Polyethylene plastic degradation: The dual pathways from macroplastics to nanoplastics

Plastics degrade in the environment through complex physical and chemical processes. Here, we demonstrate that nanoplastics (NPs) can be directly released from macroplastics, and not solely generated via intermediate microplastic (MP) fragmentation, thereby challenging the conventional stepwise degradation paradigm. Using a multi-technique approach combining scanning electron microscopy (SEM), µ-Raman spectroscopy, Chemical mapping (sSNOM), and optical infrared spectroscopy (OPTIR), we show that chain scission and oxidation drive structural embrittlement, promoting direct NP detachment from macroplastic surfaces. These findings emphasize the urgent need to reconsider plastic pollution mitigation strategies, moving beyond a sole focus on MPs and NPs to include macroplastics as a primary and active source of nanoscale pollutants. Expanding regulatory frameworks to address plastic degradation across all size scales, from macro to nano, is essential to limit long-term environmental and ecological risks. • Direct evidence shows nanoplastics can detach from macroplastics, bypassing microplastic formation. • Combined UV irradiation and mechanical stress drive early nanoplastic release from polyethylene. • SEM and advanced spectroscopy confirm nanoscale fragments originate from embrittled macroplastic surfaces. • Nanoplastics display higher oxidation and reactivity, raising concerns for pollutant transport and toxicity. • Findings challenge current plastic degradation models, urging regulatory updates to include nanoscale risks.