Longitudinal assessment of the intestinal microbiota of a birth cohort exposed to environmental pollutants during the perinatal period: Childhood and Environmental Pollutants Project (PIPA)

This study is part of the Childhood and Environmental Pollutants Project (PIPA). Contamination of the environment with a wide variety of environmental pollutants can impact ecosystems, decrease environmental microbial diversity and alter the microbiota associated with the gastrointestinal tract. However, the effect of exposure to environmental pollutants on the developing gut microbiota is still poorly investigated. This thesis aims to study the effect of exposure to environmental pollutants on the intestinal microbiota during the first six months of life. In addition to investigating the relationship between maternal consumption of ultra-processed foods and levels of pollutants in umbilical cord blood. The 16S rRNA gene was evaluated in meconium and feces samples from babies aged one, three and six months and the infant microbiome was associated with the concentrations of metals (arsenic, cadmium, mercury and lead), perfluoroacylated substances (PFAS) and pesticides measured in maternal blood and urine and in umbilical cord blood. Maternal consumption of ultra-processed foods was investigated using a food frequency questionnaire. The results show that the effect of exposure to pollutants was greater when associated with early life stressors such as caesarean section and preterm birth compared to babies born vaginally. The effect of exposure to pollutants on the fecal microbiota was also greater in babies who were exclusively breastfed, which suggests contamination of breast milk. The changes observed in the microbiota associated with exposure to pollutants were different when the pollutants were measured in maternal blood or in the umbilical cord – suggesting that the time of exposure may be important. Finally, despite the high variability intrinsic to the developing microbiota, microbial communities were consistently affected by all pollutants, with clusters of taxa present in samples from babies with high exposure to pollutants. In addition, newborns born to mothers who consumed three or more subgroups of ultra-processed foods had higher levels of PFAS in the umbilical cord. The results show that perinatal exposure to environmental pollutants is associated with changes in the developing microbiota, which may be relevant to health. Our findings show that the consumption of ultra-processed foods is a potentially important route of exposure to these substances.

Keywords: Environmental pollutants. Intestinal microbiota. Microbial colonization. Child development. Ultra-processed food.