University of Missouri biology professor Frederick vom Saal has been sounding the alarm about bisphenol A for a decade. Has he got your attention?

On a spring day one year ago, scientists in life vests and blue jeans invaded the bucolic slice of nature where Perche Creek empties into the Missouri River. The scientists, representing the U.S. Geological Survey and a lab from the University of Missouri-Columbia, suspended mesh cages in the river's current and filled them with fathead minnows — the white rat of the aquatic world, ideal for biological testing. Meanwhile, from the river's edge, National Geographic cameras took in the scene.

The TV crew was filming a special about bisphenol A, a synthetic material commonly used to make plastic. When it's formed into a polymer, bisphenol A makes a hard, clear plastic that isn't brittle, which is why nearly all water bottles are made from it, as well as eyeglass lenses and the linings of aluminum food cans.

Chemists know that bisphenol A has characteristics of estrogen, a hormone that determines sexual traits and is key in the development of brain function and nerve cells. Though toxicologists long ago deemed bisphenol A to be safe at high quantities, recent studies have linked it to several human epidemics, including breast and prostate cancer, enlargement of the prostate, early onset of puberty, hyperactivity in children and obesity.

National Geographic was invited on the river to record two days of fieldwork by Don Tillitt, a biochemist with the Geological Survey. Joining Tillitt was Frederick vom Saal, a biology professor at the University of Missouri and a leading expert on the harmful biological effects of bisphenol A.

Vom Saal is a controversial figure in his area of expertise — at least where the manufacturers of bisphenol A are concerned. His willingness to speak frankly about his findings is alarming to the top five makers of bisphenol A: Dow Chemical, Bayer Material Science, Sunoco Chemicals, SABIC Innovative Plastics and Hexion Specialty Chemicals.

More than 6 billion pounds of bisphenol A are produced every year.

"If I were to say to you, 'Oh, here's a pack of birth control pills. I'm going to extract out the hormone and make plastic out of them,' you'd think I was crazy," vom Saal says. "And indeed, the idea that you're using sex hormones to make plastic is just totally insane."

For a decade, vom Saal has seen the chemical industry distort his research and government regulators ignore it.

But after years of quietly publishing studies in scientific journals and presenting papers at toxicological conventions, vom Saal is starting to be heard. Since the first study of bisphenol A came out of his lab in 1997, he has been interviewed about the chemical for PBS' Frontline series and by ABC's 20/20. For FOX News, he has measured the amounts of bisphenol A that leach out of plastic baby bottles, and he has even been quoted in subculture-celebrating Vice magazine regarding the Texas-sized island of discarded plastic floating in a remote part of the Pacific Ocean. Recently, he has flown around the country to testify in front of state legislators writing measures against the use of bisphenol A.

Vom Saal was on the river with Tillitt a year ago because his measurements picked up meaningful quantities of bisphenol A in the waterways around Columbia that feed into the Missouri River. Tillitt's lab at the Columbia Environmental Research Center will spend the rest of this year trying to determine whether the quantities of bisphenol A in the water are causing measurable changes — what Tillitt calls a "fingerprint" — in the genes of the fathead minnows swimming in the cages set up on Perche Creek.

Bisphenol A is only one of several chemicals being scrutinized by the U.S. Geological Survey, and for Tillitt, the research holds special significance. Scientists who study Missouri wildlife have come across unusually high instances of hermaphrodism — when an individual displays both male and female sex organs — in the endangered pallid sturgeon. Hermaphrodism occurs normally in certain species of fish, but sturgeon isn't one of them. It could be caused by a multitude of different environmental pollutants.

"We're a little bit concerned about that," Tillitt says. "We want to know: Is this the canary in the coal mine?"

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Vom Saal saw his canary in the coal mine in the early 1990s.

He was testing dozens of natural estrogens — the estrogen found in soy, for instance — to observe their interactions with cells. He decided to test some synthetic estrogens as well, including bisphenol A. In the experiment, vom Saal noted that, unlike natural estrogens, bisphenol A molecules did not bind to blood proteins, which normally act as barriers, keeping the estrogens from entering cells.

"Since this barrier system was failing for this chemical, it means that the majori­ty of this chemical that would get into your blood would go into your cells and potentially cause harm," vom Saal says. "So we did some very simple biochemical calculations. We gave a dose 25,000 times lower than any toxicologist had ever studied, and it wreaked havoc with the developing reproductive organs."

Vom Saal is speaking from his office at MU's Lefevre Hall, a two-story, white stone building where biology classes are held, including vom Saal's popular graduate class on mammal­ian reproduction. Several framed photographs of vom Saal's wife, their daughter and his single-engine Cessna 210 (he's a pilot) sit atop file cabinets, but the rest of the office is dominated by shelves of document-stuffed accordion folders and thick academic texts.

Soon, he's joined by Wade Welshons, a professor of biomedical sciences, and Susan Nagel, a professor of obstetrics, gynecology and women's health. They are two of vom Saal's research partners who, along with four other professors, make up the Endocrine Disruptors Group. It's a new field of study that vom Saal, Welshons and Nagel helped establish.

Nagel has a cheerful voice and an infectious laugh; she pulls up a chair in vom Saal's office. She came to vom Saal's lab as a grad student in 1993, working with breast-cancer cells. Not long after vom Saal had made his first observations using bisphenol A, he suggested to Nagel that she take up the work.

Nagel recalls, "He said, 'I have this project that's just guaranteed to be a short study, and you'll get a publication out of it. You already know how to do the techniques, so all you have to do is go over to his [Welshon's] lab and just turn this out.'"

The "short study" ended up taking her more than two years, but Nagel did come out of it with a publication — a landmark. Toxicologists' tests on bisphenol A claimed that it was non-toxic at extremely high doses, but Nagel's study showed that bisphenol A was hormonally "active" — meaning it caused an effect — in cells at levels thousands of times lower than toxicologists had previously deemed to be safe.

These "low-level effects," as Nagel's findings came to be called, represented a whole new way of thinking about chemicals and human safety. Toxicologists look at high doses of chemicals to find out how much is necessary to cause serious harm — birth defects or death. But endocrinologists know that the amounts of a substance necessary to cause harm on a hormonal level are tiny and can pack profound consequences. Exposing a developing fetus to additional estrogen, for example, can permanently alter crucial phases of development, irreversibly altering systems that are designed to react to the most miniscule changes in hormone levels.

To his students, Welshons explains low-dose hormonal effects this way: A cubic millimeter of a chemical is a milligram, which is a relatively large amount. If you take one thousandth of that, you have a microgram, which is visible to someone with excellent eyesight. (It's the smallest particle a human eye can resolve.) If you take one of those microgram particles, waft it onto the floor, step on it and grind it into a thousand more particles, you have nanogram particles, which are invisible to the naked eye. If one of those nanogram particles floats into the air and lands in a 1-liter container of liquid and dissolves there, it creates a solution that, in the case of bisphenol A, will stimulate human breast-cancer cells in a cell culture, causing the cancer cells to proliferate.

Nagel's first study showed that low doses of bisphenol A could have effects; further research indicated that bisphenol A enlarged the prostates of laboratory mice. She demonstrated that the effects in mice occurred at doses close to what humans are exposed to each day from sources such as food packaging. Her study was published in the January 1997 issue of Environmental Health Perspectives, a journal put out by the National Institute of Environmental Health Sciences.