- Florey researchers have identified a biological link by which exposure to a common plasticiser in pregnancy may increase autism and ADHD symptoms in early childhood.
- Their study found high levels of exposure to DEHP during pregnancy leaves an “epigenetic signature” in umbilical cord blood DNA, indicating altered baby brain development.
- DEHP is a manufactured chemical used to make everyday plastic items flexible.
New Florey Institute of Neuroscience and Mental Health research has found unborn babies exposed to higher levels of a chemical used to soften plastic are at greater likelihood of developing symptoms of autism and ADHD in early childhood.
DEHP is found in a range of plastic products — including food packaging, vinyl flooring, garden hoses and waterproof coats — and readily leaches into food and the environment.
Lead author Sam Tanner said while previous studies have linked prenatal DEHP exposure to neurodevelopmental problems, exactly how the chemical affects the developing brain is unclear.
“What we have found is a possible biological explanation and one that provides new evidence that exposure to DEHP in pregnancy may contribute to autism and ADHD,” Mr Tanner said.
“Our study found infants exposed to higher levels of DEHP before birth showed distinctive changes in DNA methylation — an epigenetic switch that turns genes on or off — in their umbilical cord blood at birth.
“Children who carried this ‘epigenetic signature’ went on to show more autism- and ADHD-related symptoms at ages two and four, with clearer effects in males than females.”
The researchers used data from more than 800 mothers and their babies collected as part of the Barwon Infant Study, a large Australian birth cohort.
Instead of analysing individual genes as is common in this type of research, they looked at almost one million DNA sites in each child, identifying a network of 531 genes that changed together in response to DEHP exposure.
The ‘epigenetic signature’ included changes in genes that are known to play roles in the development of the brain, including some previously linked to autism and ADHD. Crucially, the researchers showed that the changes were present in post-mortem brain samples from individuals diagnosed with autism compared to those without, in an independent US database, providing external validation of the finding.
The study also revealed that the gene network that is disrupted by the plasticiser is positively influenced by a maternal wholefood diet rich in fish, nuts, eggs, green vegetables and wholegrains — a diet independently associated with better neurodevelopmental outcomes.
It appears that the chemical DEHP and high-quality nutrition during pregnancy act on the same network but in different directions. This suggests that epigenetic regulation of this gene network may function like a “dial” for brain development that both harmful and protective exposures can turn in either direction.
Head of The Florey’s Neuroepidemiology Research Group, Professor Anne-Louise Ponsonby, said the findings call for a rethink on safe levels of DEHP exposure and other plastic chemicals during pregnancy.
“Almost all women in this Australian study showed exposure to the common DEHP chemical,” Professor Ponsonby said.
“Chemical exposure levels are mainly determined at the population level and are not easily a matter of personal choice. Plastic chemicals like DEHP are often ingested, so government safety regulations around food processing and packaging are very important.
“Global plastic control efforts should take into consideration recent evidence as it emerges on the need for health protection, particularly for vulnerable populations such as pregnant women and young babies.”
The research was partly funded by the Minderoo Foundation. Neither Minderoo nor its benefactors had any influence on the conduct or the reporting of this study.
The study’s findings have been published in the Cell Press journal Med.
