Micro/Nanoplastic-Enhanced Oxidative Potential, Antioxidant Depletion, Inflammation in PM2.5 and Cytologic and Metabolomic Shifts

Micro- and nanoplastics (MNPs) are increasingly contaminating atmospheric particulates, yet their influence on PM2.5 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 PM2.5. We evaluated PM2.5 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 PM2.5 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 PM2.5, 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 PM2.5 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 PM2.5 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.