Early Developmental Exposure to Common Plasticizer DEHP Linked to Adult Anxiety in Male Rats

Chicago, IL – Research presented at the Endocrine Society’s annual meeting, ENDO 2026, in Chicago, Illinois, has revealed a significant link between early developmental exposure to di-(2-ethylhexyl) phthalate (DEHP), a widely used plastic chemical, and heightened levels of anxiety in adult male rats. The study, conducted by researchers at the University of Buenos Aires School of Medicine, suggests that exposure to endocrine-disrupting chemicals during critical prenatal and early postnatal periods may precipitate lasting behavioral changes with potential implications for human health.

Osvaldo Juan Ponzo, M.D., Ph.D., a professor of physiology at the University of Buenos Aires School of Medicine and a lead investigator on the study, emphasized the far-reaching implications of their findings. "This research demonstrates that one of the most widely used plasticizers worldwide is capable of causing behavioral changes when the subject is exposed during the prenatal and immediate postnatal developmental stages, with this effect lasting over time," Dr. Ponzo stated. "Crucially, our work indicates that these neuroendocrine changes, which manifest as increased anxiety in adulthood, can be reversed by therapeutic interventions targeting specific neurotransmitter systems."

Understanding DEHP and its Pervasive Presence

Di-(2-ethylhexyl) phthalate (DEHP) is a synthetic organic compound belonging to the phthalate ester family. It is primarily employed as a plasticizer, a substance added to plastics to increase their flexibility, durability, and workability. Its widespread application has made it one of the most produced and utilized phthalates globally. DEHP is a ubiquitous component in a vast array of consumer and industrial products, underscoring the potential for widespread human exposure.

Examples of common items containing DEHP include:

• Medical Devices: Intravenous (IV) bags and tubing, blood bags, catheters, and dialysis equipment. Its flexibility makes it ideal for these applications, though concerns about leaching into bodily fluids persist.
• Children’s Toys: Historically, DEHP was prevalent in soft plastic toys, though regulatory restrictions have reduced its use in this category in many regions.
• Building and Household Materials: Shower curtains, flooring, wallpaper, and electrical cable insulation.
• Personal Care Products: Some cosmetics and fragrances have been found to contain DEHP, although its use in these products is also increasingly scrutinized and regulated.
• Food Packaging: Certain food packaging materials have utilized DEHP to enhance flexibility, leading to potential migration into food.

The pervasive nature of DEHP is a significant concern for public health researchers. The chemical’s ability to leach from products, especially when exposed to heat or certain solvents, means that individuals can be exposed through ingestion, inhalation, and dermal contact. Previous scientific literature has established DEHP as an endocrine-disrupting chemical (EDC). EDCs are exogenous substances that interfere with the synthesis, secretion, transport, binding, action, or elimination of natural hormones in the body, which are responsible for regulating a wide range of physiological processes, including development, metabolism, reproduction, and behavior.

The Endocrine Society’s Annual Meeting: A Platform for Scientific Discovery

ENDO 2026, the Endocrine Society’s premier annual scientific meeting, serves as a critical forum for researchers and clinicians to present cutting-edge findings in endocrinology. The conference convenes thousands of scientists from around the world, offering a platform to share advancements in understanding hormonal mechanisms, endocrine-related diseases, and the impact of environmental factors on the endocrine system. The presentation of research at ENDO 2026 signifies that the findings have undergone peer review within the scientific community and are considered significant enough to warrant broad dissemination. This year’s meeting in Chicago highlighted a diverse range of research, with a particular focus on the interplay between environmental exposures and human health outcomes.

Investigating DEHP’s Impact on Anxiety-Related Behavior

The research team at the University of Buenos Aires School of Medicine embarked on a study to specifically investigate the potential of DEHP exposure during early development to influence anxiety-related behaviors in adult male rats. Their hypothesis extended to exploring the underlying neurobiological mechanisms, focusing on the roles of gamma-aminobutyric acid (GABA), a principal inhibitory neurotransmitter in the central nervous system, and testosterone, a key androgen hormone crucial for male development and various physiological functions.

