Pollution’s Effect on Sexual Development Fires Debate : Health: Some biologists blame chemicals for fertility problems, diseased organs. Others deny a problem exists.

“Every man sitting in this room today is half the man his grandfather was. And the question is, are our children going to be half the men we are?”

In all likelihood, that alarming testimony--from a reproductive biologist at a congressional hearing on the hazards of pesticides--is hyperbole. Even so, it readily dramatizes the fears of many scientists that environmental pollution could be warping human sexual development.

Many biologists theorize that man-made pesticides and industrial chemicals that mimic hormones in the womb might be lowering sperm counts, triggering diseases in ovaries, breasts, prostates and testes, and perhaps even retarding penis growth and causing children to reach puberty prematurely.

Such a link, however, remains highly speculative and fiercely debated, with some biologists maintaining that the small concentrations of man-made chemicals consumed by most people in their diets are harmless.

But scientists promoting the theory believe it could explain the puzzling array of trends in reproductive disorders that have surfaced since the advent of modern pesticides and industrial chemicals after World War II.

Sperm counts seem to have dropped by almost half in the past 50 years, according to the one highly disputed study on males in the general population. Endometriosis and breast cancer are detected in women in record numbers, and prostate and testicular cancer rates have at least doubled among men in industrialized nations in recent decades. Some fertility experts also believe more men are experiencing fertility problems.

“Although the possibilities for human health effects remain theoretical,” there is a “growing sense that some diseases or dysfunctions” could be caused by pollutants that act like hormones, John McLachlan, scientific director of the National Institute of Environmental Health Sciences, reported in a journal last fall.

Every year, billions of pounds of pesticides and industrial compounds that imitate estrogen or inhibit testosterone--hormones vital to human sexuality and reproductive health--are sprayed on crops and yards and released into waterways in the United States.

These chemicals routinely contaminate food in small amounts, with a few--the pesticide DDT and industrial compounds called PCBs--so pervasive that every person on Earth is believed to carry at least a trace in their bodies. Fish in many waterways are tainted with DDT and PCBs, a contaminant called dioxin is found in some beef and other animal fat, and some produce contains small amounts of pesticide residues.

Already, there is evidence of these commonly used chemicals disrupting sexuality in animals.

If they can disrupt human hormones, that raises the possibility of infertility passing unrecognized from one generation to the next. Parents exposed to a slight amount of a man-made hormone in their food would be unharmed, but could transfer sperm problems or disease-causing defects to their children that wouldn’t surface until sexual maturity.

“What the mother was exposed to . . . could have an effect on their children 30 years down the road,” said Ohio University reproductive biologist Brent Palmer. “It is so insidious. The adults appear healthy, but our children may be the ones who wind up infertile.”

Some toxicologists and chemical industry representatives say the threat to the general population is pure conjecture, raised by many scientists and environmental advocates to force restrictions on chemicals. They hope a panel about to be convened by the National Academy of Sciences will end the speculation within a few years.

“We’re getting the estrogen scare of the week and it’s making your head spin,” said John McCarthy, vice president of science and regulatory affairs for the American Crop Protection Assn., which represents major pesticide manufacturers.

“Speculation is going on all over the place, especially when it comes to sperm counts. Will the real information please stand up? Let’s take a look at the science and do this right.”

Texas A & M University toxicologist Stephen Safe also is highly skeptical that the chemicals are affecting human health, explaining that people constantly are bombarded with potent, naturally occurring hormones in their food that seem to cause no ill effects.

“Everyone is running around saying the male is doomed. But the evidence does not support an effect in the overall human population,” Safe said. “I’m not saying ignore it, but let’s have some more information.”

Much of the concern has grown out of the research on animals.

Studies on animals from Florida alligators to Southern California sea gulls that depend on highly contaminated waterways show these hormone-like pollutants are tampering with embryos, blurring the lines between the sexes in newborns. Tests on laboratory rats confirm that when pregnant animals are exposed, their offspring often are born with half-male, half-female sex organs and defective sperm.

The worries over human reproductive health stem from one basic rule of anatomy. People have the identical hormones--estrogen and testosterone--as a rat, a bird or an alligator, and their fetuses would seem just as vulnerable to damage from minute amounts of pollutants.

If not for the real-life saga of DES mothers, it might seem far-fetched to believe humans could pass sexual disorders on to their sons and daughters.

DES, or diethylstilbestrol, was a powerful synthetic estrogen prescribed to 3 million to 4 million women between 1948 and 1971 to prevent miscarriages. Although the mothers were unscathed, their daughters suffer a high incidence of ovarian abnormalities and vaginal cancer and their sons have abnormal rates of infertility and testicular disorders.

But DES is hundreds of times more potent in its estrogenic effects than most pesticides and industrial chemicals.

