Organ-specific accumulation and toxicity analysis of orally administered polyethylene terephthalate microplastics

Microplastics (MPs), plastic particles with a diameter of < 5 mm, are intentionally produced or formed by the breakdown of a variety of larger plastics. Polyethylene terephthalate (PET) is a common source of MPs and PET-MPs are prevalent in the environment. Owing to their persistence, PET-MPs can enter ecosystems, air, and food sources, posing significant health risks. This study aimed to investigate the toxicological effects and in vivo accumulation of PET-MPs smaller than 10 µm. To track their biodistribution, fluorescently labeled PET-MPs were prepared. Particle size and morphology were confirmed using physical and chemical characterization. Following the oral administration of PET-MPs in ICR (CD-1®) outbred mice, accumulation occurred predominantly in lungs, as confirmed by IVIS spectrum CT analysis and in vivo and ex vivo imaging. Toxicity assays revealed the development of granulomatous inflammation in the lungs at medium and high doses, indicating a concentration-dependent response. The recorded no-observed-adverse-effect levels were 1.75 mg/kg for males and 7 mg/kg for females. This study highlights the potential of PET-MPs to induce persistent inflammation in respiratory tissues and reveals the need for further research to support the regulatory standards and long-term health effects of MP exposure.