The researchers also conducted experiments with mice, and found that when the genes for the aromatase enzyme were deleted, it induced repetitive behaviours in the animals. In humans, repetitive behaviours is one of the flags for an autism diagnosis.

Ponsonby said the aromatase enzyme was important in brain development, especially for boys as it converts androgen hormones into brain oestrogen. The research also pointed to a compound found in royal jelly as a potential antidote, but Ponsonby said more research was needed.

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Dr Ian Musgrave, a senior lecturer in medicine at the University of Adelaide, said “autism is hugely more prevalent in boys”, and while it was possible this was partly because of under-diagnosis in girls, there were biological factors as well.

Musgrave added that previous research had suggested air pollution from nitrogen dioxide, a common greenhouse gas, also contributed to autism.

Musgrave said the Florey research was an excellent study, but it was unclear how transferable the findings about animal behaviour was to real-world autism in humans, which could range from high-functioning to non-verbal. He also said the level of BPA in the environment in Australia was much lower than in this research.

Professor Ian Rae, an expert on chemicals in the environment at the University of Melbourne, said BPA chemicals could leach into the environment or food. The first way was in the manufacturing process, if there were leftover chains that were not incorporated into the polymer, and the second way was if the polymer broke down, which could occur by heating it.

Rae said there was not as much BPA contamination in the wider environment as for PFAS chemicals, which are in the soil and drinking water because of being used in products such as firefighting foams.

“If you’ve got these things in the landfill and the landfill is leaking, as some of them do, it can leach into the environment, but the main concentration here has been about getting into food contamination,” Rae said.

The final round of United Nations talks to agree an international plastic treaty will be held in South Korea in late November, with Australia part of a coalition of countries pushing to reduce new plastic production.

The Minderoo Foundation, founded by billionaires Dr Andrew Forrest and his former wife Nicola Forrest, funded the research as part of its commitment to building evidence on the harmful effects of plastic pollution.

Minderoo Foundation director Jay Weatherill said: “From the water we drink to the products we use, plastics are an inescapable part of modern living. These new findings strengthen the call for a comprehensive and ambitious global plastics treaty to protect human health from the impact of plastic chemicals.”

Food Safety Australia & New Zealand website states the evidence suggests there is no safety concern with BPA chemicals at the levels people are exposed to.

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