How babies from this small Australian city – and a team of brilliant researchers – may have solved the decades-long mystery of what causes autism

Hundreds of young boys and their mothers from a small Australian city who were involved in a world-first study may have helped solve the mystery of what causes autism.

The ground-breaking research, which was led by a crack team of Australian scientists from the Florey Institute at the University of Melbourne, found a possible link between autism and exposure to common plastic chemicals in the womb.

If the chemical bisphenol A (BPA) was discovered in a pregnant mother’s urine, it more than tripled the chances a young boy would develop autism symptoms by age two.

Worse, those same boys were six times more likely to be diagnosed with autism by age 11 — compared to those whose mothers had lower BPA levels during pregnancy.

BPA, which is a chemical intended to harden plastics and prevent metals from rusting, is found in everything from food and drink containers, cosmetics, packaging and even paper receipts.

It can enter food in tiny particles from contact with plastic wrapping, plastic bags and the plastic lining on tins.

The chemical mimics natural hormones and can disrupt them in developing babies and children.

The ground-breaking research, which was led by a crack team of Australian scientists from the Florey Institute at the University of Melbourne , found a possible link between autism and exposure to common plastic chemicals in the womb

BPA, which is a chemical intended to harden plastics and prevent metals from rusting, is found in everything from food and drink containers, cosmetics, packaging and even paper receipts

The researchers studied almost 1,800 children over a decade across two cohorts of mothers and children: one based in Geelong and the other in New York. 

Over 1,000 children and their mothers in Geelong were part of the Barwon Infant Study (BIS) taking place at Barwon Health hospital in collaboration with the Murdoch Children’s Research Institute and Deakin University.

Within the BIS data, 676 infants had sufficient testing on early age autism symptoms for the team to draw statistical conclusions.

These assessments, drawn from the Autism Spectrum Problems scale of the Child Behavior Checklist (CBCL ASP), were weighted to cancel out for any genetic predispositions or other variables to isolate the role that BPA plays during pregnancy.

Professor Anne-Louise Ponsonby, co-author of the study which was first published in Nature Communications, said their work had solved ‘part of the autism puzzle’.

‘Exposure to plastic chemicals during pregnancy has already been shown in some studies to be associated with subsequent autism in offspring,’ study co-author Professor Ponsonby said.

The researchers studied almost 1,800 children over a decade across two cohorts of mothers and children: one based in Geelong (pictured) and the other in New York

‘Our work is important because it demonstrates one of the biological mechanisms potentially involved. 

‘BPA can disrupt hormone-controlled male fetal brain development in several ways, including silencing a key enzyme, aromatase, that controls neurohormones and is especially important in fetal male brain development.’

Professor Ponsonby stressed that autism is a multifactorial condition and that BPA is just a single possible contributing factor.

Aromatase, the study noted, helps to convert some male sex hormones in the brain, known as neural androgens, into neural estrogens.

These estrogens help all people, regardless of gender, to regulate inflammation in the brain, maintain the flexibility of the synapses that help neurons communication within the whole nervous system and also aid in managing of cholesterols.

The brain is the human body’s most cholesterol-rich organ — employing roughly 20 percent of the whole body’s stores of these fatty molecules to do its vital functions.

The study also studied the impact of BPA on mice.

‘We found that BPA suppresses the aromatase enzyme and is associated with anatomical, neurological and behavioural changes in the male mice that may be consistent with autism spectrum disorder,’ study co-author Dr Wah Chin Boon said. 

‘This is the first time a biological pathway has been identified that might help explain the connection between autism and BPA.’

The work was cautiously hailed by Australian scientists as a major first step in understanding the possible link between BPA and autism.

Professor Ian Rae, an expert on chemicals in the environment at the University of Melbourne who has advised the United Nations, cautioned that ‘”association” cannot automatically be assumed to be “causation”.’

‘Suspicions about its (BPA) toxic effects are strong, but the effects are usually weak and hard to detect, requiring extensive population studies, so it has proved extremely difficult to see exactly how BPA exerts its effects—something that’s need to link cause and effect,’ Professor Rae said. 

Study co-author Professor Anne-Louise Ponsonby (pictured) stressed that autism is a multifactorial condition and that BPA is just a single possible contributing factor

He added: ‘What’s really new about their results is that they were able to pin the effect to a biological pathway that is important in brain development. 

‘In other words, BPA is acting as a “rogue” hormone to out-compete the natural hormone that is usually involved in this pathway.’

Professor Elisa Hill-Yardin, the head of the Gut-Brain Axis Laboratory and Deputy Director of the Healthy Foundations Research Group at RMIT University, said it was ‘interesting research worthy of further investigation’.

‘But it’s important to understand there are many other genetic variations that are possible contributors to autism that have similar amounts of evidence.,’ Professor Hill-Yardin added. 

‘Ultimately we still don’t know for sure what causes autism for most people and a normal healthy diet and lifestyle advice should be followed during pregnancy.’

Oliver Jones, professor of Chemistry at RMIT University in Melbourne, said that the study showed a ‘showed a plausible biological mechanism by which the effect could occur’. 

BPA, which is found in many plastics, has been linked to higher risks of obesity, asthma, diabetes, and heart diseases across over two decades of increasing scrutiny on the compound

‘However, just because something can occur, does not mean that it does so,’ he said.

‘The levels of BPA in this study (involving mice) were higher than we are generally exposed to.

Professor Jones added: ‘BPA is one of the most well-studied chemicals on earth with thousands of papers published on it and while still the topic of a lot of debate nobody has shown any effects of this compound at the levels to which we are exposed.’

BPA has been linked to higher risks of obesity, asthma, diabetes, and heart diseases across over two decades of increasing scrutiny on the compound.

It has also been has been dubbed a ‘gender-bending’ chemical due to its apparent role spurring hormonal and sexual disruptions in humans, fish and other species. 

‘BPA can disrupt hormone-controlled, male fetal brain development in several ways,’ public health physician Dr Anne-Louise Ponsonby explained, ‘silencing a key enzyme, aromatase, that controls neurohormones and is especially important in fetal male brain development’