MONDAY, June 27, 2011 (Health.com) — Male mice who are exposed in the womb to bisphenol A (BPA), a chemical compound found in some hard plastics and can linings, appear to be less masculine and less attractive to females once they mature, raising the possibility that the controversial chemical could subtly affect boys in similar ways.
In a new study, male deer mice whose mothers were fed BPA while pregnant had more difficulty navigating a maze and displayed less interest in exploring than unexposed males—a sign of “demasculinization,” researchers say, since navigational skill and a propensity for exploration are considered classic male traits in this particular species of mice. (In the wild, these traits help young male mice find potential mates.)
What’s more, this reduction in masculinity appears to make BPA-exposed mice less attractive to those potential mates. In another experiment, female mice who were released into cages containing two male mice, only one of which was exposed to BPA, spent roughly half as much time in “nose-to-nose contact”—an expression of sexual interest in the rodent world—with the BPA-exposed mice, perhaps because the females sensed differences in their behavior, pheromones, or both.
“The [BPA-exposed] mice outwardly look normal,” says Cheryl Rosenfeld, PhD, the lead author of the study and an associate professor of biomedical sciences at the University of Missouri–Columbia. “We have measured their motor skills and done sensory skill assessments, and they look normal; you can’t tell which were exposed. But when you go deeper, that’s when you find this difference emerging. The fact that we found this sexually selected behavior is different.”
The findings were published Monday on the website of the journal Proceedings of the National Academy of Sciences. As with most animal studies, it’s too soon to tell exactly how these findings might translate to humans, if at all.
The limited research on BPA exposure in humans, including studies of male factory workers involved in the manufacture of products containing the chemical, has found associations between higher levels of BPA exposure (as measured in urine) and erectile dysfunction, loss of libido, low sperm quality, and—somewhat counterintuitively—higher testosterone. But there is no indication that BPA exposure has any effect on the masculinity of boys or men.
The definition of masculine and the factors females use to choose a mate are much more complex in men than in mice, of course. And the gap between birth and sexual maturity is much longer in men—roughly 12 years versus about 60 days in deer mice.
Still, Rosenfeld and her colleagues say their study may lead to new ways of exploring the effects of BPA exposure in humans.