An epidemiological study conducted by Inserm on the families of the EDEN cohort (500 boys born between 2003 and 2006 and their mothers) shows that exposure during pregnancy to certain phenols and phthalates is associated with behavioral disorders in boys between 3 and 5 years old. The compounds of most concern in this regard are bisphenol A, triclosan, and di-n-butyl phthalate, or DBP.
Bisphenol A was banned from all food containers in France in January 2015, a date after this study was conducted. Triclosan is an antibacterial agent found in some toothpastes and soaps, DBP is used as a plasticizer in PVC-type plastics, some glues, nail polish and hairspray. Toxicological studies in vitro and in animals have demonstrated that these compounds are endocrine disruptors and may interact with hormonal systems involved in the normal development of the central nervous system. The precise mechanisms that could explain an effect of endocrine disruptors on neurodevelopment and behavior could go through an alteration in the functioning of thyroid hormones, steroid hormones, such as estrogen, or other hormones, such as oxytocin or vasopressin. , hormones secreted by the hypothalamus.
Faced with these initial findings in animals, the researchers wanted to study the association between exposure to endocrine disruptors during pregnancy and the subsequent behavior of children.
From 70 to 100% of mothers exposed to endocrine disruptors
The study involved 529 little boys. The pregnant women participating in this cohort were recruited between 2003 and 2006 in the University Hospitals of Nancy and Poitiers. At the child’s third and fifth birthdays, these mothers completed a standardized questionnaire evaluating certain aspects of their child’s behavior such as hyperactivity, emotional disorders and relational disorders. This standardized questionnaire, which has been in use for about twenty years, entitled “Questionnaire of the strengths and difficulties” of the child, makes it possible to establish a score in different dimensions of behavior such as emotional symptoms, problems with relationships with peers, driving problems, hyperactivity and inattention. A urine sample taken during pregnancy allowed the determination of biomarkers characteristic of exposure to phenols and phthalates.
From 70 to 100% of the women in the Eden cohort, recruited during their pregnancy between 2003 and 2006, were then exposed to detectable levels of various substances. Urinary levels were in the range of 1 to 3 µg per liter for bisphenol A, 10 to 100 µg per liter for triclosan, and 50 to 200 for methylparaben. The results suggest that maternal exposure to certain phenols and phthalates is associated with behavioral disorders in young boys.
Child’s hyperactivity or withdrawal
Exposure to bisphenol A was associated with an increase in relational disorders at 3 years and hyperactive-type behaviors at 5 years. The researchers note that this work thus confirms that the effects of bisphenol A on behavior observed in laboratory animals are found in humans at low exposures, probably lower than those recommended by the European food safety authority. ‘EFSA. The metabolite of DBP was associated with more emotional and relationship problems, including withdrawal behaviors, at 3 years, but not at 5 for emotional problems. Associations between these compounds and behavior had already been demonstrated in previous studies in young boys and in animals.
Triclosan decreases skull size in newborns
The results of this study also showed an association between triclosan and an increase in emotional disturbances at 3 and 5 years. This is the first study evaluating the effects of this compound on behavior, for which the environmental epidemiology team in Grenoble had already demonstrated a decrease in the cranial circumference at birth, in this same population. At the molecular level, triclosan is able to interact with the thyroid axis which, during pregnancy, is involved in the development of the brain of the fetus.