Exposure to Di(2‐Ethylhexyl) Phthalate Increases the Internalization of Polystyrene Microplastics by Human Hepatocellular Carcinoma Cells and Leads to Cell Damage

ABSTRACT Microplastics (MPs) and the plasticizer di(2‐ethylhexyl) phthalate (DEHP) frequently co‐occur, presenting substantial health risks to both humans and animals. While animal studies indicate adverse effects from exposure to MPs and DEHP, their potential toxicity in humans remains uncertain. This study examines the response of human hepatocellular carcinoma (HepG2) cells to concurrent exposure to synthetic spherical polystyrene (PS) particles and DEHP. We analyzed the effect of particle size on the internalization of PS‐MPs using HepG2 spheres as a 3D model. The results showed that MPs at 100 nm had the highest internalization efficiency, which gradually decreased as the particle size increased to 1 and 5 μm. In addition, DEHP significantly improved the internalization of MPs, especially for 5 μm particles, which showed a 26% increase in internalization efficiency. We also evaluated changes in physiological activity. Co‐exposure to MPs and DEHP resulted in significantly higher cytotoxicity than exposure to MPs alone, with a 20% reduction in cell viability. Larger particle sizes led to greater cellular damage, indicated by a 20% increase in reactive oxygen species (ROS) and a 40% rise in lactate dehydrogenase (LDH) release, suggesting membrane rupture. This study offers new insights into the potential toxicity of short‐term exposure to MPs and DEHP, using HepG2 spheres to closely replicate in vivo conditions.