Evaluating Postharvest Washing Methods for Micro-Nanoplastic Removal from Edible Vegetable Leaves

Micro and nano-plastics (MNPs) have become a significant contamination concern in various ecosystems. In agriculture, they contaminate edible plants through different sources, such as irrigation and air deposition, threatening food safety and human health. It is uncertain whether post-harvest cleaning methods can effectively remove MNPs from the surface of edible plants. This study used confocal Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) to assess the efficacy of household and industrial postharvest washing methods in removing MNPs from vegetable leaf surfaces. In particular, the cleaning techniques included tap water washing, vegetable detergent washing, and sonication cleaning. The plastic particles tested included 42 µm polystyrene (PS), 6 µm polymethyl methacrylate (PMMA), and 61 nm PS. In evaluating cleaning methods to remove MNPs from basil leaves, the tap water washing method demonstrated high removal efficacy for 42 µm PS (93.1%) but lower efficacy for 6 µm PMMA (51.6%). Vegetable detergent was the most effective method for PMMA removal (73.3%). The sonication method exhibited the highest removal efficacy of 59.8% among the three washing methods for removing 61 nm PS. This is the first time that the efficacies of common washing methods to remove MNPs from fresh produce were evaluated and compared using confocal Raman spectroscopy and SERS. The research offers critical insights and approaches for assessing the removal efficacy of commonly used washing techniques in decontaminating MNPs from fresh produce. The findings highlight the need to develop more effective washing methods to enhance MNPs removal in the future.