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Tucson Realtor Erika O'Dowd switched from hard plastic to soft plastic bottles for her year-old daughter after reading a recent magazine article warning that chemicals in the hard plastic are dangerous.

"We decided it wasn't worth the risk, and we might as well toss them," O'Dowd said.

But longtime Tucson hiker Linda Miller isn't about to stop drinking water out of hard plastic bottles when she's on mountain trails unless someone proves they cause serious illness.

Their opposite reactions reflect divisions across the country over the safety of a key chemical used to make these bottles, bisphenol A.

Manufactured since the 1930s, used more heavily each decade, it is growing more controversial by the month.

There are no federal restrictions on the use of bisphenol A, which some scientists say leaches out of certain hard plastic bottles and into the liquids we drink.

The chemical has been found at low levels in the blood of a sample of people large enough to represent 95 percent of all U.S. residents, says the federal Centers for Disease Control and Prevention.

But even scientists working for federal agencies and review panels disagree over the risks.

Few, if any, human health studies have been done on bisphenol A, known as BPA, which is the key component in hard, clear plastic.

Reports issued this summer reached conclusions worlds apart over whether the chemical can damage the reproductive systems of people, as dozens of studies have shown it can do to rats, mice and other laboratory animals. The reports came from two scientific panels operating under different divisions of the National Institutes of Health.

Their debate is among several now roiling nationally over what many scientists call endocrine disruptors: chemicals that can interfere with hormones affecting reproduction and development.

The conflict over bisphenol A cuts to the heart of how the United States decides how much of a potentially toxic compound people should be exposed to.

There are other chemicals in dispute, for which there are also no federal restrictions:

● Phthalates used in many plastic compounds contained in toys, shower curtains, some clothing and medical equipment. In October, California Gov. Arnold Schwarzenegger signed a law banning six varieties of phthalates in toys.

● Certain classes of flame retardants used in electronic equipment. The states of Maine and Washington recently banned their use in TVs and personal computers.

● Perfluorinated compounds, best known for their use in Teflon, the non-stick compound for cookware. Some manufacturers have voluntarily agreed to phase them out.

Dozens of studies — almost all of them in animals, not humans — have linked these chemicals to smaller-than-normal heads and shrunken penises in infants, obesity, diabetes, asthma, decreasing male-to-female birth ratios, undescended testicles, hyperthyroidism and decreased sperm counts.

In each case, companies that manufacture these products counter that they are safe and that studies showing ill effects are too limited, scientifically unsound or improperly designed.

The debate over whether bisphenol A harms humans has become particularly ferocious.

One National Institutes of Health panel of 38 scientists said it's likely that humans are having the same problems found in animal studies. That's because people are exposed to the chemical at higher levels than those known to cause damage in animals, they said.

The other panel, of a dozen scientists, called the danger to human reproductive systems from BPA negligible or minimal. It expressed "some concern" about the chemical's effects on the central nervous system and on behavior of pregnant women, fetuses, infants and children.

The second panel rejected most studies indicating BPA is hazardous, saying the chemical had been injected into lab animals — but that the most common way people are exposed to it is through eating or drinking. The other side stood behind the tests, though, saying BPA can be inhaled or absorbed through skin, not unlike having it injected.

The two groups have challenged each other's science and credibility.

The smaller panel, for instance, declined to consider many of the studies that found bisphenol A harmful. It didn't allow members who had done research on the chemical, saying that could pose a conflict of interest.

"We don't have any ax to grind," said that panel's chairman, Robert Chapin, an executive for drug manufacturer Pfizer Corp. "We don't have any stake in the outcome."

His panel did use a consultant from the chemical industry, drawing criticism from the other side.

The chemical's most outspoken critic in academia, developmental biologist Frederick vom Saal of the University of Missouri, sees a huge divide.

There is a lopsided discrepancy between the outcomes of industry-financed studies of BPA — 13 of 13 showed no major health problems — and studies financed by academia or government — well over 90 percent of 180 studies showed problems, he said.

"It's like you have two coins and you flip one, and you always get tails, and you flip the other one and you always get heads," said vom Saal, who was on the 38-member panel that criticized BPA.

The strong differences of opinion about BPA extend to its lack of regulation, too.

There are two choices for regulation: banning it or requiring a label, such as cigarettes have, about potential health dangers.

Numerous government agencies around the world have agreed with industry trade groups such as the American Chemistry Council that bisphenol A is safe and restrictions and labeling aren't needed.

They include the U.S. Food and Drug Administration, the Japanese Ministry of the Environment, the European Union and the European Food Safety Authority.

"It is apparent that there is no need for additional legislation or regulation for bisphenol A," said the chemistry council in a statement. "Existing regulatory processes are adequate to protect human health."

But the researchers on the 38-member bisphenol A panel disagreed, saying the federal government should be safe rather than sorry — that chemicals whose safety is in question shouldn't be used unless they can be proven safe.

One is Laura Vandenburg, who worked on six BPA studies at Tufts University in Massachusetts.

She said it's almost impossible to prove beyond a reasonable doubt that BPA can harm people because we can't ethically do experiments on human beings with it, and it's hard to isolate a group of people who aren't exposed to it. But she believes it is dangerous to people.

This debate is stirring fallout across the country, including Tucson.

The Babies "R" Us chain, which has a store here, has seen a significant rise in sales of glass bottles in the past year, a company statement said.

Tucson's two Summit Hut camping-supply stores started selling stainless-steel water bottles in the past six months. Since then, sales of stainless-steel bottles have grown, although plastic bottles still outsell them by five or six to one, said Logan Lichtenhan, floor manager for Summit Hut's store at 5045 E. Speedway.

Hard-plastic bottles are much cheaper, with a 32-ounce bottle fetching $8.25, compared with $19.95 for a 27-ounce stainless steel bottle and $28.95 for a 40-ounce steel bottle. Still, Lichtenhan said, he personally recommends the stainless steel bottles to customers because the plastic leaches into the water, and he doesn't like the taste.

But leaders of the Southern Arizona Hiking Club say they have rarely if ever heard members discuss the plastic-safety issue on the trail.

"I didn't know there was an issue," said Scott Casterlin, who produces the club's monthly bulletin. "If it was a problem, I can't act like I'm too scared about it because there are so many environmental threats all over."

Realtor O'Dowd said that when her husband read the article warning about plastic bottles, he was shocked someone would manufacture a baby bottle from a material with even a chance of being dangerous.

"Feeding your baby is such a wholesome act. You do it several times a day," she said. "It just seemed so wrong to make something like that that is supposed to be so healthy for a baby."

Link to pregnancy woes?

Researchers see a rising trend of women struggling to get pregnant, but is there lone link to chemicals? Page A5

Thousands of chemicals

How does the government check on safety and what consumers can do. Page A5

On StarNet: For a multimedia look at the toxic homes series, visit go.azstarnet.com/toxic.