Micro/Nanoplastic-Enhanced Oxidative Potential, Antioxidant Depletion, Inflammation in PM_2.5 and Cytologic and Metabolomic Shifts

Micro- and nanoplastics (MNPs) are increasingly contaminating atmospheric particulates, yet their influence on PM_2.5 chemistry and toxicity remains poorly understood. This study investigates how secondary MNPs derived from common products (water bottles, coffee cups, and food plates) alter the properties of PM_2.5. We evaluated PM_2.5 leaching characteristics, oxidative potential, inflammatory activity, and bacterial-based cytological and metabolomic responses after 24 h of exposure to three MNP doses. MNPs markedly altered PM_2.5 chromophoric composition, with bottle-derived (PET) MNPs inducing the strongest increases in aromaticity, humification, and slope factor, followed by coffee cups (PLA/paper) and food plates (PP). These leaching shifts aligned with polymer-specific redox behaviors: bottle-derived MNPs enhanced antioxidant enrichment at high PM_2.5, whereas cup-derived MNPs produced the most pronounced protein-denaturation-based inflammatory activity. Escherichia coli assays showed non-linear growth responses, elevated reactive oxygen species, altered carbohydrate secretion, and membrane and protein perturbations that paralleled PM_2.5 chemical reactivity. FTIR metabolomic fingerprints revealed dose- and polymer-dependent disruptions in polysaccharide, lipid, and protein domains. Overall, the results demonstrate a mechanistic cascade in which MNP exposure reshapes PM_2.5 chemistry, amplifies oxidative and inflammatory potential, and culminates in measurable cytological and metabolic stress, with polymer identity (PET > PLA/paper > PP) as the dominant driver.