Common Plastic Chemical DEHP Linked to Autism and ADHD Signs in Study

A chemical commonly added to plastics to make them more flexible may affect genes that play a critical role in brain development and could be linked to symptoms of autism and attention-deficit/hyperactivity disorder (ADHD), according to a study led by researchers at the Florey Institute of Neuroscience and Mental Health in Australia. The study, published in the journal Med, compared blood and urine screens from pregnant mothers with behavioral assessments of their children.

The chemical, di-(2-ethylhexyl) phthalate (DEHP), is a phthalate added to polyvinyl chloride (PVC) plastic to make it soft and flexible, and is found in products including hoses, raincoats, medical equipment and plastic food bags. Phthalates can mimic hormone-related chemicals in the body and have previously been linked to declining testosterone levels and reduced sperm quality. Using cord blood collected through the Barwon Infant Study, the researchers found a strong correlation between a network of more than 500 genes with epigenetic changes, prenatal DEHP exposure levels, and an increase in behaviors associated with autism and ADHD at ages 2 and 4.

Senior author Anne-Louise Ponsonby, an epidemiologist at the University of Melbourne, said almost all the women in the Australian study showed exposure to DEHP. Further testing on independently collected blood samples and post-mortem brain tissue samples supported the conclusion that DEHP can change how genes are expressed, though the researchers noted differences between the blood test results and the post-mortem findings that complicate interpretation.

Mirko Uljarevic, a senior principal research fellow at the Kids Research Institute who was not involved in the study, said the authors offer a plausible biological explanation but that this still weakens a simple story about how the mechanism works. As an observational study, he said, the research is limited in how it can prove cause and effect, and autism and ADHD are multifactorial conditions unlikely to be meaningfully changed by any single exposure on its own. Ponsonby said chemical exposure levels are largely determined at the population level rather than by personal choice, making government safety regulations around food processing and packaging important.