Developmental neurotoxicity evaluation of di(2-ethylhexyl) phthalate (DEHP) and three alternative plasticizers in human neurospheres

Plasticizers like di-(2-ethylhexyl) phthalate (DEHP) are commonly used in medical devices to enhance plastic flexibility. DEHP is classified as a CMR1b substance due to its adverse effects on reproduction and fertility, and it has been linked to neurodevelopmental disorders such as ADHD, autism spectrum disorder, and learning disabilities. While DEHP is scheduled for phase-out by 2030, data on the developmental neurotoxicity (DNT) of alternative plasticizers remain scarce. We evaluated the DNT potential of DEHP and three alternative plasticizers: di-(2-ethylhexyl) terephthalate (DEHT), di-(2-ethylhexyl) adipate (DEHA), and tris-(2-ethylhexyl) trimellitate (TOTM), aiming to identify safer substitutes, particularly for neonates in neonatal intensive care units (NICUs). The human Neurosphere Assay was used to assess plasticizer effects on seven key neurodevelopmental processes: neural progenitor cell (NPC) proliferation, migration of radial glia, neurons, and oligodendrocytes, neurite outgrowth, and differentiation of neurons and oligodendrocytes. Concentration-response analyses provided benchmark concentrations (BMCs) and lowest observed adverse effect concentrations (LOAECs). Gene expression profiling provided mechanistic insights, and toxicity was ranked using the most sensitive endpoint (MSE) and ToxPi Tool. DEHP and TOTM showed the highest DNT potential, with NPC proliferation as the MSE. DEHT impacted oligodendrocyte differentiation, while no BMC was determined for DEHA within the tested concentrations. Considering an exposure scenario in NICUs, the estimated neonatal DEHP plasma levels exceeded the LOAEC for NPC proliferation, raising concerns for DNT. Overall, DEHA emerged as the least hazardous alternative for neurodevelopment, highlighting the value of combined human-relevant in vitro phenomics and human biomonitoring for DNT hazard evaluation.