This is a well balanced article from the United Press International.  At the bottom of the page are links to different articles on this same topic.

EcoWellness: Paying a price for plastic?

By CHRISTINE DELL'AMORE

UPI Consumer Health Correspondent
WASHINGTON, Aug. 25 (UPI) -- A new study shows bisphenol-A -- a man-made chemical that mimics estrogen in the body -- can not only enter cells, it can make breast cancer cells multiply.

The research, although conducted in vitro in a laboratory, could take the teeth out of a previous argument that the chemical is not able to penetrate cells in the body.

Bisphenol-A, or BPA, is a synthetic compound commonly used in the manufacture of consumer plastics, particularly polycarbonate plastic items such as sunglasses, water bottles, CDs and baby bottles.

In recent years, the chemical has polarized opinion over the purported negative health effects of low-dose exposure.

Critics of BPA claim the molecule tricks the body's estrogen receptors into acting like true estrogen, causing physiological changes that possibly lead to cancers of the breast and prostate.

Yet some scientists say that's not possible. As the rationale goes, once BPA enters the body, it undergoes a modification to make it negatively charged, or ionized, and thus unable to move into cells.

Lead author Theodore Widlanski, a chemistry professor at the University of Indiana, found the cells are subject to a second process, in which enzymes on the surface of breast cancers cells convert the modified BPA back into a natural form -- and therefore allow BPA to enter the cells.

These processes are called "sulfation" and "desulfation": sulfation occurs when the BPA molecules are modified upon entry into the body, and desulfation occurs when the enzyme turns the molecule back into the original BPA.

Because it takes on the properties of estrogen, BPA causes the breast cancer tumor cells to grow.

Widlanski's research, published in the Aug. 28 issue of Chemistry and Biology, a Cell Press journal, is the first to show BPA's ability to enter and grow breast cancer cells, albeit in a laboratory setting. It's unknown whether this scenario would also occur in a living, breathing human, he noted.

A self-labeled agnostic on the issue, Widlanski said there's too much emphasis placed on BPA compared to the countless other pseudo-estrogens in nature.

"We're surrounded by a universe of chemicals," he said.

Even vegetables carry estrogen that could masquerade as human estrogen -- and we have no idea if they affect us, he said.

The key, Widlanski said, is figuring out if the same mechanism he found in vitro exists in people.

"If the mechanism were operative in people, and did allow for pseudo-estrogen to (travel) into tissues, then people would start saying, 'whoa,'" Widlanski said.

Chemicals that mimic natural estrogen are called endocrine disruptors, and also include pesticides such as DDT. The U.S. Environmental Protection Agency has deemed endocrine disruption as one of its top six research priorities, and it is currently studying the phenomenon as part of the Endocrine Disruptors Research Initiative.

Yet skeptics, particularly the plastics industry, assert there are no known health risks occurring from BPA.

"BPA is not carcinogenic and does not selectively affect reproduction or development," says a statement on www.bisphenol-a.org, a Web site run by the Bisphenol A Global Industry Group of the American Plastics Council, the Association of Plastics Manufacturers in Europe and the Japan Chemical Industry Association.

People would have to eat more than 500 pounds of food and beverages in contact with polycarbonate plastic or epoxy resins -- an adhesive used commonly in industry -- every day of their lives to exceed the reference dose for BPA, according to the Web site. The reference dose, set by the EPA, is 50 mg/kg/ daily.

The organizations point out under "exaggerated conditions," polycarbonate plastics can release BPA, but this is not a concern in reality.

But that's where the issue becomes increasingly opaque: No one knows what a lifetime of BPA really amounts to, although scientists mostly agree everyone carries BPA in their bodies. It's also unknown whether exposure at high levels for short periods of time is comparable to low levels for a long period of time.

What did concern Widlanski was the high concentration of pure BPA he found in the breast cancer cells. It suggests the breast tumor cells function as a "lightening rod," attracting BPA as a sulfate, converting it back into regular BPA, and absorbing it into the cells.

Other studies have revealed mixed findings on BPA. But in one analysis of published research, a well-known BPA researcher, Frederick vom Saal, reported 100 percent of studies funded by the chemical industry conclude BPA has no adverse effects.

Vom Saal, a professor at the University of Missouri-Columbia, has done research on low doses of natural estrogens and estrogen-mimicking receptors such as BPA in utero. He discovered low doses of BPA do "irreversibily alter the course of fetal development."

United Press International also reported in June that male rodent fetuses mildly exposed to BPA in the environment may become predisposed to developing prostate cancer later in life. Rats given injections of BPA had a significantly higher incidence of precancerous lesions in the prostate than rats who did not receive the chemical injection.

These findings can't be extended to human biology just yet, but it's a relevant question for future study, Gail Prins, leader of the research team and a professor of physiology at the University of Illinois, Chicago, told UPI in an earlier story.

Because men get prostate cancer through many causes, "to be able to pinpoint it to an exposure to a chemical 50 years prior, during fetal life, is going to be extremely difficult to do," Prins said.

Some people would rather not wait around for the final verdict. San Francisco passed a law in June amending their health code to prohibit the sale of toys and childcare articles made with BPA.

"Bisphenol-A has been shown to have hormone-disrupting effects," the ordinance states. The law, which takes effect in December, bans anyone within the city or county of San Francisco from selling or distributing toys for children under 3 that contains the chemical.

In 2005, the European Union also banned phthalates, another kind of endocrine disruptor used in toys.

Even so, Widlanski remains doubtful of BPA's potency. Biology is so complicated, he says, no one can make cut-and-dry conclusions at this point in the game.

"If someone wants to tell me bisphenol-A causes frogs to grow two heads, I'd want to see the facts," Widlanski said.

© Copyright 2006 United Press International, Inc. All Rights Reserved

Here are several more articles on the subject.

Large Effects from Small Exposures

Effect of Bisphenol A on Snails - super feminization

Bisphenol A affects our reproductive organs

Bisphenol A and metabolic syndrome

Bisphenol A and Breast Development in Puberty

Your Exposure When Pregnant Will Last into Your Daughters Adult Life