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

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She initially studied deer mice, which are not monogamous. In a startling study released in 2011, she found that male offspring from a female mouse who was exposed to BPA during pregnancy were "demasculinized," and behaved more like females, suggesting that the chemical had damaged behavioral and cognitive traits that are unique to each sex and important in reproduction.

But she wanted to do a similar study involving mice that are more like humans in their social and reproductive lives. So she turned to the California mouse, and found that exposure to BPA resulted in male offspring that neglected to mark their territory. That's an essential function in protecting the home and foraging for resources. In short, the males lost interest in the family.

"Even if you don't affect the reproductive system per se, just by affecting the behaviors that are essential for animals to reproduce has long term consequences," she said. "Those animals exposed to BPA will have decreased likelihood of finding a mate and reproducing. And if they do reproduce, our studies suggest they will essentially be passing on those compromised traits to future generations.

"So the long term will see a decrease in the reproductive fitness of the subsequent generations."

That finding, published in the journal PLOS One, along with research at several other labs, has pushed concerns higher, but so far little has been done to deal with the issue.

"There hasn't been one legislation passed to date to control the most alarming way we are being exposed to BPA, and that's through the pregnant mother" Rosenfeld said.

One of the most troubling findings in her latest study is that prenatal exposure to the chemical caused reproductive changes in the offspring that did not go away with the passage of time. The changes got stronger, not weaker.

Her research adds substantially to a growing body of literature showing there is need for real concern, and prompt action, but the data so far is not likely to convince everyone. What's true for the California mouse does not necessarily apply to humans -- because there is obviously a wide gap between humans and mice -- and it would not be ethically possible to replicate Rosenfeld's experiments with human subjects.

Two years ago, the American Medical Association called for legislation to force companies to label products that have BPA in them.

"That should be mandatory, but it's not required at this time," Rosenfeld said. However, some manufacturers have voluntarily pulled it from their products.

The widening use of plastics in all types of containers is likely to worsen the situation. Currently, "we produce about eight to 10 billion pounds per year, and that number is going to go up astronomically," Rosenfeld said.

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