Early-Life Exposure to a Mixture of Phenols and Phthalates in Relation to Child Social Behavior

Is child social behavior at three years influenced by prenatal and postnatal exposure to a mixture of phenols and phthalates?

Phenols and phthalates are environmental chemicals with the ability to interfere with hormonal activity. Prenatal and early-life exposure to endocrine disrupting chemicals is suspected to increase the risk of diverse diseases including neurodevelopmental impairments. Phthalates and synthetic phenols are chemicals of special concern since they are widely used in plastics, food-packaging materials and cosmetics. More than 90% of the population is exposed continuously at low doses. Prenatal exposure to phthalates and some phenols has been linked to a poorer ability to socialize in both experimental animals and some human studies. Moreover, there is concern that exposure to these chemicals may increase the risk of autism spectrum disorders.

How does the Sepages cohort bring new knowledges?

The originality of the Sepages cohort lies on:

• 1) precise exposure to endocrine disrupting chemicals based on multiple urine samples (in mean, 42 samples during pregnancy and 14 samples during the first year of life)
• 2) frequency of exposure measures: from pregnancy up to the first year of the child.

Moreover, to better interpret our results, we additionally conducted a structured literature search to a priori identify the phthalates and phenols for which the animal toxicological and human evidence was stronger.

How to measure child social behavior?

Around the three years if the child, parents completed a questionnaire untitled “Social Responsiveness Scale (SRS) ». Based on the answer to the questions, we were able to calculate scores to study child social behavior.

Results

Results showed that, out of the periods investigated (second pregnancy trimester, third pregnancy trimester, neonates aged 2 months and infants aged 1 year), the most relevant one was the infant period. Thus, higher exposure to phthalates (particularly mono-ethyl phthalate) and triclosan during infancy at 1-year of age was associated with higher social behavior problems at three years. When we analyzed the effect of infant exposure to the mixture of chemicals in a combined way: higher exposure to the mixture of phenols and phthalates was linked to strengthened effects on social behavior problems, including poorer social communication skills. Moreover, the chemiclas included in this mixture had been identified in the context of a structured literature search as those for which animal and human toxicological evidence was strongest regarding an effect on behavior.

Why those results are important?

The results of our study identify early infancy as a critical window in which exposure to mixtures of phenols and phthalates can increase the risk of abnormal social behavior during childhood. On a population scale in France, this could indicate that these exposures might lead towards higher risk of autism spectrum disorders.