Chemical exposure, Gut microbiota and child neurodevelopment

What is the gut microbiota?

The gut microbiota represents the collection of bacteria, parasites, fungi, and viruses that live in our intestines. These microorganisms play a crucial role in our health throughout life, but the microbiota develops most intensely during the first years after birth.

Is the gut microbiota influenced by exposure to phenols, phthalates and poly- and perfluoroalkyl substances (PFAS)?

The gut microbiota is influenced by several factors such as the mode of delivery, the duration of pregnancy, breastfeeding, and exposure to molecules such as antibiotics. However, very little is known about its sensitivity to widely distributed chemicals such as phenols, including parabens, which are used as preservatives in cosmetics; phthalates, which are used as plasticizers in food packaging; and poly- and perfluoroalkyl substances (PFAS), which can be found, for example, in non-stick coatings, water-resistant textiles, firefighting foams, and certain food packaging.

How was exposure to phenols and poly- and perfluoroalkyl substances (PFAS) assessed?

Phenols and phthalates exposure was assessed through repeated urine samples collected from women during pregnancy and from children at 2 and 12 months of age. Poly- and perfluoroalkyl substances (PFAS) were evaluated in pregnant women through blood samples.

How was the gut microbiota of children assessed?

After collecting stool samples from the children, we extracted DNA from the samples and sequenced a "marker" gene present in all bacteria. This gene allows us to identify which bacteria are present in the feces and in what quantity.

How was the children's neurodevelopment assessed?

We assessed the children's neurodevelopment using various questionnaires completed by their parents or by a healthcare professional.

Results

Perinatal exposure to certain parabens was associated with gut microbiota diversity and the bacterial groups Firmicutes and Proteobacteria. Suggestive associations were observed between some phenols and bacterial genera from the Lachnospiraceae and Enterobacteriaceae families.
Phthalates assessed at 12-month were associated with higher diversity of the child gut microbiota. DEHP exposure at 12 months was associated with higher Coprococcus genus and tended to be associated with higher Firmicutes bacterial group.
Certain bacterial groups in the gut microbiota appear to be associated with child behavior: The Proteobacteria and Bacteroidetes phyla were associated with better socio-emotional development; the Firmicutes phylum was associated with increased planning and organizational problems; the bacterial genera Lactococcus, Coprococcus, Oscillibacter, Clostridium XVIII, Veillonella, Parabacteroides, Subdoligranulum, and Saccharibacteria were associated with lower socio-emotional development, while the bacterial genera Enterococcus and Butyricicoccus were associated with higher socio-emotional development.

What’s next?

Do the disruptions in the gut microbiota at one year of age associated with phenol and phthalate exposure persist over time? Do they have long-term health effects on the child? Research continues using data from the SEPAGES cohort to answer these questions.

The gut microbiota can vary greatly from one child to another: children on the left side of the graph have a gut microbiota mainly composed of bifidobacteria, while the children on the right side of the graph have a gut microbiota with few bifidobacteria, replaced by other groups of bacteria.