New BPA scare: Male mice less hunky to females?

Is your significant other turned off after you consume canned food? Do you have trouble finding your way home after touching a cash register receipt?

If so, this news release from the University of Missouri (the home of BPA nemesis Fred vom Saal) may resonate with you — or maybe not:

… The latest research from the University of Missouri shows that BPA causes male deer mice to become demasculinized and behave more like females in their spatial navigational abilities, leading scientists to conclude that exposure to BPA during human development could be damaging to behavioral and cognitive traits that are unique to each sex and important in reproduction.

“The BPA-exposed deer mice in our study look normal; there is nothing obviously wrong with them. Yet, they are clearly different,” said Cheryl Rosenfeld, associate professor in biomedical sciences in the College of Veterinary Medicine and investigator in the Bond Life Sciences Center. “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. This study sets the stage for BPA researchers to examine how BPA might differentially impact the behavioral and cognitive patterns of boys versus girls. Investigators looking for obvious BPA-induced differences, such as chromosome deletions or DNA mutations, could be missing subtle behavioral differences that eventually lead to long-term adverse outcomes, including demasculinization of male behaviors with ensuing decreased reproductive fitness.”

In the study, female deer mice were fed BPA-supplemented diets two weeks prior to breeding and throughout lactation. The mothers were given a dosage equivalent to what the U.S. Food and Drug Administration considers a non-toxic dose and safe for mothers to ingest. At weaning (25 days of age), the deer mice offspring were placed on a non-supplemented BPA diet and their behavior tested when they matured into adults.

When sexually mature, researchers tested each mouse’s ability to navigate a maze to safety. This enhanced spatial navigational ability of male deer mice is important because it allows them to find mates that are dispersed throughout the environment. Females do not have to search to find mates and thus their navigational abilities have not been enhanced by evolution. It was these navigational skills, among others, that were tested in the laboratory setting. Each animal had two five-minute opportunities per day, for seven days, to try to find its way into a home cage through one of several holes placed around the edge of an open maze which was marked with a set of visible navigational cues. Many male mice that had been exposed to BPA early in their development never found the correct exit. By comparison, male mice that had not been exposed to BPA consistently found the hole leading to their home cage within the time limit, some on the first day. In addition, 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, Rosenfeld said.

In addition, male deer mice exposed to BPA were less desirable to female deer mice. Females primed to breed were tested in a so-called mate choice experiment. The females’ level of interest in a stranger male was measured by observing specific preferential behaviors, such as nose-to-nose sniffing and the amount of time the female spent evaluating her potential partner. These behaviors assess a potential mate’s genetic fitness. Rosenfeld said that both non-exposed and BPA-exposed females favored control males over BPA-exposed males on a two-to-one basis.

But just one of the limitations of this “study” is that it examines only a single mega-dose of BPA. The researchers claim that the dose-level is comparable to human exposures, but actually it’s about 250,000 times higher than typical human exposures based on extensive urine biomonitoring data from CDC.

With only one relatively high dose, it’s difficult to assess whether the findings have any relevance to humans or animals in the environment, even if you accept their findings as valid. I don’t know of any reason to expect that animals in the environment could be exposed to BPA at any level even remotely close to the one dose examined. More likely animal exposure would be much lower than humans since animals in the environment are not big consumers of canned foods and don’t typically work as cashiers handling thermal paper receipts.