Researchers at the Florey Institute have discovered a potential link between prenatal exposure to the chemical BPA and autism in boys. 

The finding is based on a combination of human studies, laboratory experiments with mice, and cellular analyses. 

The study, published in Nature Communications, sheds light on the biological mechanisms that might explain this association.

The study revealed higher levels of bisphenol A (BPA) in the urine of pregnant women who later gave birth to sons diagnosed with autism. 

BPA is a chemical commonly used in food packaging and other consumer products. 

Dr Wah Chin Boon and Professor Anne-Louise Ponsonby, who led the research, analysed data from the Barwon Infant Study (BIS) in Australia and the Columbia Centre for Children’s Health and Environment in the USA.

“Exposure to plastic chemicals during pregnancy has already been shown in some studies to be associated with subsequent autism in offspring,” Professor Ponsonby said 

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

The research focused on the enzyme aromatase, which converts testosterone to neuroestrogen in the brain. 

This enzyme plays a crucial role in male foetal brain development. 

BPA was found to disrupt this process by silencing aromatase, which could lead to autism. 

The study highlighted that boys in the top fifth of vulnerability to BPA - those with lower aromatase levels - were significantly more likely to develop autism.

The researchers say boys born to mothers with high BPA levels in late pregnancy were 3.5 times more likely to show autism symptoms by age 2.

By age 11, these boys were six times more likely to have a confirmed autism diagnosis compared to those whose mothers had lower BPA levels.

Dr Boon's laboratory work with mice reinforced these findings. 

“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,” she said. 

This marked the first time a biological pathway has been identified that might explain the connection between BPA and autism.

BPA and similar chemicals are pervasive in the environment, making them almost impossible to avoid. 

“We all ingest plastic chemicals in many ways,” Professor Ponsonby noted. 

“It’s important for us to understand how these plastics affect our health.” 

The study’s findings could inform public safety regulations concerning exposure to manufactured chemicals during pregnancy and early life.

The researchers also explored potential interventions. 

Dr Boon says that 10-hydroxy-2-decenoic acid, a type of fatty acid, showed promise in animal studies for mitigating the effects of BPA. 

“It warrants further studies to see whether this potential treatment could be realised in humans,” she said.

Experts have weighed in on the study’s findings, highlighting both its significance and limitations.

“This study looks at possible links between BPA and autism. While the research is detailed and shows a plausible biological mechanism, further work is needed to show similar results in humans,” said Professor Oliver Jones from RMIT University.

“This is a technically excellent study, but the doses of BPA used were higher than typical human exposure,” said Dr Ian Musgrave from the University of Adelaide.

“The marginal effect on autism markers in mice is less than compelling evidence for BPA’s role in autism.”

“This is interesting research worthy of further investigation,” noted Professor Elisa Hill-Yardin, also from RMIT University.

“However, there are many genetic and environmental factors that contribute to autism.”