Our modern environment exposes us to all kinds of harmful chemicals, from the plastics on our electronics to food packaging. Among them are phthalates, a class of products known to interfere with hormonal function and development. Recently, a study found that when an expectant mother is exposed to these substances, there is a real risk that the child will have cognitive impairment from birth.
Researchers at the University of Illinois Urbana-Champaign reported an alarming result: They found a reduced rate of brain processing in infants whose mothers were exposed to higher levels of phthalates. . They also found that boys were more likely to be affected, depending on the chemical involved and the order of the information presented.
This new study is part of the Illinois Kids Development Study (IKIDS), which tracks the effects of hormone-disrupting chemicals on the physical and behavioral development of children from birth to childhood. The IKIDS study, which is in its seventh year, has recruited hundreds of participants and tracks exposure to chemicals in pregnant women and the development of their children.
” IKIDS is part of a larger initiative funded by the National Institutes of Health, the Environmental Influences on Child Health Outcomes program. It tracks the impact of prenatal chemical exposures and maternal psychosocial stress on children’s growth and development over time Said study lead author Susan Schantz, neurotoxicologist and professor emeritus of comparative biosciences at the University of Illinois Urbana-Champaign. ” We measure many birth outcomes, including birth weight and gestational age. We also assess the cognition of infants by studying their observational behavior. This allows us to obtain measurements of working memory, attention and speed of information processing. “.
Reduced brain processing speed
The researchers analyzed the metabolites of three common phthalates in urine samples taken regularly from pregnant women participating in the study. Data on chemical exposure were used in conjunction with infant assessments when the children were 7.5 months old.
To do this, they used a well-established method that provides insight into the reasoning of children still too young to express themselves verbally. It consists of showing two types of events on video: familiar or unfamiliar. Infants typically watch unfamiliar or unexpected videos or events longer, which helps set a certain speed of brain processing.
The team used an infrared eye tracer to track each child’s gaze during several lab tests. With the infant sitting in the caregiver’s lap, the researchers first familiarized the infant with two identical images of a face. Once the infant learned to recognize the face, the researchers showed him that same face associated with an unfamiliar face.
” In repeated trials, half of the 244 infants tested saw a set of faces as familiar, and the other half learned to recognize a different set of faces as familiar. Said Schantz. ” By analyzing the time spent looking at faces, we were able to determine both how quickly infants processed new information and to assess their attention span. “. Details were published in the journal International Journal of Environmental Research and Public Health.
Phthalates: an indirect action on brain development
This assessment found a link between exposure of pregnant women to most of the phthalates tested and slower information processing in their infants, but the outcome depended on the specific chemical, the sex of the infant and the the series of faces considered familiar by the infant. Male babies, in particular, tended to process information more slowly if their mothers had been exposed to higher concentrations of phthalates, which are known to interfere with androgenic hormones.
The specific features of the faces presented to infants during familiarization trials also appeared to play a role in the outcome, the researchers said. Children exposed to phthalates who were first familiarized with faces from “Set 2” were more likely to have a slower processing speed than those who were familiar with faces from “Set 1”. This finding is puzzling, says Schantz, but it is likely related to differences in infant preferences for the faces of the two sets. It could also indicate that familiarization with the faces of Set 2 is a more sensitive detector of changes in processing speed associated with exposure to phthalates.
” Most of the previous studies on the relationship between prenatal phthalate exposure and cognition have focused on infancy and middle childhood. », Explains Schantz. “ This new work suggests that some of these associations may be detected much earlier in a child’s life. “.
Video presentation of the study and the results: