BPA is controversial because it exerts weak, but detectable, hormone-like properties, raising concerns about its presence in consumer products and foods contained in such products. In testing the effects of the controversial chemical BPA on zebrafish, UWM (University of Wisconsin Milwaukee)scientist Daniel Weber found himself in familiar territory. The results he observed were similar to those heâ€™d seen when exposing the fish to mercury during their early development â€“ profound behavioral changes occurred not only immediately after hatching, but also in adulthood. Like developmental exposure to mercury, adult fish that had been exposed to tiny amounts of BPA as embryos had learning and memory problems, compared to fish that had not been exposed.
"What was amazing is that exposure only happened at the embryonic stage," says Weber, "but somehow the wiring in the brain had been permanently altered by it. Itâ€™s an example of why children are not just little adults when it comes to gauging the effects of contaminants."
BPA is widely used in plastic food containers and container liners. Conflicting reports of its safety have made it the subject of vigorous public debate.
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. Results of this study, however, suggest that lower concentrations may be more potent during early-life exposures. This study tested three different small amounts considered environmentally relevant.
The compound, which mimics the hormone estrogen, was added to the aquatic environment of fish embryos in their first two days of life. Then they were returned to clean water for the ensuing 10 months while they grew into middle-age adulthood.
Tanguay says the low concentrations of BPA they used donâ€™t cause physical malformations or cardiac defects. But even without physical abnormalities, behavioral deficits can still occur, as this study indicates.
For comparison, the team also exposed some of the zebrafish embryos to two other substances â€“ one a natural estrogen and the other a synthetic version. Similar to equal amounts of BPA, the other two substances caused hyperactivity at the larval stage.
Weber says multiple behavioral outcomes are not only changed by BPA, but those behaviors â€“ immediate hyperactivity and later-stage learning impairment â€“ may be inter-related.
More behavioral research also is needed, says Weber. He expected to see differences in the resulting behaviors of the sexes since BPA is a kind of estrogren. But he found no evidence of that. Social behaviors, however, may show a sex-based effect due to BPA exposure and that is the subject of his next experiments.
For further information: http://www5.uwm.edu/news/2012/04/03/early-life-exposure-to-bpa-affects-adult-learning/