A recent study has drawn attention by suggesting a link between early-life symptoms of autism and ADHD and in-utero exposure to a widespread plasticizer. This adds to the ongoing quest to unravel complex questions, such as the rise in autism and ADHD diagnoses and the increase in behavioral issues globally among children, and the potential impact of plastic chemicals on brain development.
While the study contributes to current research, it offers specific insights into what it can and cannot reveal about these pressing scientific topics and the patterns that may be emerging.
The study, published in the peer-reviewed journal Med by Cell Press, examined behavioral traits in children at ages two and four, exploring their correlation with prenatal exposure to DEHP, a common plastic additive.
DEHP (di-(2-ethylhexyl) phthalate) is a synthetic chemical used to make plastics more flexible, found in products such as vinyl furniture upholstery, garden hoses, shower curtains, medical tubing, and vegan leathers. It is known to leach from materials, potentially entering food, water, and ultimately, human bodies.
Anne-Louise Ponsonby, a neuroepidemiologist at the University of Melbourne in Australia, explains, “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.”
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Both animal experiments and human observational studies have suggested links, though not causation, between DEHP exposure in the womb and neurodevelopmental issues like ADHD and autism symptoms. This new study delves deeper into this association, particularly exploring the epigenetic factors that may play a role if a causal link exists.
Epigenetics studies how environmental factors, such as DEHP exposure, influence gene function without altering DNA sequences. DNA methylation is one mechanism of epigenetic effect, where methyl (CH3) groups attach to genes, altering their expression.
Sam Tanner, the study’s lead author and a bioinformatics analyst at the University of Melbourne, states, “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. 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.”
This observational study utilized data from 847 Australian mother-child pairs from the Barwon Infant Study, with complete data from 589 pairs. Data collection began before birth, with each mother providing a urine sample at 36 weeks of pregnancy. Researchers used these samples to estimate daily DEHP intake through metabolites, which are reliable indicators of DEHP exposure.
Upon birth, DNA was extracted from the infants’ umbilical cord blood to analyze epigenetic signatures potentially linked to DEHP exposure. A group of 531 genes, affected by coordinated methylation patterns, appeared to mediate 21 percent of the link between estimated DEHP exposure and the autism and ADHD symptoms observed at ages two and four. Another methylation test across 1,000 genome sites supported this finding, suggesting a potential contribution of DEHP to these symptoms. Notably, these effects were more pronounced in boys.
Several methodological concerns warrant caution. A single urine sample may not represent typical exposure over time. The estimation of DEHP exposure is based on a proxy measurement (urine), not direct measures of DEHP levels in the fetus or related tissues. Additionally, Mirko Uljarevic, a medical researcher, emphasizes that this is an observational study and cannot establish cause and effect.
Uljarevic, who did not participate in the study, notes, “Autism and ADHD are complex conditions; however, the measures used by the authors were not developed for the purpose of comprehensively assessing autism or ADHD; rather, they provide very limited information.” The behaviors assessed, based on parental questionnaires, are not clinical diagnoses but may indicate the need for further assessment as the child grows.
He adds, “Crucially, the authors could not test the full chain from chemical exposure to brain changes to symptoms, only part of it.” While the findings reveal intriguing patterns, they do not definitively establish DEHP’s health effects.
Related: A Low-Plastic Diet Has Detectable Impacts on Urine Levels Within a Week, New Experiment Shows
Uljarevic concludes, “The current study offers important avenues for future research; however, autism, ADHD, and other neurodevelopmental conditions are multifactorial conditions that arise from many genetic and environmental factors together. No single exposure like this is likely, on its own, to meaningfully change an individual child’s risk.”
The research findings were published in Med.
This article was fact-checked by Michael Irving and edited by Michael Irving. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.