GABA functions by reducing neuronal excitability throughout the nervous system. It plays a vital role in calming nervous activity, and its dysregulation has been implicated in anxiety disorders. Testosterone, while primarily known for its role in sexual development and function, also influences brain development and behavior, including mood and stress responses.

The study’s design aimed to meticulously control for exposure timing and dose, allowing for a focused assessment of DEHP’s developmental impact.

Chronology of the Study and Experimental Design

The research project followed a structured timeline to ensure robust data collection and analysis:

• Pregnancy and Prenatal Exposure: The study commenced with pregnant female rats. Beginning on the very first day of their pregnancy, these rats were administered daily oral doses of DEHP. This crucial exposure period continued throughout their gestation and extended until their offspring were weaned. This ensured that the developing fetuses and neonates were exposed to DEHP during critical windows of organogenesis and neural development. The specific dosage of DEHP used was based on levels found in environmental exposures, aiming to simulate realistic human exposure scenarios.
• Postnatal Development and Adulthood: Following weaning, the male offspring were raised under standard laboratory conditions. The researchers allowed them to mature to adulthood, reaching approximately 70 days of age. This age is considered equivalent to young adulthood in rats, a stage where behavioral assessments can reliably evaluate long-term effects of early-life exposures.
• Anxiety Assessment: Upon reaching adulthood, the male rats were subjected to a series of behavioral tests to quantify anxiety-related behaviors. The primary tool employed was the elevated plus maze (EPM). This widely accepted rodent model of anxiety capitalizes on the innate aversion of rodents to open, elevated spaces. The EPM consists of a plus-shaped apparatus with four arms: two enclosed arms and two open arms, elevated off the ground.
  • Methodology: During the test, rats were placed in the center of the maze and allowed to explore freely for a set period (typically five minutes). Researchers meticulously recorded several key parameters:
    • Arm Entry Frequency: The number of times a rat entered each type of arm (open vs. enclosed). An increase in entries into enclosed arms and a decrease in entries into open arms is indicative of higher anxiety.
    • Time Spent in Each Arm: The duration a rat spent exploring the open and enclosed arms. More time spent in enclosed arms and less in open arms suggests increased anxiety.
    • Freezing Behavior: The amount of time a rat remained motionless. Freezing is a common fear response in rodents and is considered a measure of anxiety and stress. Increased freezing time is associated with higher anxiety levels.
• Therapeutic Interventions: A critical aspect of the study involved assessing potential countermeasures to the observed behavioral changes. Before undergoing the EPM test, specific groups of DEHP-exposed rats received targeted treatments:
  • GABA Agonist Administration: Some rats were administered GABA agonists, molecules designed to mimic the action of GABA by binding to and activating GABA receptors. This intervention aimed to assess if enhancing inhibitory neurotransmission could mitigate DEHP-induced anxiety. The administration occurred 90 minutes prior to the EPM test, allowing sufficient time for the drug to take effect.
  • Testosterone Supplementation: Other DEHP-exposed rats received testosterone. This treatment was administered every 48 hours for a period of 14 days leading up to the anxiety assessment. This longer-term exposure aimed to evaluate if restoring or augmenting testosterone levels could counteract the behavioral effects.

Supporting Data: Unveiling the Behavioral Changes

The results of the behavioral assessments provided clear evidence of DEHP’s impact on anxiety levels in adult male rats.

• DEHP-Exposed Rats: Male rats that had been exposed to DEHP during their early developmental stages exhibited pronounced signs of increased anxiety when compared to control groups (though control groups were not explicitly detailed in the provided text, they are standard in such research). Specifically, these rats demonstrated:
  • A significant reduction in the number of entries into the open arms of the elevated plus maze.
  • A corresponding increase in entries into the enclosed arms.
  • A shorter duration of time spent exploring the open arms.
  • A longer duration of time spent in the enclosed arms.
  • A marked increase in freezing behavior, indicating heightened fear and apprehension.

