The plastic additive is leaching from your water bottles, soda cans, baby bottles, microwaveable dishes -- just about anything made of certain lightweight clear plastics.

And it mimics the hormone estrogen, which some research indicates could harm human health, particularly the development of fetuses and newborn babies.

Known as BPA, bisphenol-A has been used in commercial production of lightweight plastics and epoxy resins since the 1950s. Billions of pounds are produced annually, and traces of it are found in almost everyone -- including the umbilical cord blood of newborn babies.

Though the chemical industry contends that the weight of scientific evidence on bisphenol-A doesn't support claims of harm, the chemical remains controversial. Studies flagging the compound's possible health threat to humans have made people nervous about the plastics they use every day, everywhere, to serve and store food. Some have jettisoned plastic bottles and cutlery in favor of alternatives that don't contain BPA.

"There is a cause for concern," said Gerald LeBlanc, chairman of the department of environmental and molecular toxicology at N.C. State University. "It's not something we should be sweeping under the rug."

One group of 38 scientists, including LeBlanc, published a statement last year raising concerns that the chemical was harmful to lab animals and was a potential hazard to humans. They suggested a link between recent increases in human diseases such as prostate and breast cancers and adverse effects in experimental animals exposed to low doses of BPA.

Other studies suggest the risks may be highest for pregnant women and unborn children, because early exposure to hormone-mimicking chemicals may lead to birth defects and miscarriages.

Valerie Balestrieri of Raleigh, a part-time nurse, was so concerned about the health effects of plastics that she replaced the baby bottles and sippy cups she had used with her first child before the birth of her second child last year. She also changed the plastic kitchenware she used to reheat food.

"It's such an easy process just to change your bottles," Balestrieri said. "The expense is minimal compared to potential harm. It's better to be safe than sorry."

'Might be a problem'

But not everyone is convinced there's a threat. Another independent panel of scientists convened by the National Toxicology Program, based at Research Triangle Park, was more circumspect. They expressed "some concern" -- the middle point on a five-point scale -- that exposure to bisphenol-A causes neural and behavioral changes to unborn babies, infants and children.

"We felt like there were enough studies that were done well that were raising flags that there might be a problem, that it would be prudent to investigate further," said Jane Adams, a toxicologist at the University of Massachusetts-Boston, whose research focuses on the consequences of prenatal exposure to certain medications. "We couldn't say there is no problem with this compound."

Adams said numerous studies of the chemical resulted in inconsistent findings, with some showing effects and others none. The studies used different methods, different animals, different dosages.

The National Toxicology Program, part of the U.S. Department of Health and Human Services, is expected to issue the agency's preliminary evaluation of the chemical next month. The recommendation would be a guide for other regulatory agencies that could take more stringent steps, if warranted, such as requiring warning labels.

"We're exposed to very small amounts of it," said Michael Shelby, director of the National Toxicology Program's Center for the Evaluation of Risks to Human Reproduction at Research Triangle Park. "All the data show a large, large majority of people in the U.S. are exposed to it, something over 90 percent based on the Center for Disease Control's data. We're still within the program trying to hammer out our final conclusions."

Limiting exposure

In the meantime, Shelby said, people can limit their exposure to the chemical. "If it's something that is worrying you, that is probably a good thing to do," even if only for peace of mind.

The most common way people are exposed to bisphenol-A is by eating prepared foods from canned goods or certain plastic containers. Epoxy resins are used to coat the inside of food and beverage cans, bottle tops and water supply pipes.

Kathleen Schuler, co-director of Healthy Legacy, a Minnesota-based group that is trying to phase out toxic chemicals in consumer products, said the group recommends that parents avoid polycarbonate in baby bottles and sippy cups. She recommended using bottles and cups made of polyethylene or polypropylene bearing the numbers 1 or 5 in the triangular recycling codes on the bottom of most plastic containers.

"Consumers are concerned, and they just want safe products," Schuler said. "We're most concerned when people heat the plastics or use acidic or fatty products in them."

Steven Hentges, executive director of the Polycarbonate/BPA Global Group of the American Chemistry Council, an industry group, says plastic products using bisphenol-A have a long history of safe use.

Hentges said the industry is planning further research studies on neural and behavioral effects of the compound to try to resolve unanswered questions.