Pesticides May Be Linked to Breast Cancer, Scientists Warn : Health: Experts tell House members that 19 chemicals believed to disrupt the human hormone system are in wide use on U.S. crops.

A number of widely used pesticides and the residues of banned substances still in the nation’s food supply may be contributing to an alarming surge in breast cancer and reproductive disorders, five scientists told Congress on Thursday.

The scientists, testifying before a House subcommittee, cited in particular a class of pesticides that behave like female sex hormones when broken down by the human body and may boost both the incidence and the virulence of certain breast cancers.

Nineteen chemicals believed to disrupt the human hormone system are in wide use on U.S. crops. More than 220 million pounds of these endocrine disrupters are applied to 68 different crops annually, according to the Washington-based Environmental Working Group, a nonprofit research organization.

At least three of those chemicals, including endosulfan--a compound heavily used on California grapes, lettuce and tomatoes--are classified as “estrogenic” pesticides. Early studies by specialists in the field suggest that they could cause breast and other female cancers.

But the Environmental Protection Agency does not test for the kinds of hormonal effects suggested by the scientists Thursday.

Dr. Ana M. Soto, a research physician at Tufts University Medical School in Boston, told lawmakers that endosulfan has as powerful a hormonal effect as DDT and PCBs--two chemicals that were banned in 1972 and 1976, respectively, after they were found to cause cancer in wildlife and to accumulate in humans, possibly to dangerous levels.

Some lawmakers, pointing to the rising evidence of an association between some pesticides and breast cancer, are demanding new measures that would require the government to study the health effects of hormone-disrupting pesticides with an eye toward banning or restricting their use.

“We just don’t know the extent of the threat to our food supply,” said Rep. Henry A. Waxman (D-Los Angeles), chairman of the House Energy and Commerce subcommittee on health and the environment, who presided at Thursday’s hearing.

Speaking of a pesticide called vinclosolin, which was found to cause sexual abnormalities in exposed laboratory rats, Waxman added that “the public is being made an involuntary guinea pig” as such pesticides remain in use.

At the same time, researchers stressed that their preliminary findings, while ominous, have not yet established a clear causal link between pesticides and breast cancer or reproductive abnormalities in humans. They said that research funds--which have more than quadrupled in recent years--should be used to conduct further tests.

“I think there is no proven evidence that pesticides cause breast cancer,” Soto told Waxman’s panel. “But I think we can use this excellent data to articulate a strong hypothesis.”

Waxman called Thursday’s hearing during a week of unprecedented political action to promote research on breast cancer. Only three days earlier, thousands of women delivered 2.8 million petitions to the White House calling for more breast cancer research and a national action plan to stem the rise in the incidence of the disease, which is expected to kill 46,000 women in 1993.

The researchers told Waxman’s committee that environmental factors, such as exposure to occupational hazards and agricultural chemicals, may help explain why women who are in no known risk group for breast cancer may get the disease.

Scientists believe that estrogenic pesticides may affect a woman either through repeated exposure or through exposure during some critical phase in her sexual development--as a fetus in the womb, as she reaches puberty or as she approaches menopause. Certain pesticides, or the residues of them, may remain in a woman’s body and mimic the effects of estrogen.

Researchers have found that no single factor is more important in determining whether a woman will develop breast cancer than her lifetime exposure to estrogen: the higher it is, the greater her chance of developing the disease.

In turn, the growth of most cancerous breast tumors is actually fueled by estrogen in a woman’s body.

Soto told lawmakers that in a trial she conducted using human breast cancer cells, estrogenic pesticides accelerated the reproduction of the cells. Moreover, Soto found that different estrogenic pesticides--like endosulfan, dicofol and methoxychlor, all of which remain on the market--accumulate together as if they were the same chemical.

That finding is especially controversial. The EPA currently gauges the safety of pesticides with tests that assume different agricultural chemicals do not interact with each other or have such an “additive” effect.

If some pesticides do have an additive effect, the scientists said, estrogenic pesticides still on the market may be adding to residues of dangerous estrogenic chemicals that have been banned for years.

“The American food supply is saturated with a complex, low-level soup of pesticides,” said Richard Wiles, director of agricultural pollution prevention at the Environmental Working Group.

He added that laboratories working for the supermarket industry found residues of one or more endocrine disrupters in more than one-third of a sample of seven fruits and vegetables.

The presence in her body of metabolized “estrogenic” pesticides may not only place a woman at greater risk of developing breast cancer, the researchers said, it also may affect her offspring by exposing a fetus to hormones that could confuse and disrupt the normal development and functioning of sex hormones and organs.

A study conducted by a University of Florida wildlife biologist showed that wild alligator populations in a Florida lake heavily contaminated with one estrogenic pesticide suffered a variety of sexual abnormalities.

Three out of five alligators exposed to the pesticide difocol, which is now used widely in the United States, had what Louis J. Guillette Jr., University of Florida director of biotechnology for conservation sciences, described as “greatly reduced phallus size.” Two males were born without external male sex organs and many alligators suffered extremely low testosterone levels and difficulties in reproducing.

A research scientist from the Environmental Protection Agency described similar sexual abnormalities in lab rats exposed to vinclosolin, which is used to treat California’s strawberry crop, as well as on lettuce, peaches, nectarines and plums grown in the state.

“I strongly doubt that many parents would choose to be the vector for their progenies’ exposure to these chemicals,” said Dr. Theo Colborn, the coordinator of the World Wildlife Fund’s Toxics and Wildlife Project. “Nor would many mothers appreciate the fact that their lifetime exposure to a chemical--or a large mix of chemicals, which is really the case--could have more control over how their babies develop than the genes their children inherit from them.”