A chemical thought to be a safe replacement for one banned for use in baby bottles also causes developmental issues in fish embryos, according to a study released on Monday.

In a study published on the Proceedings of the National Academy of Sciences, researchers from the University of Calgary found that bisphenol S (BPS), the chemical that replaced Bisphenol A (BPA) after that was connected to obesity, cancer, and childhood anxiety and hyperactivity, also causes changes in brain development in zebra fish that caused them to become hyperactive.

The study subjected the fish to the same levels of both chemicals that are found in Alberta's Bow and Old Man rivers, which flow east out of the Rocky Mountains, and found that both BPA and BPS caused changes in the brain development of the zebra fish embryos.

"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 Debra Kurrasch, the lead researcher from the university's Cumming School of Medicine.

The study could be a blow to plastics manufacturers who replaced BPA with BPS and labeled water bottles and other items as "BPA Free". The U.S. Food and Drug Administration banned BPA from baby bottles in 2012, but said there was not enough evidence for a more widespread ban and has found the chemical safe at very low levels.

The American Chemistry Council, an industry trade association, said the study may overstate the effect of BPA on humans.

"The relevance of this limited study on zebra fish to human health, as asserted by the authors, is not at all clear," Steven Hentges, with the council's Polycarbonate/BPA Global Group, said in a statement. "The study examines effects of relatively high concentrations of BPA on zebra fish embryos in water, and the authors claim the results are directly relevant to humans, in particular to women during the second trimester of pregnancy. In contrast, humans are exposed to only trace levels of BPA through the diet ... and quickly eliminate it from the body."

The University of Calgary researchers, which include Hamid Habibi and Cassandra Kinch, said further research is needed to determine if the BPS also affects human fetuses but recommended pregnant women limit their exposure to items containing bisphenols.