Plasticizer Mixture Tied to Lower IQ Scores in Young Children

Prenatal exposure to common plastic additives tied to food packaging and cosmetics is linked to a notable drop in children’s intelligence scores by age three, according to a new French study tracking hundreds of families.

The research, published in Environmental Health Perspectives, investigates how chemical mixtures impact early neurodevelopment while overcoming previous measurement flaws by pooling multiple urine samples over sensitive exposure windows.

Plasticizers and Child Brain Development

Plastic pollution is a widespread environmental challenge, with hundreds of chemicals leaching from everyday materials and resulting in continuous human exposure. Among them, phthalates and phenols act as plasticizers and additives that improve the flexibility and durability of plastics. These compounds are detected in virtually all human populations and function as endocrine-disrupting chemicals capable of altering the neuroendocrine system during critical phases of development.

Neurobehavioral impairments, including intellectual disability and intelligence quotient point loss, affect millions of children worldwide and carry immense societal costs. While mother-child cohort evidence has grown, data remained limited for newer chemical substitutes like bisphenol S and for specific developmental windows such as early infancy. Previous studies often relied on a single spot urine sample, creating exposure misclassification issues due to the short half-life and high variability of these chemicals. The current work addresses this shortcoming by collecting and pooling multiple urine samples over sensitive exposure windows.

Study Design and Advanced Statistical Modeling

The research team utilized data from the French SEPAGES mother-child cohort, which recruited 484 pregnant women between July 2014 and July 2017. Pregnant participants collected three urine samples daily for seven consecutive days during both the second and third trimesters. After birth, parents collected one urine sample per day for a week using cotton gauze in the child’s diaper during neonatal and infant periods. A total of 12 phenols, 12 phthalates, and two non-phthalate plasticizer metabolites were measured using high-performance liquid chromatography coupled to mass spectrometry.

To handle multiple comparisons and avoid discarding true associations or reducing mixture model precision, the authors combined a structured literature review with meta-analyses to determine the weight of evidence for each chemical. This weight of evidence informed priors in Bayesian single-chemical models and prioritized relevant compounds for mixture analysis. Child IQ was evaluated by trained neuropsychologists at a median age of 36.9 months using the French version of the Wechsler Preschool and Primary Scale of Intelligence, Fourth Edition.

Weighed Mixture Effects and Individual Chemical Risks

Analysis of the prioritized chemical mixture, which included bisphenol A, bisphenol S, mono-ethyl phthalate, mono-n-butyl phthalate, mono-isobutyl phthalate, and di­(2-ethylhexyl) phthalate metabolites, revealed clear patterns. A simultaneous quartile increase in the concentration of each prioritized chemical during the third pregnancy trimester was associated with decreased full-scale, visual-spatial, and verbal IQ scores across all children. Bisphenol A and mono-ethyl phthalate showed the highest relative contribution, accounting for approximately half of the mixture weight.

In single-chemical Bayesian models, third-trimester bisphenol A exposure was linked to decreased full-scale IQ scores. Bisphenol A at one year of age also showed negative associations with full-scale and visuospatial scores. Prenatal exposure to mono-ethyl phthalate was associated with lower full-scale and visual-spatial scores, while mono-n-butyl phthalate during the third trimester correlated with reduced visual-spatial scores and a marginal trend toward lower working memory. Furthermore, second-trimester di­(2-ethylhexyl) phthalate exposure showed sex-specific differences, lowering full-scale IQ in boys while showing positive associations in girls.

Public Health Implications and Prevention Opportunities

The observed mixture effect indicates an average loss of nearly three IQ points for each quartile increase in third-trimester exposure, a magnitude comparable to early-life lead exposure. Because phenol and phthalate exposures are widespread yet modifiable, these findings highlight a significant opportunity for primary prevention. The authors emphasize that plasticizer chemicals should be regulated as mixtures rather than in isolation to better protect children’s cognitive development.

The research was published in Environmental health perspectives on November 8, 2026.