Early exposure to BPA affects learning

Young children who are exposed to the controversial chemical bisphenol A (BPA) could develop learning and memory problems as adults, according to a study by Daniel Weber, a researcher at the Children's Environmental Health Sciences Core Center at University of Wisconsin-Milwaukee (UWM) and Robert Tanguay of Oregon State University.

The pilot study, which exposed zebrafish during their early development as embryos to tiny amounts of BPA, resulted in "profound behavioral changes" that occurred not only immediately after hatching, but also into adulthood, according to.

At issue is the amount of exposure, with some studies concluding BPA is a health risk only at concentrations that are higher than environmental levels, according to a UW press release. Results of this study, however, suggest that lower concentrations may be more potent during early-life exposures.

Weber and Tanguay tested three different small amounts considered environmentally relevant. The compound was added to the aquatic environment of fish embryos in their first two days of life. The fish were then returned to clean water for 10 months while they grew into middle-age adulthood.

During the test, unexposed fish took seven to 10 trials to learn Weber's instructions around a T-shaped maze. Exposed fish, however, took two to three times as many trials to learn it. And almost none of the fish exposed to the highest levels of BPA learned even the first part of the task, Weber said.

Even though the exposure only occurred at the embryonic stage, it appeared to permanently affect brain functions, Weber noted.

Multiple behavioral outcomes are not only changed by BPA, the researchers found, but those behaviors -- immediate hyperactivity and later-stage learning impairment -- may be interrelated.

He noted that being hyperactive -- or even hypersensitive to an environmental stimulus -- makes it difficult to learn, behavior which has been observed in children.

The study is the first to identify a neurobehavioral effect of BPA using a zebrafish model exposed to concentrations comparable to what humans might encounter in the environment.

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