New Project 1 Research Finds Negative Associations between Multiple Prenatal Phthalate Exposure and Early Child Neurodevelopment
A recent PROTECT Project 1 paper published in the International Journal of Hygiene and Environmental Health assesses potential associations between prenatal exposure to phthalate mixtures and major child neurodevelopment outcomes. The paper, led by Project 1 trainee Seonyoung (Shannon) Park, provides better understanding of how exposure to multiple phthalates at once impacts neurodevelopment outcomes across adaptive, cognitive, communication, motor, and personal-social domains.
Phthalates are a class of non-persistent chemicals used widely as plasticizers and solvents in popular consumer products like personal care items and food packaging to improve flexibility and processability. Phthalates are chemically bound to polymers, meaning they can be released into the environment and lead to human exposure through multiple avenues, like Superfund sites, tap and bottled water, food packaging, soil, and dust. Past research shows that phthalates are endocrine disruptors that can interrupt hormone homeostasis and lead to adverse health effects in infants, children, and adults. In terms of chemical exposure, pregnancy is a critical period for both maternal and fetal health as multiple physiological changes occur. Despite this knowledge, pregnant women are exposed to a mixture of phthalates on the daily.
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There is increasing evidence indicating that phthalate exposure may impair child neurodevelopment, which encompasses the development of cognitive, speech and language, motor, and personal-social skills. Potential neurodevelopment issues are especially impactful in the first three years of life as the foundational structure and framework of the brain are established. Neurodevelopment status between ages two to three is even an important predictor of neurodevelopmental issues, like ADHD, later on.
Previous studies on the impacts of multiple phthalate exposure on early neurodevelopment have reported inconclusive or inconsistent findings. Unfortunately, the reality is that people are exposed to multiple phthalate chemicals simultaneously every day. To address this, Shannon and co-authors set out to (1) capture the combined association of multiple phthalates beyond that of individual phthalates and (2) identify phthalates that contribute more heavily to any associations between the mixture and adverse neurodevelopment. To do so, researchers utilized the Battelle Developmental Index-2 (BDI), a clinically administered assessment that evaluates age-specific neurodevelopmental skills across the five main domains, and biological data, both from the PROTECT cohort.
Using multiple mixture analysis, researchers identified several metabolites as key predictors of worse child neurodevelopmental outcomes across multiple domains. MCOP consistently exhibited a strong negative association with the cognitive and social-personal domains. The metabolites MCNP, MBP, and MHP showed negative associations with the motor domain. Some other metabolites, like MIBP and MEHHP, surprisingly did not demonstrate negative associations. Still, researchers did observe overall negative trends of the combined effect of all phthalate metabolites for all neurodevelopmental domains, besides communication, and total BDI scores.
These findings indicate that specific phthalate metabolites contribute more strongly to adverse neurodevelopmental outcomes in children than other metabolites. However, overall exposure to phthalate mixture is associated with poorer neurodevelopment, which is significant considering that people are exposed to multiple phthalates at once. These results underscore the risk of delays across multiple neurodevelopment domains for those who are prenatally exposed to higher levels of multiple phthalates. Shannon and co-authors emphasize that these results also demonstrate the need for preventive measures and significant public-health interventions to reduce prenatal phthalate exposure and protect vulnerable populations.