Found in the liners of canned foods and drinks containers, as well as many plastics and cash-register receipts, BPA is a hormone-disrupting chemical linked to all sorts of health problems, including infertility, obesity, brain damage, and certain cancers. Researchers from the University of Missouri, Westminster College, the U.S. Geological Survey, and the Saint Louis Zoo have determined that BPA, which mimics estrogen, can also alter a turtle's reproductive system.
"Normally, the painted turtle's sex is determined by the temperature of the environment during their development in the egg—cooler temperatures yield more male turtles, while warmer temperatures mean females are more likely to develop," explains Dawn Holliday, adjunct assistant professor of pathology and anatomical sciences in the MU School of Medicine and assistant professor of biology at Westminster College in Fulton, MO. "However, when turtle eggs are exposed to environmental estrogens, their sex is no longer determined by the temperature, but rather by the chemical to which they're exposed."
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Researchers applied a liquid form of BPA to hundreds of painted turtle eggs that were then exposed to cooler temperatures, comparable to those needed to produce male turtles. Then, the scientists examined the turtles' sex organs to determine the effects of BPA on their development. They found that the male turtles had developed sex organs with features typically found in females.
"We already know the genetic marker where the temperature-dependent sex determination occurs, which provides us a good indication of where the endocrine disruption is taking place," says Sharon Deem, director of the Saint Louis Zoo Institute for Conservation Medicine and a lead investigator on the study. "Our findings show that BPA essentially overrides the temperature in determining the sex of the turtle, creating turtles that are probably unable to reproduce."
For the study, scientists mimicked the levels of BPA found in samples from waterways. Turtles are known as an "indicator species" because they can be used as a gauge for the health of the entire ecosystem. By understanding the possible effects chemicals have on turtles, researchers might be able to understand the possible effects the chemicals have on other species—even humans—Holliday said.
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What we do know is that the most common impacts of BPA have been feminization, as noted in a number of species, including humans, the study authors point out. "The fact that exposure to BPA can override the temperature-dependent sex determination pattern in a turtle species—cool dudes and hot babes—by feminizing embryos that are incubating at male-producing temperatures should be a wake-up call to all of us. If BPA can do this to developing reptiles, what might it be doing to other species, including humans?" the authors told Rodale News.
"There is increasing data out there on the role of BPA and its reproductive and neurodevelopmental and behavioral impacts across many taxa and including humans," they add."In fact, these concerns for human health, including the carcinogenic qualities, is the reason that the FDA banned BPA in baby bottles and sipping cups back in 2012."