Boys' Play Behavior Linked to Phthalate Exposure in Experimental Study
In a groundbreaking study published in the International Journal of Andrology (2025), researchers have found a significant association between prenatal exposure to the phthalates DEHP (di(2-ethylhexyl) phthalate) and DBP (dibutyl phthalate) and altered male-typical play behavior in preschool children.
This research, led by the University of Rochester Medical Center, suggests potential neurodevelopmental disruptions that could affect masculine brain development. The study reports that elevated concentrations of these common phthalates in mothers' prenatal urine are associated with their sons being less likely to play with male-typical toys and games.
Phthalates, such as DEHP and DBP, are known anti-androgens, meaning they can disrupt the actions of male hormones (androgens) during critical periods of brain development. Since male-typical play behavior is strongly influenced by prenatal androgen exposure, phthalate interference can lead to reduced masculine-typical play patterns in boys, reflecting delayed or altered masculine brain organization.
The study used the Preschool Activities Inventory (PSAI) to examine boys' play behavior in relation to the concentration of phthalate metabolites in their mothers' prenatal urine samples. Higher concentrations of metabolites of DEHP and DBP were associated with less male-typical behavior in boys on a standard play questionnaire. No other phthalate metabolites measured in-utero were linked to less-masculine behavior.
Researchers were concerned about how the choice of toys available in any given household might skew results, so they also asked about parental views toward atypical play. The PSAI addresses three aspects of play: types of toys children choose, activities, and child characteristics.
The study's lead author, Shanna H. Swan, Ph.D., professor of Obstetrics and Gynecology, director of the Center for Reproductive Epidemiology, and an expert in phthalates, hypothesized that phthalates may lower fetal testosterone production during a critical window of development, between eight to 24 weeks gestation.
This research aligns with a growing body of evidence that environmental phthalates act as neurotoxicants affecting early brain sexual differentiation and behavior. Metabonomic studies point to metabolic mechanisms in cord blood that may underlie these behavioral outcomes, suggesting underlying biochemical mechanisms linking phthalate exposure and neurodevelopment.
The study was conducted on 145 preschool children and was funded by the U.S. Environmental Protection Agency, the National Institutes of Health, and the state of Iowa. Co-authors from various institutions, including Amy Sparks, Ph.D., of the University of Iowa Hospitals and Clinics, Christina Wang, M.D., UCLA School of Medicine, J. Bruce Redmon, M.D., University of Minnesota School of Medicine, Robin Kruse, Ph.D., University of Missouri School of Medicine, and Melissa Hines, Ph.D., University of Cambridge, United Kingdom, contributed to the research. Co-authors from the University of Rochester Medical Center include Bernard Weiss, Ph.D., and Fan Liu, M.S.
Interestingly, girls' play behavior was not associated with phthalate levels in their mothers, according to the study. This finding underscores the importance of focusing on the specific impacts of phthalates on male development.
The study's findings have significant implications for public health, as phthalates are found in various everyday items such as vinyl and plastic tubing, household products, and many personal care products like soaps and lotions. Further research is needed to understand the long-term effects of phthalate exposure and to develop strategies for reducing exposure during pregnancy.
