Identification and characterization of microplastics released during 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) discharged from plastic cups in everyday situations and assessed the emission of MPs from disposable cups, including polypropylene (PP) and polystyrene (PS). We systematically examined the impact of the material, temperature, and liquid type on the release of MPs using laser direct infrared (LDIR) spectroscopy. The findings indicated that all cups released of irregularly shaped MPs smaller than 50 μm. When filled with water at 95°C for 15 min, the average MPs in the PP and PS cups were 1340 and 980 particles/L, respectively. The disposable plastic cups exhibited higher average MPs values at elevated temperatures. Similar profiles were observed for the two types of cups, in which the MP release capacity at 95°C was 1.5 times that at 50°C. Low temperatures facilitated the self-release of MPs from disposable cups. Furthermore, reusable disposable cups decreased MP release compared with 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 contact with MPs.