Hundreds of young boys and their mothers from a small Australian town took part in a globally unique study that may have helped solve the mystery surrounding the cause of autism.
The groundbreaking research, led by a team of Australian scientists from the Florey Institute at the University of Melbourne, discovered a possible link between autism and exposure to common plastic chemicals in the womb.
When the chemical bisphenol A (BPA) was found in a pregnant mother’s urine, the chance of a boy developing autism symptoms before the age of two tripled.
Worse yet, these same boys were six times more likely to be diagnosed with autism at age 11, compared to boys whose mothers had lower BPA levels during pregnancy.
BPA is a chemical that makes plastics harder and prevents metals from rusting. It is found in everything from food and beverage containers, cosmetics, packaging and even paper receipts.
It can enter food in small particles through contact with plastic packaging, plastic bags and the plastic lining of cans.
The chemical mimics natural hormones and can disrupt them in babies and children.
The groundbreaking research, led by a 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, a chemical designed to harden plastics and prevent metals from rusting, can be found in everything from food and beverage containers, cosmetics, packaging, and even paper receipts.
The researchers studied nearly 1,800 children over a decade, divided into two cohorts of mothers and children: one in Geelong and the other in New York.
More than 1,000 children and their mothers in Geelong took part in the Barwon Infant Study (BIS), which was conducted at Barwon Health in collaboration with the Murdoch Children’s Research Institute and Deakin University.
Within the BIS data, 676 infants were sufficiently tested for early-onset autism symptoms for the team to draw statistical conclusions.
These ratings, based on the Autism Spectrum Problems scale of the Child Behavior Checklist (CBCL ASP), were weighted to rule out genetic predisposition or other variables and thus isolate the role BPA plays during pregnancy.
Professor Anne-Louise Ponsonby, co-author of the study first published in Nature Communications, said their work had solved “part of the autism puzzle”.
“Some research has already shown that exposure to plastic chemicals during pregnancy is linked to autism in offspring,” said Professor Ponsonby, co-author of the study.
The researchers studied nearly 1,800 children over a decade in two cohorts of mothers and children: one in Geelong (pictured) and the other in New York
‘Our work is important because it shows one of the biological mechanisms that may be involved.
‘BPA can disrupt the hormone-driven development of the brains of male fetuses in several ways. For example, it can suppress an important enzyme, aromatase. Aromatase regulates neurohormones and is particularly important for the development of the brains of male fetuses.’
Professor Ponsonby stressed that autism is a multifactorial condition and that BPA is just one possible contributing factor.
The research shows that aromatase helps convert a number of male sex hormones in the brain, called neural androgens, into neural estrogens.
These estrogens help all people, regardless of gender, regulate inflammation in the brain, maintain the flexibility of the synapses that promote communication between neurons throughout the nervous system, and help regulate cholesterol.
The brain is the organ in the human body that contains the most cholesterol. It uses about 20 percent of the body’s total supply of fat molecules to perform its vital functions.
The study also looked at the impact of BPA on mice.
“We found that BPA suppresses the aromatase enzyme and that this is associated with anatomical, neurological and behavioral changes in male mice that may be consistent with autism spectrum disorder,” said study co-author Dr. Wah Chin Boon.
“This is the first time that a biological pathway has been identified that could help explain the link between autism and BPA.”
Australian scientists cautiously welcomed the work as an important first step in understanding the possible link between BPA and autism.
Professor Ian Rae, an expert on environmental chemicals at the University of Melbourne who advises the United Nations, warned that “an association cannot automatically equate to a causal relationship.”
‘There is strong evidence of toxic effects of BPA, but the effects are generally weak and difficult to detect. This requires large population studies. It has also been extremely difficult to see exactly how BPA exerts its effects. A cause-and-effect relationship is needed,’ said Professor Rae.
Study co-author Professor Anne-Louise Ponsonby (pictured) stressed that autism is a multifactorial condition and that BPA is just one possible contributing factor
He added: ‘What’s really new about their results is that they were able to link the effect to a biological pathway that’s important for brain development.
‘In other words, BPA acts as an ‘unreliable’ hormone that competes with the natural hormone normally involved in this process.’
Professor Elisa Hill-Yardin, head of the Gut-Brain Axis Laboratory and deputy director of the Healthy Foundations Research Group at RMIT University, called it “interesting research that is worth exploring further”.
“But it is important to realise that there are many other genetic variations that may contribute to autism for which there is similar levels of evidence,” adds Professor Hill-Yardin.
“Ultimately, we still don’t know for sure what causes autism in most people. During pregnancy, it’s important to maintain a normal, healthy diet and lifestyle.”
According to Oliver Jones, a professor of chemistry at RMIT University in Melbourne, the research “shows a plausible biological mechanism by which the effect could occur”.
BPA, found in many types of plastic, has been linked to a higher risk of obesity, asthma, diabetes and heart disease, after more than two decades of increasing scrutiny over its composition.
“But just because something can happen doesn’t mean it will,” he said.
‘The BPA levels in this study (in mice) were higher than the levels we are normally exposed to.
Professor Jones added: ‘BPA is one of the most researched chemicals on the planet. There have been thousands of papers published on it. Although it is still much debated, no one has shown any effect of this compound at the levels we are exposed to.’
BPA has been linked to an increased risk of obesity, asthma, diabetes and heart disease for over two decades due to increasing scrutiny of the substance.
It has also been called a “gender-bending” chemical because of its alleged role in causing hormonal and sexual disruptions in humans, fish and other species.
‘BPA may disrupt the hormone-driven development of the male fetal brain in several ways,’ explains public health physician Dr Anne-Louise Ponsonby, ‘by suppressing an important enzyme, aromatase, which regulates neurohormones and is particularly important for male fetal brain development.’