Toxicologists--even skeptics like Safe--agree the most vulnerable people are fishermen, Eskimos and other Native Americans whose diets rely heavily on fish and marine mammals gathered from waters contaminated with hormone-like chemicals.

Some of the nation’s worst contamination has been found in sport fish caught close to Los Angeles County’s shoreline and in harbors of the Great Lakes, which contain DDT and polychlorinated biphenyls, or PCBs. The compounds were used in large volumes until banned in the 1970s, but high concentrations remain in the environment.

The big unanswered question is whether an average person’s diet, which is much more varied, contains large enough quantities of these and other man-made hormones to endanger an unborn child. And, do humans, unlike animals, have some defense mechanism that wards off small quantities?

Scientists are struggling with these questions, but the answers, in all likelihood, remain years away.

“We’re certainly not having massive epidemics,” said toxicologist Linda Birnbaum at the U.S. Environmental Protection Agency’s health effects laboratory in North Carolina. “Whether we’re having subtle effects is a more difficult question to answer.”

Most people get a much smaller dose of the chemicals in their diets than wildlife such as alligators and birds, which often feed on fish from one polluted source during their entire lives.

“I have no doubt that when given an appropriate dosage level during the right phase of gestation, that you can see disruption of sexual development,” said assistant EPA administrator Dr. Lynn Goldman. “But the doses that humans receive are lower. It is a leap to go from that evidence to a conclusion that sperm levels are being lowered due to these exposures.”

So far, the most disturbing evidence that the general population may be at risk comes from rats studied at the University of Wisconsin. Mothers-to-be injected with a single, minute dose of one industrial pollutant, dioxin, during the onset of their embryo’s sexual development gave birth to males with reduced sperm counts and malformed testicles.

The small dose given to the rodents--measured in parts per trillion--is not much higher than the average accumulation the EPA has found in human bodies. Dioxins, which are widely dispersed by the paper industry and in other manufacturing processes, apparently block testosterone development.

“If this work is correct, and I have no reason to think that it isn’t, the real concern is the general population may be at risk,” said Earl Gray, the EPA’s chief of developmental reproduction and toxicology research. “This data is really critical because it’s at such low doses.”

Toxicologists suspect if people are harmed, the damage is much more subtle than what they are seeing in wildlife and lab animals. Gray said sons born to exposed parents might have a slight decrease in sperm count or shortened penises.

While reduced sperm probably would have a minimal effect on overall human populations, the result could be tragic for some individuals--the difference between fathering a child or not.

“For those men who already have low fertility or borderline fertility, this kind of an effect, if it’s occurring, could render them infertile,” said James Overstreet, a UC Davis obstetrics and gynecology professor who directs the Institute of Toxicology and Environmental Health.

Physicians in fertility clinics have long noticed what seems to be a decline in male fertility, but say the reasons could vary. More than 2 million couples are involuntarily childless, and between 1965 and 1982, infertility among young couples increased from 4% to 10%, according to a 1989 National Research Council report.

“I don’t think we’re going to go extinct,” said Theo Colborn, senior scientist with the World Wildlife Fund. “But if we don’t do something about this, life is going to be miserable.”

The EPA is trying to pinpoint the risk so it can issue advice, especially to pregnant women. The most vulnerable stage is the first trimester when the fetus develops sexually.

One general warning, Birnbaum said, is to avoid eating fat--from beef, fish or any animal--because most pollutants accumulate there and it contributes to other health risks as well.

At this point, the EPA has not analyzed how much of these chemicals an average person consumes, a void which magnifies the uncertainty of how much risk the public might face.

The agency, for instance, doesn’t know how much residue from a fungicide called vinclozolin people are eating in their fruits and vegetables. Rats exposed to high doses--100 parts per million per day during pregnancy--gave birth to half-male, half-female offspring, according to two recent EPA studies. Scientists suspect humans consume far less but have no proof.

Other than DDT and PCBs, most hormone disrupters, including vinclozolin, leave no trace in the human body. They could inflict hormonal damage on a fetus and pass through a parent’s body without researchers knowing the person was exposed.

Since human experimentation is outlawed, toxicologists say tests on wildlife and lab animals are the best--and sometimes only--forewarning they have.

“There is no absolute proof about a human connection, but that’s the whole basis of biomedical research. You do work with non-human animals,” said University of Texas, Austin, zoologist David Crews, who found small amounts of PCBs produced turtles born with both ovaries and testes.

Others argue, however, that the rodent and other animal data is irrelevant because humans may have a defense system animals lack.

Gray called that “the last line of defense” from people who have “almost a religious” belief that humans are better than animals.

“If humans are at all like rats,” Gray said, “they have enough DDT in them to really have a reproductive effect.”