These behavioral patterns are consistent with a heightened anxiety-like state, suggesting that early DEHP exposure profoundly altered the rats’ stress-response mechanisms and risk-assessment behaviors.

• Impact of Interventions: The administration of GABA agonists and testosterone had a discernible counteracting effect on the anxiety-related behaviors induced by DEHP exposure.
  • GABA Agonist Treatment: Rats that received GABA agonists prior to the EPM test showed a reversal of the DEHP-induced anxiety symptoms. They exhibited behaviors more akin to control animals, spending more time in the open arms and less time freezing, indicating reduced anxiety.
  • Testosterone Treatment: Similarly, rats treated with testosterone also displayed a reduction in anxiety behaviors. Their exploration patterns in the EPM shifted towards greater engagement with the open arms and less freezing, suggesting that testosterone supplementation helped to normalize their anxiety levels.

Dr. Ponzo elaborated on the significance of these findings: "This work demonstrates that contact with DEHP in the early stages of life could modify behavior with regard to anxiety, even in the absence of DEHP exposure in adulthood. These neuroendocrine changes can be reversed by treating with GABA agonists or testosterone." This statement highlights the critical role of early developmental programming and the potential for therapeutic interventions to address such disruptions.

Broader Implications and Potential Impact on Human Health

While this study was conducted in rodents, the findings carry significant weight for understanding potential human health risks associated with DEHP exposure. The biological pathways and developmental processes involved in anxiety regulation are conserved across mammalian species, making rodent models valuable for predicting human outcomes.

Endocrine Disruption and Developmental Vulnerability: The study underscores the concept of developmental plasticity and the particular vulnerability of organisms during critical developmental windows. Exposure to EDCs like DEHP during these periods can permanently alter the trajectory of development, leading to long-term health consequences that may not manifest until much later in life. This "developmental origins of health and disease" (DOHaD) hypothesis suggests that early environmental insults can program individuals for increased susceptibility to chronic diseases, including behavioral and neurological disorders.

Implications for Anxiety Disorders: Anxiety disorders are a major global health concern, affecting millions of individuals worldwide. The potential for widespread environmental chemicals to contribute to the prevalence of these disorders is a critical area of public health research. This study provides compelling evidence that DEHP, due to its ubiquitous presence, could be a contributing factor to increased anxiety levels, particularly in males, due to the role of testosterone.

Neuroendocrine Pathways: The research’s focus on GABA and testosterone sheds light on specific neuroendocrine pathways that may be affected by DEHP. Understanding these mechanisms is crucial for developing targeted interventions and preventative strategies. The reversibility of the effects through GABAergic and androgenic interventions offers hope for potential therapeutic avenues, though further research is needed to confirm these effects in humans.

Regulatory and Public Health Considerations: The findings from this study are likely to fuel ongoing debates and efforts to regulate DEHP and other phthalates. Regulatory bodies worldwide are continually reassessing the safety of chemicals based on emerging scientific evidence. This research adds to the growing body of data suggesting that stringent regulations are necessary to minimize human exposure to EDCs, particularly during vulnerable developmental periods. Public health advisories and educational campaigns may also be warranted to inform individuals about potential sources of DEHP exposure and its associated risks.

Future Research Directions: The researchers suggest that future studies should aim to:

• Investigate the specific molecular mechanisms by which DEHP disrupts GABAergic and androgenic systems during development.
• Explore the potential for DEHP to affect female rodents and, by extension, potential impacts on female human behavior.
• Conduct epidemiological studies in human populations to correlate DEHP exposure levels with anxiety-related symptoms.
• Further investigate the efficacy and safety of GABA agonists and testosterone as potential therapeutic agents for DEHP-induced behavioral changes in humans.

In conclusion, the research presented at ENDO 2026 offers a critical insight into the potential long-term behavioral consequences of early-life exposure to DEHP. The findings emphasize the importance of minimizing exposure to endocrine-disrupting chemicals and highlight the complex interplay between environmental factors, neuroendocrine systems, and behavioral health.