BPA, Common Chemical, Affects Sex in Mice; Warning for Us?

PHOTO: California mice

In California there's a mouse called, not surprisingly, the California mouse (Peromyscus californicus) that has attracted the attention of scientists because of a reproductive trait that is not always celebrated among humans. The mouse is monogamous, and the male even hangs around to protect the home and help raise the kids.

And now the big-eared critter may just help protect future generations from reproductive disasters. That's true for mice, and quite possibly for humans.

New evidence suggests that exposure to a chemical that is now carried in nearly all of us can alter the reproductive system for many generations to come. The chemical, known as bisphenol A (BPA), has been the subject of environmental debate for years. It is present in food and beverage containers ranging from soup to beer, and it is common for it to leach into the contents and thus become part of our diet.

The Centers for Disease Control and Prevention found detectable levels of the chemical in 93 per cent of 2,517 urine samples from people six years and older.

"It's everywhere," Cheryl Rosenfeld, associate professor of biomedical sciences at the University of Missouri, said in a telephone interview. "It does not break down in the environment. Almost every water source that has been tested to date has been found to contain detectable levels, so this is a global concern."

BPA has mostly been used in hard plastics and as a sealant in metal containers. But it became highly controversial in 2008 when several studies suggested it might be toxic, especially to young children. There has been much controversy ever since over whether the chemical is harmful, and government agencies have sent mixed messages.

Canada, for example, bans it in baby bottles, but has twice concluded it does not "pose a health risk to the general population, including newborns and young children." The U.S. Food and Drug Administration has banned it in all baby products, but has consistently declared that the evidence is not sufficient to merit further measures, at least for now. However, the FDA says on its website that recent research has left the agency with "some concerns" about BPA's safety.

Rosenfeld has taken a somewhat different approach than other researchers. Her evidence indicates that an expectant mother who has been exposed to BPA may jeopardize reproduction in many subsequent generations. And chances are that mom's getting BPA without even knowing it.

Boys and girls are different, as we all know, and that basic fact became the focus of several research papers by Rosenfeld and her colleagues. She wanted to know if BPA could affect prenatal development in a mother's womb, because the chemical mimics the role of important sex hormones, specifically testosterone and estrogen.

"It will bind to the same receptors that the natural hormone would bind to," she said. "But it's not regulated in a tight fashion like the natural hormones would be. So it kind of indiscriminately acts, and there's no ability to regulate it."

It becomes a rogue hormone during the most critical phase in an organism's life, the development period prior to birth.

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