Those skeptical of a human connection also point out that most environmental contaminants are hundreds of times less powerful than the body’s natural estrogen, estradiol. Numerous natural compounds in vegetables, called flavonoids, also are potent estrogens or estrogen inhibitors and they seem to pose no harm to people.

“Just because something is estrogenic does not necessarily make it a monster,” said Safe of Texas A & M. “The important thing is, what is our exposure?”

The most heated argument, however, is focusing on whether sperm counts are actually declining.

In 1992, reproductive biologists in Denmark thought they had an answer. After examining medical reports on almost 15,000 healthy, fertile men from many nations between 1938 and 1990, they found sperm concentrations were almost half what they had been--66 million per milliliter in 1990 compared with 113 million per milliliter in 1938.

The findings spurred concern that post-World War II chemicals and pesticides were to blame. Researchers already had been worried after small studies showed some industrial and farm workers handling large quantities experienced sperm problems.

But other researchers recently pointed out that the steepest sperm decline detected in the Danish study occurred in the 1940s and 1950s, before environmental contamination peaked.

“This data is very, very suspect,” Safe said. “It looks like it is probably more fiction than fact.”

Still, many reproductive scientists call the data credible. Even if sperm counts are declining, proving the cause may be difficult. Men are exposed to a large number of factors that might be to blame, from hot tubs to venereal disease.

Research into breast cancer has been equally inconclusive. Four separate studies show high concentrations of DDT or PCBs in the tissues of women with breast cancer, but a study completed this year that was the largest of its type found no correlation. The debate continues.

“Here again, it’s the classic case of one study says maybe and another study says no and another says, ‘Gee, we’re not sure.’ We need an answer,” said McCarthy of the pesticide association.

Health experts also are studying potential effects on disease immunity and brain development, since hormones control how the fetus develops its immune system and the behavioral part of its brain.

Women who ate fish two to three times a month for six years from Lake Michigan before pregnancy gave birth to babies with low birth weights, smaller heads and learning and behavioral defects, according to a 1984 study by two researchers at Wayne State University in Michigan.

“My concern is that we are dealing with a phenomenon in which the basic physiological process can be affected,” said Glen Fox, a toxicologist at the Canadian Wildlife Service. “You may not need large amounts of a substance to have an impact, particularly at the stage an embryo is developing.

“It has a potential to affect everybody. Not just the guy who applies a pesticide. Everybody.”

Next: Cleaning up old chemicals and avoiding new problems.

Hormones and Humans

Some scientists speculate that human fetuses exposed to environmental pollutants that mimic or block hormones might be born with reproductive disorders, many of which do not surface until adulthood. These are some of the suspected impacts on humans, based largely on animal studies.

LOW SPERM COUNTS

A study of medical records over 50 years shows that sperm counts have dropped by 40%. Researchers wonder if exposure of the fetus to pesticides and other chemicals that disrupt hormones may be a factor. Similar sperm problems have been noted in industrial workers exposed to high levels of dioxin, which is believed to block testosterone.

BREAST CANCER

Reports of this disease have increased by 1% per year over the past 50 years. Studies at Mt. Sinai School of Medicine have found high levels of DDT and PCBs in the tissue of women with breast cancer. Another recent study in California found no correlation. Some researchers believe chemicals that act as estrogens might promote breast cancer cells, but studies have been inconclusive.

OTHER CANCERS

Testicular cancer, which strikes young men, has tripled in the United States and England over the past three decades. Prostate cancer has doubled in some countries in 10 years. Researchers say exposure of a fetus to pollutants that act like estrogens could be a cause. Cells of men with testicular cancer resemble the primitive cells in embryos, which makes scientists believe their sexual development was interrupted in the fetal stage.

UNDESCENDED TESTICLES

This problem appears to be increasing among newborn boys, although there are no statistics available. Exposure to estrogenic chemicals in the environment could block development of male reproductive organs, causing cryptorchidism, or undescended testicles. In some cases this can lead to fertility problems.

HYPOSPADIAS

Young boys and infants can be afflicted with a urethra abnormality which, although rare, in extreme stages makes the penis resemble a vagina. This same type of “intersex” condition occurs in laboratory animals exposed to estrogenic chemicals during fetal development.

ENDOMETRIOSIS

This mysterious, painful disease afflicting 10% of women in their childbearing years appears to be increasing. Recent studies link it to exposure to dioxin and PCBs, both hormone-mimicking chemicals. Symptoms are the worst when a woman’s estrogen level is highest. Many women who are infertile also have endometriosis.

EARLY PUBERTY

Girls are reaching puberty earlier, and some researchers suspect that exposure to environmental estrogens may be a cause. Studies on rodents exposed to DDT and other estrogenic chemicals show accelerated puberty.

Source: U.S. Environmental Protection Agency, National Institute of Environmental Health Sciences