Mounting evidence suggests a plastic additive common in baby and sports bottles and used to line the inside of soda and tin cans is accumulating in our bodies at levels far beyond those known to cause considerable health problems in lab animals.

At least that's the conclusion in research underwritten by the government or an independent source such as a university, a new review of 115 peer-reviewed publications has found. Industry-sponsored research has so far found no problem with the additive, bisphenol-A.

And that, say the authors of a report published in the current edition of Environmental Health Perspectives, contributes to a dangerous naivete as regulators and society assesses the chemical's threat.

Bisphenol-A's menace, said lead author Frederick vom Saal, is that in low doses the additive acts almost identically to hormones in birth control pills.

The body is extremely sensitive to hormones, with extremely tiny amounts able to trigger a cascade of events.

Vom Saal, a researcher at the University of Missouri, Columbia, said the low doses found in the environment pose a grave concern for fetuses and the very young.

"This chemical we once thought was very weak is an extremely potent sex hormone," vom Saal said. "The problem with bisphenol-A is it disrupts almost the entire reproductive system as well as brain function.

"When fetuses are exposed ... all of these systems are permanently damaged by a sex hormone-like chemical

like bisphenol-A. These organs can never function properly again."

What's more, vom Saal said, the consensus is we all receive a daily shower of the compound, with the Centers for Disease Control estimating median exposure for the U.S. at 1.3 parts per billion.

Meanwhile, in vitro studies of human breast cancer cells show bisphenol-A stimulates growth at levels at and below 0.02 ppb.

Animal studies have shown bisphenol-A in females leads to increased fat production, early puberty and — at doses equivalent to "drinking out of a polycarbonate bottle that's been damaged" by heating or in the microwave, vom Saal said — chromosomal damage of the female's eggs. Males see decreased testosterone and lower sperm counts. Both sexes see changes in brain chemistry and behavior: hyperactivity, increased aggressiveness, altered social behavior. All are trends scientists have increasingly noticed in humans over the past 50 years.

Industry and other experts took sharp issue with the review's analysis, criticizing the authors' willingness to imply an effect found in laboratory animals also would impact humans. They also questioned why vom Saal discounts credible research showing little or no environmental impact from bisphenol-A.

"We know nothing about the link between hyperactivity in animals and hyperactivity in humans," said George Gray, executive director of the Harvard Center for Risk Analysis, a predominately industry-supported group that conducted one of the studies vom Saal skewered. "Governments around the world have spent a lot of time looking at this."

Indeed, the United States, Japan and the European Union have all concluded the compound poses no threat to humans at levels found in the environment, said Steve Hentges, executive director of the polycarbonate business unit for the American Plastics Council.

"The sum of weak evidence doesn't make strong evidence," he said. "Based on the weight of the evidence, we continue to be very confident there is no risk to human health."

Bisphenol-A is used to make plastic hard and is found almost everywhere in modern life — airplane wings, skis, cans of food. More than 6 billion pounds were put into products in 2004 alone.

And the science, vom Saal said, suggests it doesn't stay long there. Throw a plastic container in a microwave, fill a hard plastic sports bottle with hot tea, warm your baby's milk in a plastic bottle, and the bonds holding bisphenol-A in the plastic break down. Acids in sodas and tomatoes leach the compound from can linings, he added.

"We are told there are microwave-safe plastics. This is a concept that has to be eliminated," vom Saal said.

As that plastic ends up in landfills, studies from both Asia and the United States reveal that up to 90 percent of the estrogen-mimicking compounds leaching from landfills is bisphenol-A.

"This work is not coming from Dr. vom Saal's lab, but many other labs across the world," said Dr. George Lucier, former director of the National Institute of Environmental Health Sciences' environmental toxicology program. "The low dose effects are consistent with how we know hormones work."

This newspapers' special report on chemical pollutants in our bodies is available at www.insidebayarea.com/bodyburden.

Contact Douglas Fischer at dfischer@angnewspapers.com