on wildlife be extrapolated to humans?

Consider the vast array of chemicals that are able to lock into the estrogen receptor.

"Molecules of all shapes and sizes, man-made and natural, seem to fit, but that doesn't mean they are all the same," says John Katzenellenbogen, a University of Illinois chemist. The potency and effect vary greatly. "Some compounds are weakly active others can be 10 million times more potent -- but they all fit."


In addition, when they lock in, some promote cell activity, while others inhibit it. It has been theorized that a small amount of some of these chemicals may be beneficial, because it may block dangerous promoters.

Katzenellenbogen pointed out that what is considered a healthy human diet "contains large quantities of weak estrogenic substances." These substances are found in grains, berries and nuts.

Researchers theorize that plants may produce these pseudo-estrogens as natural birth control chemicals to limit the population of grazers that feed on the plants.

"Some species may be much more sensitive to hormonally active compounds," says Michael Gallo at Rutgers. "For instance, we know alligators are exquisitely sensitive to estrogens."

"Human diets are so varied, lifestyles are so varied. A blue heron eats the same thing every day. I'm not sure that is a good comparison with humans."

In addition, some of the studies that show possible human impacts -- such as a decline in male sperm counts -- are still being debated.


"New studies on sperm counts are showing mixed data," Safe says. "Sperm counts are declining in France and Denmark, but are up in New York and San Francisco. So is this a widespread problem or a geographic problem?"

"There are certainly local pockets of the extreme -- wildlife and workers -- that have been affected," says Katzenellenbogen. "The question is, what is the effect of low levels in the environment? That isn't as clear."

There is also a debate over whether the rise in cancer rates is a result of an increase in the disease or just better detection through better screening procedures, such as mammograms and prostate-specific antigen tests.

John McLachlan, director of the Tulane-Xavier Center for Bioenvironmental Research in New Orleans and one of the top researchers in the field, said: "We are at a point where this is still pretty new science, and a pretty new idea. But what we have now is a much better idea of what to look for."

Pub Date: 5/17/96