Polymer Types, Concentrations, and Analytical Methods for Microplastics and Nanoplastics in Human Blood

The presence of microplastics and nanoplastics in human tissues can be attributed to systemic distribution via the bloodstream. This narrative review summarizes the polymer types, reported concentrations, analytical methods, and cross-study comparability in human blood with a study-level appraisal of analytical reliability. We searched PubMed, Scopus, and Web of Science through October 2026 and identified eight peripheral blood studies in non-pregnant adults (462 study-level participants), one bone marrow study, and reports of thrombi and atherosclerotic plaques. Detection and quantification rates varied with the analytical thresholds applied. Mass concentrations and particle counts were reported using different statistical denominators, different treatments of values below the limit of quantification, and inconsistent particle-size ranges. Polyethylene, polystyrene, polyethylene terephthalate, polypropylene, polyvinyl chloride, poly(methyl methacrylate), and polyamide 66 have been reported in the blood, and imaging studies have identified additional polymers. The observed polymer rankings varied with the targeted polymers, analytical markers, and detection limits, and the specificity of polyethylene and polyvinyl chloride markers in blood remains unresolved. None of the studies separately quantified microplastics and nanoplastics at the 1 µm boundary. Limited coverage may lead to underestimation, whereas matrix interference and contamination may inflate the reported concentrations. Overall, we suggest that standardized collection protocols, matrix-specific validation with orthogonal confirmation, paired mass and particle measurements, and clinically relevant exposure assessments should be prioritized in future work.