Micro- and Nanoplastics as Potential Chronic Abiotic Stressors: Cellular Senescence, Hallmarks of Ageing, and an Oxidative–Mitochondrial–Inflammatory Framework

Micro- and nanoplastics (MNPs) are increasingly detected in human tissues, but whether they influence biological ageing remains unresolved. This critical narrative review evaluates whether experimental evidence supports MNPs as potential chronic abiotic stressors that engage ageing-relevant cellular processes. The literature was identified through structured searches of PubMed/MEDLINE, Scopus, Web of Science and Google Scholar (final search: 31 July 2026) and reference-list screening. Evidence was classified qualitatively using explicit criteria (endpoint specificity, replication, model relevance, exposure realism and proximity to human evidence), without formal risk-of-bias assessment or quantitative grading. Studies report perturbation of redox balance, mitochondrial function, DNA integrity, autophagy and inflammatory signalling, with senescence-associated phenotypes in selected models. Support is strongest experimentally for mitochondrial dysfunction and moderate to strong for cellular senescence; genomic damage, autophagy and inflammatory signalling show moderate support, whereas other hallmarks have emerging or insufficient evidence. Many studies use pristine polystyrene, high concentrations and short exposures, and human internal dose remains poorly defined. We propose an oxidative–mitochondrial–inflammatory framework as a hypothesis-generating model, not as evidence that MNPs accelerate human ageing. Chronic low-dose experiments and longitudinal human studies linking quantified internal burdens to validated ageing biomarkers are required.