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Susan Schantz and her colleagues found an association between prenatal exposure to phthalates and slower processing speeds in 7.5-month-old infants.

Photo by L. Brian Stauffer


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CHAMPAIGN, IL. – Exposure to phthalates, a class of chemicals widely used in packaging and consumer products, is known to affect normal hormonal function and development in human and animal studies. Now researchers have found evidence linking pregnant women’s exposure to phthalates to altered cognitive outcomes in their infants.

Most of the findings related to slower information processing in infants with higher phthalate exposure, with men more likely to be affected depending on the chemical involved and the order in which information was presented to the infants.

The study was published in the journal Neurotoxicology and is part of the Illinois Kids Development Study, which examines the effects of hormone-disrupting chemicals on the physical and behavioral development of children from birth to middle childhood. Now, in its seventh year, IKIDS has enrolled hundreds of participants and is tracking chemical exposure in pregnant women and development outcomes in their children. Susan Schantz, neurotoxicologist and Professor Emeritus of Comparative Biosciences at the University of Illinois’ Urbana-Champaign, is the study’s lead researcher. She is a faculty member at the Beckman Institute for Advanced Science and Technology, which hosts the IKIDS program in Illinois.

IKIDS is part of a larger initiative funded by the National Institutes of Health, the Environmental Impact on Child Health Outcomes program. It tracks the effects of maternal prenatal chemical exposure and psychosocial stress on child growth and development over time, ”said Schantz. “We measure numerous birth outcomes, including birth weight and gestational age. We also evaluate infants’ perception by examining their appearance. In this way we can measure working memory, attention and the speed of information processing. “

The researchers analyzed metabolites of three common phthalates in urine samples collected regularly from pregnant women in the study. Chemical exposure data were used in combination with ratings of infants from women 7.5 months of age.

The researchers used an established method that provides insight into the reasoning of children who are too young to express themselves verbally: infants typically look longer at unknown or unexpected images or events.

The team used an infrared eye tracker to track each child’s gaze during several laboratory tests. While the child was sitting on a caregiver’s lap, the researchers first introduced the child to two identical facial images. After the child learned to recognize the face, the researchers showed the same face paired with an unfamiliar one.

“In repeated trials, half of the 244 infants tested saw one group of faces as familiar and the other half learned to recognize another group of faces as familiar,” said Schantz. “By analyzing the time we spent looking at the faces, we were able to determine both the speed at which the infants processed new information and their ability to pay attention.”

The assessment included exposure of pregnant women to most phthalates, which were assessed to have slower information processing in their infants. The result, however, depended on the specific chemical, the infant’s gender, and the faces that the infant was considered familiar. Male infants in particular tended to process information more slowly when their mothers were exposed to higher levels of phthalates, which are known to interfere with androgenic hormones.

The specific features of faces presented to the infants in the induction trials also appeared to play a role in the outcome, the researchers reported. Children exposed to phthalates who were first familiar with faces from set 2 were more likely to have a slower processing speed than children who were familiar with faces from set 1 – the faces in the two sets. This may also indicate that incorporation into the Set 2 areas is a more sensitive detector of changes in processing speed related to phthalate exposure.

“Most previous studies on the association between prenatal phthalate exposure and cognition have focused on early and middle childhood,” said Schantz. “This new work suggests that some of these associations can be seen much earlier in a child’s life.”

The U.S. Environmental Protection Agency, the National Institute of Environmental Health Sciences, and the National Institutes of Health’s ECHO program supported this research.

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