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Findings Conflict With Earlier Studies Suggesting Plastics Chemical Is a Health Hazard
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Reviewed By Louise Chang, MD
Feb. 19, 2010 -- In two new studies, researchers conclude that the plastics chemical bisphenol A (BPA) is not toxic to the brain or act as a hormone disrupter, altering the age of puberty or reproductive function.
Both studies are published in Toxicological Sciences. One was funded by the plastics industry; the other, by a state university and the Environmental Protection Agency.
Although the plastics industry praises the findings, an environmental expert says the studies -- both conducted on animals -- are flawed and the findings don't undo what she sees as an abundance of evidence suggesting BPA is hazardous.
"Together the two studies provide complementary, corroborative data, and neither found effects of low-dose BPA on the developing brain or behavior," says Steven Hentges, PhD, executive director of the Polycarbonae/BPA Global Group of the American Chemistry Council, the industry group that funded the study looking at neurotoxicity with BPA exposure. Hentges is a co-author on the paper, published online Feb. 17.
Sonya Lunder, MPH, senior analyst with the Environmental Working Group, who has researched BPA and health, counters, "You have to read these findings against all the other work that's been done [suggesting a hazard linked with BPA]."
Just a month ago, the FDA reversed its previous stance finding BPA was safe, calling for more research and offering suggestions on how parents, in particular, can minimize their families' exposure to the chemical. BPA is found in a wide range of products, such as plastic bottles, liners of food cans, feeding cups, and some baby bottles (although several baby bottle manufacturers have stopped using it).
Some experts are concerned that exposure to BPA and its weak estrogen-like effects, especially during critical periods of development, may be linked to a range of health hazards, including behavioral effects, reproductive problems, cancers, heart disease, and diabetes.
BPA and Neurotoxicity Study
In the neurotoxicity study, researchers from WIL Research Laboratories in Murrysvillle, Pa., and colleagues exposed female rats and their litters to dietary concentrations of BPA at different doses from the time of gestation through the 21st day of breastfeeding.
They tested the animals for their auditory startle response, motor activity, learning, and memory by using a water maze, brain and nervous system pathology, and brain measurements.
No adverse effects were noted.
BPA and Sexual-Reproductive Effects Study
For the other study, researchers focused on the effects of maternal exposure to relatively low oral doses of the oral contraceptive ethinyl estradiol or BPA in utero and during breastfeeding to see if either would change the expression of sexually specific behaviors, the age of puberty, or affect reproductive functioning in female rats.
Although the estrogen exposure was associated with changes such as reduced fertility and litter size, malformation of the genitals, a reduced preference for sugary drinks (considered a male behavior), and absence of a sexual posture typical for females, the exposure to BPA didn't have any of those effects.
"We found dose-related effects from the estradiol," says the study's lead author Earl Gray, PhD, a research biologist and reproductive toxicologist at the Environmental Protection Agency, but not with the BPA.
The doses used were low, he says. The accumulated findings, he says, are conflicting. "There are a large number of studies that don't show low-dose effects and there are studies that do show low-dose effects."
BPA and Its Effects: Pro, Con
In a commentary accompanying the study led by Gray, Richard Sharpe of The Queen's Medical Research Institute in Edinburgh, Scotland, says the Gray study and others "more or less close the door on the possibility that bisphenol A is an environmental chemical to be concerned about" because of its estrogen- like activity.
Although BPA might contribute to the additive effects of a mixture of estrogen-like chemicals, Sharpe contends that the contribution of BPA "will be minute."
Lunder strongly disagrees, pointing to the studies that show the chemical does indeed disrupt the hormone system in different ways. She says the new research did not adequately address the effects of sexual disturbances.
"BPA is connected to some of the biggest health problems in America," she says. She points to a monograph issued by the federal National Toxicology Program, finding some concern that everyday exposure may be linked with neural and behavioral changes.
Gray says there is "no conclusive evidence that the chemical is harmful" at low doses. If consumers are concerned, he says, taking steps to avoid BPA-containing products "is probably a reasonable thing to do."
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Steven Hentges, PhD, executive director, Polycarbonate/BPA Global Group of the American Chemistry Council, Arlington, Va.
Sonya Lunder, MPH, senior analyst, Environmental Working Group, Washington, D.C.
Ryan, B. Toxicological Sciences, March 2010; vol 114: pp 133-148.
Stump, D. Toxicological Sciences, online Feb. 17, 2010.
Sharpe, R. Toxicological Sciences, March 2010; vol 114: pp 1-4.
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