Identification and characterization of microplastics released during the actual use of disposable cups using laser direct infrared imaging†

Disposable plastic cups are commonly used as beverage containers. This study investigated the characteristics of microplastics (MPs) released from plastic cups under everyday conditions and assessed the emission of MPs from disposable cups, including polypropylene (PP) and polystyrene (PS). We systematically examined the impact of material, temperature, and liquid type on the release of MPs using laser direct infrared (LDIR) spectroscopy. The findings indicated that all cups released irregularly shaped MPs smaller than 50 μm. When filled with water at 95 °C for 15 min, the average MP concentrations in the PP and PS cups were 1340 and 980 particles per L, respectively. The disposable plastic cups exhibited higher average MP concentrations at elevated temperatures. Similar profiles were observed for both types of cups, with the MP release capacity at 95 °C being 1.5 times higher than that at 50 °C. Low temperatures facilitated the self-release of MPs from disposable cups. Furthermore, reusable cups released fewer MPs than single-use cups. The study estimated that regular use of a cup three times a day could lead to the unintentional ingestion of 294–402 MPs per day. These results provide a basis for evaluating possible health hazards associated with human exposure to MPs.