Release of Nanoplastics from Polypropylene Food Containers into Hot and Cold Water

Plastic particles can be released from food containers, potentially contaminating food and leading to human exposure through ingestion. While microplastics (MPs, 1–5000 μm) release has been widely studied, data on nanoplastics (NPs, < 1 μm) remain limited due to analytical challenges associated with their small size. This study investigated the release of NPs from Australian-sourced polypropylene (PP) food storage containers under simulated-use conditions. Total mass concentrations ranged from 0.01 to 3.7 μg/L for NPs and 0.4 to 10.8 μg/L for MPs, with higher concentrations observed after rinsing containers with Milli-Q water at 90 °C compared to at room temperature. Nanoparticle tracking analysis (NTA) revealed heterogeneous particle size distributions (122–397 nm). Crucially, PP NPs were isolated via asymmetrical flow field-flow fractionation with multiangle light scattering (AF4-MALS) and chemically confirmed using pyrolysis–gas chromatography–mass spectrometry (Pyr–GC–MS/MS). This multitechnique approach allowed both quantitative and chemical characterization of the released particles. The findings provide clear evidence of PP nanoplastic release under typical usage conditions and highlight a potential route for human exposure. This work advances our understanding of nanoplastic contamination from plastic food packaging and underscores the importance of assessing NP release in exposure and risk assessments.