Miami (AFP) -Fish exposed to low levels of bisphenol A (BPA), a common chemical used in plastics, canned goods and cash register receipts, showed evidence of hyperactive behaviour, according to research published Monday.
However, some experts warned that the results do not prove that the chemical affects humans the same way, and that more research is needed.
The study in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal, was led by the University of Calgary.
Scientists exposed zebrafish embryos to concentrations of BPA and bisphenol S (BPS) – the chemical that often replaces it in products labeled “BPA-free” – that are found in the Bow and Old Man rivers of Alberta, Canada.
They found that both exposure changed the timing of when neurons formed in the brains of the fish.
These changes in development led to hyperactivity later in life in zebrafish, which are considered a good medical model for the human brain because they develop similarly and about 80 per cent of human genes have a counterpart in the zebrafish’s genetic makeup.
“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,” said co-author Deborah Kurrasch, a member
of the Alberta Children’s Hospital Research Institute and the department of medical genetics.
“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.”
Researchers were also surprised to see that the BPA and BPA targeted androgen receptors in the zebrafish brains. Previous studies have suggested BPA may induce physical changes by mimicking estrogen, not testosterone.
“Finding the mechanism linking low doses of BPA to adverse brain development and hyperactivity is almost like finding a smoking gun,” said co-author Hamid Habibi, a professor of environmental toxicology and comparative endocrinology in the University of Alberta’s the Faculty of Science.
The research team said more work is needed to explore whether the chemicals may act the same way in humans, but in the meantime urged pregnant women to avoid exposure to bisphenols as much as possible.
“While a very interesting paper, it is not cause for alarm,” said Ian Musgrave, senior lecturer in the Faculty of Medicine at the University of Adelaide.
Musgrave, who was not involved in the research, said the concentrations of BPA in the study were much higher than
the levels at which humans would be exposed.
“The concentrations of BPA the zebrafish embryos were exposed to that resulted in hyperactivity were roughly 1,000 times higher than found in the blood of children with high exposure to BPA,” he said.