Tuesday, March 09, 2010

Yale study details how and why of BPA's dangers

Exposing a female fetus to a chemical found in plastics causes permanent changes in a daughter's uterus that might result in cancer - and a research team led by a Yale doctor has figured out why.

Bisphenol A is commonly found in plastics (those with a "7" code on the bottom), in the lining of aluminum cans and in dental sealants. The U.S. Food and Drug Administration has expressed concern about potential effects of BPA on the brain and reproductive organs, though the link is not definitive.

Dr. Hugh S. Taylor, director of reproductive endocrinology and infertility section of the Yale School of Medicine, said even brief exposure to BPA in the uterus causes permanent damage.

“We already know that mice that are exposed to BPA already have a higher risk of breast cancer, uterine cancer and infertility,” he said.

In this study, one group of mice was exposed to BPA as fetuses and compared to a control group to see how much the DNA in the uterus had been modified. The findings, Taylor said, reveal that BPA strips off a part of the DNA, which permanently alters the genetic structure.

“It chemically modifies the DNA by removing methyl groups from the DNA backbone and that makes the DNA more accessible,” he said. The genes then become permanently altered to be supersensitive to estrogen, which can lead to cancer and other consequences.

He said the damage might occur in females after birth as well.

“It’s not as clear,” he said. “It very well may be. I think that’s still more controversial. I think pregnancy is the more dangerous time.”

Taylor said the effect of BPA is reminiscent of the problems with DES (diethylstilbestrol), which was prescribed to women from 1938 to 1971 to prevent miscarriages, according to the Centers for Disease Control and Prevention. DES was linked to a rare form of vaginal cancer.

“Now it looks like (as they grow older) those women who were exposed as a fetus have a higher risk of breast cancer,” Taylor said. He also is studying a potential link between BPA and breast cancer.

Taylor said it’s a good idea for women who may become pregnant to avoid BPA, especially products that are brand new and unwashed or old and cracked. Plastics with BPA shouldn’t be microwaved, he said.

Environmental groups also have called for BPA to be removed from consumer products; some companies have begun manufacturing BPA-free items, such as water bottles.

“I always tell my patients, as a physician as well as a scientist ... to me it’s an easy decision. There’s so much benefit of eating fresh vegetables instead of (eating) out of a can,” he said.

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