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A chemical commonly found in plastic packaging and the lining of canned food increases the risk of autism in young boys, a new study finds.

The study, published in Nature communicationResearch has found that boys exposed to bisphenol A, better known as BPA, in the womb are more likely to show symptoms of autism at age two and are six times more likely to be diagnosed with autism at age 11.

Autism is a neurodevelopmental disorder with a broad spectrum of behavioral and cognitive changes.

The study, conducted by the Florey Institute, the largest brain research centre in the Southern Hemisphere, examined BPA levels in pregnant mothers and followed the development of their children over a 10-year period.

It revealed that higher BPA exposure is associated with suppression of aromatase, an important enzyme in brain development, particularly in boys. The suppression is linked to an increased risk of autism diagnosis.

The findings were supported by experiments in mice, which showed that when the gene responsible for producing aromatase is deleted, the animals exhibit repetitive behaviors, a common feature of autism in humans.

“Some research has already shown that exposure to plastic chemicals during pregnancy is linked to autism in offspring,” Professor Anne-Louise Ponsonby, one of the study’s authors, said in a statement.

“Our work is important because it shows one of the biological mechanisms that may be involved. BPA can disrupt hormone-driven development of the male fetal brain in several ways, including silencing a key enzyme, aromatase, which controls neurohormones and is particularly important in male fetal brain development. This appears to be part of the autism puzzle.”

Professor Ponsonby said autism stems from a combination of genetic and environmental factors, but that BPA exposure appears to play a contributing role, particularly in boys. “This does not mean that BPA is the only cause of autism,” she explained, according to The Sydney Morning Herald“Some children may be genetically predisposed, while others may be influenced by various environmental factors.”

BPA is used in the production of plastic food containers and metal can liners. It is often found in items such as water dispensers, food containers and reusable bottles. The chemical helps make these plastics strong and clear, but it can leach in small amounts, raising concerns about its impact on human health.

BPA usually enters our bodies in trace amounts through food, but it can also be inhaled or absorbed through the skin.

Previous studies have linked BPA to possible negative impacts on the brains and prostate glands of fetuses, infants and children. The findings linking it to autism are new.

“Autism is the result of a complex interaction between genes and the environment, and the nature of the interactions with the environment is still largely unclear,” said Dr Ian Musgrave, senior lecturer in medicine at the University of Adelaide.

Professor Ian Rae, an expert on environmental chemicals at the University of Melbourne, explained how BPA works in the body: “Bisphenol A is an industrial chemical that mimics natural hormones and can disrupt their function, particularly in developing babies and children.”

“BPA is most commonly used in plastics — epoxy resins and polycarbonate — and in that form it is quite safe. However, BPA can leach out of these plastics, circulate freely in the environment, and enter our bodies as a trace contaminant in food.”

Concerns about BPA have led to calls for its ban. The European Union is set to ban BPA from food contact materials, including plastic packaging, coated containers, reusable bottles, water coolers and kitchenware.

The ban will come into effect at the end of 2024, pending an evaluation by the European Parliament and the Council.

Many other harmful plastic chemicals and microplastics such as PFAS have also been linked to health risks. PFAS are called “forever chemicals” because of their persistence in the environment and are used in a variety of products including non-stick cookware, waterproof clothing and food packaging.

Microplastics, tiny plastic particles that can contaminate food and water, are found everywhere, from the deep oceans to our food and water supplies to our internal organs.

This new study comes as the world prepares for the final round of UN negotiations in South Korea later this year to conclude a global treaty against plastic pollution.