Pthalates are in the class of endocrine (hormone) disrupting chemicals (EDC). Unfortunately, phthalates are everywhere in the U.S.–in our personal care products, home care products and in processed food packaging where they migrate into the food we put into our bodies. Now researchers examining the effects of pregnant women exposed to toxic chemicals in their homes have substantiated evidence linking exposure to phthalates to altered cognitive outcomes in their infants. Most of their findings involved slower information processing among infants with higher phthalate exposure levels, with males more likely to be affected depending on the chemical involved and the order of information presented to the infants.
The study is part of the Illinois Kids Development Study, which tracks the effects of hormone-disrupting chemicals on children’s physical and behavioral development from birth to middle childhood. Now in its seventh year, IKIDS has enrolled hundreds of participants and is tracking chemical exposures in pregnant women.
The researchers analyzed metabolites of three commonly occurring phthalates in urine samples regularly collected from the pregnant women in the study. The chemical exposure data were used in combination with assessments of the women’s infants when the children were 7.5 months old.
The researchers used a well-established method that gives insight into the reasoning of children too young to express themselves verbally: Infants typically look longer at unfamiliar or unexpected images or events.
The team used an infrared eye-tracker to follow each infant’s gaze during several laboratory trials. With the infant sitting on a caregiver’s lap, researchers first familiarized the child with two identical images of a face. After the infant learned to recognize the face, the researchers showed that same face paired with an unfamiliar one.
“In repeated trials, half of the 244 infants tested saw one set of faces as familiar, and half learned to recognize a different set of faces as familiar. By analyzing the time spent looking at the faces, we could determine both the speed with which the infants processed new information and assess their ability to pay attention.”
-Dr. Susan Schantz, neurotoxicologist and professor emerita of comparative biosciences at the University of Illinois Urbana-Champaign, and principal investigator of the study
The assessment linked pregnant women’s exposure to most of the phthalates that were assessed with slower information processing in their infants, but the outcome depended on the specific chemical, the sex of the infant and which set of faces the infant viewed as familiar. Male infants, in particular, tended to process information more slowly if their mothers had been exposed to higher concentrations of phthalates known to interfere with androgenic hormones.
Journal References: Kelsey L.C. Dzwilewski, Megan L. Woodbury, Andrea Aguiar, Jessica Shoaff, Francheska Merced-Nieves, Susan A. Korrick, Susan L. Schantz. Associations of prenatal exposure to phthalates with measures of cognition in 7.5-month-old infants. NeuroToxicology, 2021; 84: 84 DOI: 10.1016/j.neuro.2021.03.001