Polyurethane-Derived Microplastics and Nanoplastics: Sources, Human Exposure, and Toxicological and Health Effects

Polyurethane (PU) is one of the most widely used synthetic polymers, yet polyurethane-derived microplastics and nanoplastics (MNPs) have received less attention than particles derived from polyethylene, polypropylene, or polystyrene. This narrative review summarizes current evidence on the sources, environmental release, aging, human exposure pathways, biomonitoring findings, biological effects, and research gaps associated with PU-derived MNPs. The review synthesized 200 sources from database searches without publication-date restrictions and supplementary contextual literature, integrating environmental, experimental, biomonitoring, and clinical evidence, considering methodological limitations and publication status. PU-derived MNPs originate from diverse consumer, industrial, textile, medical, and agricultural products and undergo physicochemical transformations during environmental aging that may alter particle behavior and chemical release. Human exposure may occur through inhalation, ingestion, dermal contact, and medical procedures, while PU-containing particles have been detected in biological matrices, including respiratory samples, placenta, blood, reproductive tissues, and urine. Experimental evidence suggests that PU-derived particles and their associated leachates may induce oxidative stress, inflammation, barrier dysfunction, cytotoxicity, and immune responses, although direct evidence linking PU exposure to human disease remains limited. Integrating environmental monitoring, human biomonitoring, toxicology, and One Health approaches can improve exposure assessment, harmonize analytical methods, and clarify the ecological and clinical relevance of PU-derived MNPs.