Unveiling nanoplastic release from single-use eyedrop vials: A particle-based approach for identification and quantification

Microplastics have been detected in vitreous samples, providing evidence of ocular health risks associated with direct exposure to micro-nanoplastics (MNPs). However, the primary sources, abundance, morphology and size distribution of these particles remain unclear. Here, we employed pyrolysis-gas chromatography-mass spectroscopy (Pyr-GC/MS) to verify the release of synthetic polymers from commercial disposable eye-drop containers. Due to small sample volumes, this conventional mass-based analytical method struggled to quantify the MNPs concentration effectively. In contrast, the single particle-based analytical techniques, including surface-enhanced Raman spectroscopy (SERS) and scanning electron microscopy, reveal thousands of MNPs released upon opening the container, with 88 % of particles measuring less than 5 μm. Another release mechanism is attributed to pre-existing particles within the container. The detection of oxygenated MNPs further suggests an increased potential for ocular toxicity. This research highlights the feasibility of particle-based methods when it comes for targeting the nanoscale of plastic particles. Furthermore, integration of SERS and SEM identifies a previously uncharacterized direct exposure route of nanoplastics to the human eye via commercial eye drops and emphasizes the importance of single-particle characterization in accurately assessing their implications for ocular health.