Association of Bishenol-A with prostate cancer
Plastic component boosts prostate cancer cells.
04.02.2005 |Sascha Gabizon
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Reuters Health
Plastic component boosts prostate cancer cells
Last Updated: 2005-01-20 15:25:18 -0400 (Reuters Health)NEW YORK (Reuters Health) - An estrogen-like chemical widely used in the production of plastic food containers called bisphenol A (BPA) can ultimulate the growth of prostate cancer cells in the laboratory, cancer researchers have learned.
"These preliminary findings are very interesting," Dr. Karen E. Knudsen of the University of Cincinnati in Ohio told Reuters Health, "and could potentially raise concerns about exposure of prostate cancer patients to estrogen-like chemicals. However, these observations should be validated in other systems before any lifestyle changes should be suggested," she added.
BPA plastics are used in food and drink packaging and resins are used to line food cans, milk containers, and water pipes. Close to one million tons of BPA are produced each year in the US.
Many prostate cancers depend on androgens like testosterone to grow, in which case anti-testosterone hormonal therapy may be given. During hormonal therapy, some tumors develop mutations in a receptor for testosterone called the androgen receptor.
For patients with mutated androgen receptors, exposure to BPA may put them at higher risk for increased cancer cell growth, according to the new study in the medical journal Cancer Research.
"In this study, we showed that cultured tumor cells with this type of mutation can be stimulated to grow by an estrogen-like compound found in certain plastics," Knudsen explained. Moreover, this stimulation takes place "at low, environmentally relevant doses."
The safety of BPA has been debated for several years. Some argue that human exposure to the chemical is not harmful, while others believe that it may promote the growth of human cancer cells.
The current findings as well as others hint that BPA can serve as a potential "hormone sensitizer" of the mutant androgen receptors present in advanced prostate cancers, the researchers note in their report.
SOURCE: Cancer Research, January 1, 2005.
Debate over a leaching chemical heats up
By Elizabeth Weise, USA TODAYIs it possible that a chemical's effect is in the eye of the beholder? That's the implication of a paper published this week in a prominent environmental health journal.
It concerns a debate over the safety of low doses of a chemical used to make hard, clear plastics such as those found in baby bottles, food-storage containers and the lining of soda cans.
When the plastic industry examines the health impact of a ubiquitous chemical called bisphenol A, everything's fine. If the government or a university funds the study, there are big problems.
Those are the conclusions drawn by Frederick vom Saal, a developmental biologist at the University of Missouri who reports his findings in Environmental Health Perspectives, published by the National Institute of Environmental Health Sciences. Vom Saal and others seek revised risk assessments for the chemical in the light of a new research into its effects.
Bisphenol A mimics the sex hormone estradiol in the body, acting "like birth control pills," says vom Saal. The body is exquisitely sensitive to sex hormones, needing only tiny amounts to trigger major changes. That's why scientists are concerned about the impact of even the extremely low levels of bisphenol A found in people.
In mice and rats there is evidence that low doses of bisphenol A can cause structural damage to the brain, hyperactivity, abnormal sexual behavior, increased fat formation, early puberty and disrupted reproductive cycles. Vom Saal looked at 115 published studies concerning low-doses of bisphenol A. Overall, 94 of them reported significant effects in rats and mice, while 21 did not.
Eleven of the studies were funded by chemical companies. None of those 11 found harmful effects of the chemical, which the Centers for Disease Control and Prevention says is detected in 95% of all people tested.
But more than 90% of the studies conducted by independent scientists not associated with the chemical industry found adverse consequences, says vom Saal. He called the disparity between the industry and government or university conclusions "stunning."
Steven Hentges of the American Plastics Council counters that the article is not a research paper but a commentary * "an op-ed" piece rather than a scientific paper. The real issue is the weight of evidence, he says, not the number of studies.
"You can have 1,000 studies, but if they're all weak, adding up weak evidence doesn't necessarily give you strong evidence of anything," Hentges says. "Jumping to who sponsored it is a way to dodge the facts."
He says that, in the view of the plastic industry, vom Saal has presented nothing new to change the conclusion that there's no cause for concern. "Government bodies worldwide have reached the conclusion that bisphenol A is not a risk to humans at very low levels." Over 6 billion tons of bisphenol A are used each year to make polycarbonate plastics, which have the useful property of not becoming brittle over time. First synthesized in 1957, the material didn't come into widespread use until the 1970s.
Chemical bonds that bisphenol A forms in plastic can unravel when heated, washed or exposed to acidic foods, causing the chemical to leach into foods. "There's good evidence to show cause for concern," says Patricia Hunt, whose research found abnormalities in developing egg cells in female mice when exposed to low levels of bisphenol A.
"We now know enough to know that we need to look at this stuff in great detail," she says.
