University of Calgary children’s hospital medical genetics researchers stated in a press release that they believe they have found “the smoking gun” that links common contaminants leaching from plastics to “adverse brain development and hyperactivity.” In the Proceedings of the National Academy of Sciences, they describe the mechanisms by which Bisphenol A and its allegedly healthier replacement Bisphenol S both contributed to brain and behavior changes in zebrafish, even at extremely low doses.

The researchers exposed zebrafish embryos to concentrations of BPA and BPS that regularly occur in major rivers in Alberta, Canada. They described zebrafish as “a widely accepted biomedical model for understanding embryonic brain development.” In the study, they found that “the timing when neurons were formed in the brains of the zebrafish” changed significantly from the BPA and BPS exposures.

“In the second trimester, brain cells become the specialized neurons that make up our brain. What we show is that the zebrafish exposed to BPA or BPS were getting twice as many neurons born too soon and about half as many neurons born later, so that will lead to problems in how the neurons connect and form circuits,” researcher Deborah Kurrasch said in the press release. “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.”

“Finding the mechanism linking low doses of BPA to adverse brain development and hyperactivity is almost like finding a smoking gun,” said researcher Hamid Habibi in the press release.

The researchers said there is a need to more directly explore the processes in human brains in the womb, but the findings add weight to other studies suggesting the use of bisphenols needs to be completely eliminated.

“Here we demonstrate that bisphenol A (BPA) exposure during a time point analogous to the second trimester in humans has real and measurable effects on brain development and behavior,” wrote the researchers. “Furthermore, our study is the first, to our knowledge, to show that bisphenol S, a replacement used in BPA-free products, equally affects neurodevelopment. These findings suggest that BPA-free products are not necessarily safe and support a societal push to remove all structurally similar bisphenol analogues and other compounds with endocrine-disruptive activity from consumer goods. Our data here, combined with over a dozen physiological and behavioral human studies that begin to point to the prenatal period as a BPA window of vulnerability, suggest that pregnant mothers limit exposure to plastics(.)”

Kinch, Cassandra D., Kingsley Ibhazehiebo, Joo-Hyun Jeong, Hamid R. Habibi, and Deborah M. Kurrasch. “Low-Dose Exposure to Bisphenol A and Replacement Bisphenol S Induces Precocious Hypothalamic Neurogenesis in Embryonic Zebrafish.” Proceedings of the National Academy of Sciences, January 12, 2015. doi:10.1073/pnas.1417731112. (Abstract)

BPA and BPS (substitute for BPA) affect embryonic brain development in zebrafish: Low levels of chemicals linked to hyperactivity (University of Calgary press release on ScienceDaily, January 12, 2015)