Hundreds of young children and their mothers from a small Australian town who took part in a world-first study may have helped solve the mystery of what causes autism.
The groundbreaking research, led by a team of Australian scientists from the University of Melbourne’s Florey Institute, has found a possible link between autism and exposure to common plastic chemicals in the womb.
If the chemical bisphenol A (BPA) were discovered in a pregnant mother’s urine, it would triple the chances of a young child developing autism symptoms before age two.
Worse yet, those same children were six times more likely to be diagnosed with autism at age 11, compared to those whose mothers had lower levels of BPA during pregnancy.
BPA, a chemical meant to toughen plastics and prevent metals from rusting, is found in everything from food and drink containers to cosmetics, packaging and even paper receipts.
It can enter food in tiny particles through contact with plastic wrappers and bags and the plastic lining of cans.
The chemical mimics natural hormones and can disrupt them in developing babies and children.
Pioneering research, led by a team of Australian scientists from the University of Melbourne’s Florey Institute, has found a possible link between autism and exposure to common plastic chemicals in the womb.
BPA, which is a chemical meant to toughen plastics and prevent metals from rusting, is found in everything from food and drink containers, cosmetics, packaging and even paper receipts.
Researchers studied nearly 1,800 children over a decade in two mother-child cohorts: one in Geelong and the other in New York.
More than 1,000 children and their mothers in Geelong participated in the Barwon Children’s Study (BIS) which was conducted at Barwon Health hospital in collaboration with Murdoch Children’s Research Institute and Deakin University.
Within the BIS data, 676 infants were screened sufficiently for early autism symptoms for the team to draw statistical conclusions.
These assessments, drawn from the Child Behavior Checklist Autism Spectrum Problems (CBCL ASP) scale, were weighted to cancel out any genetic predisposition or other variables to isolate the role BPA plays during pregnancy.
Professor Anne-Louise Ponsonby, co-author of the study which was first published in Nature Communications, said her work had solved “part of the autism puzzle”.
“Some studies have already shown that exposure to plastic chemicals during pregnancy is associated with later autism in offspring,” said Professor Ponsonby, co-author of the study.
Researchers studied nearly 1,800 children over a decade in two mother-child cohorts: 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 may disrupt hormonally controlled male fetal brain development in several ways, including silencing a key enzyme, aromatase, which controls neurohormones and is especially important in male fetal brain development.’
Professor Ponsonby stressed that autism is a multifactorial condition and that BPA is only one of the possible contributing factors.
Aromatase, the study noted, helps convert some male sex hormones in the brain, known as neuronal androgens, into neuronal estrogens.
These estrogens help all people, regardless of gender, to regulate inflammation in the brain, maintain the flexibility of the synapses that help the communication of neurons within the entire nervous system and also help in the control of cholesterol.
The brain is the organ in the human body that is richest in cholesterol: it uses approximately 20 percent of the body’s total reserves of these fatty 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 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 connection between autism and BPA.’
The work was cautiously hailed by Australian scientists as an important 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 “one cannot automatically assume that ‘association’ is ‘causation’.”
“Suspicion of BPA’s toxic effects is strong, but the effects are often weak and difficult to detect, and require extensive population studies, so it has been extremely difficult to see exactly how BPA exerts its effects, which is necessary to link cause and effect,” Professor Rae said.
Study co-author Professor Anne-Louise Ponsonby (pictured) stressed that autism is a multifactorial condition and BPA is only one possible contributing factor.
He added: “What’s really novel about their results is that they were able to link the effect to a biological pathway that is important in brain development.
In other words, BPA acts as a “rogue” hormone that competes with the natural hormone normally involved in this pathway.
Professor Elisa Hill-Yardin, head of the Gut-Brain Axis Laboratory and deputy director of the Healthy Foundations Research Group at RMIT University, said it was “an interesting piece of research that deserves further investigation”.
“But it’s important to understand that there are many other genetic variations that can contribute to autism and that have similar amounts of evidence,” Professor Hill-Yardin added.
‘Ultimately, we still don’t know for sure what causes autism in most people, so a healthy diet and normal lifestyle should be followed during pregnancy.’
Oliver Jones, a professor of chemistry at RMIT University in Melbourne, said the study showed “a plausible biological mechanism by which the effect could occur”.
BPA, found in many plastics, has been linked to increased risks of obesity, asthma, diabetes and heart disease over more than two decades of increasing scrutiny of the compound.
“However, just because something can happen doesn’t necessarily mean it will happen,” he said.
‘The BPA levels in this study (in which mice participated) were higher than those to which we are generally exposed.
Professor Jones added: “BPA is one of the most studied chemicals on the planet, with thousands of papers published on it and, although it is still the subject of much debate, no-one has demonstrated any effects from this compound at the levels we are exposed to.”
BPA has been linked to increased risks of obesity, asthma, diabetes and heart disease over more than two decades of increasing scrutiny of the compound.
It has also been called a “gender-bending” chemical due to its apparent role in stimulating hormonal and sexual disorders in humans, fish, and other species.
“BPA may disrupt hormonally controlled fetal male brain development in several ways,” explained public health physician Dr. Anne-Louise Ponsonby, “by silencing a key enzyme, aromatase, which controls neurohormones and is particularly important in fetal male brain development.”
