Chemical in plastic containers makes male mice act like females

WASHINGTON — Male mice who were exposed as babies to BPA, a chemical common in canned foods and plastic containers, act more like females and are seen as less desirable mates, a US study showed Monday.

The findings could have implications for how BPA, or Bisphenol A, may affect human development and behavior, said the study published in the Proceedings of the National Academy of Sciences.

"The BPA-exposed deer mice in our study look normal; there is nothing obviously wrong with them. Yet, they are clearly different," said lead author Cheryl Rosenfeld at the University of Missouri.

"Females do not want to mate with BPA-exposed male deer mice, and BPA-exposed males perform worse on spatial navigation tasks that assess their ability to find female partners in the wild."

Mother deer mice were fed a diet with levels of BPA that were proportional to the amount the US government considers safe for pregnant women to ingest.

The lab mice were fed this diet for two weeks prior to breeding and throughout lactation.

After their babies were weaned, the offspring were fed a BPA-free diet and their behaviors were monitored into adulthood.

The male mice who were exposed to BPA showed less ability to navigate a maze safely. This skill -- useful in the search for potential mating partners -- is well developed only in male mice, since females do not seek out mates.

"The untreated mice quickly learned the most direct approach to finding the correct hole, while the exposed males appeared to employ a random, inefficient trial and error strategy," said the study.

When scientists observed how fertile females regarded the BPA males compared to the unexposed males, they found females preferred the chemical-free males by a factor of two to one.

"These findings presumably have broad implications to other species, including humans, where there are also innate differences between males and females in cognitive and behavioral patterns," Rosenfeld said.

"Whether there are comparable health threats to humans remains unclear, but there clearly must be a concern."

The US Food and Drug Administration has noted "some concern" with BPA, an industrial chemical that has been widely used in packaging since the 1960s, and is studying the risks of exposure, the regulatory agency said in January 2010.

The European Union and Canada have banned the use of BPA in baby bottles. However, there is no scientific consensus on the dangers BPA poses, the study said.