Researchers found evidence that bisphenol A (BPA) and bisphenol S (BPS), which is used in many common household plastics, can cause alterations in brain development and lead to hyperactivity in zebrafish.
BPS has often been thought of as a safer alternative to BPA, and products containing it are often labeled "BPA free" leading consumers to believe the product comes with less risk, the University of Calgary reported. About 80 percent of the genes found in humans have a counterpart in zebrafish, and the fish also possess similar developmental processes to humans.
"I was actually very surprised at our results. This was a very, very, very low dose, so I didn't think using a dose this low could have any effect," said Deborah Kurrasch, a researcher in the University of Calgary's Cumming School of Medicine and corresponding author on the paper.
To make their findings, the researchers exposed zebrafish embryos to concentrations of the chemicals found in the Bow and Old Man rivers of Alberta, Canada. They found this exposure changed the timing of which neurons were formed in their brains.
"These findings are important because they support that the prenatal period is a particularly sensitive stage, and reveals previously unexplored avenues of research into how early exposure to chemicals may alter brain development, " said Cassandra Kinch, a PhD student.
In the second trimester of pregnancy, cells become the specialized neurons that make up our brain structure. Exposed zebrafish were shown to develop twice as many neurons that were born too soon and only half as many that were born late. The number of neurons that developed in the zebrafish's brains were observed to increase by 180 percent compared to unexposed fish. Fish exposed to BPS in other experiments showed a 240 percent increase in the number of neurons developed. This was found to lead to hyperactive behavior later in life.
The team was also surprised to find the receptors targeted by BPA and BPS were androgen receptors.
"Finding the mechanism linking low doses of BPA to adverse brain development and hyperactivity is almost like finding a smoking gun," said University of Calgary researcher Hamid Habibi.
Further research is needed to confirm these findings, but the study brings support to the idea that pregnant women should try to limit their exposure to these chemicals.
The findings were published in a recent edition of the Proceedings of the National Academy of Sciences (PNAS).
